20 meter shortened loaded yagi

[N5AD]

FOUND IT!! thanks to all who replied.
the arrl website isn't too friendly anymore like it once was, however, once you find the 'door' to the archives, all is good. I found the original article and it looks like it has a bit better explanation of construction. agian thanks and 73

n5ad

[N5AD]

the 1954 article was the original and was reposted in 1961 handbook. fyi

[KM1H]

I'll scan it without bothering to worry about it, which articles and send to where?

Carl

[W9GB]

ARRL has already scanned these articles. WEB LINKS BELOW .. ARRL Members Only.
May 1954 issue of QST magazine -- BOTH are 20 meter antennas - one 2-element, the other 3-element.

A Compact Two Element Beam for Twenty - Page 25
by Carl Getter, W1MU
http://p1k.arrl.org/pubs_archive/33551

The VP (Vest-Pocket) Beam Antenna - Page 27
by Jerry Hemmen, W0VZC and Wyman Pigg, W0QFG
http://p1k.arrl.org/pubs_archive/33561

===
w9gb

[N3OX]

There is a high probability that the 1961 Handbook DIY article is from the earlier 1954 QST articles.

I have a 1964 A.R.R.L. Antenna Book with a three-element, center-loaded, link-coupled yagi in it that is clearly the Vest Pocket yagi of the QST article... the authors' calls are in the caption, in fact.

If you want to build a single-band beam at least, link coupling is an EXCELLENT idea from the standpoint of keeping common mode currents off the feedline.

I've been thinking about experimenting with link-coupled beams for that reason.

[AB4BE]

can someone tell me how the author of the vest pocket beam came to the conculsion that the coil needed to be "42 turns on the coil form" how do you determin this value of inductance when building a beam ? is there a certain reactance value of a coil at a given frequency needed when building a beam? if so what is the ratio of the reactance to frequency ballpark fugire? I know when building a choke you want a reactance ratio of 5-1 or better for a choke. I'm trying to gather information to homebrew a beam and experiment with it by building an antenna.

[N3OX]

can someone tell me how the author of the vest pocket beam came to the conculsion that the coil needed to be "42 turns on the coil form" how do you determin this value of inductance when building a beam ? is there a certain reactance value of a coil at a given frequency needed when building a beam?

Yes, it's critical.

if so what is the ratio of the reactance to frequency ballpark fugire?

It fundamentally depends on the length of the elements. You need to have all of the elements loaded pretty close to resonance, otherwise they don't couple to each other.

When I'm just trying to fiddle with a short parasitic beam in EZNEC, the first thing I do is check one element's impedance, which has a big capacitive reactance, and then I add a coil to cancel that. Then I put in other elements with identical coils. Then I modify the reactance of the coils to get the pattern and SWR I'm looking for.

The same would work if you wanted to do it purely experimentally. Build the driven element and resonate it with a coil. Then build other identical elements with the same coils. Make sure that the coils can be fairly easily modified, because you'll probably have to change them on ALL the elements. Then set up to measure things you want to know... gain, F/B, SWR, and start tweaking coils until it works the way you want it to.

73,
Dan

[VU2CDW]

FOUND IT!! thanks to all who replied.
the arrl website isn't too friendly anymore like it once was, however, once you find the 'door' to the archives, all is good. I found the original article and it looks like it has a bit better explanation of construction. agian thanks and 73

n5ad

Sir,

Can you send me this article- my e mail ID is good on QRZ- I can not open the ARRL page given by W9GB

Looking for making a better antenna design- BTW I possess a short loaded beam for 20 mtr band but of late it has started giving trouble

73
VU2CDW