Posted: 7/2/2010 3:10:38 PM EDT
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A diplexer, or triplexer, is a filtering device that allows 2 or 3 transceivers on different bands to share the same coax and antenna. I've seen them for HF/VHF or 6m / 2m, etc.
In the June 2010 issue of QST magazine, page 37 there is a do-it-yourself triplexer project for HF. It is set up for 20 m, 15 m, and 10 m. So I was thinking... ( Uh-oh!!!  )
Our Field Day antennas work 75, 40, 20, 17, 15 and even 10 meters. We worked 40 m, 20 m, and a bit on 15 m. It would really save some real estate and simplify things if we could modify this design to cover 40, 20, and 15. (17 meters is a no-contesting band) I can easily wind a coil to allow use of 40 meters. But before I go to all of this trouble, are there any commercial units that will do this that I am not finding? I can make one from the plans in the June issue. Questions? Comments? Buehler? Buehler? |
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Quoted:
Could probably just use the ICE individual bandpass filters connected in parallel as a multiplexer. June QST has an article explaining an interaction if you do this that I was unaware of - you have to decouple/desense the bandpass filters from each other. Personally I am not eager to risk the front ends of two additional radios to field test this - if it doesn't work there is a likely to be a bit of "smoke let out" in the aftermath..... 73 Steve K9ZW BLOG: With Varying Frequency - Amateur Radio Ponderings |
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Quoted:
Quoted:
Could probably just use the ICE individual bandpass filters connected in parallel as a multiplexer. June QST has an article explaining an interaction if you do this that I was unaware of - you have to decouple/desense the bandpass filters from each other. Though my answer won't be as technical  this is the first thing I thought of. Even if you don't fry radios in the process I'd imagine that if one radio was transmitting you'd get enough desense on the other radios to render them useless. From a single op point of view it could work, having multiple radios monitoring on one antenna only because you can't be listening and transmitting at the same time.
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Quoted:
I was looking for a way to use up or require less real estate for future Field Days. I'll just let this idea go, then. There is the expense side - three high quality high duty cycle bandpass filters at a time are needed. If the transceivers are "locked" to a specific band the three would be $300-400 for the set. If you wanted to be able to switch the band trio things would get pricey quick. The decouple/desense box looks to be cheaper - maybe $80 and perhaps a have dozen hours build time. You will need a bunch of quality jumpers as well. You can put up an awful lot of wire dipoles for the $500+ to do this triplex set-up, though in fairness the bandpass filters really should be part of a close-coupled station set-up regardless. Wonder if the tri-plexer idea would work with tuning stubs or other less costly filtering? 73 Steve K9ZW |