Reversal of a VHF Duplexer?

[601]

I had someone ask me a question today about a duplexer and I after a lot of research, I came up with nothing, maybe my terminology is off?

I have someone who purchased a VHF duplexer on ebay. The repeater they intend on attatching the duplexer to is on 151rx and 158tx requencies. They, however, sent the repeater split in reverse to have it tuned. Are duplexers directional or can they just hook this up like normal and still have it work ok?

I don't know all that much about them, I hope someone would be able to educate me on this

[Bill_G]

Duplexers are not directional. They are simply a series of cavities with precision jumpers and three connectors. Normally they are named tx, rx, and ant. That said, some models have a high side and a low side. It doesn't matter if tx is high or low as long as you connect it to the correct one.

[601]

That's what I thought, but wasn't 100% sure. Thank you so much!

It is labeled at TX and RX... that's where the confusion came in.

[Bill_G]

It will be fine. It's the tuning of the cavities that is important, not the labels. There is nothing in the duplexer to stop rf from passing both directions. That is why we put directional couplers (circulators) on systems. Peel the labels off if you can, and place them appropriately.

[AEC]

With most sites being high in, low out on UHF,I can see how the connection to the cavities can cause confusion...My super did this very thing at an LTR site we installed near Appleton many years ago.
Connected the transmit line to the RX cavities and vice versa for RX.
He had to play with the site, even though it wasn't ready.
Came in monday and said we tuned the combiners wrong.....One look said it all...He blew out the multi-couplers on transmit...ALL the RF was sent to the 16 ports and it wiped out the GaAs FET preamp as well as the entire multi-coupler tray.

His favorite word was: Basically, so we plastered that on the window to his van...Mike BASICALLY BLEW UP YOUR LTR SYSTEM....We thought it funny, mike did not appreciate our humor!

Okay, back on topic...sorry.

[601]

Yeah, I kinda didn't want to blow anything up lol. I need to read up on duplexers and how they work and tuning...etc.... Last thing I'd want to happen. But hey, we all learn from our mistakes... especially the expensive ones like that!

[Bill_G]

Hooking up cables wrong can be disastrous, but it proves the point that cavities are bi-directional.