Re: [amsat-bb] Drake frequencies

[Mahlon Haunschild <mahlonhaunschild@xxxxxxxx>]

Floyd, 

The stock crystal frequency in the Drake 2880 MMDS converter is 8.89843
MHz.  The formula is:

(2400 - X) / 256 = 8.89843; solving for X, I get 122.00192 MHz, if I've
got my sums right.

Per the AMSAT Web site, the AO-40 S-band frequencies (give or take a few
hertz) are:

S1Tx      General Beacon   Middle Beacon    Engineering Beacon
           2400.188 MHz     2400.338 MHz     2400.588 MHz

S2Tx      General Beacon   Middle Beacon    Engineering Beacon
           2401.168 MHz     2401.318 MHz     2401.568 MHz

So, if you have a receiver you are comfortable with that can receive on
122-124 MHz, and meets all of the usual technical requirements for
satellite work, then no, you don't need to change the crystal.

For exactly the reasons you mention, I ordered a crystal yesterday for
my Drake to position 2400 MHz at 140 MHz (my IC-821 won't transmit below
144 MHz, but receives just fine below that frequency).  I just realized
this morning that Eglin AFB's high-power IRIG-B time code transmitter
(S9+60 dB here) operates at 141.200 MHz, and occupies a bandwidth of 100
KHz.  This may render 2401.150 to 2401.250 useless to me!!  BANTHA
POODOO!!

Praying for well-shielded feedlines,

Mahlon - K4OQ

Floyd Rodgers wrote:
> 
> What is the output frequency of the unmodified Drake as related to AO40
> downlink frequency?
> 
> Why should I modify the drake output frequency to be in the trasmitter
> output rage (i.e. 144mhz) ? If drake downlink freqency is outside the
> normal transmit range, the radio will protect the converter by not
> transmitting out of band. I assume then the uplink signal would be sent
> from the 432 side of the same radio or another separate radio via transverter.
> 
> Floyd Rodgers KC5QBC
> Multi ended candle burning artist in training
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