[amsat-bb] RE: S band for 6 bucks

["Woody" <kj4so@xxxxxxxxx>]

I finally had a chance to bench test one of the 130215 S-band 
downconverters yesterday.  I can confirm that the LO is 2380 MHz., 
divided by 256 and locked to a 9.29687 MHz. crystal.

I was able to retune the combline input filter to 2.4 GHz. without any 
of the tuning screws grounding out.  However, without changing the LO 
frequency, the IF output is 20 MHz. with an input of 2.4 GHz.

I used finger nail polish remover to soften the black thread lock on the 
tuning screws.  This stuff is very tough. I had to let the finger nail 
polish soak for several minutes before the screws could be tuned.  They 
are very soft and are easily damaged.

I have two of the 130215 S-band downconverters.  The following are 
preliminary measurements between an unmodified 130215 S-band 
downconverter and one that I retuned the combline input filter.  No 
other modifications have been done to the 130215 so far.

Downconverter input level = -70 dB

Input Freq.                        Unmodified 130215             Retuned 
130215

2.40 GHz. 
                                    -58
2.42 GHz. 
                                    -60
2.44 GHz. 
                                    -45
2.45 
-58                                      -45
2.46 
-54                                      -45
2.48 
-42                                      -42
2.50 
-38                                      -40
2.57 
     -40


I have some 8.8125 MHz. crystals (somewhere) that I had bought for use 
in converting some AIDC downconverters.  Once I find the crystals, I am 
going to replace the crystal in the 130215 downconverter.  I will post 
my test results as soon as I can.

So far, I think that my test results are very encouraging.  I still have 
not found any published specs or documentation on this downconverter. 
However, I did find some specs on similar California amplifier 
downconverters at:
http://www.satellitentechnik.de/Converter.htm

73,

Woody
KJ4SO
AMSAT # 5562
----
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