I need help to find any good design for the 2m to 10.7MHz downconverter which I'll try to use for presentation linear transverter.

While not 10.7 MHz you may find the circuit diagrams of the 145/29 MHz linear transponders for the RS series of satellites of interest.

They are on the RadioSkaf website at http://tinyurl.com/RadioSkaf - Click on the Forum menu option - Under  Satellite "Radioskaf" select the Transmitter topic - Then click on Schemes of repeaters

There are a number of circuit diagrams there available for download as JPEGs Also see the Receiver -> Receiver CL (Command Radio Link) section

73 Trevor M5AKA

----- Original Message ----- From: "Andy Brian" [email protected] To: "AMSAT-BB" [email protected] Sent: Friday, October 04, 2013 6:45 AM Subject: [amsat-bb] 2m--> 10.7Mhz downconverter

Hi,

I need help to find any good design for the 2m to 10.7MHz downconverter which I'll try to use for presentation linear transverter. Please if you have any or point me to any good books where to find?

Thanks for all answers,

BR Andy

Hi Andy,

I have never seen in the market a 2 meters downconverter with an IF of 10.7 MHz

If your 10.7 MHz IF is a value strictly mandatory the only way for you is to modify a 144 to 28 MHz downconverter in wich the local oscillator is made with a original XTAL of 144-28 = 116 MHz

The new XTAL must be 144 - 10.7 = 133.3 MHz overtone wich is difficult to find and must be ordered to a company that cut crystals.

Remember that who cut crystals must have precise specifications in order to know if it must be series resonant and if it must be 3° or 5° overtone and the best way is to send to the above company a photocopy of the original downconverter schematic diagram.

Actually it is very difficult to find in Europe labs that cut only one XTAL per frequency except the EISCH ELECTRONIC in 89079 Ulm Gogglingen wich cut and supply one XTAL in a week or two at a price of about US $ 35,00. Here the internet address:

http://www.eisch-electronic.com/index.html

In addition you must retune the local oscillator coil and trimmers to get the circuit to oscillate at 133.3 MHz

Also you must retune the IF output circuit after the mixer to get the maximum output at 10.7 MHz IF.

Another choise easier for you should be to buy an old downconverter 144/28 MHz and convert the 28 MHz IF into a second IF of 10.7 MHz using a single mixer and a local oscillator with a XTAL of 28 - 10.7 = 17.3 MHz...........VERY EASY !

have fun

73" de i8CVS Domenico