Re: PD526 Duplexer Tuning
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It's only capable of 1024 points max. I think everything else I can set to your specs.
On Sun, Apr 27, 2025, 8:41?AM Part 15 Engineer < kc8gpd@...> wrote: I measured the cable lengths and it's rg214 and it's approx 11.5 in for jumpers but they might be a hair over 11.5 inches. I'm not sure how critical the length is or how exact it must be.
The first two plots are typical of each individual cavity. In this case the high side. The second two are with the two coupling loops in line on the 3 high side cavities minus the coupling tee. So I'm guessing like you guys stated earlier it's the coupling cables? I didn't tune the cavities anymore. Just tuned them individually and installed the cables and this is from input to output with two coupling loops installed. Does anyone have a good set of harness cables? I bought these from an individual on here but apparently they are not the right cables?
Thanks
Robert
A number of things: ? - You¡¯re sweeping 30 MHz wide with only 401 points.? You need to either narrow down your sweep just to the range of interest, use more points, or more likely a combination of both.? I¡¯d typically be using a 10 MHz span and 1601 points (I don¡¯t have a NanoVNA, I don¡¯t know what it¡¯s capabilities are).
- Something is either very wrong with the cavity, or the calibration.? It is showing you have 3.129 of insertion loss in the bandpass; it should be about 0.25 dB for a properly-functioning PD526 resonator.? Likewise, at the notch frequency, it¡¯s showing that you have 4.77 dB of return loss ¨C it should be a lot closer to zero.? If I were to take a WAG, you have 3 dB or more of cable loss that isn¡¯t compensated for, and/or something is wrong with your calibration kit.
- No since in working on the full duplexer harnessed together until the above are first addressed and you know each cavity is properly tuned individually.
? --- Jeff WN3A ? ? Here is the plot for a single cavity. ? Ok, I'm tuning the pd526 on the nvna. I can't seek to get everything to line up on both reject and pass simultaneously. It seems to be one or the other. I have attached pic of my latest plot. This is the best I got it so far. I did tune cavities individually then hook them together. And I got multiple peaks and valleys on the plot instead on one nice peak on the pass and valley on the reject. Does anyone have a link to the plot for the pd526 and what it should look?like? Thanks
![]() ? I think I finally got the pd526 tuned. It has 1db difference in sensitivity between direct input and going through duplexer and very little tx power loss coming out of duplexer. Probably only a few watts of loss. Tomorrow I will do some field testing to see if it gets put as far as the txrx 28-70-15h duplexer I was using. I'm not seeing any signs of desense yet. ? It will have the opposite effect.? To get more dynamic range you would really need an amplifier or a way to drive in more signal.? The pads are just to match the impedance as the output/input terminals may not be the nominal 50 ohms.? That is just for the notches.? If tuning the pass with a RLB do not use a pad as this will give a false match/very low RL . On Thursday, April 24, 2025 at 11:28:09 AM EDT, Part 15 Engineer via <kc8gpd=[email protected]> wrote: Will a pad give the nanovna more of a dynamic range to see? the notch depth? Iirc the dynamic range of a standard nvna is about 60 to 80db. So if I put a 10 or 15db pad that should help with tuning the notches? ? Pads can be helpful on the generate side of a VNA providing a good resistive match to the device under test. Many years ago working at Hughes Aircraft we always terminated our generate cables with a 6dB pad.?
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