9
votes
Looking for a schematic of a DIY circulator
Puh! That's a big one you're planning:
Most circulators are passive, magnetic material circulators:
These circulators are basically a three-port resonant cavity in a cylindric shape, where the ...
- 17.4k
6
votes
Accepted
Using a Duplexer and Diplexer in Series
Yes, it will work with the proper attention to details. I have done the same in the past at two repeater sites to take advantage of the coverage of the dual band antenna.
Do take care as the third ...
- 18.6k
5
votes
Why is my diplexer such a spectacular failure?
Like you, I modeled your diplexer in LTSpice, but I don't find the results to be acceptable. At 147-MHz, the input impedance is 87$\Omega$; at 443-MHz, it's 24$\Omega$. Also, the crossover frequency ...
- 7,912
5
votes
Why is my diplexer such a spectacular failure?
You have soldered a 68nH inductor instead of 100nH!
Maybe the layout and the wiring also play a key role.
Here's a vintage commercial one.
It's quite compact. The size, inclusive of the coaxial ...
- 767
5
votes
Looking for a schematic of a DIY circulator
A circulator can probably be constructed from coaxial cable. However, you will also need ferrite and magnets.
From https://wa8dbw.ifip.com/Circulator.html :
A circulator is best thought of as a "...
- 8,174
3
votes
Accepted
A passive splitter/combiner in full-duplex mode
Couplers or splitters are passive, bi-directional components.
As long as the power is within limits, they don't mind if they are transmitting or receiving. The loss from ports C to 1 is the same as ...
- 12.2k
2
votes
DMR Physical RF connectivity
I think you're looking for a splitter/combiner that will accept the feed-lines from both yagis on one end, and the feed line from your duplexer on the other end.
You'll need to be very intentional ...
- 4,658
2
votes
Why do repeater duplexers have notch cavities between transmitter and antenna?
The transmitter doesn't need protection from the receiver, because the receiver doesn't transmit any signal.
Indeed. The notch filter in the transmit side is instead to protect the receiver from the ...
- 356
2
votes
Why is my diplexer such a spectacular failure?
The added capacitance of the RG58 stubs may also be an issue. I suggest using flat copper strip instead between the port connectors and the PCB. While you can probably get away with SO239's for just ...
- 21
2
votes
Is power output or something else to blame for my duplexer failing?
In the absence of test equipment there is no way to know for certain what went wrong, or what to do about it. The duplexer sounds like the most likely culprit, but the problem could be something else,...
- 9,320
1
vote
Why do repeater duplexers have notch cavities between transmitter and antenna?
The transmitter doesn't need protection from the receiver, because the receiver doesn't transmit any signal.
Perhaps not, but consider:
The transmitter makes broadband noise and intermodulation ...
- 52.5k
1
vote
Retuning 2m Duplexers (Q2330E) with Spectrum Analyzer and Tracking Generator
There is a trick to balance the notch tuning johannsen cap adjustment with the coupling ring loops to meet the required rejection per side with minimum insertion loss. I believe I tuned mine to reject ...
- 11
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