Bud,
Having never used a 2 element 40m array I can't speak on that *particular*
antenna.
However I've used hundreds of other types on all bands. 160m-70cm
I have had a 80m 2el broadside/endfire array & also have the same for 6m on
my CAR!
I ended up years ago settling for a full-size delta loop on 40m. It was a
lot better than anything I've tried previously.
I thought I was really doing well with that until late this summer I
installed a CC D40 rotatable dipole @ 55'.
Man that thing rocks!
(I just worked VP8THU South Sandwich Expedition on 7.024MHz on about the 3rd
call in a massive NA/EU pileup)
If you can swing it, do the verts or a high rotatable dipole.
GL, Mike VE9AA
Michael, Coreen & Corey Smith
(VE9AA, VE9AAA & Little-VE9 to be)
271 Smith Rd
Waterville, NB
E2V 3V6
Canada
http://members.tripod.com/~ve9aa/index.html
http://www.geocities.com/RainForest/Vines/2174/
----- Original Message -----
From: "David Aslin" <daslin@bayarea.net>
To: "Bud Semon N7CW" <n7cw@san.rr.com>; <towertalk@contesting.com>
Sent: Saturday, January 19, 2002 8:02 PM
Subject: Re: [TowerTalk] Advice on 2 el 40M Vertical Array
>
> Bud, I had a real estate-constrained location when I was in UK. Solution
> on 80m was 2 Force12 EF180BVs (37 foot tall, linear loaded) spaced 1/8
> wavelength i.e. 30 feet. Didn't have room for extensive radials.
>
> What I found was that laying a good number of radials between the bases of
> the verticals in a diamond pattern (imagine the radials leaving the
> vertical bases only in the 180 degree sector that lies in the direction of
> the other vertical) gave me a 2-ele array that worked well. I did have a
> ground line, bonded to the phasing box, to which I terminated the
> between-the-verticals radials. Later I added some really short radials
> (varying from 10-20 feet long) in the 'outer' 180 degree sectors and
> noticed some improvement in performance. Total area occupied around 60
> feet by 40 feet - so a 40 meter version would fit into the smallest of
> lots.
>
> Performance? Consistent top 5 finishes in CQWW single band 80 and 285
> countries in ca. 18 months. (No beverages, loops etc on receive - just
the
> array). Great f/b to nullout Europe on the short path to the US. The
> array wasn't great in the broadside direction, but still allowed me to
work
> all the countries I need off the side. I'd guess 3-9dB down.
>
> A couple of details - I used the Lewallen method per ON4UN, with
> guesstimates of the C and L values as I had no access to a vector analyser
> or accurate noise bridge. The MFJ 259 was unhelpful, except as rough
> esimate that each vertical had a similar impedance - the measured values
> did not yield the right answers for the phasing componets. My technique
> was to buid a xtal oscillator for the band, connect it to a mobile whip
> antenna and park my truck about 5 wavelengths away in line with the
> verticals. Then connected a trusty IC-735 at the phasing box and tweaked
> the C and L for minimum S meter reading with the array firing away from
the
> truck/oscillator. A little crude, but effective. Similar should work with
> the Christman method, but adjustment is tricky. Just using ON4UN's
example
> lengths of coax won't cut it - the impedances in your array will
inevitably
> be different than his, so you'll have some cut-and-try to do. That's why
I
> used the Lewallen, wth an Airdux coil/alligator clip and a couple of big
> variable C's (don't forget to replace the clip with a hard-soldered
> connection after setup if you pln to use power - I fried mine first time
> out! And if as I did you use receive type variable Cs, replace them with
a
> combination of fixed Cs to the same as the adjusted value - and use
> doorknobs or similar, there's a lot of current circulating.)
>
> Biggest losses in the array are close in to the base of the verticals - I
> used 3ft x 3ft sheets of aluminum at the bases, with holes every couple of
> inches around the edge through which I bolted s/s hardware with solder
tags
> to attach the radials. I worked on the principle that since I could only
> have short radials, I'd better have many of them - ended up with about 80
> per vertical, all of 20ga wire - just kept adding them when I had spare
> time in the yard.
>
> Hope this helps
>
> 73
>
> Dave
> WJ6O
> G3WGN, 80m op at M6T
> ----------
> From: Bud Semon N7CW <n7cw@san.rr.com>
> To: 'towertalk@contesting.com'
> Subject: [TowerTalk] Advice on 2 el 40M Vertical Array
To: <towertalk@contesting.com>
> Date: 16 January 2002 18:17
>
>
> I'm looking for a small improvement in my 40M signal and have the
following
>
> thoughts and constraints. I'm currently using an 80/40M trapped vertical
> (similar to the BattleCreek Special, without the 160M section) over a
> limited
> set of radials. The yard is fairly small and 80M radials can only cover
> one
> 90 degree quadrant.
>
> For the moment, I will do without 80M. I can squeeze in 2 40M verticals
> with
> 1/4 wave spacing, but the radials would only cover about 270 degrees
around
>
> each vertical. If I use 1/8 wave spacing, I can pretty much cover 360
> degrees.
>
> Since I am mostly a DXer, with limited contesting and my location is in
San
>
> Diego, the most important directions for me are NE and SW, which is
> convenient
> for locating the verticals. I haven't seen a way to phase 1/8 wave
> verticals
> for a broadside pattern, but I don't really care too much about those
> directions. Also, being in the most southwestern corner of the country, I
> have
> no QRM from the SW when I point NE (the ocean is out there) and little QRM
> from
> the NE when I point SW (this is the LP and the sun is up to the east of
> me).
> Consequently, I think working hard for the last couple of dB of F/B is
not
>
> worth it.
>
> So....looking through ON4UN's book, the 1/8 wave spaced array with the
> Christman coax feed method seems like a good fit. Does anyone have a
> better
> suggestion?
>
> I also have a couple of specific questions. Are the impedance
measurements
> I
> can make with the MFJ259 accurate enough for proper phasing calculations
> (including the mutual impedance)? For radials that run between the 2
> verticals, should I terminate them in a ground line that bisects the
> verticals?
>
> Thanks in advance for any thoughts and 73, Bud N7CW
> n7cw@arrl.net
>
>
>
> ________________________________________________________________________
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> ________________________________________________________________________
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> Order online at http://store.eham.net.
> -----------------------------------------------------------------------
>
> -----
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>
________________________________________________________________________
Where do you get ICE bandpass filters & beverage matching boxes? The
same place that pays for the hosting of this list: The eHam Store.
Order online at http://store.eham.net.
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