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Re: AO-40 Mode U/S Report of this morning.



Bonsoir Bernard. This is Yoshi.

At 2001/05/07 19:05:40 Bernard Crumiere wrote:
> Could you gives me the frequency you listened on vhf after the DRAKE
> downconverter ??

  My 2880 had basic modified. 

1) Replaced Xtal with 8.8125MHz. The conversion is now 2401.00->145.00.
2) IF modified with replacing 2 pair of red coil and chip-c. Then add
   22pF at pararel with the chip-c of input side of green coil.
3) BPF length extended to peak it at 2400MHz.
4) Put a 30mm tin wire between RF input and GND. It works as quarter
   wavelength short stub of 2400MHz (BPF).
5) No modification on RF stage.

  So I was hearing 145.323MHz for the S2-MB of 2401.323MHz.

  I used LNA last night. But without LNA, maybe the S2-MB can be heard.
This is a capture image of AO40RCV compairing with LNA / without LNA.

http://plaza16.mbn.or.jp/~palau/images/LNA-result.jpg

> Because i use a DRAKE already modified but i don't heard something about
> AO-40 !!
<snip>

  Did you checked it with some sort of SG signals? You should check your
2880 working or not at first. If it works, you might be get the strong
S2-MB signals.

  Please note that the original RF circuit of Drake2880 is not so good
for static protection. The first FET is too much sensitive. If you used
non-DC-grounded type antenna, the RF FET will be destroyed very easyly.
I fried two 2880s already :-( so that is why I put a 30mm tin wire at the
RF stage to protect FET from Static High voltage.
  After fried, I tried to repair my 2880 with some sort of FET, but finally
I used MiniCircuit ERA-3 MMIC as RF stages. It is working well now.

73  de Yoshi.


Yoshihiro Imaishi JF6BCC/KH2GR
GL:PM53JV, ex KC6IY(T88IY),V63BP
mailto:jf6bcc@jarl.com or jf6bcc@jamsat.or.jp
<http://plaza16.mbn.or.jp/~palau/> Sorry, Japanese only now.
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