It's tough to find a way to express a tuner's capability in some succinct and meaningful way. This was my attempt: http://www.karinya.net/g3txq/temp/aat_chart.png Each "cell" represents a particular
Dave, Thank you for the clarification, and for confirming my points: * dBi is always referenced to an isotropic radiator *in free space* * EZNEC is consistent with the industry definition and is not
Power handling really isn't an issue in this application. Connected to a multiband doublet, the SWR wont get much higher than 10:1 on 300 Ohm or 400 Ohm cable. That would put the maximum localised cu
Reading many articles about the advantages of window line you could be forgiven for thinking it is virtually loss-less in most applications; that isn't necessarily the case. For example, when used in
To illustrate Ken's point, here are some measurements I made on the feedpoint resistance of my 160m 40ft top-loaded vertical as I added radials. Rrad for this antenna should be about 5 Ohms. 6ft Grou
Frank, Efficiency was calculated, knowing that Rrad should be 5 Ohms. So for example with just the ground rod, efficiency = 5/33 = 15.15% 73, Steve G3TXQ Frank
"Efficiency" is a term well understood by most professional engineers as: Efficiency = Pout/Pin If we are talking specifically about an antenna's efficiency - not an antenna *system* - the expression
Jerry, Not sure if it helps much, but NQ6Z was obviously on the same quest. In one posting, he claimed that the earliest reference to the term he had found was a 1972 Fort Monmouth report: http://www
Ladderline behaves differently from coax, and there might be a small impedance "bump" if you turn it abruptly through 90 degrees; however, in many ladderline applications that wont matter. It certain
Jerry, That shouldn't happen with a well-designed 1:1 Guanella Balun, which is the preferred choice for wide-band, wide-impedance-excusion, applications. Unlike a 4:1 Guanella balun or 4:1 Ruthroff b
Jerry, I was addressing my comments to your application, which I assumed - maybe wrongly - was a balanced-line-fed multiband doublet. The balun I referenced is aimed at 160m thru 40m use; but even at
Of course, the Johnson Matchbox has its secondary capacitors "centre-tapped" to ground; that makes it a "stiff" voltage source. In other words it's a VOLTAGE balun, just like the 4:1 Ruthroff found a
If that's a problem I would prefer to use a couple of high value resistors to leak the charge to ground, rather than compromise the current balance on the TL. Steve G3TXQ
Jim, I agree! I've been doing some balance measurements on a 100ft doublet I have fed with ladderline. Because of its local environment it's a pretty unbalanced antenna system. I measured ladderline
In my experience, all those harmless fractions of a dB have a nasty habit of getting together and adding up to something more substantial ;) Steve G3TXQ On 14/11/2010 18:38, Jim Brown wrote: On 11/14
Jerry, I must challenge you again on that statement - it simply isn't true of a 1:1 Current Balun at the output of a tuner. The core flux of that Balun - and therefore its loss - is determined by the
Jerry, You obviously didn't read what I wrote about running: "the ladderline through a single ferrite core wound with pick-off turns to overcome the phase imbalance "uncertainty problem" ! 73, Steve
If you do the thermal calculations on the cores commonly used in these chokes you'll find it's almost impossible to saturate them - for typical amateur mode duty-cycles they will over-heat and fractu