Excellent summary, Bill.
That is entirely in agreement with the calculations I was doing back in 2004. I
figured that, from a contest perspective, if limited to a single antenna it was
probably better to have it a little too high than too low, since the area on
the ground and (typically) the population base of potentially workable stations
covered by a pattern with good performance at low elevation angles was more
than what was covered at the higher elevation angles (coverage of which also
depended on the much rarer short skip).
Now if I only had a chance to put this into practice !
73,
Steve VE3SMA
--- On Tue, 6/29/10, Bill VanAlstyne W5WVO <w5wvo@cybermesa.net> wrote:
> From: Bill VanAlstyne W5WVO <w5wvo@cybermesa.net>
> Subject: Re: [VHFcontesting] Optimum 6 meter yagi height
> To: "Steve Kavanagh" <sjkavanagh1@yahoo.ca>, dave@egh.com,
> vhfcontesting@contesting.com
> Received: Tuesday, June 29, 2010, 2:07 PM
> 50-60 feet is a good average height
> to shoot for. (Wish I could get my 2x5el stack that high.)
> However, sporadic-E can want take-off angles all the way
> from flat (0 degrees) up to around 16 degrees for very short
> skip. The length of the skip depends on the intensity of the
> cloud's ionization (the Es MUF). When the Es MUF is very
> high and the skip very short, you're much better off with a
> lower antenna (as low as 20 feet), assuming your surrounding
> ground is relatively clear so you can make best possible use
> of the ground bounce gain.
>
> Apart from a low take-off angle (not always what you want,
> but often) -- The other thing that greater antenna height
> affords you, and a lot of people overlook this fact, is that
> the higher the antenna, the further it is from man-made
> noise sources on the ground. A quieter band is a band where
> you can hear (and work) weaker signals! Noise is also
> discrimminated against in the azimuth plane, so a longer
> yagi with a narrower beamwidth not only has more gain on
> transmit, but picks up less noise (unless it's pointed right
> at the noise source). That is assuming the long yagi has
> been computer-modeled properly and has minimal side- and
> back-lobes.
>
> Putting a 6-meter yagi REALLY HIGH (like, over 100 feet)
> will give you the maximum possible signal at the horizon for
> tropo and bleeding-edge Es and F2 DX -- but it will also
> give you lots of ugly NULLS in the elevation pattern where
> your signal can drop by as much as 15-20 dB. So you might be
> pinning somebody's S-meter at 1,450 miles away, but the guy
> who is 900 miles away isn't going to hear you anywhere near
> that loud, all other things being equal. Then you need to go
> to a lower antenna to cover that nulled take-off angle.
>
> As all the 6m Big Guns will tell you, the ideal solution
> for 6 meters is a stacked set of long-boom yagis at various
> heights from "real low" to "real high" that you can switch
> around either for single use or for use in phased
> combinations. Since most "normal people" can neither afford
> nor find space for an antenna system like that, it all comes
> down to compromises and trade-offs.
>
> Bill W5WVO
>
>
> --------------------------------------------------
> From: "Steve Kavanagh" <sjkavanagh1@yahoo.ca>
> Sent: Tuesday, June 29, 2010 4:34 AM
> To: <dave@egh.com>;
> <vhfcontesting@contesting.com>
> Subject: [VHFcontesting] Optimum 6 meter yagi height
>
> > Dave
> >
> > I did look briefly at this subject a few years
> ago....no measurements, just some simplistic analysis along
> the lines of what W2PV did much earlier for HF. This
> work was published in the 2004 Central States VHF Society
> Conference Proceedings. I could send you an electronic
> copy of that article if you are interested.
> >
> > For sporadic E, assuming flat land, it appeared that
> the best compromise height was about 50-60 feet. For
> tropo, on the other hand, the higher the better.
> There's a strong argument for having antennas at different
> heights for different purposes.
> >
> > Urban development around the station, sloping ground,
> etc. will change things, of course.
> >
> > Meanwhile, I do most of my contesting as a rover, with
> a dipole at 12 feet, which is definitely the wrong height !
> >
> > 73,
> > Steve VE3SMA
> >
> >
> >
> >
> > _______________________________________________
> > VHFcontesting mailing list
> > VHFcontesting@contesting.com
> > http://lists.contesting.com/mailman/listinfo/vhfcontesting
> >
> >
>
>
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