Hi Vic,
I hope you don't mind me sharing my answer with the reflector but I don't
want to cause confusion with my replies so I thought this might answer
others who had the same questions about my post.
Yes, my remote (meaning - controlled from the shack) relays are in the
single elevated radials of each 4SQR element. I started out with manual
knife switches which I needed to run out in the field to set but moved up to
relays which are very nice to have. Heck, wire nuts work too if you just
want to manually strap on some wire.
My tuning steps are these:
The length of the each radial is tuned for CW resonance (3540 in my case).
All of the vertical elements are the same fixed length and all tuning is
done with the elevated radial length. After all 4 radials are tuned to 3540
individually (by checking SWR at the base of each of the 4 elements), I then
check for the "dump" power minimum frequency (measured at the dump port of
the Comtek/DXE box). In my installation, dump minimum was about 3475 so I
shortened (physically cutting) each of the 4 radials in 6" increments until
the dump minimum was 3540. Great, now the system is good for CW. I forgot
what the actual length was but let's say it was 66' for discussion (is
probably closer to 68 in real life). Then I started working on the SSB dump
minimum. I calculated the ratio of 3540 divided by 3750 and multiplied that
by 66'. That is about 62.3 feet. I cut my CW radial at 62.3 feet and
inserted a relay in each of the 4 elevated radials which I can control from
the shack. There is no change in my feed point or vertical length.all
adjustment is handled by the radial length. This ONLY applies to an
elevated radial system. I've had a little side conversation with Jorge,
CX6VM, and I had not made that distinction clear but my system is the
elevated radial 4SQR (single radial per element) described in several of
ON4UN's Low Band DXing revisions. ON4UN tried to add more radials to his
earlier elevated radial 4SQR experiments and "it is impossible" to tune 2
or more radials per vertical in a 4SQR like this. If you look at all the
test equipment and calculus ON4UN uses to tune his antennas, I am too lazy
to argue his "it is impossible" to tune declaration. I have been VERY happy
with the elevated radial 4SQR with a single radial per element. When I get
the dump minimum in the correct place (less than 5 watts dumped with 1500
watts into the Comtek/DXE box), I know I've got it tuned correctly. I also
run a dump power coax from the Comtek/DXE box back to the shack so I can
constantly verify on a watt meter that my antenna is working properly AND
that I have the SSB/CW relay in the correct position. If I'm on CW and the
relay switch is on SSB, my 20 watt dump meter scale is getting pounded by
the needle and I know to throw the switch. During the CQWW 160 CW contest
this year, I saw the dump power jump up in the middle of the first night.
As it turned out, cows had knocked over one of my wire vertical supports
(element suspended from a Dacron rope on top but held off the ground by a
15' 4 x 4). Since the 160M 4SQR literally covers 8 acres by the time all
rope supports (off a 160' tower) and radials are considered, cows are just a
factor I live with. I've trained them to look NE during EU sunrise to add a
db or two to my signal which offsets any inconvenience though.
I highly recommend ON4UN's books if you are considering a 4SQR because he
REALLY has spent a lot of time developing his theories and real world
antenna systems. You'll need to read it and then re-read it because it is
full of helpful suggestions and math that is beyond me. I'm just a lazy guy
who distilled out the key points and have been rewarded with an antenna
system that has amazing F/B (and the implied corresponding gain from a
system with good F/B). I have never measured gain but when the F/B is
there, I trust ON4UN's claim that gain is also at (or comfortably near)
maximum. It is fun to run tests with a guy 1500 miles to my NE and then
switch the 4SQR to SW, then get the comment "I couldn't hear you on SW". It
has taken a number to corrections, changes, re-soldering and luck to get it
right but I'm please with the results. My 80M 4SQR uses Rohn 20 and 25 for
elements while my 160 4SQR is all Dacron rope and top loaded wire elements
hung off a 160' tall tower. It was a beast to put up since I do most of my
antenna work by myself.
Here are some random thoughts which didn't fit above but should be
mentioned:
1) Current chokes are needed at the base of each element.
2) I ended up paying the big bucks to have DXE build my 75 ohm vertical
feed lines and have been pleased with the quality and accuracy of their
construction which includes the current chokes under shrink tubing on one
end.
3) Thinking back, I should have built the SSB radials first and then
added the extra length for the CW segment.
4) Intuitively, it doesn't make sense that a single radial should work
but it REALLY does if you take the time to tune the array correctly.
5) If you don't see at least 25 db F/B, you have not measured your dump
wattage correctly.
6) 4SQRs are amazingly quiet receiving antennas. I have four 1000'
beverages and use the 4SQR 75% of the time.
7) Make sure your 80M and 160 4SQRs are built a good distance
apart.like in the next pasture. I think ON4UN recommend a wavelength or
two.
8) Don't let the low SWR across the band on a Comtek/DXE 4SQR fool you
into thinking you've got a good antenna. Trust the dump minimum.
9) I'm finding about 100KHz bandwidth of reasonable (less than 10
watts) dump minimum on 80M and 50 KHz on 160M (less than 20 watts dump).
10) I have seen no RF issues by having my 12VDC radial relays' wiring
running next to the radial wire or coax. ON4UN would probably cringe at
that one as well as several other "customizations" I have done. ;-)
11) ON4UN recommends tuning each element of a 4SQR only when removing or
shorting out the other three elements. I didn't always do that and got
lucky that it probably didn't hurt me too badly.
12) On the DXE system with the Omni (the 4SQR acts like a single vertical)
position, if all 4 elements individually have the same resonance, the same
SWR will be best at that frequency when OMNI is used.
As you can tell, I enjoy this antenna and can talk about it WAY too long but
I'll shut up for now.
Hope you have the same or better results that I've had.
Bob K5WA
From: Victor Walz N2PP [mailto:n2pp@frontiernet.net]
Sent: Thursday, March 10, 2016 8:44 AM
To: K5WA@Comcast.net
Subject: 4 Square for 80 Meters
Hi Bob,
I read your post on tuning for the CW and SSB sub-bands and need some
clarification.
How are you "subtracting" length on SSB with the remote relays? Are you
re-positioning the feed point to a different point on the vertical element
or are you just shortening your radial?
I really appreciate any time you spend responding to this.
Vic N2PP
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