A quick reply... > "w6nct" <[EMAIL PROTECTED]> wrote: > I am setting up my duplexer using four Phelps-Dodge cavities (all > in series for Rx), and two Cell-wave cavities (in series for Tx). > All of these are individual, cylindrical, PASS-REJECT cavities.
Are the 5 or 8 inch... or some other size diameter cavities? > At this point, I have a setup and test methodology to tune the > PASS and REJECT adjustments; and have done so for the individual > Phelps-Dodge cavities (mostly as a pre-tune and confidence > building exercise). Nothing wrong with taking the time to learn... I do it all the time and it really pays off. Undestand a single cavity adjusted location will be different from a dual series cavity setup... and different from a triple cavity setup. Broadly speaking you might see how additional cavities change the final adjustments. So starting from scratch you'll get single cavities in the ballpark and the final assembly will require a second or third final adjustment. > I have not re-tuned them in the full duplexer system configuration > as I am still > trying to make up the "proper" length cables (see > other related topic thread, "measuring coax for duplexer"). I'm > still a little stuck in making these cables, due to the unknown > length and velocity factor for the loop inside the cavities. If > you have any thoughts on this topic, please add them to the > associated thread. You didn't mention the type of coax you are using...? Consider the physical loop/probe length to be added to the coax length. The coax will have a velocity factor of say... .66 to .93 typical and the internal loop/probe lenght is most often considered free space, which is also known as vel= 1.0 I don't march with the crowd on this one... every time I try to follow the various posted cable length text the results never seem to work out. So I use my own methods and test gear, which gives me the nearly exact performance of the specific network I'm working with. If you want some rules of thumb I like to consider... I'd need to know more about the cavity loops/probe assemblies. Email me direct if you like. > Beyond that, I have the Tx/Rx sections of the repeater operational; > and am trying to figure out how to best interface my (NHRC-5) > controller and (ComSpec TS32) PL decoder/encoder (see other related > topic thread, "Controller connection to RPT-21"). This portion is > still in progress, trying to figure things out. If you have any > thoughts on this topic, please add them to the associated thread. An original Standard RPT-21 ..? > I've figured out a lot about using the Wavetek 1080. It's a pretty > amazing piece of equipment; but I still haven't gotten the manual(s) > for it. Yes... the Wavetek gear is really nice... > QUESTION 1: Do you have the same model Wavetek (i.e., 1080)? > If so, do you have the manual(s) for it? I have two models... but the one on the bench here right now is the 1062. No I don't have the manual for it or any of the Wavetek units. Manuals plus might have the book if you really want/need it. > QUESTION 2: I'm curious about the "Marker" input on the front. Do > you know what it is for, and how it is used? Depends on which model Wavetek you have. The Markers on some models are fixed at various intervals (1 MHz as one example, 30 & 60 MHz on other models) and show up as blips on the display. We can and do input an external rf generator on one of our setups to allow an adjustable/agile marker at or near your project frequency. The MFJ 269b antenna unit works as an excellent signal source. > QUESTION 3: Do you know how to read the display in terms of the > calibrated signal amplitude, given a specific setting of the > "Output" (in dBm)? It's relative to how you have the various knobs adjusted. In operation you set the display to represent various values as desired. It's one of those instruments easily learned by watching someone use it. Out of the starting gate it's a pain to figure out the first few times. > More specifically, a friend was saying something like "in order > to read the actual bandwidth of the PASS and NOTCH, I needed to > measure it a the 6 dB point". Does that make sense? Yes... kind of. Your friend sounds like he's reading from page 134 of a Malvino Electronics Text Book. It would be kind of windy to start talking bandwidths of cavities here. In very short simple terms you get what you get related to the Q of the cavity and the possible adjustments you might make/set. > Do you know how I would do it using the Wavetek 1080's display on > an oscilloscope? I suspect that it's just a libration/ > visualization thing that I am missing. > I appreciate any wisdom and experience you can offer; especially > relating to the Wavetek 1080. > <<< vern >>> Mostly visualization... Depends on how you have the wavetek set up. We get different results doing different things with it. Probably easier to talk to you about using it on the phone some time. Email me direct if you want to try and yack on the phone about it. cheers, skipp
