The Magic of Half-Duplex Cross-Band Repeat
Posted on January 29, 2026
Several repeaters in the area do not want hams using full-duplex X-band because it can lead to repeater loops, lock-outs and can be a general pain for the repeater owner when these issues occur.
The other issue with full-duplex is that when you put your base / mobile radio in X-band repeat mode (assuming your radio has the functionality... and most do) it is in 100% duty-cycle... in that it continuously and simultaneously receives and transmits.
This is fine for a repeater that is not very busy and you use it intermittently... perhaps during races, but if you are on a busy morning roundtable net for an hour... your radio is working very hard because there is not much down-time... someone is always transmitting. There are lots of stories out there of hams who have blown out the finals on their base/mobile rigs due to heat buildup.
Many hams only know full-duplex operation, which is the default of most radios. They don't know much about using half-duplex. I was one of those hams until recently.
Half duplex avoids the issues that repeater owners have about full-duplex.
Using half-duplex will not result in your radio going up in smoke.
Half-duplex ONLY works when you can HEAR the repeater on your HT. If you can't hear it directly, as my friends in New York say ... fergetaboutit!
But it is often the case where you can hear but can't 'hit... your HT copies the trasmissions from the repeater but it does not have the power to trip it. If this is the case, half-duplex might be something you want to try.
There are tons of sites on the net that will show you how. I'll give a brief description how I use it with K6BER which I can hear with my HT but can't hit. They have a very busy morning roundtable starting at 7 AM.
On my Yaesu FTM-300DR mobile/base radio I set VFO-A to a UHF frequency... one no one uses.. like 439.975... use whatever you like. I set it with no offset and no PL tone... pure simplex. It is the frequency that will be used between the base and my HT. I set the power to low since I'm just in the next room.
I set VFO-B to the VHF frequency that the repeater LISTENS to... which is the frequency that you transmit to.. which is basically the shift frequency... usually + or - 600. k6BER transmits on 145.970 and that is what you listen to. The repeater LISTENS on 600 less or 146.370. I set VFO-B to that and set the PL to the repeater... 123.0... but I do not set a shift. I set the power to high since that is what I need to hit this repeater.
On my dual-band HT (iCOM ID-50) I set one band to the memory channel I have for K6BER...with tone and offset... my normal repeater setting. I will NOT transmit on that frequency (I can't hit it if I did... but I turned the volume up so I can hear it.)
The other band I set to THE SAME UHF frequency as the mobile... 439.975... pure simplex. THAT is the frequency I will transmit on.
I then put my mobile radio into X-band repeat mode (see your manual on how... each radio is different.) Here is what happens. I listen to K6BER directly on my HT. When I transmit on the HT (using the UHF frequency,) my signal goes out the UHF frequency on my iCOM HT radio into the UFH frequency on the Yaesu base... which than "cross-bands" it out to the repeater's 'listen' frequency.
It's magic!
About the Author
Alan Canton has been a writer and a publisher in addition to his lifetime work as high-tech consultant. He is the author of several books (long out of print) as well as the author of the long-running Saturday Rant blog (also now dormant.)
Alan Canton has spent just over 40 years as a high-tech consultant... have ticked all the buzz-word checkboxes... programmer, analyst, system engineer, systems architect and the latest... full-stack engineer. If it has to do with computer code, he has done it... or at least most of it.
He is the managing partner of NewMedia Create which designs websites for authors, publishers, and small businesses... most often for small biz people who have "no money" but who want a simple but nice site at an reasonable price.
Ham radio is his main hobby. His callsign is K6AAI. You can see his station at his QRZ webpage.
He also runs a QSL card company and has hams from all over the country as customers. See RadioQSL.com. His favorite ham radio quote is:
"I am often asked how radio works. Well, you see, wire telegraphy is like a very long cat. You yank his tail in New York and he meows in Los Angeles. Do you understand this? Now, radio is exactly the same, except that there is no cat."
- Attributed to Albert Einstein