From: N1BUG <paul@n1bug.com>
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To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>,
        "600MRG@mailman.qth.net" <600MRG@mailman.qth.net>
Message-ID: <6592833a-cbef-41df-f99a-a55778efde90@n1bug.com>
Date: Wed, 21 Nov 2018 09:41:18 -0500
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Subject: LF: Thoughts on SlowJT9 testing
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Reply-To: rsgb_lf_group@blacksheep.org

First I want to thank Rik for his work trying to bring back the slow
JT9 submodes! I also want to thank everyone who has been helping
with tests. I truly believe these modes can be helpful in making
long distance QSOs on MF and LF. But first we have to prove this
implementation is working as expected and useful.

I think it is difficult to know how well the slower submodes perform
with the testing we are doing so far. It is all very subjective.

If we could find some stations within daytime range of each other,
one of them having the ability to step transmit power in 1 dB steps
I think we could do much better in testing. The idea is to start
with JT9-1 and enough power to ensure decodes at the receiving
station. The transmitting station steps power down in 1 dB
increments, allowing a few cycles at each level to check decoding
and the receiving station. Keep doing this until decoding stops or
becomes intermittent. Record the transmit power.

Switch to JT9-2 leaving power the same. If it is now decoding again,
keep stepping power down 1 dB at a time until it stops decoding and
record that power level.

Switch to JT9-5 and do the same thing.

I think these tests would need to be done more than one day to
ensure results are not affected by propagation or noise level
changes. Any volunteers???

I can listen but I cannot control my transmit power accurately
enough to be the transmitting station for such tests.

***

I am trying to create local tests in a similar manner. I can put a
lot of attenuation between my U3S exciter and the transmitting
antenna, using the receiving antenna as normal. Yesterday I could
get my signal to -27 dB SNR on JT9-1 mode. The problem is I do not
have 1 dB steps to test with. I just purchased a pair of step
attenuators which I hope will do what I want. It will take some days
to receive them and verify the setup works. A lot can go wrong with
a setup like this (unintended signal egress / ingress bypassing the
controlled attenuation path). Careful evaluation of the setup will
be needed. Stay tuned...

73,
Paul N1BUG