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RE: For those with some money to burn......



A cheaper solution I use is a simple general purpose broadband SSB/CW
receiver.
The principle is to measure (in the shack) any offset of the local
oscillator of the converter (remaining on top of the mast).

1) Let the receiver warm up in the shack for a reasonable time (I use an
ICOM PCR-1000 receiver)

2) Check the freq. accuracy of your receiver ( note the frequency offset) by
zero beating in USB or LSB mode on a frequency standard transmitter (caesium
oscillator broadcast transmitter, or WWV, or ...)

3) Connect the 2,4 GHz converter (remaining on top of the mast) to the
receiver and apply power supply to the converter.

4) Tune your receiver on the highest harmonic frequency of the local crystal
oscillator of the converter you can listen to (in my case, using a 2400/144
MHz converter fitted with a 94 MHz fundamental frequency xtal oscillator, I
listen to the 13 th harmonic freq, which is 1222 MHz).
Carefully tune the receiver and measure the frequency offset (checking zero
beating by ears or by looking at the S meter needle) and compute the
frequency offset induced by your converter.
For example, if I measure 1222.001234 MHz (including the receiver possible
offset) instead of 1222.00000 MHz, I can determine that my converter LO
offset is 2256 -(1222.001234/13*24) = 2,278 kHz.
So I'll have to adjust my 144 MHz IF receiver on 145,3253 MHz instead of
145,323 MHz (Doppler excluded) to listen to the AO-40 beacon.
The reason for choosing the highest harmonic freq of the LO you can listen
to, is to get the best accuracy during the zero beating measurement.
With that method, the converter remains on top of the mast. It means that
you can easily measure any converter LO drifts related to seasons (hot
summer, cold winter ...).
I also checked that method with the Drake 2880 converter with its 8.8125 MHz
xtal oscillator and it works pretty well.
I even used a FFT software (such as Spectrogram) analysing the audio output
of the receiver to record the middle-term frequency drift curve of the
converter.

Hope it helps.

 73 de Jean-Louis F6AGR

> -----Message d'origine-----
> De: Jens H. Jensen [mailto:dsl9968@vip.cybercity.dk]
> Date: dimanche 25 novembre 2001 18:01
> À: amsat-bb@AMSAT.Org
> Objet: [amsat-bb] For those with some money to burn......
> 
> 
> Frequency standards.
> 
> http://www.helmut-singer.de/stock/2031607592.html
> 
> This will NOT answer the question of where AO-40 are, 
> frequencywise, at any 
> given time, but will at least let you know where YOU are :-) 
> (which is a 
> good startingpoint!)
> 
> There's one more here: 
> http://www.helmut-singer.de/fix/new.html (look for 
> "efratom")
> 
> Disclaimer: I'm not connected with this firm in any way, but 
> always amazed 
> at what you can find there!
> 
> 73 de OZ1LRG, Jens
> 
> ----
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