I have had several people send me Emails and questions – so I am putting some notes down here for anyone that finds it via a search engine. Your mileage may vary...

We recently acquired several sets of "used and stored away for years" Remec-Wacom WP-747L3/447L1 duplexer cavities from Clay W8JVV . I have had great luck with them! Have no fear, these will work great for you too!  The cable lengths aren't nearly as critical as people would make you believe...  But, shorter is better...

I got several sets of cans from him at once, and a few extra "spare cans" because he and I both thought that maybe I would run into a few that were corroded or "stuck" because they had been in storage so long.  Luckily for me, not a single one had a problem...  Most of my sets came with “stock from the factory” cables and T's, but not all of them.

To be honest, I have dog-robbed all of those good old factory cables off of the un-used cans for my other sets of cans for OTHER frequencies on 440, 900 and 52 MHz.  As long as things are EQUAL, they will tune up just fine.  The lengths aren't near as critical as some would make you believe.  Here's the really important thing - the cables you end up using MUST be double shielded, they MUST be equal down into the micro-MM range (measured tip to tip) and they should have SILVER PLATED connectors, not Radio Shack or otherwise equivalent junk.  That right there will make the most difference.

There's some wiggle-room but not much – read on...

Most of the cables on ALL my cans are either 6 inch, 9 inch or 18 inch.  All the T's are silver plated.  Each side of these 220 can sets or “chains” needs to have at least 2 band pass cavities (the ones with two ports) and 1 or 2 notch cavities (the ones with 1 port).  You tune the notch cavities to the freq of the other freq to keep it out of each other, passing everything else.  Like notch the transmit freq out of the receive chain and notch the receive freq out of the transmit chain.  Just remember that a notch cavity will notch out one freq and pass all others, whereas a bandpass cavity will pass one frequency and notch out all others.  Keep that in mind when you mix and match the different cavities.  I started with 3 notches and one bandpass on each side and ended up using two band pass and two notch cavities on each side in my final configuration for best separation, best notch of the "other" freq. and least amount of cumulative loss.

In the following photo, every short thick black cable is one I dog robbed off of the 220 can's I got from Clay...  The big box on top is a 900 MHz set of notch cavities, the big round cans below that is the 900 MHz band pass cavities.  Below that, the row of little looped cables on a box is the 441.625 repeater cavities and the big black panels on the bottom is the set of 220 MHz cavities.

I no longer solder my own connectors.  It's just no longer worth the trouble for me, personally.  I get my cables made up by a company on ePray, (I call it that because I am always praying nobody bids against me!)  they arrive in less than a week and after buying over about a hundred cables for myself and other hams, I have only had ONE bad cable in the last three years - now THAT'S AWESOME SERVICE! 

My favorite eBay Cable assembly provider - these guys are great!  <---  Click it and see the rest of their store and cables.  They have good "buy it now" prices.  They are convenient and they WORK!

I have started using all RG400 (the thin reddish cables in the photos) to connect almost everything in my repeater hut...  6m, 2m, 220, a couple of 440 and one 900 MHz repeaters all in one big rack cabinet.  They are just easier to work with than the thick stuff!  The difference in loss is negligible for me.

Below is a photo of the backside of the cavity rack and the 2m set of cans on the floor showing the birds nest of cables...  I don't bother routing everything and tie-wrapping it down tight because I often rearrange and move things!  With so many repeaters all in the same place, I keep changing things, adding things, upgrading things and to tie it all down would be a major pain in the butt!  Besides, letting things hang in free space and NOT all wrapped up tightly together keeps the RF intermixing and intermod down to a minimum!
 

To reiterate - As long as things are EQUAL, they will tune up just fine.  The lengths aren't near as critical as some would make you believe. However, if you are in one of those situations where you have a LONG antenna feed line run in a hostile RF environment, co-located with a LOT of other repeaters and RF transmitters at a downtown building or commercial broadcast site the lengths DO become very critical and they need to be done to commercial engineering specs!!! My repeater tower is way out in the middle of nowhere with no other RF on the tower other than my own. So “I” have a lot of wiggle-room that some people are NOT afforded – keep that in mind when reading these notes!

Here's the important thing - the cables you end up using MUST be DOUBLE shielded, NOT foil wrapped but braided and they MUST be equal down into the micro-MM range (measured tip to tip) and they should have SILVER PLATED connectors, not Radio Shack or otherwise equivalent junk if you make up your own. Most of MY cavity interconnecting cables are either 6 inch, 9 inch or 18 inch.  All the T's are silver plated but the connectors on the RG400 are not.  Each side of the 220 MHz cavity chains needs to have at least 2 band pass cavities (the ones with two ports) and 1 or 2 notch cavities (the ones with 1 port).

One other little worthy note - the cables to and from the cavities and the radios, for each band, in my rack of repeaters, are all equal length as well!  Some are as long as 12 ft. to reach the cavities in the rack or sitting on the floor.  Some are as short as 2 ft.  But, I use equal length cables for the transmitter and receiver on each band.  I use flexible hardline where possible but have RG400 lines as well.  RG400 works fine for lower power repeaters.  When I step up to a 100w or larger amp, I use flexible hardline ONLY to connect to the cavities and from the cavities to the antenna hardline run up the tower.

EQUAL, EQUAL, Equal is the biggest deal of all...  The same, the same, the same is the second biggest deal.  Double shielded is PARAMOUNT and silver plated connectors whenever and wherever possible.  (They aint cheap!)

Tuning notes - The first time I tuned my 220 cans, I didn't have a service monitor.  I tuned them for maximum power throughput and the least SWR. with an HT on the input and output frequencies.  Tune each can individually first.  Then connect everything together and then tune the "chain" of cans again starting with the power input side first, moving to the middle and ending with the cans closest to the antenna port - all done with a precision 50 ohm load (on the end of the chain and “other port”) like you find on circulators or test equipment.  Go back and forth multiple times, every tweak you do has a cumulative effect on every other can attached to the chain!  Going back and forth over ten times is NOT unusual!  This got them really, really close - when I eventually tweaked them up with the service monitor I ended up making some VERY small adjustments for less loss.  And I made several passes to get them tweaked up the best I could.  I ended up with less than 2db loss through the entire set!  That's pretty darned good...

These cans will last forever and once you get them tuned up right, you shouldn't ever have to touch them ever again!