[TowerTalk] Log Periodics

Tim Makins, EI8IC ei8ic@eircom.net
Fri, 8 Dec 2000 11:35:03 -0000

----- Original Message -----
From: <i4jmy@iol.it>
> An LP antenna has a gain that mostly depends by size (lenght) and
> number of elements of the active cell.
> The active cell, when antenna elements are few and boom is short, is
> generally composed by 2 or 3 dipoles properly phased but closely spaced
> and stated a band, the rest of the antenna out of the active cell is
> practically uninfluent.
> In other words, hardly a small LP can show a better gain than a
> properly designed 2 elements yagi and such LP gain is 2 or 3 dB less
> than a 3 elements yagi.
> On the other hand, a long LP can have consistent gain but still it's
> like to have different monobanders along the boom, each one using only
> a part of it.
> In terms of pure gain/boomlenght, an LP that covers a wide spectrum is
> a quite poor performer compared with a monobander where active elements
> are along the entire boom.

This makes a lot of sense to a semi-technical person like me.  I would thus
be interested to hear comments on single-band log periodics versus single
band yagis, with the same number of elements.  I have recently been reading
a series of articles from Ham Radio magazine by W4AEO; in the May 1973 issue
he constructed some wire 5-element 40m log periodics that he suspended at
50', and claimed very good results for them. In the September 1973 issue he
built vertical monopole log periodics for 40m and 80m, and in the August
1973 issue he built a 17 element for 10,15,20m.

It strikes me that, buck for buck, wire log periodics are possibly???!!!???
the best value for a low budget contest station.  The disadvantage is that 4
supports are needed instead of one.  But, these can be simple guyed masts,
not towers, and no rotator is needed.  If, as has been suggested in recent
posts, the lp has a broad beamwidth, then judicious pointing gives you a
good antenna for pile ups from Europe to the USA or vice versa.

Where are the errors in this suggestion, please, gentlemen ?

Tim Makins, EI8IC

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