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More AIDC 3373 & newbie.



I got quite a few suggestions about the diode/resistor multiplier for a
2.4Ghz signal generator.  Thanks to all.

This is somewhat lengthy, but hopefully it'll help others who might be
struggling with similar lack of equipment.

The diode multiplier is this one:
http://members.aol.com/k5oe/signal_gen.gif

That image can be found on K5OE's pages under "Drake 2880 Mods"
http://members.aol.com/k5oe/

His site has MANY great article and projects.  Well worth a look see.

So now I've found that the downconverter is working.  Transmitting at
50.01mhz gives 2400.480, which is 122.480Mhz IF.  I heard my signal at
122.512 (32Khz off).. But my transmitter calibration is unknown.  32Khz
translates down to 667Hz off in the transmitter.  That seems a bit too much
for the tx to be off, but I cant find my frequency counter!

I also tried a hand held transmiting out of band at 150.06 (2400.960), but I
didnt hear a tone, just some garble.  I couldnt pin point the frequency, it
appeared to be 2400.980 or so.  +20Khz off?  Still, in the ball park.  I
switched my IF reciever to wideband FM mode and hit a DTMF key.  It came
back out of the receiver with very little distortion.  I would think 5khz
times 16 = 80Khz deviation.  I thought my it would be too wide even for
wideband FM to copy well.  But it worked.  I went back to SSB to try to copy
the tone, but still just heard garble.  I'm assuming that what I'm hearing
is an oscillator with lots of phase or frequency noise, considering that its
only intended for FM use.

Going back to 50.01Mhz on the other rig, I proceded to try the same FM test,
well, here the wide band was indeed too wide.  However the unmodulated FM
carrier was very clean, when heard on the IF receiver is SSB mode.  I did
detect a little bit of garble however.  I found that if the transmitter was
in AM mode, I heard more "garble" on the signal.  My conclusion was that
some RF was probably getting into the audio, even with no mic attached.

Conclusions:

1) The AIDC 3373 is probably +20 to +30 Khz off. (could someone tell me if
this is acceptable, my gut reaction is that it is well within the norm)

2) A handheld multiplied up is a poor signal generator.

The next step:
There is a pass tomorrow morning with MA=240 at 9:15 local time.  I'll be
trying things out again from MA=240 to 250, as per Ian's suggestion.  My
experiments here reinforce the fact that I should have heard something on my
prior attemts.  Things seem to be closer to the 100khz that I was searching
through the first times.

Can someone check my sat tracking program:  At 14:14UTC on April 9, 2001,
will AO-40 be at MA=240?


Kevin Uhlir
N0BEL
kevinu@flochart.com

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