Diplexer

[wqzw301]

Anyone know where to look for a good commercial vhf / uhf diplexer? I have my CommScope 4 bay repeater antenna and marine band vhf antenna on the same mast.

I got a good deal on some heliax  but only enough for one 40ft run... terminated on both ends with times microwave N connectors. 

All the diplexers I have found, in endless searches, are for low band or ghz cellular...

Repeater-builder warns against the ham products like commet, mfj and diamond diplexers.

I did get my hands on supposedly "recent working pull"  - Austin Antenna Combiner for UHF, VHF. 130-190 Mhz, 400 - 500 Mhz .

Anyone know these, I believe Austin hasn't made these in decades.... based on "internet info"....

I do have good isolation on both vhf and uhf sides - band pass / reject on rx/tx sides. And also circulators/isolators on the transmitter sides with harmonic filters.

Please and thank you for any advice 

 

d

 

 

Edited February 24, 2022 by wqzw301

[gman1971]

Most ham diplexers I've tested were about 50-60 dB isolation. For most cheap radio stuff that could be a problem, since the receivers have no front end filtering, even when tuned to VHF, anything coming in the UHF could degrade performance.

For commercial grade radios, the 50-60 dB isolation U/V + the radio front end filtering should probably be good enough to get you by. Now, you can always use those diplexers with a preselector or a cavity, which will further reduce the signal so there should be no issues at all.

G.

[tweiss3]

I use Comet in my vehicle, and 60dB is enough isolation with commercial UHF and Yaesu VHF. 

A quick search of Tessco brings up one item:

EMR $560 https://www.tessco.com/product/vhf-uhf-crossband-coupler-535434

Listed as still only 60dB isolation.

 

[wayoverthere]

36 minutes ago, tweiss3 said:

I use Comet in my vehicle, and 60dB is enough isolation with commercial UHF and Yaesu VHF. 

A quick search of Tessco brings up one item:

EMR $560 https://www.tessco.com/product/vhf-uhf-crossband-coupler-535434

Listed as still only 60dB isolation.

 

I'm using the CF416A in my base setup  (which cuts the low side at 170mhz, and starts the high side at 300mhz), between a pair of monoband vertex standard decks (vx4207/vx4204) and a comet gp1.

[gman1971]

I really don't think it will be a problem, even without preselectors or cavities...

Currently using two CF-4160N on the same heliax run to multiplex two radios. Which works quite nicely and saves you from having to use multiple cables. No issues with desense.

G.