Stuart,
Very very interesting.
I had expected your reply to be something like "all radios were Ten-Tecs or
Elecrafts".
Amazing what a difference it makes with proper antenna planning.
(Remember what I always say: "It's the antenna, stupid.")
Cross station interference is a major problem at most multiple station
events.
I have been to a few Multi-Multi events, and of course we were running 1kw
or more on all bands all the time, and then the only thing which helps in
addition to antenna planning is band filters on each transmitter.
I've been to a lot more Multi-Single operations where we only had two
transmitters (Run and S&P).
We generally found that if both transceivers were an Omni-6, we could place
the Run station on any band, and the Search & Pounce (we called it "Multi
Station" back then) could work on any other band WITHOUT any interference
from the run stations. I did this on two of my three trips to 4U1VIC for
CQWW CW and there all antennas were located on top of the same building! On
one of my trips we had an FT-1000 and it had trouble all the time. It was
constantly interfered with by the run station.
Now in support of what you (Stuart) found out, at a Multi-Multi CQWW SSB
operating on top of the highest mountain in Liechtenstein (HB0CSZ), I was on
the 80m team. We had a Drake C-Line and an Omni (A) sitting side by side.
The C line was the Run station, running 1KW, and the Omni was the S&P
station. The run antenna, a full size delta loop, was located about 100
meters north of the cabin and a vertical was located about 100m south of the
cabin. While the run station was working one after another, I was searching
for multipliers on the same band (within the tiny European SSB band on 80m)
with the Omni. As long as I was about 15 kHz below him, I could receive
without interference. Antenna choice and placement is VERY important.
- Sometimes the choice of radios helps
- Type and placement of antennas always helps
- Sometimes you need Band filters (ie. Ice, Dunestar, etc.)
- Using double-shielded coax probably helps a lot. I have added that one
to my list.
Note: Band Filters do not help if you are running two transmitters on the
same band. However a very good tunable preselector helps a lot. The older
Ten-Tec rigs (Original Omni and Triton) had preselectors and may possibly
have performed even better than newer Ten-Tec transceivers under that
specific condition.
BTW, if anyone enjoys pictures of this kind of operations, you can see
pictures of our HB0CSZ expedition here:
http://www.dj0ip.de/my-expeditions/hb0csz-1988/
73
Rick, DJ0IP
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Stuart Rohre
Sent: Thursday, July 19, 2012 12:44 AM
To: tentec@contesting.com
Subject: Re: [TenTec] OT: Field Day Drill
Rick,
The radios used with the double shielded coax were our usual assortment of
radios we use for FD, a Club owned TS 450 for SSB phone, a school club Icom
707 for GOTA on 40m (sharing with the SSB phone above part of the time)
(GOTA on a half wave 40m dipole about 45 feet from center of the SSB 88 foot
doublet, and at right angles to it. (The ends were within a few feet). The
third (CW) rig in the same room as the above two was an Icom 756 pro II.
Mostly on 20m CW, but also did RTTY. The SSB phone station was mainly for
20m but moved to 40m when most of 20 available stations had been worked.
With the GOTA station operating at a low rate with new ops or visitors, we
put the responsibility on their coach to pick spots on 40m phone band where
we were not using the other phone station. Thus, same band interference was
pretty minimal. I did not hear of GOTA bothering either of the other
stations.
Interesting that you asked if we had tested the radios before this co-
location. What was supposed to happen was we reserved a room for GOTA and
the SSB phone stations, and the CW /RTTY station was to have a room unto
itself. However, a scheduling mixup had the CW room in use that Sat., and
we had to move CW next door with GOTA/ phone. The good spirits were with
us, and we had no co-location issues that watching to stay in opposite ends
of a band could not solve. CW mostly stayed in lower 25kHz of 20, or in the
RTTY area. The SSB station trolled the whole SSB sector, and simply moved
the opposite of any frequency where the other stations gave a problem. It
was trial by necessity; but I am glad it worked out so well. Had GOTA had
more operators, it might have been more of a problem, but they had periods
with no activity.
I am sure the double coax shields helped some; but the siting of antennas to
space them in directions of least interaction helped as well. The CW/ RTTY
vertical antennas were 125 to 170 feet away from the GOTA dipole, and 125 to
150 away from the SSB phone 88 foot doublet inverted Vee.
-Stuart Rohre
K5KVH
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