[600MRG] Thoughts on SlowJT9 testing

[jrusgrove at comcast.net]

Paul

Don't overlook testing at night as well. From the tests John W1TAG and I did years ago some software 
that worked great during the middle of the day fell flat on it's face with nightime static and 
signal fading. The daytime tests provided an accurate portrayal of sensitivity while nightime tests 
indicated static immunity and fade recovery abilities.

Jay W1VD


----- Original Message ----- 
From: "N1BUG" <paul at n1bug.com>
To: <rsgb_lf_group at blacksheep.org>; <600MRG at mailman.qth.net>
Sent: Wednesday, November 21, 2018 9:41 AM
Subject: [600MRG] Thoughts on SlowJT9 testing


> 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
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