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8 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 ...
Marcus Müller's user avatar
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 ...
Glenn W9IQ's user avatar
  • 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 ...
Brian K1LI's user avatar
  • 7,858
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 ...
vu2nan's user avatar
  • 757
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 "...
Mike Waters's user avatar
  • 7,986
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 ...
tomnexus's user avatar
  • 11.3k
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 ...
Graham G8URP's user avatar
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 ...
Ngineer's user avatar
  • 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,...
rclocher3's user avatar
  • 9,242
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 ...
Phil Frost - W8II's user avatar
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 ...
user17178's user avatar

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