----- Original Message ----- From: "Andy Brian" briaandy@gmail.com To: "AMSAT-BB" amsat-bb@amsat.org 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