Dave is right, I WAS talking about dead band conditions. It doesn't make much
sense designing a rover station based on the "band opening up". But that DOES
remind me. I remember a few years ago roving during the June contest. I had a 4
element 6M beam on top of the car (probably at about 8 or 10 ft) and I was
travelling west on US Rt 2 in maine, FN54. Being fairly remote, I had worked
very few stations on 6 meters and was a little discouraged about it, when all
of a sudden the band opened and i was working 6-land stations one after the
other. I practically drove off the road!!!! I realized only later that my
antenna was probably set at the exact right height for a takeoff angle that was
perfect for double hop to the west coast!!! I think i worked 10 or 12 grids
during that short opening. Well the reason I had my antenna at that height was
more due to the fact that that was how high I could get it easily and also i
didn't know any better.. I was having a really hard time worki
ng stations only 100 miles away on the horizon, but for Eskip the thing was
perfect!!! I guess for June roving when Eskip would be more prevalent, a rover
might think about a small beam at 20+ feet AND something else switchable, maybe
a halo or dipole type antenna at 8 or 10 feet to use while "in motion" and
during band openings.
As far as the stacked loops at 6 and 12 ft goes, I am quite sure they would
work BETTER at 16 and 22 ft if working stations on a dead band (i.e. on the
horizon). But as Nate says, they still work just fine for what he is doing..
Mainly, as Dave says, and I meant to say in the previous post, don't let the
fact that you can't get your antenna at the "optimum height" STOP you, go out
there and WORK people!!!!
bill, k1DY
> From: k1whs@metrocast.net
> To: nate@natetech.com; vhfcontesting@contesting.com
> Date: Fri, 7 Mar 2008 13:06:17 +0000
> Subject: Re: [VHFcontesting] A question of altitude
>
> Hello Nate et al,
> RE the two loops at 6 and 12 ft, I think Bill K1DY was talking about dead
> band conditions. When there is Es or other like phenomena, all bets are off,
> and a low antenna can be quite effective. We actaully did try a 50 MHz test
> (in November of 2006) with a small 3 element yagi at 15 ft vs a 35 ft high
> single loop. The location was Camelback Mountain in FN21HB (I think), where
> the Packrats, W3CCX, operates. The path distance was over 300 miles up to
> Maine. I saw a huge improvement with the high loop here in Maine at FN43MJ.
> I think the improvement was over 6 dB, and closer to 10 dB. (hard to peg
> with band QSB etc) but it was very noticeable. Now that spot on Camelback
> was reasonably flat with a drop off in the direction we were trying to use.
> There was minimal foliage in the path. Still, with such low antennas, there
> is considerable interaction with the ground reflected signal. In short we
> still do not have 1st Fresnel zone clearance. (The only way to utilize a
> dropp off or cliff, is to hang the antenna over the cliff!) By raising the
> antenna, we minimized the interaction with the ground reflected signal and
> improved the takeoff angle considerably. The interesting thing about the
> test was that the station on Camelback Mtn did not get the big improvement
> that I heard in Maine, as the omni pattern of their loop introduced much rfi
> crud and his noise floor went way up. Reception on Camelback was a wash
> between both antennas. So I guess 50 MHz is always the most difficult
> problem in a rover vehicle. In my opinion, a small antenna way up high is
> the way to go, but you have to pay attention to rfi issues on any band as
> well. A well engineered receiver is a must at any hilltop site in the
> northeast. There are many high powered signals that can kill 50 MHz on the
> 30-50 MHz commercial band as well as 70 MHz and the TV and FM broadcast
> freqs. The antenna pattern will affect how your receiver "behaves" as well.
> I suppose that if you go out in June, and the band opens wide, then almost
> anything will seem to work like a champ, and you will have plenty of fun. My
> comments are geared to the lunatic fringe rovers trying to make 300 mile
> plus contacts on tropo scatter under dead band conditions. Don't feel that
> if you can't get your antenna up 35 ft you must stay home!! The important
> thing is to to just go out and do it.
>
> Dave K1WHS
>
> http://en.wikipedia.org/wiki/Fresnel_zone For more info on Fresnel zones
>
> ----- Original Message -----
> From: "Nate Duehr" <nate@natetech.com>
> To: "VHF Contesting" <vhfcontesting@contesting.com>
> Sent: Friday, March 07, 2008 1:31 AM
> Subject: Re: [VHFcontesting] A question of altitude
>
>
> > Bill Olson wrote:
> >> In real life, at K1WHS, I seem to remember having problem working rovers
> >> with low antennas (7-10ft) on 6M, and they nearly always had a drop off
> >> in front of them.. I guess what I'm saying is, over a, say, 200 mile
> >> path, with the same rover, there didn't seem to be much difference if he
> >> was on flat ground or overlooking a cliff.. the signal was still a lot
> >> weaker than we thought it should be.. I guess we really need some testing
> >> here.. Guess I'll do that in June and report back...
> >>
> >> bill, K1DY
> >
> > Anecdotally, my dual W0KVA home-brew 6m square loops, one at 6' and one
> > at 12' -- fed with a power divider -- have produced some of the best 6m
> > contacts I've ever worked, even compared to many high towered 6m
> > beams... both during contests and casually.
> >
> > No time to model it... it "just works" and I'm not changing it unless
> > someone proves to me that something else would work a LOT better. :-)
> >
> > And of course, when the band is open... it's just open... it doesn't
> > matter much. I've got FM01, 02, and 03 from DN70, DM79, DM78, etc...
> >
> > FM01/02/03 was NO problem -- when the double-hop E-skip was in here in
> > 2006. 2007... nada.
> >
> > Most often, if the band's not up... the first stuff to come in is Texas
> > (thunderstorm lines from the Rockies to the Gulf -- tropo) and the Gulf
> > states, and California going the other way, usually San Diego.
> >
> > If the band opens some more, the midwest becomes "easy" and often
> > Northern California, Oregon, Washington, Idaho (if there were anyone
> > there to work) and then down into Baja and most of Southern Canada and
> > Mexico.
> >
> > If aurora comes up... point north from here and enjoy working the entire
> > northern U.S. and Canada.
> >
> > In other words... for a Rover, having a "feel" for what 6m openings are
> > happening and learning a bit about how to listen for callsigns, usually
> > tells a better tale about what you'll be able to work, than the height
> > of even modest 6m antennas... if the band's up... it's up. Just kinda
> > how 6m seems to go.
> >
> > Nate WY0X
> > _______________________________________________
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> > VHFcontesting@contesting.com
> > http://lists.contesting.com/mailman/listinfo/vhfcontesting
>
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