I have the AT1KM. It has a nice big 4:1 balun built in. Have you tried it to see if it gets hot too? That little BL2 may be rated for 250 watts but this is for a resistive load or 200 ohms. It's not going to be able to handle the extreme reactance of that antenna system. Even 25 watts would be asking a lot of it. I quote the BL2 manual: "Power Rating 250 watts with a MATCHED LOAD". Your load is far from matched. 73
Steve N4LQ n...@carolina.rr.com ----- Original Message ----- From: "Ron D'Eau Claire" <r...@cobi.biz> To: <n...@live.com>; <elecraft@mailman.qth.net> Sent: Thursday, November 19, 2009 11:32 PM Subject: Re: [Elecraft] BL-2 Balun Heating > Yes, you are reaching the "curie temperature" of the core. At that point > it's magnetic properties change dramatically. > > Of course that heat comes from RF that is becoming heat instead of being > radiated by the antenna. A bigger core isn't the answer. You'd still be > losing the same amount of power even if a much larger core felt cooler. > Same > with a heat sink. > > You didn't say what band you are using. Heating a balun is usually a sign > of > excessive current flowing -that is you are at a current loop. You can > change > that by changing the length of the feedline or just do away with the balun > and connect one side of the open wire feeders to the center pin of the > tuner > output and the other to the case. That does not introduce anything like > the > degree of "unbalance" that some suggest. Indeed, the balance in the > feedline > is much more strongly affected by the antenna than the source. > > Ron AC7AC > > > -----Original Message----- > I recently built a BL-2 Balun. It is connected between my Palstar AT1KM > tuner and my doublet antenna. The antenna consists of a 100' wire up > 25' and fed by 95' of 600 ohm open wire feeder. I'm using the 1:1 > setting on the balun. There is a 4" section of RG-213 between the balun > and a coax input of the tuner. I'm driving it with 125 watts from a > TS-850. After no more than a few minutes of CW or RTTY transmission, > the balun is too hot to touch, the SWR rises and the power goes down. > The balun is obviously saturated. > > Does anyone have an idea how I can reduce the overheating? I've tried > adding a heat sink but it doesn't make any difference. > > Tnx for reading! > > Gary N2UM > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.707 / Virus Database: 270.14.73/2514 - Release Date: 11/19/09 14:42:00 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
