[amsat-bb] Re: 2m--> 10.7Mhz downconverter

[i8cvs]

----- Original Message -----
From: "Andy Brian" <briaandy at gmail.com>
To: "AMSAT-BB" <amsat-bb at 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