Thanks to Joel, Stan, Kevin, and Bill.  

I now understand the issues.  Kevin’s info was enlightening.  I had no idea big stations went to those extremes for in-band rigs.  

It seems that <>700 feet separation or more is about right.  I think KL9A said his in-band antennas were verticals, RX only, and 825 feet from the main tower.  

Stan mentioned special filtering - Yaesu used to make a rig that had a very narrow tunable front end filter.  I always wondered how it worked.  

Bill talked about quality rigs.  At our local FD, we used either an Elecraft K3 or a Kenwood TS-590S on the CW station.  We set up about 400 feet from everybody else and almost never heard a peep from anyone else, even when they were on the same band.

At Mt Nebo one year, we operated two stations with two dipoles in line with the tips about 20 feet apart.  No interference.  The rigs were a K3 and a Ten-Tec Omni 7.  QRP, of course (100 watts).

People are always concerned about blowing out the front end.  At our FD one year, an SSB op asked me to come see why his SWR/wattmeter was reading upscale when he wasn’t transmitting.  It turns out he had a big OCF antenna and the digital station had a big OCF antenna and the tips were about 15 feet apart.  Way too close, and those antennas are a common-mode nightmare.  That was a cheap Yaesu rig and since then I haven’t been too concerned about rig damage.  

Joel, we will look forward to anything you put out.

So, to apply the things I’ve learned to small events like FD…
If 700 ft separation is good for QRO, with 10 db less power, we should be able to cut that quite a bit.  I’ll see if I can figure how much.  
If dipoles are used, they should not be broadside or too close, but if they are multiband antennas, the pattern can be material.  Single band antennas would have several advantages.  
We  don’t tend to put up yagis but if they are there, be careful in pointing.  I think W3AO used to line their towers up in echelon so all yagis were side by side when pointing out into the middle of the country.
Good rigs are essential.   My 590S does a good job, and has a RX antenna port.  The RX port gives me some very good options for dealing with other stations on the same band.  That’s going to lead to my next question!  

This has been interesting - thanks!

73,
Dennis/RZ


On Jul 22, 2025, at 5:29 AM, Kevin Stockton <[email protected]> wrote:


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 <[email protected]> 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: [email protected] <[email protected]> On Behalf Of Dennis Schaefer
Sent: Monday, July 21, 2025 10:14 PM
To: ADXA <[email protected]>
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

 

 

______________________________________________________________
ADXA mailing list
Home: http://mailman.qth.net/mailman/listinfo/adxa
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html