> Hello, as a personal project to become more familiar with RF circuits I
> would like to build an AM radio receiver. Online, I found a schematic which
> uses the NE612 mixer IC to create a Direct Conversion ("Syncrodyne")
> receiver. I have modified the design so that the local oscillator does not
> need a custom wound transformer.
>
> In my case, I don't require the receiver to have very good performance. I'm
> okay with the oscillator drifting and the audio "warbling" (due to
> frequency mismatch) under normal operation.
>
> I don't have any sort of matching network or filtering on the antenna
> connection; but I am hoping a 10m wire antenna will produce a sufficiently
> strong signal for the mixer. I am unsure how strongly signals and noise
> outside of the AM band are going to affect the receiver. Ideally, I'd have
> a buffer amplifier on the antenna input and a bandpass filter that covered
> the AM band, but I want to avoid making this too complex.
>
> I have attached a picture of the original schematic, a picture of my
> ltspice schematic, and zip containing my ltspice simulation.
>
> I would like to know if my design (ltspice simulation) seems reasonable
> before I try to build it. I welcome advice on improving the design, but at
> the same time I do wish to keep things a simple as possible.
>
> Thanks,
> Jason White
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>
>

> Hi Jason,
>
> I'm not sure about some of the detailed points of your schematic (such as
> whether your oscillator tuning circuit will result in continuous
> oscillation), but it looks to me like it will probably work to some degree
> but I'd expect it to have very poor selectivity when faced with strong
> signals. This is because the mixer will have some tendency to rectify
> strong input signals, which for AM signals, will result in their being
> present on the IF output even if the LO is not tuned close to the frequency
> of the strong signal. I would expect that there would be several strong
> stations which you will hear all the time, regardless of the tuning, and
> then weaker stations that would be tuned in and out by the LO.
>
> A preselector circuit would help greatly with this.
>
> Another pathology which DC receivers have is feedback where they receive
> their own LO AND strong audio signals can modulate their LO through
> unintended power supply coupling. This can result in motorboating or other
> oscillations in the audio. It is also very difficult to both have enough
> gain for weak signals AND avoid picking up AC hum and even feedback from
> the audio output back in to the audio input. This is a fundamental problem
> when all of your gain is concentrated at one frequency rather than being
> spread across RF, IF, and AF stages.
>
> I would suggest you add a simple LC preselector and then try your design.
> There will likely be other issues as I have indicated above but they can be
> more or less fixed later on.
>
> Sean
>
>
> On Sat, Oct 15, 2016 at 7:23 PM, Jason White <
> whitewaterssoftwareinfoKILLspamgmail.com> wrote:
>
> > Hello, as a personal project to become more familiar with RF circuits I
> > would like to build an AM radio receiver. Online, I found a schematic
> which
> > uses the NE612 mixer IC to create a Direct Conversion ("Syncrodyne")
> > receiver. I have modified the design so that the local oscillator does
> not
> > need a custom wound transformer.
> >
> > In my case, I don't require the receiver to have very good performance.
> I'm
> > okay with the oscillator drifting and the audio "warbling" (due to
> > frequency mismatch) under normal operation.
> >
> > I don't have any sort of matching network or filtering on the antenna
> > connection; but I am hoping a 10m wire antenna will produce a
> sufficiently
> > strong signal for the mixer. I am unsure how strongly signals and noise
> > outside of the AM band are going to affect the receiver. Ideally, I'd
> have
> > a buffer amplifier on the antenna input and a bandpass filter that
> covered
> > the AM band, but I want to avoid making this too complex.
> >
> > I have attached a picture of the original schematic, a picture of my
> > ltspice schematic, and zip containing my ltspice simulation.
> >
> > I would like to know if my design (ltspice simulation) seems reasonable
> > before I try to build it. I welcome advice on improving the design, but
> at
> > the same time I do wish to keep things a simple as possible.
> >
> > Thanks,
> > Jason White
> >
> > --
> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > View/change your membership options at
> > mailman.mit.edu/mailman/listinfo/piclist
> >
> >
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>

> Hello, as a personal project to become more familiar with RF circuits I
> would like to build an AM radio receiver. Online, I found a schematic which
> uses the NE612 mixer IC to create a Direct Conversion ("Syncrodyne")
> receiver. I have modified the design so that the local oscillator does not
> need a custom wound transformer.
>
> In my case, I don't require the receiver to have very good performance. I'm
> okay with the oscillator drifting and the audio "warbling" (due to
> frequency mismatch) under normal operation.
>
> I don't have any sort of matching network or filtering on the antenna
> connection; but I am hoping a 10m wire antenna will produce a sufficiently
> strong signal for the mixer. I am unsure how strongly signals and noise
> outside of the AM band are going to affect the receiver. Ideally, I'd have
> a buffer amplifier on the antenna input and a bandpass filter that covered
> the AM band, but I want to avoid making this too complex.
>
> I have attached a picture of the original schematic, a picture of my
> ltspice schematic, and zip containing my ltspice simulation.
>
> I would like to know if my design (ltspice simulation) seems reasonable
> before I try to build it. I welcome advice on improving the design, but at
> the same time I do wish to keep things a simple as possible.
>
> Thanks,
> Jason White
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>
>

> More later maybe.
> The then Philips TDA7000 may be of interest if you can find any.
> Single IC RF/audio.
> DC IF :-).
>
> !!!
> https://www.google.co.nz/search?q=tda7000&num=100&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjA09rOid_PAhUM0mMKHXZFAmgQsAQIIg&biw=1527&bih=836
>
> Lonnnnng ago I used them in receivers for a data link for America's Cup
> yachts.
> TX x n  in pockets on sails.
> Cluster of RXs.
> Strain gauges -->  horsepower .
>
> Neither a NZ nor a US nor Australian challenger .
>
>
>   R
>
>
> On 16 October 2016 at 11:23, Jason White  
> <RemoveMEwhitewaterssoftwareinfoTakeThisOuTgmail.com>
> wrote:
>
>> Hello, as a personal project to become more familiar with RF circuits I
>> would like to build an AM radio receiver. Online, I found a schematic  
>> which
>> uses the NE612 mixer IC to create a Direct Conversion ("Syncrodyne")
>> receiver. I have modified the design so that the local oscillator does  
>> not
>> need a custom wound transformer.
>>
>> In my case, I don't require the receiver to have very good performance.  
>> I'm
>> okay with the oscillator drifting and the audio "warbling" (due to
>> frequency mismatch) under normal operation.
>>
>> I don't have any sort of matching network or filtering on the antenna
>> connection; but I am hoping a 10m wire antenna will produce a  
>> sufficiently
>> strong signal for the mixer. I am unsure how strongly signals and noise
>> outside of the AM band are going to affect the receiver. Ideally, I'd  
>> have
>> a buffer amplifier on the antenna input and a bandpass filter that  
>> covered
>> the AM band, but I want to avoid making this too complex.
>>
>> I have attached a picture of the original schematic, a picture of my
>> ltspice schematic, and zip containing my ltspice simulation.
>>
>> I would like to know if my design (ltspice simulation) seems reasonable
>> before I try to build it. I welcome advice on improving the design, but  
>> at
>> the same time I do wish to keep things a simple as possible.
>>
>> Thanks,
>> Jason White
>>
>> --
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> mailman.mit.edu/mailman/listinfo/piclist
>>
>>

> http://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=TDA7000&_sacat=0
>
> TDA7000
>
> En Sun, 16 Oct 2016 07:11:00 -0300, RussellMc <TakeThisOuTapptechnzEraseMEspam_OUTgmail.com>
> escribió:
>
>> More later maybe.
>> The then Philips TDA7000 may be of interest if you can find any.
>> Single IC RF/audio.
>> DC IF :-).
>>
>> !!!
>> www.google.co.nz/search?q=tda7000&num=100&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjA09rOid_PAhUM0mMKHXZFAmgQsAQIIg&biw=1527&bih=836
>>
>> Lonnnnng ago I used them in receivers for a data link for America's Cup
>> yachts.
>> TX x n  in pockets on sails.
>> Cluster of RXs.
>> Strain gauges -->  horsepower .
>>
>> Neither a NZ nor a US nor Australian challenger .
>>
>>
>>   R
>>
>>
>> On 16 October 2016 at 11:23, Jason White
>> <RemoveMEwhitewaterssoftwareinfoTakeThisOuTgmail.com>
>> wrote:
>>
>>> Hello, as a personal project to become more familiar with RF circuits I
>>> would like to build an AM radio receiver. Online, I found a schematic
>>> which
>>> uses the NE612 mixer IC to create a Direct Conversion ("Syncrodyne")
>>> receiver. I have modified the design so that the local oscillator does
>>> not
>>> need a custom wound transformer.
>>>
>>> In my case, I don't require the receiver to have very good performance.
>>> I'm
>>> okay with the oscillator drifting and the audio "warbling" (due to
>>> frequency mismatch) under normal operation.
>>>
>>> I don't have any sort of matching network or filtering on the antenna
>>> connection; but I am hoping a 10m wire antenna will produce a
>>> sufficiently
>>> strong signal for the mixer. I am unsure how strongly signals and noise
>>> outside of the AM band are going to affect the receiver. Ideally, I'd
>>> have
>>> a buffer amplifier on the antenna input and a bandpass filter that
>>> covered
>>> the AM band, but I want to avoid making this too complex.
>>>
>>> I have attached a picture of the original schematic, a picture of my
>>> ltspice schematic, and zip containing my ltspice simulation.
>>>
>>> I would like to know if my design (ltspice simulation) seems reasonable
>>> before I try to build it. I welcome advice on improving the design, but
>>> at
>>> the same time I do wish to keep things a simple as possible.
>>>
>>> Thanks,
>>> Jason White
>>>
>>> --
>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>> View/change your membership options at
>>> mailman.mit.edu/mailman/listinfo/piclist
>>>
>>>
>
>
> --
> Usando el cliente de correo de Opera: http://www.opera.com/mail/
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

> More later maybe.
> The then Philips TDA7000 may be of interest if you can find any.
> Single IC RF/audio.
> DC IF :-).
>
> !!!
> https://www.google.co.nz/search?q=tda7000&num=100&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjA09rOid_PAhUM0mMKHXZFAmgQsAQIIg&biw=1527&bih=836
>
> Lonnnnng ago I used them in receivers for a data link for America's Cup
> yachts.
> TX x n  in pockets on sails.
> Cluster of RXs.
> Strain gauges -->  horsepower .
>
> Neither a NZ nor a US nor Australian challenger .
>
>
>   R
>
>
> On 16 October 2016 at 11:23, Jason White <EraseMEwhitewaterssoftwareinfogmail.com>
> wrote:
>
>> Hello, as a personal project to become more familiar with RF circuits I
>> would like to build an AM radio receiver. Online, I found a schematic which
>> uses the NE612 mixer IC to create a Direct Conversion ("Syncrodyne")
>> receiver. I have modified the design so that the local oscillator does not
>> need a custom wound transformer.
>>
>> In my case, I don't require the receiver to have very good performance. I'm
>> okay with the oscillator drifting and the audio "warbling" (due to
>> frequency mismatch) under normal operation.
>>
>> I don't have any sort of matching network or filtering on the antenna
>> connection; but I am hoping a 10m wire antenna will produce a sufficiently
>> strong signal for the mixer. I am unsure how strongly signals and noise
>> outside of the AM band are going to affect the receiver. Ideally, I'd have
>> a buffer amplifier on the antenna input and a bandpass filter that covered
>> the AM band, but I want to avoid making this too complex.
>>
>> I have attached a picture of the original schematic, a picture of my
>> ltspice schematic, and zip containing my ltspice simulation.
>>
>> I would like to know if my design (ltspice simulation) seems reasonable
>> before I try to build it. I welcome advice on improving the design, but at
>> the same time I do wish to keep things a simple as possible.
>>
>> Thanks,
>> Jason White
>>
>> --
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> mailman.mit.edu/mailman/listinfo/piclist
>>
>>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

> On Oct 16, 2016, at 3:58 PM, Jason White <RemoveMEwhitewaterssoftwareinfospam_OUTKILLspamgmail.com> wrote:
>
> I created my schematic into KiCad, and intend on doing a PCB layout
> soon. PDF of the schematic is available here [1] for scrutiny.
>
> The goal is for this to be (9V) battery powered, and to it put into a
> metal box. I chose a low frequency switching power supply to get my 5V
> rail. Happily, the application circuit for the MC34036 uses the same
> value of inductor as my turning and LO circuits; I have copied it
> verbatim.
>
> Remarks:
> (1) I am aware that a superheterodyne would be better, but my design
> skills are limited and ceramic 455kHz filters appear to becoming
> obsolete. Mouser has a few filters for which the specifications are
> available, but I am not confident enough try one (yet).
> (2) Hopefully the power supply (Fswitching >75kHz) does not feed into
> the the input.
> (3) I am vaguely aware of the MC34036 's bad reputation. However, I
> have it in stock. Worst case scenario: I throw in a linear regulator
> and power it from a wall wart transformer.
> (4) The abundance of trimmers is to deal with the fact that I really
> don't know what my signal levels are going to be. I shall find out
> soon enough :) ...
>
> Schematic Download (Google Drive Shared Link)
> [1] drive.google.com/file/d/0BwP0qhqyaTIIOHZDVWhFZF9EOUk/view?usp=sharing
>
> On Sun, Oct 16, 2016 at 7:10 AM, Rodolfo <RemoveMEseoane_reTakeThisOuTspamsinectis.com.ar> wrote:
>> www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=TDA7000&_sacat=0
>>
>> TDA7000
>>
>> En Sun, 16 Oct 2016 07:11:00 -0300, RussellMc <EraseMEapptechnzspamspamBeGonegmail.com>
>> escribió:
>>
>>> More later maybe.
>>> The then Philips TDA7000 may be of interest if you can find any.
>>> Single IC RF/audio.
>>> DC IF :-).
>>>
>>> !!!
>>> www.google.co.nz/search?q=tda7000&num=100&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjA09rOid_PAhUM0mMKHXZFAmgQsAQIIg&biw=1527&bih=836
>>>
>>> Lonnnnng ago I used them in receivers for a data link for America's Cup
>>> yachts.
>>> TX x n  in pockets on sails.
>>> Cluster of RXs.
>>> Strain gauges -->  horsepower .
>>>
>>> Neither a NZ nor a US nor Australian challenger .
>>>
>>>
>>>  R
>>>
>>>
>>> On 16 October 2016 at 11:23, Jason White
>>> <RemoveMEwhitewaterssoftwareinfoKILLspamgmail.com>
>>> wrote:
>>>
>>>> Hello, as a personal project to become more familiar with RF circuits I
>>>> would like to build an AM radio receiver. Online, I found a schematic
>>>> which
>>>> uses the NE612 mixer IC to create a Direct Conversion ("Syncrodyne")
>>>> receiver. I have modified the design so that the local oscillator does
>>>> not
>>>> need a custom wound transformer.
>>>>
>>>> In my case, I don't require the receiver to have very good performance.
>>>> I'm
>>>> okay with the oscillator drifting and the audio "warbling" (due to
>>>> frequency mismatch) under normal operation.
>>>>
>>>> I don't have any sort of matching network or filtering on the antenna
>>>> connection; but I am hoping a 10m wire antenna will produce a
>>>> sufficiently
>>>> strong signal for the mixer. I am unsure how strongly signals and noise
>>>> outside of the AM band are going to affect the receiver. Ideally, I'd
>>>> have
>>>> a buffer amplifier on the antenna input and a bandpass filter that
>>>> covered
>>>> the AM band, but I want to avoid making this too complex.
>>>>
>>>> I have attached a picture of the original schematic, a picture of my
>>>> ltspice schematic, and zip containing my ltspice simulation.
>>>>
>>>> I would like to know if my design (ltspice simulation) seems reasonable
>>>> before I try to build it. I welcome advice on improving the design, but
>>>> at
>>>> the same time I do wish to keep things a simple as possible.
>>>>
>>>> Thanks,
>>>> Jason White
>>>>
>>>> --
>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>> View/change your membership options at
>>>> mailman.mit.edu/mailman/listinfo/piclist
>>>>
>>>>
>>
>>
>> --
>> Usando el cliente de correo de Opera: http://www.opera.com/mail/
>>
>> --
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> mailman.mit.edu/mailman/listinfo/piclist
>
>
>
> --
> Jason White
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

> Jason,
> A DC/DC converter right near the receiver is a NOGO!.
> the 75kHz harmonics are going to ruin your reception of small signals.
> If you are concerned about power consumption, then adjust your DC/DC switcher voltage to 5.5V and add a low noise LDO regulator to feed the receiver. the layout will be critical to avoid any spurious from the switcher(shield might be needed.
>
>
> Just my $0.02,
>
> Jean-Paul
> N1JPL
>
>
>> On Oct 16, 2016, at 3:58 PM, Jason White <spamBeGonewhitewaterssoftwareinfoSTOPspamEraseMEgmail.com> wrote:
>>
>> I created my schematic into KiCad, and intend on doing a PCB layout
>> soon. PDF of the schematic is available here [1] for scrutiny.
>>
>> The goal is for this to be (9V) battery powered, and to it put into a
>> metal box. I chose a low frequency switching power supply to get my 5V
>> rail. Happily, the application circuit for the MC34036 uses the same
>> value of inductor as my turning and LO circuits; I have copied it
>> verbatim.
>>
>> Remarks:
>> (1) I am aware that a superheterodyne would be better, but my design
>> skills are limited and ceramic 455kHz filters appear to becoming
>> obsolete. Mouser has a few filters for which the specifications are
>> available, but I am not confident enough try one (yet).
>> (2) Hopefully the power supply (Fswitching >75kHz) does not feed into
>> the the input.
>> (3) I am vaguely aware of the MC34036 's bad reputation. However, I
>> have it in stock. Worst case scenario: I throw in a linear regulator
>> and power it from a wall wart transformer.
>> (4) The abundance of trimmers is to deal with the fact that I really
>> don't know what my signal levels are going to be. I shall find out
>> soon enough :) ...
>>
>> Schematic Download (Google Drive Shared Link)
>> [1] drive.google.com/file/d/0BwP0qhqyaTIIOHZDVWhFZF9EOUk/view?usp=sharing
>>
>> On Sun, Oct 16, 2016 at 7:10 AM, Rodolfo <KILLspamseoane_respamBeGonesinectis.com.ar> wrote:
>>> www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=TDA7000&_sacat=0
>>>
>>> TDA7000
>>>
>>> En Sun, 16 Oct 2016 07:11:00 -0300, RussellMc <EraseMEapptechnzEraseMEgmail.com>
>>> escribió:
>>>
>>>> More later maybe.
>>>> The then Philips TDA7000 may be of interest if you can find any.
>>>> Single IC RF/audio.
>>>> DC IF :-).
>>>>
>>>> !!!
>>>> www.google.co.nz/search?q=tda7000&num=100&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjA09rOid_PAhUM0mMKHXZFAmgQsAQIIg&biw=1527&bih=836
>>>>
>>>> Lonnnnng ago I used them in receivers for a data link for America's Cup
>>>> yachts.
>>>> TX x n  in pockets on sails.
>>>> Cluster of RXs.
>>>> Strain gauges -->  horsepower .
>>>>
>>>> Neither a NZ nor a US nor Australian challenger .
>>>>
>>>>
>>>>  R
>>>>
>>>>
>>>> On 16 October 2016 at 11:23, Jason White
>>>> <@spam@whitewaterssoftwareinfo@spam@spam_OUTgmail.com>
>>>> wrote:
>>>>
>>>>> Hello, as a personal project to become more familiar with RF circuits I
>>>>> would like to build an AM radio receiver. Online, I found a schematic
>>>>> which
>>>>> uses the NE612 mixer IC to create a Direct Conversion ("Syncrodyne")
>>>>> receiver. I have modified the design so that the local oscillator does
>>>>> not
>>>>> need a custom wound transformer.
>>>>>
>>>>> In my case, I don't require the receiver to have very good performance.
>>>>> I'm
>>>>> okay with the oscillator drifting and the audio "warbling" (due to
>>>>> frequency mismatch) under normal operation.
>>>>>
>>>>> I don't have any sort of matching network or filtering on the antenna
>>>>> connection; but I am hoping a 10m wire antenna will produce a
>>>>> sufficiently
>>>>> strong signal for the mixer. I am unsure how strongly signals and noise
>>>>> outside of the AM band are going to affect the receiver. Ideally, I'd
>>>>> have
>>>>> a buffer amplifier on the antenna input and a bandpass filter that
>>>>> covered
>>>>> the AM band, but I want to avoid making this too complex.
>>>>>
>>>>> I have attached a picture of the original schematic, a picture of my
>>>>> ltspice schematic, and zip containing my ltspice simulation.
>>>>>
>>>>> I would like to know if my design (ltspice simulation) seems reasonable
>>>>> before I try to build it. I welcome advice on improving the design, but
>>>>> at
>>>>> the same time I do wish to keep things a simple as possible.
>>>>>
>>>>> Thanks,
>>>>> Jason White
>>>>>
>>>>> --
>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>> View/change your membership options at
>>>>> mailman.mit.edu/mailman/listinfo/piclist
>>>>>
>>>>>
>>>
>>>
>>> --
>>> Usando el cliente de correo de Opera: http://www.opera.com/mail/
>>>
>>> --
>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>> View/change your membership options at
>>> mailman.mit.edu/mailman/listinfo/piclist
>>
>>
>>
>> --
>> Jason White
>>
>> --
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> http://mailman.mit.edu/mailman/listinfo/piclist
>
>
>
>
>
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

> Jean, I will add a 5V LDO to be design and make it so that I can
> bypass and disable the 5.5V switching supply with jumpers.
>
> The PCB is going to be approximately 4"x4" (100mm square). The
> Switching power supply and the antenna input are going to be on
> opposite corners. I intend to place the LDO physically near the
> switching supply, and then to run the regulated 5V all the way to the
> other corner. This way the trace length and, hopefully, radiation from
> the switching supply is isolated to the far corner of the PCB.
>
> On Sun, Oct 16, 2016 at 8:03 PM, Jean-Paul Louis <.....louijpspam_OUTgmail.com> wrote:
> > Jason,
> > A DC/DC converter right near the receiver is a NOGO!.
> > the 75kHz harmonics are going to ruin your reception of small signals.
> > If you are concerned about power consumption, then adjust your DC/DC
> switcher voltage to 5.5V and add a low noise LDO regulator to feed the
> receiver. the layout will be critical to avoid any spurious from the
> switcher(shield might be needed.
> >
> >
> > Just my $0.02,
> >
> > Jean-Paul
> > N1JPL
> >
> >
> >> On Oct 16, 2016, at 3:58 PM, Jason White <whitewaterssoftwareinfo@
> gmail.com> wrote:
> >>
> >> I created my schematic into KiCad, and intend on doing a PCB layout
> >> soon. PDF of the schematic is available here [1] for scrutiny.
> >>
> >> The goal is for this to be (9V) battery powered, and to it put into a
> >> metal box. I chose a low frequency switching power supply to get my 5V
> >> rail. Happily, the application circuit for the MC34036 uses the same
> >> value of inductor as my turning and LO circuits; I have copied it
> >> verbatim.
> >>
> >> Remarks:
> >> (1) I am aware that a superheterodyne would be better, but my design
> >> skills are limited and ceramic 455kHz filters appear to becoming
> >> obsolete. Mouser has a few filters for which the specifications are
> >> available, but I am not confident enough try one (yet).
> >> (2) Hopefully the power supply (Fswitching >75kHz) does not feed into
> >> the the input.
> >> (3) I am vaguely aware of the MC34036 's bad reputation. However, I
> >> have it in stock. Worst case scenario: I throw in a linear regulator
> >> and power it from a wall wart transformer.
> >> (4) The abundance of trimmers is to deal with the fact that I really
> >> don't know what my signal levels are going to be. I shall find out
> >> soon enough :) ...
> >>
> >> Schematic Download (Google Drive Shared Link)
> >> [1] drive.google.com/file/d/0BwP0qhqyaTIIOHZDVWhFZF9EOUk/
> view?usp=sharing
> >>
> >> On Sun, Oct 16, 2016 at 7:10 AM, Rodolfo <TakeThisOuTseoane_re.....TakeThisOuTsinectis.com.ar>
> wrote:
> >>> www.ebay.com/sch/i.html?_from=R40&_trksid=m570.
> l1313&_nkw=TDA7000&_sacat=0
> >>>
> >>> TDA7000
> >>>
> >>> En Sun, 16 Oct 2016 07:11:00 -0300, RussellMc <TakeThisOuTapptechnzKILLspamspamgmail.com>
> >>> escribió:
> >>>
> >>>> More later maybe.
> >>>> The then Philips TDA7000 may be of interest if you can find any.
> >>>> Single IC RF/audio.
> >>>> DC IF :-).
> >>>>
> >>>> !!!
> >>>> www.google.co.nz/search?q=tda7000&num=100&tbm=
> isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjA09rOid_
> PAhUM0mMKHXZFAmgQsAQIIg&biw=1527&bih=836
> >>>>
> >>>> Lonnnnng ago I used them in receivers for a data link for America's
> Cup
> >>>> yachts.
> >>>> TX x n  in pockets on sails.
> >>>> Cluster of RXs.
> >>>> Strain gauges -->  horsepower .
> >>>>
> >>>> Neither a NZ nor a US nor Australian challenger .
> >>>>
> >>>>
> >>>>  R
> >>>>
> >>>>
> >>>> On 16 October 2016 at 11:23, Jason White
> >>>> <.....whitewaterssoftwareinfoRemoveMEgmail.com>
> >>>> wrote:
> >>>>
> >>>>> Hello, as a personal project to become more familiar with RF
> circuits I
> >>>>> would like to build an AM radio receiver. Online, I found a schematic
> >>>>> which
> >>>>> uses the NE612 mixer IC to create a Direct Conversion ("Syncrodyne")
> >>>>> receiver. I have modified the design so that the local oscillator
> does
> >>>>> not
> >>>>> need a custom wound transformer.
> >>>>>
> >>>>> In my case, I don't require the receiver to have very good
> performance.
> >>>>> I'm
> >>>>> okay with the oscillator drifting and the audio "warbling" (due to
> >>>>> frequency mismatch) under normal operation.
> >>>>>
> >>>>> I don't have any sort of matching network or filtering on the antenna
> >>>>> connection; but I am hoping a 10m wire antenna will produce a
> >>>>> sufficiently
> >>>>> strong signal for the mixer. I am unsure how strongly signals and
> noise
> >>>>> outside of the AM band are going to affect the receiver. Ideally, I'd
> >>>>> have
> >>>>> a buffer amplifier on the antenna input and a bandpass filter that
> >>>>> covered
> >>>>> the AM band, but I want to avoid making this too complex.
> >>>>>
> >>>>> I have attached a picture of the original schematic, a picture of my
> >>>>> ltspice schematic, and zip containing my ltspice simulation.
> >>>>>
> >>>>> I would like to know if my design (ltspice simulation) seems
> reasonable
> >>>>> before I try to build it. I welcome advice on improving the design,
> but
> >>>>> at
> >>>>> the same time I do wish to keep things a simple as possible.
> >>>>>
> >>>>> Thanks,
> >>>>> Jason White
> >>>>>
> >>>>> --
> >>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> >>>>> View/change your membership options at
> >>>>> mailman.mit.edu/mailman/listinfo/piclist
> >>>>>
> >>>>>
> >>>
> >>>
> >>> --
> >>> Usando el cliente de correo de Opera: http://www.opera.com/mail/
> >>>
> >>> --
> >>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> >>> View/change your membership options at
> >>> mailman.mit.edu/mailman/listinfo/piclist
> >>
> >>
> >>
> >> --
> >> Jason White
> >>
> >> --
> >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> >> View/change your membership options at
> >> mailman.mit.edu/mailman/listinfo/piclist
> >
> >
> >
> >
> >
> >
> > --
> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist
>
>
>
> --
> Jason White
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>

> First, a comment about the SDR Harold posted a link to. I would think that
> unit would have serious dynamic range problems. A decent antenna is going
> to present about 0.1V (100mV) into a 50 ohm load if you take the entire
> shortwave 2MHz to 30MHz range. You want to be able to see signals as low as
> about 100nV. This is a 1 million to 1 voltage ratio. A 16 bit ADC has a
> dynamic range of no better than 65535:1. There are tricks you can do in DSP
> post-processing which will get you a bit more than this but I am surprised
> if it has good performance on a full size antenna. SDR is awesome but there
> is still room for good RF front-end design.
>
> Now, back to Jason's design. Looks like you are making good progress. A few
> points:
>
> 1) It looks like the preselector is not tunable - is that intentional?
> 2) Is the input buffer amp intended to isolate the preselector from the
> variable antenna impedance? I do think that is a good idea, although
> another approach (which can yield a big improvement in signal strength) is
> to use a tunable preselector with only moderate to light coupling to the
> antenna and enough tuning range to tune-out some of the antenna reactance.
> This gets you an antenna tuner/matching network AND preselector in one and
> gets rid of the need for a buffer amp.
> 3) It looks to me like your strongest station is going to saturate that
> gain stage after the preselector.
> 4) You mentioned a method to compute the approximate antenna terminal
> voltage from RF E-field strength. I don't think the simple method of
> multiplying the E-field strength by the antenna length will be very good.
> The real way to do this is to convert from E field strength to power
> density (E^2/eta_o), multiply by the effective area of your antenna (for
> monopoles and dipoles it is almost independent of the antenna length
> (roughly lambda^2/(4*pi))). This gives you the total maximum power
> received. Now estimate the radiation resistance of the antenna as well as
> the reactance. Model the antenna as a voltage source with a series
> resistance of the radiation resistance and compute the voltage magnitude
> which would give you the max power received into a matched load. Then,
> augment your model by adding the reactance to your series resistance. If
> you add your load, then you can determine the terminal voltage into that
> load.
> 5) I would ditch the switching regulator completely for now. It will be
> nothing but trouble as a noise generator. I designed a switcher to use in
> an RF receiver environment once and it required massive shielding and
> multiply layers of filtering on the output lines. You won't fix the problem
> by post-regulating it with an LDO. The devil is conducted noise through the
> ground and also near-field magnetic interference.
> 6) The NE602's mixer might expect to see a particular impedance at its
> output. Typically mixers perform best if they see a fixed impedance across
> the entire output frequency range, including the image frequency range.
> This is why the filtering on the output of a mixer is typically either
> preceded by an attenuator (the easy way when signal to noise ratio is not
> critical) or it is a diplexer (a filter which has a constant input
> impedance and filters by dumping stopband energy into a separate load). If
> you don't have the proper load on the mixer, it can degrade the dynamic
> range of the mixer.
>
> Sean
>
>
> On Sun, Oct 16, 2016 at 9:47 PM, Jason White <
> spamBeGonewhitewaterssoftwareinfo@spam@spam_OUTgmail.com> wrote:
>
>> Jean, I will add a 5V LDO to be design and make it so that I can
>> bypass and disable the 5.5V switching supply with jumpers.
>>
>> The PCB is going to be approximately 4"x4" (100mm square). The
>> Switching power supply and the antenna input are going to be on
>> opposite corners. I intend to place the LDO physically near the
>> switching supply, and then to run the regulated 5V all the way to the
>> other corner. This way the trace length and, hopefully, radiation from
>> the switching supply is isolated to the far corner of the PCB.
>>
>> On Sun, Oct 16, 2016 at 8:03 PM, Jean-Paul Louis <TakeThisOuTlouijpspamgmail.com> wrote:
>> > Jason,
>> > A DC/DC converter right near the receiver is a NOGO!.
>> > the 75kHz harmonics are going to ruin your reception of small signals.
>> > If you are concerned about power consumption, then adjust your DC/DC
>> switcher voltage to 5.5V and add a low noise LDO regulator to feed the
>> receiver. the layout will be critical to avoid any spurious from the
>> switcher(shield might be needed.
>> >
>> >
>> > Just my $0.02,
>> >
>> > Jean-Paul
>> > N1JPL
>> >
>> >
>> >> On Oct 16, 2016, at 3:58 PM, Jason White <whitewaterssoftwareinfo@
>> gmail.com> wrote:
>> >>
>> >> I created my schematic into KiCad, and intend on doing a PCB layout
>> >> soon. PDF of the schematic is available here [1] for scrutiny.
>> >>
>> >> The goal is for this to be (9V) battery powered, and to it put into a
>> >> metal box. I chose a low frequency switching power supply to get my 5V
>> >> rail. Happily, the application circuit for the MC34036 uses the same
>> >> value of inductor as my turning and LO circuits; I have copied it
>> >> verbatim.
>> >>
>> >> Remarks:
>> >> (1) I am aware that a superheterodyne would be better, but my design
>> >> skills are limited and ceramic 455kHz filters appear to becoming
>> >> obsolete. Mouser has a few filters for which the specifications are
>> >> available, but I am not confident enough try one (yet).
>> >> (2) Hopefully the power supply (Fswitching >75kHz) does not feed into
>> >> the the input.
>> >> (3) I am vaguely aware of the MC34036 's bad reputation. However, I
>> >> have it in stock. Worst case scenario: I throw in a linear regulator
>> >> and power it from a wall wart transformer.
>> >> (4) The abundance of trimmers is to deal with the fact that I really
>> >> don't know what my signal levels are going to be. I shall find out
>> >> soon enough :) ...
>> >>
>> >> Schematic Download (Google Drive Shared Link)
>> >> [1] drive.google.com/file/d/0BwP0qhqyaTIIOHZDVWhFZF9EOUk/
>> view?usp=sharing
>> >>
>> >> On Sun, Oct 16, 2016 at 7:10 AM, Rodolfo <seoane_reEraseMEsinectis.com.ar>
>> wrote:
>> >>> www.ebay.com/sch/i.html?_from=R40&_trksid=m570.
>> l1313&_nkw=TDA7000&_sacat=0
>> >>>
>> >>> TDA7000
>> >>>
>> >>> En Sun, 16 Oct 2016 07:11:00 -0300, RussellMc <RemoveMEapptechnzEraseMEspam_OUTgmail.com>
>> >>> escribió:
>> >>>
>> >>>> More later maybe.
>> >>>> The then Philips TDA7000 may be of interest if you can find any.
>> >>>> Single IC RF/audio.
>> >>>> DC IF :-).
>> >>>>
>> >>>> !!!
>> >>>> www.google.co.nz/search?q=tda7000&num=100&tbm=
>> isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjA09rOid_
>> PAhUM0mMKHXZFAmgQsAQIIg&biw=1527&bih=836
>> >>>>
>> >>>> Lonnnnng ago I used them in receivers for a data link for America's
>> Cup
>> >>>> yachts.
>> >>>> TX x n  in pockets on sails.
>> >>>> Cluster of RXs.
>> >>>> Strain gauges -->  horsepower .
>> >>>>
>> >>>> Neither a NZ nor a US nor Australian challenger .
>> >>>>
>> >>>>
>> >>>>  R
>> >>>>
>> >>>>
>> >>>> On 16 October 2016 at 11:23, Jason White
>> >>>> <@spam@whitewaterssoftwareinfoRemoveMEEraseMEgmail.com>
>> >>>> wrote:
>> >>>>
>> >>>>> Hello, as a personal project to become more familiar with RF
>> circuits I
>> >>>>> would like to build an AM radio receiver. Online, I found a schematic
>> >>>>> which
>> >>>>> uses the NE612 mixer IC to create a Direct Conversion ("Syncrodyne")
>> >>>>> receiver. I have modified the design so that the local oscillator
>> does
>> >>>>> not
>> >>>>> need a custom wound transformer.
>> >>>>>
>> >>>>> In my case, I don't require the receiver to have very good
>> performance.
>> >>>>> I'm
>> >>>>> okay with the oscillator drifting and the audio "warbling" (due to
>> >>>>> frequency mismatch) under normal operation.
>> >>>>>
>> >>>>> I don't have any sort of matching network or filtering on the antenna
>> >>>>> connection; but I am hoping a 10m wire antenna will produce a
>> >>>>> sufficiently
>> >>>>> strong signal for the mixer. I am unsure how strongly signals and
>> noise
>> >>>>> outside of the AM band are going to affect the receiver. Ideally, I'd
>> >>>>> have
>> >>>>> a buffer amplifier on the antenna input and a bandpass filter that
>> >>>>> covered
>> >>>>> the AM band, but I want to avoid making this too complex.
>> >>>>>
>> >>>>> I have attached a picture of the original schematic, a picture of my
>> >>>>> ltspice schematic, and zip containing my ltspice simulation.
>> >>>>>
>> >>>>> I would like to know if my design (ltspice simulation) seems
>> reasonable
>> >>>>> before I try to build it. I welcome advice on improving the design,
>> but
>> >>>>> at
>> >>>>> the same time I do wish to keep things a simple as possible.
>> >>>>>
>> >>>>> Thanks,
>> >>>>> Jason White
>> >>>>>
>> >>>>> --
>> >>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> >>>>> View/change your membership options at
>> >>>>> mailman.mit.edu/mailman/listinfo/piclist
>> >>>>>
>> >>>>>
>> >>>
>> >>>
>> >>> --
>> >>> Usando el cliente de correo de Opera: http://www.opera.com/mail/
>> >>>
>> >>> --
>> >>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> >>> View/change your membership options at
>> >>> mailman.mit.edu/mailman/listinfo/piclist
>> >>
>> >>
>> >>
>> >> --
>> >> Jason White
>> >>
>> >> --
>> >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> >> View/change your membership options at
>> >> mailman.mit.edu/mailman/listinfo/piclist
>> >
>> >
>> >
>> >
>> >
>> >
>> > --
>> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> > View/change your membership options at
>> > mailman.mit.edu/mailman/listinfo/piclist
>>
>>
>>
>> --
>> Jason White
>>
>> --
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> mailman.mit.edu/mailman/listinfo/piclist
>>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

> I agree 100% on not using an SMPS in the system at least at the outset.  Get it working first, then add that complication if you must.
>
>
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

> More later maybe.
> The then Philips TDA7000 may be of interest if you can find any.
> Single IC RF/audio.
> DC IF :-).
>
> !!!
> ​​
> www.google.co.nz/search?q=tda7000&num=100&tbm=
> isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjA09rOid_
> PAhUM0mMKHXZFAmgQsAQIIg&biw=1527&bih=836
>
> Lonnnnng ago I used them in receivers for a data link for America's Cup
> yachts.
> TX x n  in pockets on sails.
> Cluster of RXs.
> Strain gauges -->  horsepower .
>
> Neither a NZ nor a US nor Australian challenger .
>
>
>   R
>

> Jason - did you glance at the TDA7000 capabilities.
> May be more interesting than you'd expect. Or not.
> A look at the images page gives many instant lads to DIY uses.
>
>
> https://www.google.co.nz/search?q=tda7000&num=100&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjA09rOid_PAhUM0mMKHXZFAmgQsAQIIg&biw=1527&bih=836
>
>
> Normalish
> <https://www.google.co.nz/imgres?imgurl=http%3A%2F%2Felectronics-diy.com%2Fschematics%2F1079%2FTDA7000-FM-Radio.jpg&imgrefurl=http%3A%2F%2Felectronics-diy.com%2Ffm-radio-with-tda7000.php&docid=vC5asYRt_bieSM&tbnid=IMOWQ390QpyKaM%3A&w=566&h=418&bih=836&biw=1527&ved=0ahUKEwjamZTs9OLPAhUL02MKHZsoDS0QMwhKKCMwIw&iact=mrc&uact=8>
>
> Also
> <https://www.google.co.nz/imgres?imgurl=https%3A%2F%2Fi.ytimg.com%2Fvi%2FPT_EmkEXJiM%2Fmaxresdefault.jpg&imgrefurl=https%3A%2F%2Fhttp://www.youtube.com%2Fwatch%3Fv%3DPT_EmkEXJiM&docid=WKxBavWevHhRIM&tbnid=VantSu56nvDJaM%3A&w=1920&h=1080&bih=836&biw=1527&ved=0ahUKEwjamZTs9OLPAhUL02MKHZsoDS0QMwhLKCQwJA&iact=mrc&uact=8>
>
> ! <http://www.cqham.ru/projects/tda7000_20rx/t7000-2.jpeg>
>
> :-) <http://jcoppens.com/sat/rx/img/tda_osc.jpeg>
>
>
> :-) !
> <http://2.bp.blogspot.com/-no_oBVJwZcU/Ui7TQ3wSh-I/AAAAAAAAABQ/RVTXYyb-zU4/s1600/201201265466.jpg>
>
> ! :-)
> <http://hardwaresl.0fees.net/wp-content/uploads/2009/04/photo4.jpg?i=1>
>
> !!! :-)  <http://ejenn.free.fr/images/Emetteur_2606_recepteur_tda7000.jpg>
>
>
>
>
>
> Russell
>
>
>
> On 16 October 2016 at 22:11, RussellMc <apptechnzspamBeGonegmail.com> wrote:
>
>> More later maybe.
>> The then Philips TDA7000 may be of interest if you can find any.
>> Single IC RF/audio.
>> DC IF :-).
>>
>> !!!
>>
>> www.google.co.nz/search?q=tda7000&num=100&tbm=
>> isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjA09rOid_
>> PAhUM0mMKHXZFAmgQsAQIIg&biw=1527&bih=836
>>
>> Lonnnnng ago I used them in receivers for a data link for America's Cup
>> yachts.
>> TX x n  in pockets on sails.
>> Cluster of RXs.
>> Strain gauges -->  horsepower .
>>
>> Neither a NZ nor a US nor Australian challenger .
>>
>>
>>   R

>
>> I'm quite curious about R4, which appears to be increasing the gain of
>> the LO transistor. That's odd because (at least in simulations) I have
>> had the exact opposite problem, too much gain, which yields a LO
>> amplitude of greater than the specified 300mV maximum. Maybe harmonics
>> aren't a problem in a direct conversion receiver?
>
> Yes, R4 is interesting. It's a 22k that's in parallel with the internal
> 25k. I don't think it increases the gain since this is an emitter
> follower, so the gain is limited to a maximum of 1. I'd be concerned that
> this would mess up the DC bias of the circuit. The theory of operation in
> the schematic does not explain why they deviate from the chip datasheet.
>
> So far, my SDR experience is limited to listening to websdr. But, I'm very
> impressed with what they've done.
>
> Somewhat like the NE602, I did a receiver using the SA639. This is an
> infrared data receiver (
> www.uslinc.com/index.php?option=com_virtuemart&page=shop.product_details&flypage=flypage.tpl&category_id=23&product_id=67&Itemid=65&vmcchk=1&Itemid=65
> ). It has a bunch of IR photodiodes in parallel. They are reverse biased
> through a tunable inductor becoming resonant at 1.8MHz. The data is FSK at
> 10kbps at 1.8MHz. The photodiodes drive an op amp-based preamp, then into
> the SA639. A crystal based local oscillator converts the signal up to
> 10.7MHz where it goes through IF amplifiers with ceramic filters. The
> ceramic based quadrature detector from the datasheet is used to demodulate
> the FSK. The resulting signal drives a comparator in a PIC, then the UART
> in the PIC.
>
> That's my recent "RF" design experience.
>
> Harold
>
>
>
> --
> FCC Rules Updated Daily at http://www.hallikainen.com
> Not sent from an iPhone.
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

> Hello Harold,
>
> Thanks for sharing your design, quite interesting! Both the
> application and that style of data transmission is completely new to
> me. For some reason, the idea that it is possible to do RF style
> transmissions over infrared is mind-boggling to me.
>
> -Jason White
>
>
> On Sun, Oct 16, 2016 at 8:45 PM, Harold Hallikainen
> <.....harold@spam@EraseMEmai.hallikainen.org> wrote:
> >
> >> I'm quite curious about R4, which appears to be increasing the gain of
> >> the LO transistor. That's odd because (at least in simulations) I have
> >> had the exact opposite problem, too much gain, which yields a LO
> >> amplitude of greater than the specified 300mV maximum. Maybe harmonics
> >> aren't a problem in a direct conversion receiver?
> >
> > Yes, R4 is interesting. It's a 22k that's in parallel with the internal
> > 25k. I don't think it increases the gain since this is an emitter
> > follower, so the gain is limited to a maximum of 1. I'd be concerned that
> > this would mess up the DC bias of the circuit. The theory of operation in
> > the schematic does not explain why they deviate from the chip datasheet..
> >
> > So far, my SDR experience is limited to listening to websdr. But, I'm very
> > impressed with what they've done.
> >
> > Somewhat like the NE602, I did a receiver using the SA639. This is an
> > infrared data receiver (
> > www.uslinc.com/index.php?option=com_virtuemart&page=shop.product_details&flypage=flypage.tpl&category_id=23&product_id=67&Itemid=65&vmcchk=1&Itemid=65
> > ). It has a bunch of IR photodiodes in parallel. They are reverse biased
> > through a tunable inductor becoming resonant at 1.8MHz. The data is FSK at
> > 10kbps at 1.8MHz. The photodiodes drive an op amp-based preamp, then into
> > the SA639. A crystal based local oscillator converts the signal up to
> > 10.7MHz where it goes through IF amplifiers with ceramic filters. The
> > ceramic based quadrature detector from the datasheet is used to demodulate
> > the FSK. The resulting signal drives a comparator in a PIC, then the UART
> > in the PIC.
> >
> > That's my recent "RF" design experience.
> >
> > Harold
> >
> >
> >
> > --
> > FCC Rules Updated Daily at http://www.hallikainen.com
> > Not sent from an iPhone.
> > --
> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > View/change your membership options at
> > mailman.mit.edu/mailman/listinfo/piclist
>
>
>
> --
> Jason White
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

> Jesus - $194 on abebooks!
>
>
> ________________________________
> From: spamBeGonepiclist-bouncesKILLspam@spam@mit.edu <piclist-bouncesspam_OUT@spam@mit.edu> on behalf of Tony Miller <spamBeGonetmillaz@spam@gmail.com>
> Sent: Monday, October 17, 2016 5:16 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Building a Direct Conversion AM Radio Receiver?
>
> Jason,
>
> If you looking for basic RF design, you might find useful the Amateur Radio
> Relay League (ARRL) book, "Experimental Methods in RF Design" by Wes
> Hayward, et al.  I   It's a  getting a bit dated but It will take you from
> direct conversion to advanced super heterodyne receivers.
>
> Tony
>
>>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> PIClist, Microchip PIC<http://www.piclist.com/techref/piclist>
> http://www.piclist.com
> The PICList is a collection of people interested in the Microchip PIC and other similar processors who have joined the RemoveMEPICListEraseMEKILLspamMIT.EDU mailing list.
>
>
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

>
>> Well, IR is RF in the terahertz range, so what was described was
>> amplitude modulation of a signal using a frequency modulated signal as
>> input?  ;-)
>
> Yes, it's FM subcarriers on the terahertz "RF." This is the similar to the
> DSB-SC subcarrier on FM used to carry the stereo difference signal. The
> original definition of FM stereo used this frequency division multiplex
> description. But, you get the same thing if you use time division
> multiplex spending a little time on the left channel and a little on the
> right. It's amazing how you can look at the same signal in different ways..
>
> Thinking about the direct conversion AM receiver, I'm thinking there will
> be problems due to the presence of both sidebands unless the local
> oscillator is phase locked to the received carrier. If the local
> oscillator is phase locked at 0 degrees, you will get DC plus the audio
> (plus two times carrier that is taken out by the low pass filter). If the
> local oscillator is 90 degrees out of phase with the received carrier, you
> will get nothing. If the local oscillator is not the same frequency as the
> received carrier, you'll get a tone corresponding to the difference in the
> frequencies plus a mix of the audio shifted up a bit in frequency and the
> audio shifted down a bit in frequency. If the frequencies are very close
> (say 0.1 Hz apart),  I suspect you will hear the audio disappear and
> reappear over a 10 second period as the phase between the two rotates.
>
> The null at 90 degrees is an interesting situation. You can transmit two
> signals on the same frequency without interference by setting the carriers
> 90 degrees apart. This is the basis of QAM or Quadrature Amplitude
> Modulation. This is a common digital modulation system where, for example,
> 8 levels are transmitted on the I (in phase) carrier and 8 are transmitted
> on the Q (quadrature) carrier. For each transition of the carrier (a
> baud), 3 bits are transmitted on I and 3 bits are transmitted on Q for a
> total of 6 bits per baud. It turns out that when you add sine waves that
> are 90 degrees apart and vary the amplitude of each, the result is a sine
> wave whose amplitude is the square root of the sum of the squares of the
> amplitudes and the resulting phase angle is the arcsine of the Q amplitude
> over the I amplitude. You can plot the resulting signal on a
> "vectorscope." With the 8x8 QAM mentioned before, you get dots in 64
> different positions (an 8x8 array). This is "64QAM."
>
> But, the QAM signal could carry analog signals. In NTSC color television,
> the "baseband" carries a linear combination of red, green, and blue that
> produces a good picture on a monochrome television. Another linear
> combination of red, green, and blue modulates the I subcarrier at 3.58MHz..
> Another linear combination of red, green, and blue modulates the Q
> subcarrier at 3.58MHz. Through the baseband, I, and Q signals, we are
> transmitting three signals that are "linearly independent." In the
> receiver, we can multiply each of the signals by different constants, then
> add them to yield the original red, green, and blue. Very clever!
>
> But then, a monochrome signal does not modulate the I and Q subcarriers at
> all. As such, we can adjust the gain of the I and Q signal to vary the
> color saturation (no gain gives monochrome). Further, adjusting the phase
> of the local I and Q signals relative to that at the transmit end (and
> transmitted in the color burst for reference) varies the "hue" of the
> resulting color. So here we have a QAM signal, but the amplitude and phase
> have their own meaning. When you put up color bars, you should see dots in
> specific locations on a vectorscope.
>
> Modulation... It's fascinating!
>
> Harold
>
>
>
>
>
>
> --
> FCC Rules Updated Daily at http://www.hallikainen.com
> Not sent from an iPhone.
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

> The revision B schematic is available for viewing at [1]. I'm not
> super happy about needing 20 varactor diodes to get a turning range of
> 700kHz to 1600kHz (both preselector and LO get their own bank of 10
> diodes). I could avoid the need for so many diode by using a 10x
> larger inductor, but then the Q of the preselector and the LO drop
> significantly.
>
> Based off of the fact that ZZRX-40 works and that my design is
> essentially a copy of that, I am optimistic that I will only need to
> alter a few component values (like the LO feedback capacitors) to have
> the design receiving audio.
>
> Work has begun towards the PCB (enclosure selection/footprint creation/etc...)
>
> [1] https://drive.google.com/file/d/0BwP0qhqyaTIIcEdFMTkwQXlwWFk/view?usp=sharing
>
> On Mon, Oct 17, 2016 at 10:38 PM, Harold Hallikainen
> <harold@spam@mai.hallikainen.org> wrote:
>>
>>> Well, IR is RF in the terahertz range, so what was described was
>>> amplitude modulation of a signal using a frequency modulated signal as
>>> input?  ;-)
>>
>> Yes, it's FM subcarriers on the terahertz "RF." This is the similar to the
>> DSB-SC subcarrier on FM used to carry the stereo difference signal. The
>> original definition of FM stereo used this frequency division multiplex
>> description. But, you get the same thing if you use time division
>> multiplex spending a little time on the left channel and a little on the
>> right. It's amazing how you can look at the same signal in different ways.
>>
>> Thinking about the direct conversion AM receiver, I'm thinking there will
>> be problems due to the presence of both sidebands unless the local
>> oscillator is phase locked to the received carrier. If the local
>> oscillator is phase locked at 0 degrees, you will get DC plus the audio
>> (plus two times carrier that is taken out by the low pass filter). If the
>> local oscillator is 90 degrees out of phase with the received carrier, you
>> will get nothing. If the local oscillator is not the same frequency as the
>> received carrier, you'll get a tone corresponding to the difference in the
>> frequencies plus a mix of the audio shifted up a bit in frequency and the
>> audio shifted down a bit in frequency. If the frequencies are very close
>> (say 0.1 Hz apart),  I suspect you will hear the audio disappear and
>> reappear over a 10 second period as the phase between the two rotates.
>>
>> The null at 90 degrees is an interesting situation. You can transmit two
>> signals on the same frequency without interference by setting the carriers
>> 90 degrees apart. This is the basis of QAM or Quadrature Amplitude
>> Modulation. This is a common digital modulation system where, for example,
>> 8 levels are transmitted on the I (in phase) carrier and 8 are transmitted
>> on the Q (quadrature) carrier. For each transition of the carrier (a
>> baud), 3 bits are transmitted on I and 3 bits are transmitted on Q for a
>> total of 6 bits per baud. It turns out that when you add sine waves that
>> are 90 degrees apart and vary the amplitude of each, the result is a sine
>> wave whose amplitude is the square root of the sum of the squares of the
>> amplitudes and the resulting phase angle is the arcsine of the Q amplitude
>> over the I amplitude. You can plot the resulting signal on a
>> "vectorscope." With the 8x8 QAM mentioned before, you get dots in 64
>> different positions (an 8x8 array). This is "64QAM."
>>
>> But, the QAM signal could carry analog signals. In NTSC color television,
>> the "baseband" carries a linear combination of red, green, and blue that
>> produces a good picture on a monochrome television. Another linear
>> combination of red, green, and blue modulates the I subcarrier at 3.58MHz.
>> Another linear combination of red, green, and blue modulates the Q
>> subcarrier at 3.58MHz. Through the baseband, I, and Q signals, we are
>> transmitting three signals that are "linearly independent." In the
>> receiver, we can multiply each of the signals by different constants, then
>> add them to yield the original red, green, and blue. Very clever!
>>
>> But then, a monochrome signal does not modulate the I and Q subcarriers at
>> all. As such, we can adjust the gain of the I and Q signal to vary the
>> color saturation (no gain gives monochrome). Further, adjusting the phase
>> of the local I and Q signals relative to that at the transmit end (and
>> transmitted in the color burst for reference) varies the "hue" of the
>> resulting color. So here we have a QAM signal, but the amplitude and phase
>> have their own meaning. When you put up color bars, you should see dots in
>> specific locations on a vectorscope.
>>
>> Modulation... It's fascinating!
>>
>> Harold
>>
>>
>>
>>
>>
>>
>> --
>> FCC Rules Updated Daily at http://www.hallikainen.com
>> Not sent from an iPhone.
>> --
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> http://mailman.mit.edu/mailman/listinfo/piclist
>
>
>
> --
> Jason White
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> mailman.mit.edu/mailman/listinfo/piclist

> You could use mosfets to switch in capacitors in binary values, then maybe
> use a varactor or two for fine tuning.
>
> They DO still make the old 365pF variable caps, BTW.
>
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>

> There are also older varactor diodes with a much larger capacitance, such
> as the MVAM109 or MVAM125. There are a few sellers on eBay who have these..
> I don't know if they are made anymore but there are still sources. I used
> some in a receive-only remote antenna tuner I made. They have about 10x the
> capacitance of the ones you are using now, and almost as large a cap ratio.
>
> On Thu, Oct 20, 2016 at 12:16 PM, Van Horn, David <david.vanhorn@
> backcountryaccess.com> wrote:
>
>> You could use mosfets to switch in capacitors in binary values, then
>> maybe use a varactor or two for fine tuning.
>>
>> They DO still make the old 365pF variable caps, BTW.
>>
>>
>> --
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> mailman.mit.edu/mailman/listinfo/piclist
>>
>
>

> There are also older varactor diodes with a much larger capacitance, such
> as the MVAM109 or MVAM125. There are a few sellers on eBay who have these..
> I don't know if they are made anymore but there are still sources. I used
> some in a receive-only remote antenna tuner I made. They have about 10x the
> capacitance of the ones you are using now, and almost as large a cap ratio.
>
> On Thu, Oct 20, 2016 at 12:16 PM, Van Horn, David <
> david.vanhornspambackcountryaccess.com> wrote:
>
>> You could use mosfets to switch in capacitors in binary values, then maybe
>> use a varactor or two for fine tuning.
>>
>> They DO still make the old 365pF variable caps, BTW.
>>
>>
>> --
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> mailman.mit.edu/mailman/listinfo/piclist
>>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist