Elecraft balun
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I want to use my Elecraft BL-1 1:1 balun on field day.
The balun would serve as center insulator, but the coax line plugged into it is a phasing line. Here is my question: Will the windings on the balun, introduced between the antenna and the phasing line, effectively increase the length of the phasing line? I think it will, and I am wondering by how much to shorten my phasing line to account for it. I think the windings are six to seven inches in length and would imagine the velocity factor to be high. 73 Fred - kt5x K2 # 700 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Fred
You didn't give many details of the antenna but my first thought is use the same type of balun at the feedpoint of each antenna and don't worry about the delay. 73 John WA8KNE Indy wrote: > I want to use my Elecraft BL-1 1:1 balun on field day. > > The balun would serve as center insulator, but the coax line plugged into it is a phasing line. > > Here is my question: Will the windings on the balun, introduced between the antenna and the phasing line, effectively increase the length of the phasing line? > > I think it will, and I am wondering by how much to shorten my phasing line to account for it. I think the windings are six to seven inches in length and would imagine the velocity factor to be high. > > 73 > > Fred - kt5x > K2 # 700 > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Cloud Runner-3
Fred,
If you have a phasing line connected to the antenna, and attach the balun at the junction of your coax and the phasing line, all should be well - you can then use any length of coax from the balun to the shack. BUT - you said your phasing line was coax (which is unbalanced), so I figure you would not want to introduce a balun at a junction of coax to coax (however a unun may be appropriate). If your coax phasing line is attached to a balanced antenna, then I would think you would place the balun right at the antenna center feedpoint. OTOH, if this is one of those special offcenter-fed antennas, you may not want to use a balun at all - at least one of the Elecraft BL1 configuration. If you want to keep RF off the outer shield of the coax, then a ferrite bead balun or a coil of coax is the best solution - place thone of those either at the shack entry point or at a half wavelength interval from the antenna. To answer your direct question, one would have to know the relative impedances of your entire antenna system as well as the lengths of each part of it - even if one knows the transmission line characteristics of the Elecraft balun for a 50 ohm load that is no assurance that the behavior will be similar at other impedance levels. We would have to calculate the feedpoint impedance of the line at the point where the balun is inserted. 73, Don W3FPR > -----Original Message----- > > I want to use my Elecraft BL-1 1:1 balun on field day. > > The balun would serve as center insulator, but the coax line > plugged into it is a phasing line. > > Here is my question: Will the windings on the balun, introduced > between the antenna and the phasing line, effectively increase > the length of the phasing line? > > I think it will, and I am wondering by how much to shorten my > phasing line to account for it. I think the windings are six to > seven inches in length and would imagine the velocity factor to be high. > > 73 > > Fred - kt5x > K2 # 700 > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Cloud Runner-3
Indy wrote:
> I want to use my Elecraft BL-1 1:1 balun on field day. > > The balun would serve as center insulator, but the coax line plugged > into it is a phasing line. > > Here is my question: Will the windings on the balun, introduced > between the antenna and the phasing line, effectively increase the > length of the phasing line? > > I think it will, and I am wondering by how much to shorten my phasing > line to account for it. I think the windings are six to seven inches > in length and would imagine the velocity factor to be high. You said it's a phasing line, so I presume you have a multi-element antenna. In this case, just use a similar balun in the same place on all the elements. That will preserve the phase relationship. If it's just one element, maybe you meant that the additional coax is a matching section. In that case, you can use a 1:1 balun without changing anything -- the impedance transformation required will be the same. -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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