Batboard

My Celwave PD 497-1-1 VHF duplexer just can't seem to provide adequate tx/rx isolation (Micor 100 watt repeater with 0.6 MHz tx/rx separation). Everything else seems to check out okay; jumper cables, connectors, receiver, and hard line.

I inherited care of the duplexer within the past 2 years; I estimate it's probably about 25 years old. The operating environment now is a climate controlled cell site, although at one time I believe it was installed in a utility shed at a water tank.

I've heard the PD 497-1-1 isn't the latest in duplexer design and was wondering what other VHF repeater owners might recommend with regard to high performing, closed spaced duplexers for moderate power applications.

Thanks.



Tony

The PD497, while not being the absolute best spec-wise, should provide plenty of isolation even on a 600KHz split. I would suggest finding someone who knows duplexers inside and out and can disassemble the unit, clean it out, replace the harness with a new one, and retune the thing completely.

If you want to look at a new duplexer, I'd strongly suggest EMR. Their people are great, you get to talk to a real engineer when you call in, and they'll turn stuff around quickly. They built and tuned a 6-cavity pass/notch with dual isolator for a fire repeater I maintain and had it to me inside a week (ordered Monday, delivered Friday) with no rush fees. They are also about half the price of Celwave... however, a 6-can with isolator rated for 150 watts continuous will still run you about $2500.