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Re: Cross Boom



I participated in the original discussion of this many months ago and I
think that the article referred to is being "under quoted". It is NOT just
mounting the antenna in the "X" configuration. That is NOT what the article
says. It also REQUIRES careful placement of the driven element distance to
the cross boom. Doing the "X" alignment is a "necessary" but not
"sufficient" condition to get the results that the article claimed.

Two conditions have to be met:

1. X configuration
2. Distance from the feed to the cross boom

Many people have testified anecdotally to the metal cross boom working. The
work of the WA5 in the article made careful measurements. I wouldn't
hesitate to try it, but follow the instructions in the article assiduously.
The half-baked representations I have seen discussed lately are unlikely to
produce the "tenths of dB" performance hit described by the original author.

My comments aren't to discourage the metal cross boom approach. The article
convinced me. However, let's not forget the second requirement.

...hasan, N0AN

p.s. every 0.1 dB matters, at least before the 1st RF amp....start adding
these "inconsequential" losses to the NF of your first RF amp and watch your
MDS drop.

Here a tenth, there a tenth, pretty soon you're talking about "real" losses.
(thankyou Everett Dirksen)

----- Original Message -----
From: "Jon Ogden" <na9d-2@speakeasy.net>
To: "Franklin Antonio" <antonio@qualcomm.com>; "Art Goldman"
<artg@comcast.net>
Cc: <amsat-bb@AMSAT.Org>
Sent: Thursday, March 06, 2003 6:39 AM
Subject: Re: [amsat-bb] Cross Boom


> While fiberglass is "ideally" the correct material, many, many people
spend
> far less money and use metal cross booms with little to no signal
> degradation.
>
> Kent Brittain, WA5VJB, determined that when mounting a CP yagi in an X as
> opposed to a + that the distortion of the pattern is minimal - on the
order
> of tenths of a dB.
>
>
> Is a tenth of a dB, shipping hassles, etc. worth all that much?
>
> 73,
>
> Jon
> NA9D


----
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