LF: Re: [600MRG] Thoughts on SlowJT9 testing

[N1BUG <paul@n1bug.com>]

Hi Jay,

Yes of course night time testing is needed also. I am only thinking
first steps to establish some kind of base line for sensitivity.
I've seen some conflicting hunches so far based on night time one
mode beaconing. I think there is a tendency to take software SNR
numbers a bit too literally, especially when comparing to a
different mode.

73,
Paul



On 11/21/18 10:13 AM, jrusgrove@comcast.net wrote:
> 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@n1bug.com>
> To: <rsgb_lf_group@blacksheep.org>; <600MRG@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