Re: [amsat-bb] AIDC-2733 gain measurement

[Mahlon Haunschild <mahlonhaunschild@xxxxxxxx>]

Thanks for confirming my suspicions, Pieter.  Not to mention identifying
the PLL and VCO parts!

regards,

Mahlon - K4OQ

Pieter Ibelings wrote:
> 
> 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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