Received-SPF: neutral (google.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org)
Message-ID: <008001c7998e$b3f608c0$34556a58@wgt01>
From: "Gary - G4WGT" <g4wgt@tiscali.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <ySM$64Ar6gTGFw98@g3xaq.demon.co.uk>
Date: Fri, 18 May 2007 21:54:18 +0100
MIME-Version: 1.0
Subject: LF: Re: G3XAQ on 502.0 KHz
Content-Type: text/plain;
	format=flowed;
	charset="iso-8859-1";
	reply-type=response
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Status: O

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" <alan@g3xaq.demon.co.uk>
To: <rsgb_lf_group@blacksheep.org>
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
> alan@g3xaq.demon.co.uk
>
>
>