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I'm looking at a set (not physically yet) for VHF. They are in a cabinet which has seen better days but the cavities look good. He said they are 6" in diameter (4 ea) and they have a tuning stub mounted on each one. Best guessing is the Q204 series. Currently tuned to 146 range. Any thoughts? Value?
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Clif Holland KA5IPF
www.avvid.com

Clif, No thoughts on the value, but it looks like a BpBr type, similar to the Wacom brand.? If you have a way to check it out prior that would be best. If the bottom of the cans can be open then in the worse case you can do repairs.? Most of this type are secure with ether a set of screws or rivets.
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Regards, Karl Shoemaker
To contact me, please visit SRG's web site at?
for the current email address.
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I have only see those trombone notch tubes on Old WACO's from the 1960's...
My recommendations... I recalled a "duplexer repair guy" in Alabama 8-10 years ago.. I googled this.. It may help:

I priced a pair of new Teledyne and TX-RX duplexers for W?VFW/R club repeater this past year. East Coast-West coast.
Shipping is EXPENSIVE to Kansas..in both cases the "bid" was within $4 each from either company at median $1776. Quote was over 9 months ago.
site shows some printouts of spectrum performance? before and after rebuild.
So you know W?VFW duplexers were "flakey". Some member kept coming in ever 2-3 months and tuning with an old IFR 1200- or 2000.
I took over the tech committee as he threw up his hands and said get new duplexers.? WE replaced the Final PA amp (old Toshiba plastic Brick to Mitsibutshi FET Metal brick) and the TX to duplexer coax line with 3/4wave RG 223. (prior TX to duplexer was showing 4:1 to 6:1 SWR without a EMR "tuner" into the 1st can)? Then retuned the duplexers using a NanoVNA. When we 1st started we carefully calibrated the NanoVNA and have before and after picture of the spectrum. We also used a 20dB preamp in line to in effect raise the 70dB noise floor? of the NanoVNA. Since my attack with all I had, -- 2meter rigs, WWV, 3 VHF-UHF SWR bridges, Pasternick step attenuators,? Nanovna. Some cellwave 1Ghz. dummy loads. We've gone from 3+db loss in the cavities to 1.4db.. and the "flakey duplexers" have gone away.. I later found out the members IFR was declared unstable-in need of work. So I saved the club from bankrupting the treasury for new duplexers.

Now having said that, take a Nanovna (a H4 preferred).. and take a look at those duplexers prior to buying them. See where the peaks and notches are. Take a couple of 50 ohm terminators with you.and coax adapters.. If you refer to duplex repair site you can see the poor notch on one of the spectrum printouts pre-rebuild. KNow what you're getting into.. He may say-- Oh customer is upgrading to UHF.. why?

Regarding used duplexer sales..a few years ago In flea markets I seen 6 cavity VHF sets asking $400 and then they go at the end of the day for $250.. Times are changing.. Amateur VHF repeater allocations are filled in most parts of the country. (amateurs need to re-band plan to Narrow FM 12.5kc) Plus old commercial users are finding that if they invest in new equipment going UHF is actually cheaper. UHF duplexers new can be had for under $100- granted chinese but work. unless your running high power.

Remember 4 cavity duplexers will NOT have the isolation needed to run high power.. Likewise are you adapt in building a repeater, like us old guys? I was on 2FM in 1968 with a motorola Twin V.. 1970-74 I was on the tech committee of the 2nd 2 meter repeater in the US.. A GE progline that came from GE 2way when it was in Syracuse NY where the repeater was before GE 2-way went to Lynchburg.??


Shipping is a killer. NY to KS was quoted at $345 on new TX-RX cans. Almost considered driving there. A rebulder will not quote a price til lhe seend the duplexer and it's apart.. Those duplexers are worth more than scrap metal but what I don't know.? The sale price is only what the buyer is willing to pay AND take a chance on..
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I'm looking at a pair (not physically yet) for VHF.

Pair?

They are in a cabinet which has seen better days but the cavities look good. He said they
are 6" in diameter (4 ea) and they have a tuning stub mounted on each one with a "T".
Best guessing is the Q204 series. Currently tuned to 146 range. Any thoughts? Value?

Looks like an old Q202G.

Issues that I would be concerned about:

I don't remember ever seeing hose clamps on the tuning assembly on any Sinclair cavities - there was always a setscrew. I have to wonder if there was an issue with noise, buggered-up threads, or something else that precipitated adding those hose clamps that are choking the threaded female side of the fine-adjust.

Figure you'll need to replace those old RG213 cables for starters.

Are any of the cavities noisy from age/oxidation?

Was this duplexer actually ordered for 146 MHz and 600 kHz split, or something else? From the looks of it, one of the dielectric tuning rods is near its end of travel, whereas all of the others have a lot of length extended, so I would question the "currently tuned to 146 range" as being valid, or even if they will tune to a 600 kHz split.

With the above questions unanswered combined with the time/money you'd need put into it, I'd say the as-is value approaches zero. If you had more info on it, including that the cavities weren't noisy, maybe it's worth something...perhaps $100 or $150 tops. My opinion anyway. Personally, I wouldn't put the time or money into a duplexer that old (on the order of 40 years), but that's just me...

--- Jeff WN3A



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At 1/13/2021 12:10 PM, you wrote:

[Edited Message Follows]
I'm looking at a set (not physically yet) for VHF. They are in a cabinet which has seen better days but the cavities look good. He said they are 6" in diameter (4 ea) and they have a tuning stub mounted on each one. Best guessing is the Q204 series. Currently tuned to 146 range. Any thoughts?

I had a set just like those a long time ago. It was a Q202-G.

Bob NO6B

I have the 6 cavity version and it works just fine at 130 Watts


At 01:03 PM 1/14/2021, you wrote:

At 1/13/2021 12:10 PM, you wrote:

[Edited Message Follows]
I'm looking at a set (not physically yet) for VHF. They are in a

cabinet which has seen better days but the cavities look good. He said they are 6" in diameter (4 ea) and they have a tuning stub mounted on each one. Best guessing is the Q204 series. Currently tuned to 146 range. Any thoughts?

I had a set just like those a long time ago. It was a Q202-G.

Bob NO6B

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