Bob. Your impedance is likely in the 25 ohm range, so you would need a 2:1 balun. A 4:1 likely overshot the 50 ohm mark. I'd just go with a hair pin coil between the vertical and ground. About 10 turns and maybe 3 " diameter. Spread coil to change match. Should get you to 1:1. Kenny K2KW
Sent from my iPhone, Kenny > On May 30, 2015, at 12:00 PM, [email protected] wrote: > > Send Topband mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.contesting.com/mailman/listinfo/topband > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Topband digest..." > > > Today's Topics: > > 1. vertical balun (Bob Kupps via Topband) > 2. Re: vertical balun (shristov) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 29 May 2015 21:13:50 -0700 > From: Bob Kupps via Topband <[email protected]> > To: topband <[email protected]> > Subject: Topband: vertical balun > Message-ID: > <[email protected]> > Content-Type: text/plain; charset=us-ascii > > Hi we have a 30m top loaded monopole with the feed point about 2m above a > large ground radial field. Right now we are feeding it through a 4:1 balun > (not a unun) with 12.5 ohms on the balanced side, and the SWR is 1.4 with no > matching network. Is this balun acting as a common mode choke? Do we even > need a choke? Would an unun be better? > > Thanks 73 Bob HS0ZIA > > > ------------------------------ > > Message: 2 > Date: Sat, 30 May 2015 06:40:14 +0200 > From: shristov <[email protected]> > To: topband <[email protected]> > Subject: Re: Topband: vertical balun > Message-ID: <[email protected]> > Content-Type: text/plain; charset=us-ascii > > Bob Kupps wrote: > >> Right now we are feeding it through a 4:1 balun (not a unun) with 12.5 ohms >> on the >> balanced side, and the SWR is 1.4 with no matching network. > > > You should get quite a reasonable SWR with no matching at all. > A good high-impedance common mode choke is recommended. > > 73, > > Sinisa YT1NT, VE3EA > > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > Topband mailing list > [email protected] > http://lists.contesting.com/mailman/listinfo/topband > > > ------------------------------ > > End of Topband Digest, Vol 149, Issue 17 > **************************************** _________________ Topband Reflector Archives - http://www.contesting.com/_topband
