[amsat-bb] Frequency Stabilized Local Oscillators
stanw1le at verizon.net
Tue Dec 9 16:29:39 PST 2008
Hello The Net:
Steve Hicks, N5AC, is designing frequency stabilized local oscillators
that can be used
in the (Down East Microwave Inc.) DEMI transverters or RX only, block
Frequency stability is achieved by locking to a external 10 MHz house
which could be a GPS disciplined oscillator, a OCXO, or a compact Rb
The Trimble Thunderbolt GPSDO is a very popular 10 MHz reference.
We could use your help in disclosing what RFs and IFs you are using for
present and proposed satellite
transponders. Then we can calculate the local oscillator frequencies
needed for the DEMI transverters.
This stabilized LO can be used in place of the DEMI standard MICROLO pcb.
The MICROLO pcb is used on transverters 900 MHz and higher.
Most will use a "low beat" RF/IF mixer scheme, but if you use a "high
beat" mixer scheme, let us know.
A new design by Steve will allow factory programming for 256 different
frequencies, in memory.
Just change the jumpers for the pre-programmed LO freq you need for your
The objective of this inquiry is to determine what those 256 programmed
frequencies should be.
The DEMI transverter uses 2 pcbs, the MICROLO pcb and the transverter pcb.
The transverter pcb multiplies the LO from the MICROLO pcb then mixes it.
The transverter pcb LO multiplier on the 2,304 band is X2, for 3,456 MHz
band is X3,
for 5,760 MHz band is X5, for 10,368 MHz band is X9
Examples: (low beat mixer scheme)
2,401.0 MHz RF, RX only, block down converter with a 145.0 MHz IF
output, low beat,
2,401.0 - 145.0 = 2,256.0 MHz, divided by 2 = 1128.0 MHz
2,400.0 - 432.0 = 1,968 MHz, divided by 2 = 984.0 MHz
2400.0 - 50.0 = 2,350.0 MHz, divided by 2 = 1,175.0 MHz
2439.0 - 144 = 2,239.0 MHz, divided by 2 = 1,147.5 MHz
3,400.0 MHz RF downlink with a 144 MHz IF: 3400.0 - 144.0 = 3256.0 MHz,
divided by 3 = 10.85.333 MHz
3,400.0 - 432.0 = 2,968.0 MHz, divided by 3 = 989.333 MHz
5,668.0 MHx RF uplink with a 144 MHz IF: 5668 - 144 = 5,524 MHz
10,451.0 MHz RF downlink with a 144 MHz IF, LO =
10,451.0 - 144.0 = 10,307.0 MHz, divided by 9 = 1145.222 MHz
for a 432 MHz IF, 10,451.0 - 432.0 = 10,019.0 MHz, divided by 9 =
10,386.0 MHz RF for terrestrial ops, 145.0 MHz IF,
10,368 - 145 = 10,223 MHz, divide by 9 = 1,135.888 MHz
10,368.0 MHz RF with 144.0 MHz IF, 10,368 - 144 = 10,224 MHz, divided by
9 = 1,136.0 MHz
Look to: http://www.n5ac.com/blog/?page_id=19 for the N5AC
Look to: http://www.downeastmicrowave.com/A32.htm for more
details on the synthesized LO pcb
I will summarized your RF/IF combinations.
(Hopefully there are not too many typos here)
Stan, W1LE FN41sr Cape Cod
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