Post by thread:[EE] Wireless communication...

Hi... For prototypeing purposes we bought a couple of 4 pins 'complete AM radio transmitters' from R.F. Solutions. Also bought a couple of matching receivers ofcourse (433 MHz). (http://www.rfsolutions.com). My problem with them is this: when supplying Vcc (5V) and GND to the transmitter and connecting a function generator at the data in, of 2 kHz, 50 % dutycycle (coupled AC or DC) i can't see anything at the receiving end. I can't measure if the transmitter is actually oscilating at 433 MHz becouse the fastest scopes we have is a Philips 200 Mhz scope... Also the datasheets and the technical support are far beneath appropiate, in my opinion. The units were places 20 cm apart and had just a wire of 15 cm as an antenna. Anybody couped with the same problem? Anyone have experience with these modules (i mean the AM-RT4-433 transmitter and the AM-HRR-433 receiver, of RF Solutions) Jilles

" ...Philips 200 Mhz scope... " ... should still see something as that is usually the "3 dB point" for the scope's bandwidth ... I once trouble shot a Tektronix 454 (150 MHz scope) trigger circuit using just a 10 MHz bandwidth Tek portable - the trigger circuit incorporated a tunnel diode that excited a 'tank' circuit that resonated at several hundred MHz ... the indication was only a small 'blip' when the tunnel diode was working as seen on the low bandwidth scope. Take a look at the xmtr with the Philips scope - 433 MHz is just over an octave higher frequency - and the scope should show enough to give a yea/nay indication. Watch out for the the scope probe though - they often have a much lower cutoff freq than the scope itself. You may have to rig a short piece of coax and if the scope has a built-in 50 Ohm termination switch it it to then couple the xmtr output directly into the scope. Zero dBm is about .223 V RMS (.6 V Pk-Pk) less any rolloff in amplitude the scope shows at 433 MHz. Jim P {Original Message removed}

{Quote hidden}> " ...Philips 200 Mhz scope... " > >... should still see something as that is usually the >"3 dB point" for the scope's bandwidth ... I once trouble >shot a Tektronix 454 (150 MHz scope) trigger circuit using >just a 10 MHz bandwidth Tek portable - the trigger circuit >incorporated a tunnel diode that excited a 'tank' circuit that >resonated at several hundred MHz ... the indication was only >a small 'blip' when the tunnel diode was working as seen on >the low bandwidth scope. > >Take a look at the xmtr with the Philips scope - 433 MHz >is just over an octave higher frequency - and the scope >should show enough to give a yea/nay indication. > >Watch out for the the scope probe though - they often have a >much lower cutoff freq than the scope itself. You may have to >rig a short piece of coax and if the scope has a built-in 50 Ohm >termination switch it it to then couple the xmtr output directly >into the scope. > >Zero dBm is about .223 V RMS (.6 V Pk-Pk) less any rolloff >in amplitude the scope shows at 433 MHz. > >Jim P Hmmm, you're right i guess. But the scope is a digital one. Even when i measure a voltage that goes from 0V to 5V it takes approx. 3 seconds to adjust the screen. What one will see is this: 0V ----------------------------- ('bout 1 sec later:) 5V . . 0V ----- ------------- ------------ again, 1 sec later: 5V -- --- --- 0V -- --- ---- ---- and, finaly after about 3 seconds: 5V ----------- I think this has to do with how the A/D converter works within the scope... If i measure a point were i *suspect* to be 433 MHz all i see is something like 3/4 Vcc, wich could be the avarage voltage? I want to say that i mustn't have to measure these 'ready to go'-modules! I mean, they have to work, don't they? The only thing i could find on the website of RF Solutions was a ****3**** page datasheet. And after asking some application information, they reffered to book! That application information had to be in the datasheet in my humble opinion... (frustrated, you guessed it right :) Did anyone get these modules to work? I'm interested in how they did it. Jilles

> Jilles Oldenbeuving wrote: > > > > .... i can't see > > anything at the receiving end. I can't measure > > if the transmitter is actually oscilating at 433 MHz becouse the fastest > > scopes we have is a Philips 200 Mhz scope... One poor man method is to modulate the transmitter with low frequency (let say 1KHz ) and to detect a proportional DC signal near antenna using a Schottky diode and a 1MHz bandwith oscilloscope... ********************************************* Surducan Vasile, engineer mail: .....vasileKILLspam@spam@l30.itim-cj.ro URL: http://www.geocities.com/vsurducan *********************************************

<x-flowed>Jilles How much power out is your xmtr? {Quote hidden}>From: Jilles Oldenbeuving <jillesKILLspamRENDO.DEKOOI.NL> >Reply-To: pic microcontroller discussion list <.....PICLISTKILLspam.....MITVMA.MIT.EDU> >To: EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU >Subject: Re: [EE] Wireless communication... >Date: Tue, 30 May 2000 07:23:05 +0200 > >Hmmm... I might try that today.... still, i think it just had to work... :) > > >Regards, > >Jilles Oldenbeuving >jillesspam_OUTrendo.dekooi.nl > > > >If you've got a UHF capable sig-generator around the lab somewhere, > >maybe try heterodyning the the Tx's output down into the scope's > >range? > >Just a thought. > > > >Ian > > ________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com </x-flowed>

Or use a cable TV convertor to do the same thing. The video detector should show you the modulation. North American cable channel 59 is 433.25Mhz. You'll also see a nice herringbone pattern on a TV screen from a stable carrier. (sortta like 'sound' in video when the fine tuning is off). Ian Hynes wrote: {Quote hidden}> > If you've got a UHF capable sig-generator around the lab somewhere, > maybe try heterodyning the the Tx's output down into the scope's > range? > Just a thought. > Ian > Jilles Oldenbeuving wrote: > > .... i can't see > > anything at the receiving end. I can't measure > > if the transmitter is actually oscilating at 433 MHz becouse the fastest > > scopes we have is a Philips 200 Mhz scope...