[ADXA] “in-band” contest station question

[w5znjoel at gmail.com]

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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