Thank you so much, now I understand more about spectrum analyzers, to use tracking generator and cavity filter or duplexers. Amazing in one video you teach and share a lot of knowledge material, hope you are always healthy and blessed 🙏🏿
Thanks for another great video Peter! I had a duplexer like that on my old Regency repeater. No idea what I did with it. Brought back a lot of memories with that one lol. Have a good day and take care. 73 Buddy
I think it is fascinating to watch a spectrum analyzer while a filter is being adjusted, and see what each adjustment actually does to the attenuation spectrum!
On most duplexer connections, isn't the high connection used for receiving the signal and the Low connection used for transmitting the signal. Assuming the repeater receives on the high frequency and transmits on the low frequency?
Peter, i agree with some of the other comments: The unused open port had not been terminated with a 50 Ohm load. Most, if not all duplexers need ALL the ports terminated during the tune up process as the unconnected port is still in circuit, despite not being "part" of the tune up circuit! Especially true with the small cavity multi-port duplexers that were originally designed for mobile use! Having said that, great video Peter and hope the new repeater is on air as we speak! Continue with the super work, 73, Brian EI8EJB
Hi Brian, yes you are right but as you said MOST duplexers needs to be terminated. This type is not vulnerable to it. I have tested it before with and without termination and no difference. In our final test we had both ports terminated tidily and our pre calculated and finally measured results are completely matching. But I see that I should have shown it with both termination loads simply not to confuse viewers and to teach what always is the right way and not what will only work partly. Thanks for comment 73
Wonderful reply Peter and I hope that you did not take my comment as a negative criticism; this was not my plan!! You have forgotten more electronics theory than most (including myself) will ever learn in a life time Peter! Alles gute! 73... :)
When adjusting a duplex filter, you must connect a 50 ohm termination to the port that is open, and after adjustment you must use a SWR bridge to get the correct point where the filter has its optimal and lowest SWR still with 50 ohm termination on the open port..
correct on terminating the other port properly, it wasn't done here ! simply adjusting for deepest nulls and lowest loss is insufficient without considering return loss also all these multiple rf connector adapters are highly inappropriate another serious consideration is lengths of the coax - ignored here as well poor job this repeater will work like crap
@@srdjanstanojevic4287 With a SWR bridge you get a much greater dynamics and resolution as well as a better control of the impedance in the selected frequency that you intend to tune the filter to, I recommend a very good page about tuning Duplexer and the difference between using SWR bridge, look at W2AEW's site he is tuning with both ways, 73 the SM4PDP
O.K......! Now I'm really confused ! Another video showed the opposite of how this video described the ports of the duplexer. Here he says that the High side is for the transmitter ? Another video I watched, claimed you should use the Low port for the transmitter ? Who is correct ? Or are the ports interchangeable, as long as you, the Tech/Operator understand how you designate each port ? 🤔....?
Interesting. 7.6 MHz offset? I figured it would be 5. Almost any amateur radio automatically adjusts for a 5 MHz offset. New info for me. Great video and got some great knowledge watching this. Keep them coming. 73, ad0am
Great video Peter! I have often combined these flat pack notch duplexers with additional cavity filters to help with out of band performance, essential for RF busy comms sites. One quick question, what equipment are you using for the spectrum analyser and tracking generator?
Hallo Peter, schön gemacht! Richtig lustig wird es bei den 2m Duplexern mit 600kHz Breite..Da habe ich schon eine Kaskade von "Ölfässern" gesehen, die man mit der 1/2 Zoll Ratsche abstimmen musste;-) Gruß und 73 de Olaf, DK6KF Nice Work, Peter! Another funny thing is to do the alignment to 2m band duplex filters with 600 kHz bandwith. I have seen a "cluster of oilbarrels" that needed to be aligned with a 1/2" ratchet ;)
Peter, ich schaue schon von Video 42 an zu...;-) und arbeite mich noch rückwärts. Macht Spass! PS: Falls Du mal Teile aus dem kommerziellen Bereich brauchst, habe viele Ersatzteile zum Spenden..Ich arbeite gerne mit Bosch, Ascom und Motorola.
@TRX Lab would you be kind to let me know what software and hardware you have you are using in this video to tune? I like how this one is setup and the hardware under monitor.
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Great video as always Peter. Thank you for the efforts. Would like to ask what result have to expect if leave the notch and pass frequency little bit missaligned, but match the VSWR more close to 1:1. In other words, which is better: To keep notch not so deep (let say LF at -60dB and HF at -80 or -70dB) and VSWR close to 1:1. New ham here TA1OSN, Ferit. Respect and 73!
I have 2 VHF Motorola GM300s with a jumper cable on the back which makes the unit a repeater. I run 2 antennas for the Rx and Tx. I would like to run only 1 antenna. Can I purchase a duplexer, have it tuned and get rid of the jumper cable? Also, do I have to have a repeater controller just to make the GM300s and duplexer work? I would like to get by without using a controller.
Hello, I'm wanting to setup a personal use repeater, Can I use the MX-72 Duplexer to do it? I see the one that you are using is setup high at 438.100 Mhz and low side is 430.500 on the J-unoda duplexer can you do the same with the MX-72 Duplexer? Sorry for the question, I'm new to ham radio. Or how can it be setup using the MX-72 Duplexer. I'm wanting to set it up as a GMRS repeater. I'm wanting to use just 1 antenna if possible. Thanks.
What is inside the Duplexer cans? PI/PI-L networks? (I don't know anything about these) SWR: I would think that 1.5 swr would start to matter @ 440? Thanks, 73
Hi Bud there are many different concepts how this can be achieved. The best is to google it as it is far to much to answer it all here...Sorry mate. Thanks for watching 73
Surprisingly there is little information about what is exactly inside, I only found one example, it was a cavity filter which to me a basically a notch filter. So apparently there is nothing exotic going on inside them...
K5AZE Bud not much inside. There is some element (like the other end of that tuning rod) which effectively alters the physical dimensions of the cavity favoring only certain electromagnetic oscillatory modes. It is very much like the wineglass filled with different amounts of liquid resonating at only certain (audio) frequencies.
Another great video, I have never seen a duplexer being calibrated before, so it was fun for me. So, amateurs in Germany are allowed to use 12.5 KHz steps in Germany? We are still stuck with 25 KHz here in Turkey.... :(
Just one doubt..it's possibile to use both of inputs at the same time using a single antenna with a duplexer !? Thank you for your commitment !! '73 :)
Exactly. One is used for recieve, and one for transmit, at the same time. This is the purpose of a duplexer. It allows a repeater to recieve on one frequency and re-transmit the signal simultaneously
only problema here is you need used 50ohm in port duplexer for adjust you figure for tracking generetor no is good you need setting with 50ohm terminal 73 Raul
If a signal is coming in on the "wrong" frequency it will be attenuated by the filter depth of the filter and if the filter depth is 50 dB yes it will be attenuated by 50dB
A duplexer is needed in a repeater because the transmitter needs to be active at the same time as the receiver into the one antenna. You can use separate antennas for transmit and receive, but you would still need to have some kind of filtering to keep the transmitter energy out of the receiver antenna socket. Two antennas also means two coax cable runs and often more running costs if you are leasing space on a tower.
This is one antenna repeater system for both tx and rx. The receive signal is needed to pass thru the duplexer and go to the receiver, and at the same time the information is transmitting thru the same antenna. As Peter pointed out, the duplexer will notch out the tx frequency signal at the rx port. If a switch is used while transmit, then the receiver will not be connected to the antenna to receive any signal.
Nick, do you really think we could get our final result as we have seen it if my approach if it is a fatal error? All pre calculated and finally measured results are completely matching. At the finial test both ports were terminated... So my results are meaningless? Are you sure? Thanks for watching 73
hi thanks for replying, I really enjoy your videos & appreciate the time & energy that goes into making them, hope my comment didn't cause offence! Best wishes nick
