[ADXA] “in-band” contest station question

Tue Jul 22 05:50:40 EDT 2025

Dennis,

In band radio(s) can be used to quickly work other stations, priority to multipliers but as many stations as possible while the run radio never leaves the run frequency.  The operation can be as simple as one other radio with a transfer switch swapping the transmit antenna to whichever rig is transmitting and an RX antenna to whichever one is not.  It can be as complicated as multiple in band radios each with their own amplifier and transmit antennas..  I think there are stations that operate with as many as three or four in-band radios on the same band.  If you were ever called by P33W or some of the big Multi Single stations you might send their callsign and report and then wait as much as 2 seconds for them to send theirs.  The rules for CQ WW Contest require that the rigs and antennas be located within a 500 meter diameter circle.

Both the Run and In-band radios need to be able to copy stations while the other is transmitting.  You can’t have more than one transmitted signal at a time.  Some special switching is necessary in order for the run operator to miss as little as possible.  You really don’t want the run operator to be interrupted when he is going to send W5RZ 5NN08 and he would only have sent W and then nothing while the In-Band guy calls someone.  However the in-band operation can add a lot if the run rate is not great and the In-band operator has a good idea of what he is doing.  

Attenuation between TX and RX antennas is important. I have an idea there are sophisticated stations who are using filters that are tracking frequency and automatically tune to further attenuate anything more than a few kHz away. I’m actively trying to come up with the best plan possible for ZF5T because we are going to operate CQ WW in multi-multi category thus year.

We did this about 15 years ago in field day with some simple dipoles and made a lot of contacts.  I thought about doing it this year but didn’t take the time to do it.  We used to do it on Gaither Mountain and probably did when you were there once for a multi-multi operation. Over20 years ago I built some little relay boxes that would send the run guy to a dummy load and allow the in-band station to take over the amplifier and TX antenna.  Switching the run guy back and forth to a RX antenna was done separately.  The In-Band guy always listened on the RX antenna.

Hope that help explain what’s going on with in-band.

73…Stan, K5GO

> On Jul 21, 2025, at 10:14 PM, Dennis Schaefer <dennisw5rz at gmail.com> wrote:
> 
> 
> 
> 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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