[TowerTalk] Telrex 40 M Beam restoration
Michael Tope" <W4EF@dellroy.com
Wed, 10 Jan 2001 03:22:28 -0800
---- Original Message -----
From: "Tom Rauch" <firstname.lastname@example.org>
To: "TowerTalk" <email@example.com>; "Chris Kepus" <firstname.lastname@example.org>; "Michael Tope" <W4EF@dellroy.com>
Sent: Tuesday, January 09, 2001 3:35 PM
Subject: Re: [TowerTalk] Telrex 40 M Beam restoration
> Hi All,
> This thread fits perfectly with the radials over the beach thread, and
> the Hex beam gain. It fits with the B&W dipole and GAP vertical
> stuff also. The quad fits in, as do the bad opinions about the G5RV.
> The CFA is this taken to an extreme, of course.
> We all love our antennas, and we want to believe in magic.
> Factually, things often aren't as "rosy" as they appear.
I want to love my 80 meter dipole at 27 feet, but it doesn't seem to get the message,
especially on 80 meter longpath. As they say, you can't fool mother nature.
> > Don't lose heart over my comments. Even if the 40M329 has some weakpoints,
> > I suspect that between some computer optimization work with the dimensions
> > and some mechanical modifications to the element design, you'll be able to
> > come up with a real nice antenna. This antenna is pretty old, so it was
> > probably designed before people were using NEC and knew about element
> > taper corrections.
> ....and it was done before people cared if baluns really worked
> correctly, and when there were no other large yagi's for 40 meters
Perhaps I should have qualified my comments on 40M329 by stating that there is a
possibility that by the time you fix everything electrically and mechanically that
you might have had an easier time starting from scratch homebrewing a 40 meter
> Just the sheer size of the antenna is worth 20 dB, like it is in a
> large poor (30-40%) efficiency Rhombic.
Thats what I thought when I first saw KS8S's stacked 40M329's. The on-the-air reality
seemed more like minus 20dB.
> > Jim Lawson, W2PV came out with his papers on the effects of element taper,
> > he ended up changing the dimensions on his Wilson 3 element 40 meter yagi
> > elements by something like 12" each to make it really play.
> By "really play", the gain probably increased 1 or 2 dB. The work is
> what made it seem like more. The only big change would be in null
> depth, and as almost everyone who owns a Hex beam knows
> higher F/B always means at least 3-4 dB gain over what it really is.
You would have to ask Doc to be sure, but I think he was talking about the
pattern. I believe the taper corrections improved the F/B considerably. Dunno
anything about the Hex beam other than I see it advertised in QST. Sounds
like it is like the fractal antenna. Lots of hype, but very little in the way of apples
to apples gain comparisons with other antennas.
> > booms, and masts. With an Excel spreadsheet, and the taper schedule from
> > the 40M329, you can probably figure out where it will fail, at what wind
> > speed it will fail, and how to improve it.
> On mine, the elements constantly broke right at the point where
> they exited the .058 wall 1-1/2 inch tubing and became that paper-
> thin tubing. Every time the wind hit 50 or 60 mph, an element
> I've never had any boom or insulator failures, but then the elements
> in mine (and boom) have always been strutted. The only thing I
> kept was the boom and the elements out to the first taper point.
> The rest is all new 6061 stuff.
I saw the picture of your rotating tower with the 3 element 40 meter
yagi on contesting.com - very impressive looking setup.
> I think the antennas with double wall tubing are more reliable, and
> it's easy enough to check that out. But after all the headaches I
> went through I'd never put one up with the thin single-wall tubing
> that has the strength of a wet toilet paper roll.
> 73, Tom W8JI
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