Mal,
Can you explain your RX equipment, pse. Perhaps you can even see/hear what
others just can decode? Is your TX antenna your RX antenna as well? What about
your local noise level? Would be interesting for me, since you gave me 569 in
our QSO...
Stefan/DK7FC
________________________________
Von: [email protected] im Auftrag von mal hamilton
Gesendet: Sa 23.01.2010 22:07
An: [email protected]
Betreff: Re: LF: JT4A simple guide?
There cannot be a time when JT4 or WSPR will be received and not QRS because
the trace is always visible long before a data decode. There has never been a
case of an INVISIBLE trace and a data decode. The signal trace is always
VISIBLE and therefore if KEYED would convey the transmitted message.
G3KEV
----- Original Message -----
From: Roger Lapthorn <mailto:[email protected]>
To: [email protected]
Sent: Saturday, January 23, 2010 8:15 PM
Subject: Re: LF: JT4A simple guide?
Mal,
There will be times when this may be true, but modes like WSPR and, I
expect, JT4A will get through when signals are extremely weak when CW simply
would not.
Here's an idea: why not turning your ERP down to 1mW for a few weeks and
see how you get on?
73s
Roger G3XBM
On 23 January 2010 19:32, mal hamilton <[email protected]> wrote:
Obviously not reading recent postings about no decodes from others
although the signals are visible, like I said these signals are not onljy
visible with me but audible so why complicate matters, just send qrs or cw in
the first place.
Some one even mentioned DUMMIES, there are a lot of these about.
Dummies alias Appliance operators
The word is ill-informedtry
g3kev
----- Original Message -----
From: Roger Lapthorn <mailto:[email protected]>
To: [email protected]
Sent: Saturday, January 23, 2010 7:17 PM
Subject: Re: LF: JT4A simple guide?
Mal informed.
On 23 January 2010 18:52, mal hamilton <[email protected]>
wrote:
I still see these data signals as a waste of time since had the
carrier been keyed I could read them 100% without having to wait for the right
circumstance to get a decode, no need for level 2 demodulation.
There are several traces now visible but only an odd
decode!!!!!!!!!!!!!!! Try a QRS or CW QSO if you need an immdediate report.
These signals are audible with me.
g3kev
----- Original Message -----
From: Roger Lapthorn <mailto:[email protected]>
To: [email protected]
Sent: Saturday, January 23, 2010 4:52 PM
Subject: Re: LF: JT4A simple guide?
Ok, fully understand Andy. Jim G7NKS is sending JT4A but
I'm not getting any decodes yet.
Roger G3XBM
On 23 January 2010 16:38, Andy Talbot
<[email protected]> wrote:
After posting that, I realised the JT4 PIC/DDS beacon code
is designed for 100% duty cycle operation, viz JT4, CW + carrier, which is a
bit antisocial (certainly the wide bandwidth CW bit). And more importantly, as
my PA is a low efficiency clas AB linear one - enough said...
To adapt for low duty cycle would need the PIC code
changing, so will put the idea on hold unles there is a real demand. For a
beacon, WSPR has more to offer anyway.
Incidently, WSPR and JT4 are the same mode anyway, albeit
with a bandwidth change from 1.46 to 4.375Hz with a resulting 4.75dB reduction
in S/N. The coding and demodulation are all the same, so this bandwidth
difference should be directly detectable between the two modes. The differing
message contents wont affect the efficiency, its the added error correction ,
sync and modulation that matters - and they use the same algorithm.
Andy
www.g4jnt.com <http://www.g4jnt.com/>
On 23 January 2010 14:43, Roger Lapthorn
<[email protected]> wrote:
Thanks for this help Andy.
I'd not like to derive others of your valuable 500kHz WSPR
beacon, but could you beacon in JT4A at certain pre-arranged times or days
perhaps? If JT4A looks like offering the possibility of really weak signal QSOs
to people like me running flea-power then I'd like to explore the mode some
more and having a reliable signal to test with initially would be useful. I am
sure there will be others who would value this too.
73s
Roger G3XBM
On 23 January 2010 14:26, Andy Talbot
<[email protected]> wrote:
AFAIK The is no 'simple guide' JT4x was never originally
going to be one of Joe's supported modes, although after our extensive use on
uWaves it certainly is now. JT65x was the more popular and documented code,
being heavily used for EME on 144 / 432 / 1296MHz, with JT4x just one of
those included in the WSJT suite to 'try out' If you download and read the
WSJT users guide and other supporting files, there's all you need to know to
get it going is in there.
http://www.physics.princeton.edu/pulsar/K1JT/WSJT_User_600.pdf
http://www.physics.princeton.edu/pulsar/K1JT/wsjt.html
http://www.physics.princeton.edu/pulsar/K1JT/JT2_JT4.TXT
Its still debatable as to whether JT4 is better or worse
than JT65x, but at least it does have the options of being available in a range
of bandwidths / tone spacings making it usable from DC to red light.
(Although I think I've only ever come across A, D and G being used respectively
on LF, HF and uWaves) There's probably only a fraction of a dB in it and
both are, as far as I can ascertain, only a dB or two away from the Shannon
limit. [Which knocks spots off CW or any fuzzy mode, as well as straight PSKnn
without error correction]. Wolf has a similar signalling efficiency, but
unfortunately is wider, needs a linear TX to avoid being too wide and seems
less user friendly.
A year or so ago we (the microwave community) wanted
something for use on 1.3GHz and up to 10GHz or beyond. JT4G, the widest spaced
varient of them looked suitable. After some prompting, Joe was persuaded not
to abandon that mode, and in fact he modified the code to enhance the decoder
routine so the wide spaced version would be decoded with the same S/N as JT4A.
We discovered just how good the mode was, even under severe rainscatter
conditions where each tone was spread out to 200Hz bandwidth (tone spacing in
JT4G is 315Hz for 1kH zwide overall, so this rain scattered signal still had
discrete tone energy).
There are now two microwave beacons that transmit JT4G
waveforms, the 10 and 2.3GHz ones in Dorset GB3SCX and GB3SCS www.scrbg.org
<http://www.scrbg.org/> and now GB3CSB on 1.3GHz from central Scotland
http://www.rayjames.biz/gm4cxm/id14.html Other will follow before long as it
is quite an easy mode to generate from a simple PIC keyer provided accurate
timing information is available to keep it synched.
My beacon engine - the one that currently drives the
503.7/503.85 signals - can give JT4A immediately just by reprogramming the PIC.
Would there be any interest, bearing in mind both the WSPR and "5MHz type"
waveforms will be lost for the duration?
Andy
www.g4jnt.com <http://www.g4jnt.com/>
This email has been scanned for damaging side-effects by
the health and safety police, is guaranteed to contain no substances hazardous
to health, but may contribute to dissolving the nether and polar regions
On 23 January 2010 13:48, Roger Lapthorn
<[email protected]> wrote:
Having looked on the WSJT website there is little (no?)
reference to JT4A in the help files. I assume it is similar to modes like JT6M
which I have managed to receive in the past on 50MHz but never tried TXing.
Can someone point me in the direction of a "JT4A for
Dummies" guide, or something similar that I might understand, please?
73s
Roger G3XBM
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