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Re: AIDC-2733 gain measurement

I have posted a message with info on the prescaler. To make the oscillator
go to 2400 measure the voltage on the round test pad between the resistors
marked 510 and 103. This is the lock voltage that you want to keep very
close to the voltage found in an unmodified unit. Insert the new crystal and
the VCO should try to lock moving the output frequency as high as it can.
>From your email it sounds like it does not reach 2400. Go to the etched
inductor (looks like a sine wave) and short some of the wavy lines together.
Do this while observing the lock voltage. You should be able to reduce the
inductance enough to make it lock at 2400.

Pieter N4IP

----- Original Message -----
From: "John Harrington" <johnh@ih2000.net>
To: "Mahlon Haunschild" <mahlonhaunschild@home.com>
Sent: Wednesday, April 04, 2001 22:14
Subject: Re: [amsat-bb] 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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> ----
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