[ADXA] “in-band” contest station question

Tue Jul 22 06:29:42 EDT 2025

At N2QV they have an OB12-4  that is located around 700' from the main
transmit antennas.  I was able to do in band with little interference on
40-10 on this setup.  The separation from the 12-4 to the primary transmit
antennas was an important factor but just as important to the in band
success was when firing to Europe both sets of antennas were off the side
to one another.  When either of those antennas were rotated and pointed at
the other the interference increased significantly.  In low sunspot years,
there were times when SO2R/2BSIQ wasn't possible because only 20 meters was
open during the day.  So being able to do SO2R while running and searching
on 20 meters was a great advantage.

The big multi multi stations like K3LR, KC1XX, K1LZ, etc. have massive
separate stacks for both the run station and the in band station.  For
example, K3LR has 6/6/6/6 for the run station on 15 and 8/8 for the in
band.  A little overkill in my opinion but really impressive.

73,
Kevin, N5DX

On Tue, Jul 22, 2025 at 5:00 AM <w5znjoel at gmail.com> wrote:

> Dennis,
>
>
>
> The subject matter experts in this group for this topic are K5GO and N5DX.
> There isn’t a great deal of public information on the internet but you can
> occasionally see material from some of the top contesters and contest
> stations that has been presented.
>
>
>
> You are correct, though, that it comes down to separation of antennas
> either by spacing, polarization, and/or both. I’ve operated at the W2GD 160
> meter station that is located on the southern New Jersey coast. They are
> able to come within 5 KHz of the run station and work others. It is
> impressive to experience in-person! The W2GD TX antenna is located in a
> salt marsh just a few feet from the Atlantic Ocean and all of the RX
> antennas, which are Beverages and a HiZ-8 160 are located as far away,
> within the 500 meter allowable circle, as they can be and none of the RX
> antennas must look right into the TX antenna.
>
>
>
> For the higher bands, most are using a vertical, or an array of verticals,
> for in band RX and you simply have to find the sweet spot that provides the
> best isolation. Stan has been running a few tests and I have a series of
> tests scheduled to be conducted here on my range in August using a vertical
> antenna to document different spacing -vs- attenuation from a TX antenna.
> If those tests go as planned I’ll provide the results.
>
>
>
> 73 Joel W5ZN
>
>
>
> *From:* adxa-bounces at mailman.qth.net <adxa-bounces at mailman.qth.net> *On
> Behalf Of *Dennis Schaefer
> *Sent:* Monday, July 21, 2025 10:14 PM
> *To:* ADXA <ADXA at mailman.qth.net>
> *Subject:* [ADXA] “in-band” contest station question
>
>
>
>
> I see comments from very serious contesters about having a second
> “in-band” rig.  I assume it is to work mults while the main rig runs on the
> same band.  I couldn’t find much about how this actually works.  I’m not a
> serious contester, but I would like to think about how this could apply to
> Field Day, and things like group POTA operations.  Everyone wants to start
> out on 20 meters.  At night, 80 and 40 are the only usable bands for
> several stations.
>
>
>
> Available bandpass filters and stubs work great for different bands, but
> passing 14.250 Mhz and attenuating 14.040 Mhz is a different ball game.
> W2VJN’s book shows filters for 80M CW and 75M SSB, but those frequencies
> are separated  further.
>
>
>
> I assume it is done with antenna spacing and polarization.  KL9A has a
> vertical for  the 10M in-band rig.  Cross polarization with yagis would
> give significant attenuation and spacing seems to be at least several
> hundred feet.  I’m sure the run station is QRO and the mult rig probably is
> more than 100 watts.   Is it as simple as antenna separation and type?
>
>
>
> I doubt if I would try to actually implement any of this at FD because
> I’ve slowed down a lot on FD.  I’ve participated in over 50, and I still do
> some operating and never mind telling people how they should do things even
> if I know they aren’t listening :) I am interested in how it is done,
> though, and if there are any articles I should read.
>
> Ours has been hit or miss.  Sometimes CW can operate on 14.025 and FT8 can
> operate on 14.074 within 100 feet of each other, and sometimes there is
> interference.  Usually, when there is no interference, the rigs are
> Elecraft, newer Kenwood, etc.  Some very popular rigs almost always seem to
> suffer interference.  Maybe the type of rig is the main factor?  Maybe I
> don’t have a good understanding of what they mean by “in-band”.  I know
> both aren’t allowed to transmit at the same time, but I want to know how a
> rig can tune around 20 meters and copy signals while another station on the
> same site is running.
>
>
>
> It always frustrates me when I can’t find any information on something I
> know is done.
>
>
>
> 73,
>
> Dennis/RZ
>
>
>
>
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