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[Fwd: Re: AIDC-2733 gain measurement]





Hi, Mahlon.  The idea of using a Drake LO as a signal source is a good
one, IF the VCO will go to 2400MHz.  I had the same idea several weeks
ago, and ordered a 9.375 MHz crystal from ICM, intending to use a 3733
LO.  While waiting for the crystal, I 'sacrificed' a 3733 by removing
the LO and mixer board.  I cut off the mixer microstripline circuit
and attached an SMA connector at the LO output point, just past a little
pi-net attenuator circuit.  I was delighted to find a +10 dBm output
there, with all spurious signals 30 dB down and hundreds of MHz away!
This puppy is CLEAN.  Originally, I intended to use the LNA from the
same sacrificed 3733 as a PA, but when I saw 10 mw WITHOUT an amplifier,
I figured to just pass the output through a pipe-cap cavity and use it
as-is as a beacon.  I already have some little PIC microprocessors
programed with my call as a beacon controller.  The PIC FSK's the freq.
a bit for the CWID.

Then, the crystal for 2400 MHz came.  I plugged it in and got 10mw
output,
but couldn't find the signal at 2400MHz.  Looking at the spectrum
analyzer,
there it was at around 2300MHz!  After some head scratching, including
measuring the freq of the crystal (it was right on) I determined that
the
VCO simply wouldn't go to 2400MHz.  The crystal would pull it upwards
but
it hit it's upper limit at about 2300MHz.  I hope that there are some
VCO upper/lower limit parts which can be tweaked to get it up there, but
don't know yet.  My immediate problem is that I can't identify the VCO
part.  The IC next to it is a 4046A phase-comparator, a 16-pin SM
device.
The part which must be the VCO and divide-by-256 is a little 8-pin SM
package (tiny!) with the markings '510',  '9612',  and 'M53' on it, but
no manufacturers' logo.  I think the '9612' is the code date, and the
'510'
and 'M53' identify it.  Can anyone point me to a manufacturer or data
sheet?

If I can't find enough information to get the VCO to phase-lock at
2400MHz,
all is not lost.  I still have a nice +10 dBm 2256 MHz phase-locked LO
for my next upconverter.   The +10 dBm is perfect for the Mini-circuits
level 7 double-balanced mixers.

If you folks can help me identify the VCO and get it to 2400MHz, I
promise
to take the time to build a web page with the data necessary to build a
S-band beacon with CWID, including source code for the PIC
microprocessor.
You can modify the source code with your call and grid or other
information
for automatic one-minute CW ID requirements.

Best regards,  John  W5EME

Mahlon Haunschild wrote:
> 
> Couldn't have said it better myself, John.
> 
> I'm going to re-re-crystal a Drake 2880 into a weak signal source at
> 2400 MHz, using a 9.375 MHz crystal.  That, and a stack of coaxial
> attenuators, should do the trick.  I hope the PLL locks up at that
> frequency...
> 
> regards,
> 
> Mahlon - K4OQ
> 
> John Harrington wrote:
> >
> > Hello, all.  Yes, you can easily tune the comb filter- BUT- you
> > need a stable, weak signal source to do it properly.  A satellite
> > signal is NOT suitable, because you can't peak anything on a
> >
> > <snip>
> ----
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