Just an update on the status of this project. I thought what I've found might be interesting to the group.
At the suggestion of a group member, I removed the top and side ports to the cavity. It turns out that this is quite easy to do. You just remove the three screws holding the top port, and the nut holding the side port. At this point the whole assembly lifts out easily. I inspected the assembly and could see no problems. I resoldered the connections just for good measure with no improvement. At this point, I decided to move parts around to see if I could get the problem to follow a specific part. Success!!! The bad part seems to be the UHF TEE adapter. I checked it with an ohm meter, but it seems to have DC connectivity. My only guess is that it exhibits some non-resistive reactance at RF frequencies. Regardless, into the trash it goes! I've tested each cavity with a good TEE and all show a proper BpBr curve. This brought to mind an experience had by a friend of mine. His HF station would always work great for the first 5 minutes of operation, and then the SWR would go sky high. It turned out to be a TEE used to connect a gas-gap lightning protection device at the transmitter. He hacksawed the TEE apart, and discovered that the side connection was made with a SPRING LOADED PIN! After a couple minutes of transmitting, the spring would heat up and pull away from the straight through pin, effectively cutting off the connection. I haven't torn apart my TEE to see if it is the same, but I wouldn't be surprised! Anyway, I went to the local electronics supply house and obtained a new TEE (a cheap knock-off, but that was all they had), and that worked fine until it literally broke apart. (!%$#@&!! cheap junk!) In retrospect, I'm glad it broke. I'd rather have it break on the bench NOW than have it fail on the mountain two months from now with 5 miles of 10' deep snow between me and the site. So, a new TEE is now on it's way, and I hope to have the duplexer tuned up and ready to go shortly after it arrives. The moral of the story is, check all cables, connectors and adapters before tearing apart your duplexer, AND don't use cheap knock-offs of any of those. -- Keith McQueen [EMAIL PROTECTED] 801-224-9460 On 11/17/07, Keith, KB7M <[EMAIL PROTECTED]> wrote: > > I have a Wacom model WP-652 duplexer with what I hope is a minor easy to > fix problem. Three out of the four cavities are operating correctly with a > classic BpBr curve on the tracking generator. The fourth (it is the high > frequency input cavity normally connected to the transmitter on this band), > exhibits a curve that as near as I can describe it is missing the notch. If > I loosen the connectors and wiggle them, I can sometimes get the correct > curve to show. I have loosened and inspected the tuning stub on the side > and see no visible damage. After reassembly, no change was noted. The > overall performace of the duplexer is not bad, and would probably work with > reduced isolation. > > I'm not sure where to go from here. I don't know how to inspect the > internal matching loops for damage. I also don't know how to disassemble > the cavity for possible repair. > > Has anyone repaired a Wacom duplexer? Is there anyone supporting them? > Any ideas? > > -- > Keith McQueen > [EMAIL PROTECTED] > 801-224-9460 >
