Yes, Gary, I think it's me on the grabber at G3YXM. Do any of the
grabbers capture the actual audio so I can listen to my CW note?
72,
Alan
In message <008001c7998e$b3f608c0$34556a58@wgt01>, Gary - G4WGT
<[email protected]> writes
Congratulations Alan,
I can't see anything of you up here in Lancashire but there is a signal
keeps showing on Dave's (G3YXM) 500 KHz grabber on 502.000 KHz, could
it be you ?
Go to :-
http://www.wireless.org.uk/grab/
73
Gary - G4WGT - IO83qp
http://myweb.tiscali.co.uk/wgtaylor/
Web site updated 07/05/2007
----- Original Message ----- From: "Alan Ibbetson"
<[email protected]>
To: <[email protected]>
Sent: Friday, May 18, 2007 9:38 PM
Subject: LF: G3XAQ on 502.0 KHz
I have today got my 500KHz station on the air. I am located near
Canterbury, locator JO01md. Here are some technical details.
The aerial is an inverted-L with a 15m vertical and a 35m horizontal
section. This was originally my top band aerial. I have added a 1mH
end loading coil (460 turns of 0.5mm enamelled wire on a 38mm OD white
poly waste pipe occupying 275mm of winding length). The loading coil
is 14.7m from the far end. I trimmed the 14.7m for resonance at
502KHz because I wanted a roughly resonant aerial to simplfy feeding,
but from the way the resonance wanders about as the wind blows I'm
not convinced this was such a great idea. Standard formulae suggest
this aerial has a radiation resistance of almost exactly 1 ohm.
The aerial is end fed against a reasonable earth system comprising a
20m x 20m mat of stock fencing with the sections crimped together. I
also have about twenty 30m radials. On top band I can work east coast
US easily with 100W and I have worked VK and W6 with 400W. I was
quite surprised (well, p****d off) to measure the return loss of the
aerial system at 502KHz as 22dB. This suggests the input resistance
is a little over 40 ohms, almost all of which is earth loss
resistance! So much for my "killer" top band earth mat.
I am using a link-coupled series tuned ATU with a loaded Q of 7
placed at the base of the aerial to get the SWR very close to 1:1.
The 2:1 SWR bandwidth of the aerial system is less than 2 KHz (1KHz
either side of resonance).
I have built a QRP transmitter using an ECL82 triode pentode, as
popularised by G0UPL and others. Output is 4 watts. Cathode keying
with a small choke and 0.5uF capacitor gives a clean 3msec rise and
fall on the keying waveform, but the un-neutralised PA has a backwave
that is only 40dB down. I've added a "half wave" filter after the pi
tank in an effort to avoid QRMing MW broadcast stations. Harmonics
are over 50dB down.
The main HF station FT1000MP Mk5 seems just OK on 500KHz. Band noise
is S 1 in a 500Hz passband on the meter.
The rig is crystal controlled on 502.0KHz, so you know where to find
me! All I need now is some stations to work. "Can you hear me,
Mother?".
--
Cheers,
Alan G3XAQ
[email protected]
--
Cheers,
Alan G3XAQ
[email protected]
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