With all due respect "weak signal" does not always equal "low power" (most of
the time, sure, but a signal can be pretty weak even at 1.5 KW in poor
conditions).
Can you supply actual data to support your supposition that "high power usage
is a common behavior" in the PSK areas (i.e. Something OTHER than just what is
based on what you see on the spectral display)? Case in point here, the last
time I worked PSK31, I received a severely worded email from another op who
probably had the best of intentions dressing me down for "running too much
power" saying that he could "tell I was pushing close to legal limit"based on
"what he saw" and going on about how rude I was being, etc... I politely
responded with a picture of my station at that time which was an Elecraft KX3
running on a battery on my picnic table set to 0.5 watts into a home brewed
vertical antenna next to an IMD meter monitoring my outgoing signal.
The saying "a picture paints a thousand words" isn't always applicable to what
you see on the waterfall. A lot less ops are "running power" than current
common perception seems to state.
Again, this is with all due respect.
Jim S.
> On Feb 18, 2017, at 2:12 PM, Игорь Ч <[email protected]> wrote:
>
> Hello All,
>
> There is simple answer why users prefer operate JT65 on the overloaded HF
> bands while there is underused JT9 subband.
> .
> Anyone from DX location, let's say for instance from New Zealand, have
> frequently met scenario where multiple signals coming back to his CQ call.
> .
> Due to the nature of JT9 protocol&modulation neither one of two JT9 signals
> on the same frequency will be decoded in most cases, things getting worse if
> there are more than two signals on the same frequency. To make QSO possible
> experienced JT9 users call DX stations with frequency split and DX station in
> response has to use split operation or frequency hopping.
> .
> Now one could imagine if there is propagation open between Europe and New
> Zealand and at least 10 operators calling one DX station using frequency
> split, this way JT9 spectral benefit versus JT65 is almost eliminated.
> .
> Multipass decoding will only work if at least one JT9 signal is decoded on
> the frequency, otherway there is nothing to subtract.
> .
> Now back to JT65 HF subband capacity, for evenly distrubuted JT65 signals
> between -01 and -26dB SNR to the Gaussian noise, maximum JT65 current subband
> capacity is around 100...110 decoded signals if tested with 200 simulated
> signals in the .wav file. These decoded signals have SNR to the Gaussian
> noise in range from -01 to -14 dB, week signals gone unless DX operator using
> 1kW power to try getting through.
> .
> For last 45 days number of JT65 HF users raised 25% up, and it is now usual
> event to get 35..40 decoded JT65 messages for single RX interval. Going with
> such increase rate monthly we will get out of the current JT65 HF bands
> capacity within 6 months, and similar to PSK modes, high power usage will
> became as common behaviour.
> .
> Hence there no other way to save HF JT weak signal communication but an
> increase of the occupied bandwidth and it should be good idea to act now,
> until we got to QRO JT communication instead of the weak signal one.
> .
> 73 Igor UA3DJY
>
>
>
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