> No piston trimmer that I can see, unless it's inside the
> can across the loop. I was thinking of cracking one open
> to find out. Anyway, though, it would have to be
> adjustable to peak up the cavity, so why would they hide
> it in there?
No, they wouldn't be hidden inside. Just checking.
> On the ring duplexer, it supposedly just inverts the
> notch of the can into an equally sharp bandpass....by
> making a steep cut away from the rx frequency, it should
> hold off the tx to some extent....right?
Well, it'll keep the transmitter carrier out of the
receiver, at least to a degree. But you also need to knock
down the noise generated by the transmitter on the receive
frequency. If this is to be a 600 kHz split system, you
probably need to attenuate that noise 60 dB or so...
perhaps less, probably more, depending on the particular
transmitter, receiver, etc. With cavities only on the RX
side you'll have no protection from the noise and a LOT of
desense.
> As I said, I have one additional can now, with two ports
> in/out, so I'll throw that one in the tx lead to make a
> 3-can setup. If this sounds all wet, please let me in on
> the right answer.
If you mean just inserting a pass cavity into the TX lead,
it won't give you nearly enough protection from the noise
on your RX freq. I'd suggest making another hybrid ring
for the TX side with this cavity used as a notch cavity.
Most pass cavities work fine as a notch by capping one
connector and just using the other. A hybrid ring duplexer
with two cavities on the RX and one on the TX just might
do it, although it'll be a bit marginal on the TX side. As
I understand it, you'll need to construct 3 rings, one for
each cavity.
Hopefully someone with real experience with the hybrid ring
will jump in here and help you out!
Paul, N1BUG
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