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LF: Re: Re: Re: 500 / OLB test-sig...

To: <[email protected]>
Subject: LF: Re: Re: Re: 500 / OLB test-sig...
From: "Tom Boucher" <[email protected]>
Date: Fri, 3 Aug 2007 12:38:56 +0100
Delivered-to: [email protected]
References: <005001c7d3fe$e4786d80$6400a8c0@oem17oeylz9on8> <001901c7d42b$e6fbeaa0$86048351@w4o8m9> <00a001c7d43c$f4180690$0a7ee150@o> <[email protected]> <[email protected]> <003001c7d4d1$fcaf0390$db3a383e@Tom> <000101c7d5a4$5f527220$4e69e150@o> <008901c7d5b0$eea7c040$a17d383e@Tom> <003801c7d5ba$56f3cc80$6401a8c0@JAYTERMINAL>
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Most interesting Jay. Your 136 installation looks extremely well engineered. The loading coil/variometer looks almost identical to the one I made for 136, without the gears and motor. I used an 1100' end fed wire when active on that band!

73, Tom G3OLB

----- Original Message ----- From: "Jay Rusgrove" <[email protected]>
To: <[email protected]>
Sent: Friday, August 03, 2007 11:37 AM
Subject: LF: Re: Re: 500 / OLB test-sig...


Tom

That's a lot of wire in the air...congratulations! Usually the more the better but in this case it sounds like too much. One approach would be to trim the horizontal top wire of the L to get the +j18 close to 0. Then it would be a matter of matching the R to 50 ohms. You could use a smaller version
of the tapped transformer shown near the bottom of this page:

http://www.w1vd.com/XNStxantenna.html

If a low SWR is important to you across the band you may want to shorten the antenna beyond the j0
point and add a variable inductor in series with the vertical wire.

Jay W1VD / WD2XNS



----- Original Message ----- From: "Tom Boucher" <[email protected]>
To: <[email protected]>
Cc: "Finbar" <[email protected]>
Sent: Friday, August 03, 2007 5:30 AM
Subject: LF: Re: 500 / OLB test-sig...


Rog (and others) - thank you for this. You may, or may not, be interested in the matching
arrangement for my antenna.

The antenna is an extension of my 160 metre inverted 'L' which has an 80' vertical section to a tree on a 20' bank - the effective height may therefore not be as much as 80'. This antenna sits on 19 radials which are 60 - 100' long and are either buried or lying on the ground, in order to act as
trip wires for my XYL when she trespasses on my antenna area.

An additional 358' has been added to this antenna to make the total quarter wave length of 492'. This added wire zig-zags for 50' or so then is largely in a straight line held up by 3 further tree
halyards and ends up about 30' above ground.

This antenna with no matching showed a minimum VSWR at 506KHz of 2.5:1 and impedance of 22 + j18. By empirical means (!) I established that a parallel capacitance of some 6000 pF brought the SWR to a low figure but, not unexpectedly, took the resonant frequency up to 521KHz; an L-section using part of the antenna's self-inductance. To bring the antenna back down to 502KHz, I added a small
inductance between capacitor/coax and the base of the antenna.

The final values were 9 micro-Henrys (22 turns on 1'' dia) and 6,600pF (3 x 2,200 pf 1000v
polypropylene) giving 1.1:1 @ 503 KHz, 50 + j10.

I was surprised at the high value of capacitance needed to resonate this antenna and am not sure how you go about calculating the necessary values as these were established by trial and error. Perhaps
there is an academic out there who can tell me!

73, Tom
G3OLB
----- Original Message ----- From: GW3UEP
 To: [email protected]
 Sent: Friday, August 03, 2007 8:55 AM
 Subject: LF: 500 / OLB test-sig...


 Tom,
 Hrd your test-loop ydy - steady S7 on meter - ur tidying up has wrkd!
Ur closing the gap on Mike [S9/40mls via Preseli mountain] over the ~90mls part sea-path bn us.
 Hope to improve ant nxt wk, jobs permitting.
 Rog.

----- Original Message ----- From: Gw3UEP
 To: Tom Boucher
 Sent: Monday, July 30, 2007 2:18 PM
 Subject: Re:

 Tom - what hve u done?  Fantastic sig nw - on meter S5/6...





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