Re: [Repeater-Builder] Help with Wacom WP-639 Duplexer

[Kevin Custer]

Hi Rob, Rob Martin wrote: Kevin   Thanks for tips, I had download the VHF tune up PDF but not the other pdf. I was surprised he had such problems as I had bought two sets of duplexers, one was a DB products until which he said failed as they had 2 notches and the second set being the wacom which he said wouldn’t tune down.   When you say tune them upside down could you explain a little further for me as this is my first attempt to put a repeater on air. The Wacom WP-639 is a BpBr design, meaning Band Pass - Band Reject.  The duplexer is specifically built to pass a particular frequency, and reject another.  The components of the duplexer determine if the notch falls above or below the pass frequency.  In the case of a regular duplexer, one side is HPLR (high pass low reject) and the other is LPHR (low pass high reject).  Many times, from the factory, a duplexer has its ports marked "Transmitter" and "Receiver", but those terms are meaningless unless the duplexer is used in the same band segment as it was tuned from the factory.  Let's look at it this way, say you have a repeater on 146.625 minus 600 kHz.  This repeater would be HPLR on the transmitter and LPHR on the receiver.  Follow me? Now, lets look at 147.195 plus 600 kHz.  This repeater would be LPHR on the transmitter and HPLR on the receiver, or exactly opposite.  This means if you bought a duplexer that was originally built for 146.625 - and retuned it to 147.195 +, you'd have to ignore the references to port identification "TX" and "RX" and connect them inversely.  If you tried to tune the HPLR to LPHR, the duplexer wouldn't tune; it would likely be more lossy on the pass and the notches wouldn't fall into place. (isn't that what he's complaining about?) This is why I hate the reference (especially on a 2 meter duplexer) of Transmitter and Receiver ports, as HPLR and LPHR always make sense, no matter frequency or orientation of the repeater split.   As I understood all the cavities are the same or are there two types? Two types,  HPLR and LPHR.... Also we have made our only cables to join the units together using RG214. I’m assuming all the cables should be ¼ taking into account the velocity factor or the cable? The cabling might have to be changed to optimize the notch depths, but he needs to get a little closer before worrying about that.   Bob   -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com] On Behalf Of Kevin Custer Sent: 03 June 2005 12:51 To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Help with Wacom WP-639 Duplexer   m1ror wrote: Hello All   This is my second posting but I'm not sure if my first attempt made it to the list.   I bought a set of what appear to be good condition Wacom WP-639 (144- 174Mhz) Duplexers originally tuned for 156Mhz. A friend has attempted to align the filters but is having problem aligning the notch down to 145Mhz. The problem he tells me is he can only get the notch down to 148Mhz with the Invar rods pushed all the way in. He has made up new patching loom and still the same result. Has any body played with these and could offer any advice? Have him swap the ports and try again, in other words, tune the duplexer backwards from the way it is presently tuned using the opposite sides for the receiver and transmitter.  Minimum frequency separation happens with the rods all the way in, which leads me to believe he is attempting to tune the duplexer upside down, on the 'wrong' notch; there are two notches, as explained below.... This article explains the basic principal for the Wacom WP-641 and 639 style pass notch network.  While specifically written about the 641, the effects are the same for the 639, however, the notch depth won't be as deep with the 639 as what is stated in the article: <http://www.repeater-builder.com/wacom/wacombpbrnotes.html> Complete tuning directions are available from this page: <http://www.repeater-builder.com/wacom/wp6xxVHFtuninginstructions.pdf> If you still encounter difficulty after attempting the switch-a-roo, email us back.... Kevin Yahoo! Groups Links To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/   To unsubscribe from this group, send an email to: [EMAIL PROTECTED]   Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.