[CQ-Contest] SO2R Technical Question - Round III - Antennas

[Barry]

Sorry I haven't commented sooner, but was away for a few days, busy with 
other things, etc.  I've been fairly successful with single-tower SO2R.  
For example, just received my plaque for First Place in ARRL DX CW 2007 
W/VE and had several other wins in major contests over the last 5 years 
or so.

My setup was as follows (recently downsized the station after a 
lightning strike over the summer):
Radios: FT 1000D and FT990
Amps:  2 Acom 2000A's
Switching: Top Ten Devices Band decoders and sixways.  2 sixways to 
switch antennas and another 2 to switch stubs.  I also had a bunch of 
homebew stuff involved in switching antennas between the 2 radios, Array 
Solutions NQN bandpass filters and headphone audio (I wrote an article 
in NCJ about 5 years ago on the audio switching.)
Antennas:  Single 76 ft Rohn 45 tower with a Cushcraft 402CD at 85 ft, 2 
phased TH7s @ 76 and 45 ft (using a DX Engineering (the old company) 
phase box.  A third TH7 was at 25 ft for the second radio.  I modeled 
phasing all 3 and the low one provided no significant gain to the 2 
higher ones.  On 80 I use a K8UR-style array and on 160 an inv vee (600 
ft Bev for EU rcv), both hanging off the same tower.  The top TH7 and 
402CD were rotated with a T2X and the 2 lower TH7s with TIC Rings.

Regarding multiband verticals - stay away!  I tried one when I first 
went SO2R.  It was mounted 10 ft off the ground, about 200 ft from the 
tower.  I believe it was a Hygain, or maybe a GAP, but it was 
worthless.  When I first put up the TH7 at 25 ft, the vertical was still 
up for comparison - there was regularly a 6 S-unit difference on 
20-10m!!!  I never used it on the low bands as there was no need.

Regarding isolation between radios, with the stubs and NQN filters, I 
had no problems unless I was within 10 KHz of a second harmonic.  For 
example, if I was on 7005, there would be a l9oud signal on 14010, 
pretty much preventing me from hearing 14000-14020.  However, I could 
work higher on 20m no problem - and my 40m antenna was only 10 ft from 
my 20m antenna!  There were no interference problems whatsoever if not a 
direct second harmonic (eg., 20 and 15 together, 15 and 10, etc.)  One 
cheap, but important thing - when cabling the station, use coax with 
100% shield - it really makes a difference.  For the low power cables 
(between radios, NQN filters and amps) I used LMR240.  On the output 
side of the amp (to stubs and antennas) I used LMR400.

Hope this helps...
73,
Barry W2UP


Lee Buller wrote:
> Wow....
>
> I've learned a lot about SO2R installations over the last week.  Thanks for all the emails and responses.  Now, here is another questions.....
>
> Antennas.  I think I have an issue with antennas because of make up of my location.  I have a 60 foot tower with a C3E - 80 and 40 meter inverted -V dipoles on separate feedlines but at the same height on the tower, a 160 meter Inverted-L on the tower...and a full size quarter-wave vertical in the yard with 32 radials.  I was planning on changing out the vertical for a Butternut 6 band model or something similar, but as I was looking at the installation the antenna would be very close to both the 160 -80- and 40 meter antennas....less than 15 feet.  I am on an 80 by 150 foot lot.  (I think SO2R is gonna get expensive when I tell the YL we have to move!)  So, is it worthwhile to even consider doing SO2R on such a small lot because of the proximity of the antennas.  This is a considerable investment....minus the new farmstead.
>
> Lee - K0WA
> "Going to buy a Lottery Ticket...."
>
>
>  
> In our day and age it seems that Common Sense is in short supply.  If you don't have any Common Sense - get some Common Sense and use it.  If you can't find any Common Sense, ask for help from somebody who has some Common Sense.  Is Common Sense divine?
>
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>
>   

-- 

Barry Kutner, W2UP             Newtown, PA