|
Andy, Rik
Been running a doubler for WSPR at WE2XGR/2 for the
past couple weeks. Linear exciter > doubler > push pull Class D amplifier.
So far I've tested it on WSPR, MFSK, Domino EX, Thor, Olivia and RTTY with good
results. Requires roughly 0 to +10 dBm at input...sin or square wave.
The circuit could no doubt be simplified and/or
improved. It was literally thrown together with previously used components
already sitting out on the bench...to prove the concept.
Jay W1VD WD2XNS WE2XGR/2
----- Original Message -----
Sent: Wednesday, January 27, 2010 4:56
PM
Subject: Re: LF: RE: 500 kHz JT4A
I was looking at driving push-pull transmitters from fundamental drive
signals quite recently.
How about a frequency doubler? The output doesn't have
to have 1:1 mark-space ratio as it only clocks a flip-flop.
And simple doubler can consists of a delay line (CR network with around
0.5us time constant) followed by a squarer to give a resulting waveform
shifted in phase from the 500kHz drive signal. Then apply this
one, along with the original to a two input XOR gate whose
output will then consists of a 1MHz train suitable for dividing by 2 for a
perfect 1:1 squarewave drive.
Andy www.g4jnt.comThis 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 2010/1/27 Rik Strobbe <[email protected]>
Gary,
the SNR values over the last hour or
so varied between -2 and -13dB.
Assuming a -24dB limit and your
current power (50W) anything above 5W would provide solid copy and 0.5W
occasional copy.
Impressive.
I should get QRV on JT4A, but I
blew the transformer of my "straight" 100W PA, and my 250W G3YXM-clone
PA needs 1MHz drive (at TTL level), so I cannot use that with my HF/500kHz
transverter.
73, Rik ON7YD -
OR7T
Verzonden: woensdag
27 januari 2010 22:03
Aan: [email protected]
Onderwerp: Re: LF:
RE: 500 kHz JT4A
Rik, & Andy,
Thanks for your report & comments & Andy for answering Rik's
query.
Well there has not been any response to my CQ call so I will change the
text to beacon & continue to see if there is a report from further
afield.
If you want to try for a weak decode I can reduce the power for a short
period say 30 minutes, my power is 50 watt RF (200 mW ERP) at the moment so
in view of your good report I could take it down to 10 watts RF.
Let me know.
73, Gary - G4WGT - IO83qo
2010/1/27 Andy Talbot <[email protected]>
-24dB S/N (2.5kHz ) is usually guaranteed
Andy www.g4jnt.comThis 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 2010/1/27 Rik Strobbe <[email protected]>
Gary,
solid copy here, SNR -5 to
-7dB.
But the signal is clearly audible,
CW would be armchair copy.
Any idea down to what SNR values
JT4A produces a usable decoding ?
73, Rik ON7YD -
OR7T
LF,
Running JT4A this evening on 503.600 kHz, dial frequency 502.300
kHz USB.
73, Gary - G4WGT -
IO83qo
|
