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'Boosting power of radio modules[EE]'
2000\05\24@150945 by Andrew Seddon

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I have purchased a couple of radio transceiver modules from
http://www.radiometrix.com however the rated output power is a tad on the low side.
Now I know the legal issues about boosting power but I am in the middle of
no-where and I am only talking about a little power increase. The modules
work at 433.92Mhz and output 6dbm(is that a good measure of power? I have no
RF experience). They are half duplex and the TX/RX works off the same
antenna. I was wondering if it would be possible to maybe place a transistor
and a resistor in place of the antenna to boost the power.

Any help appreciated.

2000\05\24@171050 by l.allen

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Andrew Seddon wrote:

> I have purchased a couple of radio transceiver modules
>from http://www.radiometrix.com however the rated output
>power is a tad on the low side.
> Now I know the legal issues about boosting power but I
>am in the middle of no-where and I am only talking
>about a little power increase. The modules
> work at 433.92Mhz and output 6dbm(is that a good
>measure of power? I have no RF experience). They are
>half duplex and the TX/RX works off the same antenna. I
>was wondering if it would be possible to maybe place a
>transistor and a resistor in place of the antenna to boost
>the power.
>
> Any help appreciated.

There are 3 solutions..
Boost the Rx sensitivity, boost the Rx sensitivity and
boost the Rx sensitivity.

This is FAR more effective than increasing the Tx power
"a bit". Doubling the output power of the Tx will increase
the RF power 3dB BUT you with a little care you will get
much more than 3 dB increase in sensitivity in the Rx
path without violating transmission laws.

The most obvious first choice would be a signal boost
preamp on the input to the Rx (since a directional
antenna will violate the power level spec and directional
may be unacceptable anyway).

There are a sea of published projects and kits fitting this
description available.... a UHF preamp/booster.
One of my local electronics stores sells a wideband
antenna amplifier for $30 (US$15) that covers 30 to
850MHz at 20dB boost.

The only potential gotcha is the Tx signal overloading the
booster amp but that is not likely at those power levels.
The easiest solution in that case would be a separate Rx
antenna otherwise you are into RF territory of selective
stages, filters, traps etc.


_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

http://www.psych.auckland.ac.nz

_____________________________

2000\05\24@172134 by Quitt, Walter

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On RX Preamps watch out for how much noise
is generated by it.  EX: A cheap broadband
preamp with a noise floor of 6DB wiil actually
make the reception worse as your weak received
signal will fall below the noise floor.  Not
good.  Get a good UHF low noise preamp.  433 is
close enough to the ham bands that you should
be able to get one for amateur radio use
that will do real well.

{Original Message removed}

2000\05\24@204116 by Dan Michaels

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At 07:55 AM 03/24/2000 -0000, you wrote:
.....
>Now I know the legal issues about boosting power but I am in the middle of
>no-where and I am only talking about a little power increase. The modules
....

Maybe there should be an admin heading of [FLW] - Famous Last
Words - for this kind of broadcasting <:-))). After all, with 2000
piclisters, how many do you suppose are gov't moles?? - I'd guess 30%,
from 84 different gov't agencies - US and foreign. <many G's>.

And I'm sure piclist gets scanned by "Echelon" - in case you
haven't heard of it, search on any engine.

2000\05\24@223105 by Don
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On 24 Mar 2000, at 7:55, Andrew Seddon wrote:

> I have purchased a couple of radio transceiver modules from
> http://www.radiometrix.com however the rated output power is a tad on the low
> side. Now I know the legal issues about boosting power but I am in the
> middle of no-where and I am only talking about a little power
> increase. The modules work at 433.92Mhz and output 6dbm(is that a good
> measure of power? I have no RF experience). They are half duplex and
> the TX/RX works off the same antenna. I was wondering if it would be
> possible to maybe place a transistor and a resistor in place of the
> antenna to boost the power.
>
> Any help appreciated.
>

You can certainly make an amplifier, but if you havent worked with
rf circuits, it will take you a while to get the knack. You might want
to buy an amateur radio handbook and read some of the material,
and maybe experiment some. You will also need to buy or build
some basic RF test equipment, and again, the handbook can help.
One thing to keep in mind is the nature of UHF transmissions. It is
almost line of sight, like light, so if you are down in a valley, you
might have a very large power and still not be able to tranmit as far
as a few mw on a hill top. If you are looking for range in a particular
direction, you might get improvement by building an antenna with
higher gain, and/or paying attention to the matching of the output
stage and the antenna. Again, the handbook can help here. Be
sure you don't cause interferrence....sometimes, repeaters are also
put in some pretty out of the way places.
Oh, your 6dbm figure means the output power is 6 decibels above
a milliwatt.

2000\05\24@224803 by Gennette, Bruce

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Rather than go illegally over-power in the transmitters you can boost the
receivers with a MAR6 and a couple of caps for a few of dollars.  (good
stipline construction with the MAR6 sitting in a hole in the board IS
required).

Bye.

       {Original Message removed}

2000\05\25@003828 by paulb

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Quitt, Walter wrote:

> 433 is close enough to the ham bands that you should be able to get
> one for amateur radio use that will do real well.

 In this country at least, 433 *IS* an amateur band - which is why they
(we) aren't too pleased about the proliferation of these devices.  In
effect, it's an ISM band.

 *Presuming* the modules have a poor input noise figure, a low NF
*tuned* amplifier, quite possibly using a MAR-6, better a GaAsFET, would
help.

 There is no regulation on receiver gain in this application (unless
perhaps it's a transceiver module), so by all means use a yagi, array
or dish on the receiver.  (Dishes are made of chickenwire).
--
 Cheers,
       Paul B.

2000\05\25@024340 by mike

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AFIK its right in the middle of the 70cms ham band in UK.
a web search for 70cms pre-amp should find something. Failing
that the " remote imaging group " may have something.
But did'nt he say it was a BIM tranciever?, in that case it may be
difficult to get into the RX path. I'd personally go for a beam
antennae, with the module at the feedpoint to reduce feeder losses,
if directionality is acceptable.

On 25 May 00, at 0:09, Automatic digest processor wrote:

{Quote hidden}

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2000\05\25@091350 by Andrew Seddon

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----- Original Message -----
From: Dan Michaels <.....oricomKILLspamspam@spam@LYNX.SNI.NET>
To: <PICLISTspamKILLspamMITVMA.MIT.EDU>
Sent: Thursday, May 25, 2000 12:40 AM
Subject: Re: Boosting power of radio modules[EE]


> At 07:55 AM 03/24/2000 -0000, you wrote:
> .....
> >Now I know the legal issues about boosting power but I am in the middle
of
{Quote hidden}

Thanks for the tips but I`m not going in to hiding just yet :-). The modules
will be placed on a farm. The nearest house is about 1.5-2km away. They are
currently rated at 200m open ground and I was looking for around 400-500m.

2000\05\25@111726 by mike

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On Fri, 24 Mar 2000 22:12:37 -0000, you wrote:

{Quote hidden}

If the link is fixed, I'd try directional antennas like Yagis first.
This will also reduce the chance of interference (to or from your
system).
Modules are available for other bands (I think theres one around
900MHz) that can legally operate at higher power levels.

2000\05\25@135522 by Ian Wilkinson

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On Thu, 25 May 2000 in "Re: Boosting power of radio modules[EE]", Paul B. Webster VK2BZC wrote:
>Quitt, Walter wrote:
>
>> 433 is close enough to the ham bands that you should be able to get
>> one for amateur radio use that will do real well.
>
>  In this country at least, 433 *IS* an amateur band - which is why they
>(we) aren't too pleased about the proliferation of these devices.  In
>effect, it's an ISM band.

In this country 433 Was an entire amateur band,  We now have a 2 MHz chunk taken
out of the 70cm band for these devices...  Some did say we benefitted, we now
have two 70cm's bands...

Check out amateur radio information.  These modules tend not to filter out
interference very well so you could look into filters and Amps on the Rx side
as well as high gain aerials...

If there are restrictions on aerials have some way of switching to a lower gain
aerial before Transmitting and then back to the high gain when receiving...

Ian
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The skin was moist and dry.

Uptime at  8:18am  up 10 days, 10:09,  8 users,

2000\05\25@142920 by David VanHorn

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>Thanks for the tips but I`m not going in to hiding just yet :-). The modules
>will be placed on a farm. The nearest house is about 1.5-2km away. They are
>currently rated at 200m open ground and I was looking for around 400-500m.

So you'll need 6-8dB antenna gain.
A five element yagi on the receiver, pointed at the transmitter, will do
this, and is perfectly legal.  Also, you'll probably find that they
out-perform their specified range in this quiet environment.

Look in an ARRL antenna book, under UHF antennas.

- --
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2000\05\25@161637 by l.allen

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David Wrote
>
> So you'll need 6-8dB antenna gain.
> A five element yagi on the receiver, pointed at the transmitter, will do
> this, and is perfectly legal.  Also, you'll probably find that they
> out-perform their specified range in this quiet environment.
>
> Look in an ARRL antenna book, under UHF antennas.
>
> - --
A Yagi antenna will be directional (stating the blinding
obvious) and therefore focuses power in one direction,
and since Andrew said the unit  presently used one aerial
for both Tx and Rx then a 20 to 40dB gain that some
Yagis can yield will put the field strength (in the beam)
through the roof... being up to 10,000 times more intense
than isotopic.
But as David said... good if you attach only to the Rx and
are happy with a focused path (like from building to
building).


_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

http://www.psych.auckland.ac.nz

_____________________________

2000\05\25@173647 by David VanHorn

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>for both Tx and Rx then a 20 to 40dB gain that some
>Yagis can yield will put the field strength (in the beam)
>through the roof... being up to 10,000 times more intense
>than isotopic.

40dB is going to take a pretty expensive antenna.
6-8 is cheap, and probably all he needs.

- --
Are you an ISP?  Tired of spam?
http://www.spamwhack.com  A pre-emptive strike against spam!

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2000\05\26@065657 by Andrew Seddon

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Thanks for all the help on this. I have decided to get myself a decent
antenna on one end of the link. For reasons of portability one end has to
use a crappy wip. The only question I have is how directional is a yagi?? I
wan`t an angle of acceptane of about 30 degrees on the horizontal and about
5 on the vertical.

Thanks.

2000\05\26@171117 by Andrew Seddon

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Yeh that`s what I was getting at. What I mean is that I would imagine
noise/power specs etc to be similar for similar devices.

>         Actually, I'd expect NONE of the US FCC rules to apply in the UK.
> However, most countries have very similar rules on unlicensed
> transmitters.
>
> Harold
>
>

2000\05\27@072735 by mike

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Andrew, where are you in the world?. sometimes UHF band A TV
antennae can be used straight from the box.  If I were you i'd go for
minimum acceptable gain in the antennae, this coincides with
wider apatures, for a gain of 6dbd your beamwidth should be plenty
wide. Try looking in the ARRL ( amateur radio relay league. US
based) handbook or the RSGB ( radio society of great britain. UK
based !) handbook for specific data on gain vs apature. e-mail me if
you wish for a simple design to make yourself.. Mike W

On 27 May 00, at 0:01, Automatic digest processor wrote:

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