[Antennas] Re: [dx-list] Yagi height and DX

2002年4月13日 17:52:40 -0400

Geez, George, you're everywhere! I've been reading your postings on QRP-L
for years! Ooops, the secrets out now! Is there room on the DX reflector
for QRP'rs?
Does anyone have the dimensions for this triband yagi? Seems folks are
confused about what I actually modeled. I modeled some handy dandy "I have
a dream" big monobanders that I had already analyzed just to see the
relative difference of height on each band. Like I said, the 20m yagi was a
5 element monster, probably not quite the performance you would get on a tri
band yagi.
I'll be glad to attempt to model the tribander if someone could give me the
element material, element diameters, element spacing, taper schedule and
element lengths as well as any loads (like inductors). I'll be glad to
report back with my results.
Mark, AA4MF
----- Original Message -----
From: "George, W5YR" <[email protected]>
To: "James Nipper" <[email protected]>
Cc: <[email protected]>; <[email protected]>;
<[email protected]>; "John Geiger" <[email protected]>; "Mark
Fancher" <[email protected]>
Sent: Saturday, April 13, 2002 4:31 PM
Subject: Re: [Antennas] Re: [dx-list] Yagi height and DX
> Jim, after re=reading Mark's posting, I wonder if what he stated is really
> what he meant.
>> In any event, the improvement in gain is pretty marginal, and although the
> decrease in the so-called "take-off angle" looks impressive, you have to
> look at all aspects of the predicted pattern, not just that one aspect of
> the elevation pattern.
>> The practical aspects, other than the cost, of going from 20 ft on the
> tower to 40 ft could be substantial, since it could mean the difference
> between a short tower supported by the house and the need for a fully
guyed
> structure or a much heavier self-supporting tower. There are also
> consequences as to antenna access - climbing 40 ft is more daunting to
some
> than going up 20 ft.
>> But, on the other hand, that 40 ft tower could support some pretty good
> wire antennas!
>> Trying not to nit pick, but there seems to be more here than just the cost
> of two tower sections and the relatively small gain and pattern changes.
>> 73/72/oo, George W5YR - the Yellow Rose of Texas
> Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
> Amateur Radio W5YR, in the 56th year and it just keeps getting better!
> QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
> Icom IC-756PRO #02121 Kachina 505 DSP #91900556 Icom IC-765 #02437
>>> James Nipper wrote:
> >
> > Mark, with all due respect, I disagree with your conclusions !!! The
> > extra gain noted (especially on 20M) , plus the improved take-off angle,
> > although not **huge**, would still seem to be worth the very little
extra
> > expense of two tower sections !!
> >
> > The real experts on this list can now chime in, but unless I am wrong,
your
> > data looks valid, but I don't quite understand your conclusions !!
> >
> > Anyhow, good Dx to You !!