Re: [amsat-bb] Blown downconverter transistors

["Edward R. Cole" <al7eb@xxxxxxxxxxxxx>]

>The output transistors of the California Amplifiers 31732, the Drake 2880
>and the Transystem AIDC3733 downconverters are marked RFxx and are in an
>SOT-89 package.  The 'RF' part of the code identifies the device as a
>2SC3357; as far as I can tell the last two digits (4Z,  6Z or 26 - there may
>be others) are simply date or batch codes.
>
>The 2SC3357 is not the most readily available transistor in the world,
>especially outside Japan, although RF Parts list it.  However, it's only
>function is to provide gain at 123MHz/145MHz.  The BFQ19 is a good
>substitute, and the BFG97 (which is in a slightly larger package) ought to
>work as well; both these devices should be readily available.
>
>I don't know about the Norsat D/C, I've never seen one.
>
>The information about the device codes was obtained from Roger Blackwell,
>G4PMK's excellent reference site
>
>http://www.marsport.demon.co.uk/smd/mainframe.htm
>
>regards
>
>Grant Hodgson
>G8UBN

You know I've read these queries on here and wondered why a mmic would not
be a good replacement device in these converters?  In particular thinking
of the MAR-4 or -6 which operate just fine at VHF and require no RF ckts.
Just 50-ohm input and output.  You can bias them to chose the gain you
want, as well.  I'm using two MAR-6 IF-amps at 144 MHz in my home-built
1420 MHz radio telelscope.  I get 20 dB gain using 12v supply (and
appropriate resistors).  Mine are built as separate units in die-cast boxes
I bought from Downeast Microwave (for you North American hams).  In fact, I
bought EVERYTHING needed for $35/each!  Looks like the small boxes they use
for their preamps.  The mmics are something like $5/each.

I do not use the Transystem AIDC3733, so confess not knowing much about
them (other than I read here).  Maybe the mmics are not appropriate...maybe
one of our experts wishes to reply?

dos centavos de AL7EB

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