Good post, Paul. Than you. I've added it to the notes I'm collecting for things to check when my K3 comes.
73, Bob N6WG ----- Original Message ----- From: "Paul Christensen" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Saturday, March 15, 2008 7:59 AM Subject: [Elecraft] K3 SO-239 Connectors > As indicated earlier, I included a link to a photo that shows my K3's > upgraded Amphenol SO-239 connectors. > > 216.229.20.37/images/K3.jpg > > The Mouser catalog P/N is 523-83-798. The Amphenol P/N is 83-798. > > In spending some time reviewing the placement of the K3's SO-239 connectors, > the RF connector mounting configuration can be improved with only minor > re-work as shown below. In the link to the following photo, you will see the > two panel-mounted SO-239 connectors with three (3) solder-lugs added as well > as the KAT3 ATU Board. > > 216.229.20.37/images/K3-1.jpg > > The K3 comes with both the ANT 1 and ANT 2 SO-239 connections routed to the > KAT3 board with only a single-ended wire. The connectors' RF return path > necessarily relies upon clean, tight, but unbonded connections through the > chassis and also through a path of screws washers, and an aluminum spacer > that holds the KAT3 to the K3' side panel. In the photo, you will see that > the final RF attachment point to the KAT3 is through a zinc-plated, > Phillips-head screw located at the upper left of the board. This is the > same attachment point whether its modified or unmodified. Only, in the > modified layout, bus wire connects the SO-239 connectors straight to the > zinc screw connection point. Removal of the KAT3 board is just as easy as > it was before. It's now also possible to replace the aluminum spacer with a > ceramic or fiber spacer which, will force all RF current along the new buss > wire and keep high RF current from circulating through the K3's chassis. > > At 100W of RF, I am not completely comfortable with the existing arrangement > given my past experiences with transceivers of other manufacturer who > similarly use single-ended RF wiring techniques and rely upon good chassis > and hardware connections for the RF return path. In almost all cases where > RF ingress was an issue, those cases were resolved by creating a direct RF > return path from the antenna connectors, rather than allowing 100% of the RF > current to flow and circulate through the chassis. True, in a bonded > configuration like this, the chassis will still allow for some RF current, > but the level of chassis RF current can be reduced by either: (i) running a > short buss wire from a solder-lug on the SO-239 connectors to the KAT3; or > (ii) using short (3") coaxial cable from the SO-239s to the KAT3 with > shields bonded at both ends. I suspect that ANT 1/ANT 2 antenna port > isolation may be improved by using the coaxial option. > > Since the wire length between the KAT3 and SO-239 connectors is so short, I > decided to use #20 AWG buss wire with solder-lugs, rather than use coaxial > cable, although ideally, something like 2 or 3-inch cuts of RG-174 with > Teflon dielectric would be ideal. I may switch to that at a later point and > verify port isolation results. > > Paul, W9AC > > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
