[amsat-bb] re: TranSystem FREQUENCIES

["Mark L. Hammond" <hammond@xxxxxxxxxxxxxx>]

By the way...I experimented a bit last night with some small caps and the 
frequency of this (8.8125 MHz ;-) crystal in the TranSystem downconverter....

Adding a 15 pF cap in parallel with the stock tiny vari-cap moved it UP the 
band (the wrong way from what is needed).  It went up something on the 
order of about 300 kHz.

I tried to add a 3 pF cap in series with one leg of the crystal, but I 
couldn't find the signal.  Either the value was way off from what is 
needed, or I'm adding the cap in the wrong place.  There were the only 
"easy" experiments I could do without removing the circuit board...

Thought I would share the info with the list.

73,

Mark N8MH



> > Hi Jerry,
> >
> > I just stuck an 8.8125 MHz crystal in one of the TranSystem
> > downconverters...it seems like I see exactly the same results as you--with
> > the variable cap, I could only get within 50 kHz of the "desired
> > frequency," meaning it would not tune quite low enough to get the really
> > "comfortable" 144=2400.
> >
> > So I followed your lead and put it so 144.100 = 2400 MHz.  Sounded good to
> > me!
> >
> > I'm wondering if you have any more "on the air experiences" with your
> > TranSystem unit(s)?
> >
> > 73,
> >
> > Mark
> >
> >
> > At 12:46 PM 3/23/2001, you wrote:
> > >Art,
> > >That is very consistant with my tests also (HP signal generator and
> > >monitor also).  An unmodified 3733 (after warm up) settled in at 35 kHz
> > >higher (2401.00 MHz = 123.035 MHz).  I also took another unit and
>replaced
> > >the 8.98 crystal with a 8.125 ICM (from N0NSV for a Drake) and found the
> > >conversion worked perfectly on MMDS compared to my Drake, but was also a
> > >little high in freq.  I could not get enough "spread" out of the little
> > >vari-cap to get it down to 2400.00 MHz = 144.00 MHz, so I settled for
> > >144.100 MHz as being easy to remember.  This is just a plug-in crystal
> > >replacement!
> > >
> > >I did some comparisons last weekend to my modified Drake 2880 and the
> > >TranSystem 3373 performs similarly on local ATV and MMDS.  I did not get
>a
> > >chance to try AO-40, but hope to get to it this weeekend.
> > >
> > >Anyone that is interested in these downconverters can contact Bob at
> > >K5GNA@aol.com.  He has a "cute" little corner reflector that mounts right
> > >on the unit and makes for a nifty all-in-one hand-held S-band
> > >downconverter.  I plan to use one with my FT-100 for portable/mobile
>AO-40
> > >mode U/S at the unmodified 123 MHz frequency.
> > >73,
> > >Jerry, K5OE

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