Re: [amsat-bb] AO-27 better signal than AO-51.

[AA2AE <dxdx@xxxxxxxxxxxxx>]

Pat,

The difference between 600mw and 500mw is less than 1db. Assuming the
antennas on both satellites have the same configuration, I think it's safe
to say that the difference in received power would be very small.

Since the altitude of both satellites are within 100kms, the difference in
free space path loss doesn't seem to be a big factor either. It would take
about 1.4 times the altitude to equal a 3db difference in dowlink signal
strength.

If there's something other than free-space path loss and power ratios that
would cause the difference between AO-51 and AO-27, I'm not sure what they
are. I would have to agree with you that the sensitivity of the HT might
fall off at certain freqencies. As for the antenna gain falling off with the
Arrow, I would guess anything is possible.

It could be the S-meter itself at different frequencies. It may read 2
S-units different between the two satellites, but what's the average
signal-to-noise ratio difference between the two birds on similar passes? I
wouldn't rely completely on the S-meter.

Interesting topic.

73, Tony - AA2AE


> Hi All,
>
>   I've noticed that I can hear AO-27 better than AO-51.  Has anyone
> else noticed that?  I've noticed this when AO-51 was set at 600mw
> output.  AO-27 is set at 500mw.  I get better signal strengths from 27
> than 51.  The most I've seen 51 at "normal" power is S3 where AO-27 is
> S5 on a similar pass.  I'm using an Arrow with a Kenwood TH-D7A.
> Could it be the radio is "more deaf" at 435.3 than 436.8?  I can't see
> the frequency being different enough for it to be an antenna tuning
> issue.
>
> 73 de Pat --- KA9SCF.
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