Darrell Bellerive <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- While a balun on the output side of a tuner will couple some energy it may not be very efficient at some impedances.
A balun, whether 1:1 or 4:1, is designed for a specific characteristic impedance. In most ham radio applications the transmitter side impedance is designed for 50 ohms unbalanced. So in a 1:1 balun the antenna side should have a resistive impedance of 50 ohms balanced and a 4:1 balun should have a resistive impedance of 200 ohms balanced. As the antenna impedance changes from the designed characteristic impedance by reactance and/or resistance, the efficiency and transformation ratio will deteriorate. Just how much will depend on the design of the balun windings, the core material, and the resistance and reactance of the load. As many point out, it will still work. One can lose as much as 6 to 10 dB or more in a tuner, balun, and feedline and still make lots of contacts. QRP operators prove this all the time. Heating of the core material is one indicator of lost power, but remember that the lost power will heat a small core to a much higher temperature than a large core. So just because the core does not get too warm, doesn't mean power isn't being lost to heat. Modern automatic antenna tuners are hard to beat for ease of operation, but for the highest efficiency it is hard to beat the old link coupled tuners for balanced line applications. All electrical systems are compromises between a number of variables such as efficiency, cost, ergonomics, size, weight, availability of materials, etc. Just be sure you understand the compromises you are making. 73, Darrell VA7TO On Monday 02 June 2008 03:12, Ed G wrote: > I have had great success here with what is essentially a 135 foot inverted > vee fed with 300 ohm twinlead. I use a DX Engineering 1:1 balun mounted > outside the house, with a short section of RG-8 leading into the shack (and > the MN-2000). That way I don't have to worry about bringing in the > twinlead. The 1:1 balun keeps the impedance on the transmission line from > dropping too low as might happen with the 4:1 balun. I did slightly change > the length of the twinlead (should be approx 108/F) to find a perfect match > on all bands. > > --Ed G- -- Darrell Bellerive Amateur Radio Stations VA7TO and VE7CLA Grand Forks, British Columbia, Canada ---------------------------------------------------------------------- Submissions: drakelist@zerobeat.net Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net ----------------------------------------------------------------------
