Services Available

Duplexer Repair is a service division of Alabama Broadcast Services, LLC. Duplexer Repair performs repairs, refurbishing, and tuning of a wide variety of duplexers and cavity filters. From small UHF duplexers to large HF cavities. We also offer on-site tuning of duplexers and filters within a reasonable travel distance on a per job basis — call us at (334) 787-9005 to discuss on-site work, or drop us an email at

There are many, many duplexers and cavity filters in service out there which naturally suffer from the effects of time. In the case of Amateur or Ham Radio equipment, many of the duplexers we see were actually in service in public safety or commercial installations in the past, then removed from service for whatever reasons (often because they were damaged, suffered from age, or did not meet the more rigorous specification demands of new radio equipment installed later) and wound up being acquired by Amateur Radio folks and put into service where they were considered okay for less demanding use. Yet time continues to take its toll on even the best duplexers and filters. Eventually, their performance degrades or they can fail altogether, causing the equipment owner or club headaches, restless nights, or lots of trips to the repeater or installation site trying to keep them tuned or patched up. We can usually solve that problem by repairing or reconditioning those older duplexers and cavities, adding many more years to their useful lifespan. Lightning, high SWR due to antenna failures or mistuning, feedline damage, and other system problems can cause considerable RF energy heat build-up in duplexers and cavities, damaging the delicate capacitors and other components found in duplexers and filters, rendering them useless and worthless. Again, we are here to help.

We have seen some older duplexers which had obviously left the factory with defects and poor assembly quality. It is not stretching the truth by any means to point out that in some cases duplexers and cavities have left our workshop in considerably better shape than they were in the day they left the manufacturing facility. We would like to think that given the price tag of new duplexers and filters they would be manufactured to very exacting standards and quality control being excellent — we would like… no, we’d love… to be able to say that, however it sometimes just isn’t true.

In some cases, duplexers taken out of commercial or public safety service simply will not work to factory specifications because they are being used outside the frequency range for which they were designed and built. Many (if not most) of these duplexers and filters can be modified so that they do meet or exceed factory specifications within Amateur Radio/Ham bands. This requires in-depth knowledge of the particular cavities and loop assemblies, the proper jumper and harness assemblies, and occasionally custom fabrication of the needed components (such as loops for proper frequency resonance) and other hardware.

12717283_1537018356591139_1412701328369793840_n In order to know that they are indeed performing well requires sophisticated (i.e., ridiculously expensive) test gear and equipment which most Amateur Radio licensees and repeater or system owners do not have and can not really justify because it would be (hopefully) rarely needed. We have the tools such as communications analyzers, network analyzers, return loss bridges, precision low noise amplifiers, oscilloscopes, and more, and we use those tools in order to make sure that your duplexers and filters are working right after we complete our work.

DP_003_HP_RLWhen we service, repair, or tune equipment in our shop, we test the equipment thoroughly and document the performance of the duplexer or filter(s) using high-end, lab grade test equipment. We will provide you with copies of these and will keep them on-file, which assures you of how well your equipment is operating when we finish the repairs, service, or tuning, and it provides us with the data needed to determine if and how much performance degradation has occurred over time. Duplexers and filters do suffer from natural oxidation and other effects over time — it’s unavoidable, even in the best, most climate controlled installations.

If you have an emergency situation or interest in swap-out/depot type services, we occasionally have used or reconditioned duplexers, filters, and cavities on-hand and will be glad to discuss trading-in your non-working items toward these. This can sometimes be your best option, resulting in the shortest time needed to get your repeater or communications system back in operation — plus you’ll know right away what your expense will be, instead of having to get your items to us and having to wait find out what the final cost will be. Trading in your non-working equipment results in us assuming the risk where the repair costs are concerned and all you have to worry about is getting the replacement item(s) installed and tuned. We can even deliver, install, and tune the swap-out gear for you (within reasonable travel distance) for really quick turn-around.

Need a duplexer or filter for temporary use while yours is being repaired? We can discuss that as well. It depends on whether or not we have a suitable loaner on-hand at the time, but if we do have one, we will be glad to discuss such an arrangement and the fee will be quite reasonable. If it turns out that your non-working item is simply beyond all hopes of being repaired or repairs would be cost-prohibitive, we will advise you of that fact as soon as possible and all or a significant portion of the fee we would have charged you for rental of the loaner will be applied toward trade-in or the purchase of a used or reconditioned item from our inventory.

If you would like the assurance of knowing that your duplexer or filter is being inspected and the tuning checked and touched-up on a regularly scheduled basis, we can discuss pre-paid “service contract” type arrangements whereby your equipment will be inspected on-site on a regular basis and repaired or replaced if/when needed (or a loaner put into operation while we do whatever is needed to get your equipment back in shape here in the workshop.) Like our other on-site service offerings, this will have to be discussed on a case-by-case basis. Just let us know if you’re interested in this service. It can be a great way to know and control your future duplexer/filter maintenance costs while minimizing or eliminating down-time due to unexpected equipment failures or malfunctions.

There are certain conditions under which we may decline servicing, repairing, or tuning duplexers or cavities, and these are discussed on our page on this site which describes how to request our services.