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choice of IF frequencies



Ed Cole wrote:

I just pre-ordered* my 1269 Tx conv. & 10451 Rx conv. from Steve [DEM] this morning and the schedule sounds about right.  They are holding on production to be sure of which AO-40 modes checkout good, and for some verification of link requirements by actual observation {i.e. if they make a bunch of 10w convertors and you need 20w...they are stuck with unwanted inventory}.  

Wayne Estes replies:

I notice that DEM's 1269 transmit converter and the 2400 MHz MHz RX converter both have 144 MHz IF's.  Why?

It seems obvious to me that AO40 transmit and receive converters should use DIFFERENT IF's.  The logical choice for the transmit IF is 435 MHz.  Then the 2400 MHz and 1269 MHz converters would be "plug and play" with EVERY commercially made satellite transceiver, including models that don't have HF capability.

This seems even more compelling if AO-40's 435 MHz transmitter really turns out to be dead.  435 MHz would be an "uplink only" band, perfect as the IF for ALL AO-40 transmit converters.

Has anybody asked DEM why they don't plan to offer the 1269 MHz transmit converter with a 430 MHz IF?  Is something wrong with my logic?

Wayne Estes W9AE
Mundelein, IL, USA

p.s. I just re-subscribed to AMSAT-BB.  I used to be active on AMSAT-BB in the AO13 days with callsign WD5FFH.

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