From: Rik Strobbe <rik.strobbe@kuleuven.be>
To: "rsgb-lf-group@groups.io" <rsgb-lf-group@groups.io>
CC: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>,
        "600MRG@mailman.qth.net" <600MRG@mailman.qth.net>
Thread-Topic: [rsgb-lf-group] SlowJT9 update (v0.9.15.0)
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Date: Fri, 1 Feb 2019 20:19:43 +0000
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Subject: LF: Re: [rsgb-lf-group] SlowJT9 update (v0.9.15.0)
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Hello Les, all,

WX permitting I will be QRV on Saturday (here in Europe) starting 5h30 UTC.
I will monitor JT9, JT9-2 and JT9-5 all night.

73, Rik   ON7YD - OR7T

________________________________________
Van: rsgb-lf-group@groups.io <rsgb-lf-group@groups.io> namens Les Peters, N1SV <n1sv@comcast.net>
Verzonden: donderdag 31 januari 2019 23:38
Aan: rsgb-lf-group@groups.io
CC: rsgb_lf_group@blacksheep.org; 600MRG@mailman.qth.net
Onderwerp: Re: [rsgb-lf-group] SlowJT9 update (v0.9.15.0)

I plan to be on 475 Friday and Saturday so yes would like to try!

Les, N1SV
> On Jan 31, 2019, at 5:04 PM, Rik Strobbe <rik.strobbe@kuleuven.be> wrote:
>
> Hi Paul, all,
>
> SlowJT9 vs WSJT-X: as I mentioned it was pure luck that SlowJT9 performed better that night.
> But as the only reason I can think of is a small timing difference between both it might be worth to time-shift the incoming audio by small steps, then try to decode each step nd take a "best off" as result.
>
> Frequency conversion: I will investigate that furher. Anyway, if I implement this it will be optional (can be switched off).
>
> For the moment WX is rather bad here, so the antenna is lowered. But in a few days, when the  WX permits I would like to try some TA QSO's on 475 kHz using the slower JT9 modes.
> Any takers at the other side of the pond?
> I worked Paul, N1BUG and Eric, NO3M, mid February last year.
>
> 73, Rik  ON7YD - OR7T
>
> ________________________________________
> Van: rsgb-lf-group@groups.io <rsgb-lf-group@groups.io> namens N1BUG <paul@n1bug.com>
> Verzonden: donderdag 31 januari 2019 21:43
> Aan: rsgb-lf-group@groups.io; rsgb_lf_group@blacksheep.org; 600MRG@mailman.qth.net
> Onderwerp: Re: [rsgb-lf-group] SlowJT9 update (v0.9.15.0)
>
> Hello Rik, all,
>
> Two comments, see below.
>
>> Interestingly Rik's SlowJT9 which was running in parallel,
>> managed to decode a couple of more transmissions than WSJT-X."
>
> I have seen this work both ways. Sometimes SlowJT9 will decode
> something WSJT-X does not. Other times WSJT-X will decode something
> SlowJT9 does not. Usually they are equal.
>
>> 2. Add optional internal frequency conversion to allow reception
>> at higher frequencies I have done some preliminary tests (based
>> on the code snippet Wolf, DL4YHF, sent me) and it seems to work
>> fine. But I am not sure that it will be very useful as frequency
>> conversion will not increase the usable frequeny range, but just
>> shit it. Eg: now JT9-10 can be received from 100 Hz to 415 Hz
>> audio. After USB downconversion with a 1 kHz carrier the range
>> will be 1100 Hz to 1415 Hz. The only reason I can think of to
>> want frequency conversion is if you use a fixed frequency (ofen
>> 800Hz) CW filter, so you can fit the JT9-5 or JT9-10 frequency
>> range into the filter passband. But this downconversion requires
>> a Hilbert transform (90 degrees all pass filter) that never can
>> be perfect and this will cause some distortion (in particular at
>> the lower and of the passband). So before I start the effort to
>> implement this in SlowJT9 I would like to know if there is an
>> audience for it.
>
> I think there is justification for it on 2200m if it comes without
> too high cost in lost sensitivity. Some people cannot easily tune
> antennas down to 136.4 or so. But if we operate at 137.x then
> listening stations must adjust their receiver because the usual
> 136.000 'dial' frequency will not allow receiving JT9-5 or JT9-10.
> This is not the usual setting for most who also want to monitor WSPR
> or other modes. For pre-arranged QSOs this will not matter, but for
> calling CQ it is good to operate where we can be heard without
> special receiver settings.
>
> However, if this feature comes with significant loss of decoding
> sensitivity, then I would vote to stay as we are.
>
> 73,
> Paul N1BUG
>
>
>
>
>
>


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