Re: AW: [amsat-bb] FT736r recieve gain variations?

[al lawler <alawler@xxxxxxxxxx>]

   Just a followup - I found the source of my (really huge) 
deline in recieve performance in the vicinity of the AO-40
beacon.

  It wasn't my FT736r at all.  The problem was caused by the
Hamtronics downconverter which I have also have connected to
the 2m converter output via a "Tee" connector.  (I use the 
hamtronics converter to drive a separate 10m telemetry
reciever.)

  I need to dig out the hamtronics schematic - I'm hoping
I can either re-tune (or de-tune) the input slightly such that 
this isn't as much of an issue.

  Without the hamtronics converter in the recieve chain,
the signal from the DEM preamp/3733 converter is more
than enough.  Now I just have to wait for AO-40 to stop
hiding behind the trees...  :^)

  -al
  WB1BQE





Paul Kupper wrote:
> 
> Hi Al,
> 
> I had similar problems with my Icom IC-475 70cm transceiver. There where several
> holes spread around the whole band. Audio was muted in FM but not in SSB and I could
> not transmit. A adjustment of the PLL cured the problem. The PLL was out of lock at the
> edges.
> 
> 73 de Paul
> HB9OMQ
> 
>   I've noticed that the recieve gain on my ft73r appears
> to take a severe nose-dive between 145 and 146 mhz
> (with the lowest reading right around 145.350 in the
> range of the ao-40 beacon... :^(
> 
>   I had originally noticed this effect with my drake
> converter, which was 250khz off in frequency, and
> attributed it to the drake,   but now my newly modified
> trans-system (which is on frequency) does a similar
> thing.  The "dead spot" occurs at the same 2 meter
> frequency, which would seem to rule out the converter,
> or a null in the antenna gain etc.
> 
> 
> 
>   With the antenna pointed at the daytime sky with
> the transystem in line (and a 24dbi bbq dish),  here
> are the no-signal white-noise s-meter readings I see
> as I  tune across the band on the ft736r.
> 
>   144 mhz -- S9
>   144.5   -- s9
>   145     -- s6.5
>   145.350 -- s0  (the noise gets louder at 145.400 mhz.)
>   145.5   -- s2
>   146     -- s6.5
>   145.6   -- s7
>   147.0   -- s7.5
>   147.5   -- s8
>   147.999 -- s8
> 
>   Can somebody with an FT736r do a similar experiment and
> let me know if they see the same type of 'dead spot'?
> (Prior to today, I've never tried to listen in that particular
> part of the band, so I don't know if this is normal for
> the rig or not...)
> 
>   THanks,
> 
>   -al
>   WB1BQE
> 
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