Signal does drop when you transmit multiple signals.
It is deliberately backed off in WSJT-X because of the way power is consumed.
e.g. Two 25W signals will put out 100W. So where you may transmit 100W with 1
signal you'll have to drop 6dB and transmit two 25W signals instead which will
still take 100W.The individual signals are reduced automatically by
P/(Nslots^2) so 3 slots is 9.5dB down and 4 is 12dB down.
de Mike W9MDB
On Sunday, May 13, 2018, 5:35:01 PM CDT, Tsutsumi Takehiko
<ja5...@outlook.com> wrote:
Hi Dave,
I do not have any intention to hijack your mail but I hope you allow me to
state again that we should not concede "signal would drop around 12dB when 3
channels were used" as weak signal favorites.
By my simple spread sheet calculation, we can achieve 4-3dB degradation range
at 5 channels maintaining symbol length longer than 64mS, which is sufficient
for multi-path interference guard under shortwave ionospheric propagation
model, with simple single carrier TDM frame architecture. Keep in mind that
RTTY or PSK31 symbol length is around 22mS - 32mS. Thus, I do not see any
significant reasons to adopt FDM frame architecture.
Regards,
take
de JA5AEA
On 5/13/2018 1:53 AM, David Birnbaum wrote:
Hi Joe
Bands were not helpful this morning, but I did notice something that might be
important.
Aside from the QSB there appears to be some variation in your transmitted
signal even if only one frequency is being used. I would see K1JT call CQ and
then the response with a RR73; K2xxx -yy <K1JT> response would be down about 3
dB. I did see that the signal would drop around 12 dB when 3 channels were
being used by the Fox which is expected but I did not expect to see a response
with a single channel being down relative to a CQ.
davek2lyv
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