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 ______________________________________________
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
There are some CM choke impedance measurements here: http://www.karinya.net/g3txq/chokes/ Steve G3TXQ _______________________________________________ TenTec mailing list TenTec@contesting.com http://
John, It's very difficult to get decent common-mode impedance across a 4:1 frequency band with an air-cored choke - they are too "High-Q". A further problem caused by their high Q is that their imped
Rob, Why use 100ft of coax on a 1.5ft diameter form, when 3ft or so of coax on a ferrite core would give you much higher CM impedance than that; and better still, it would be Resistive rather than Re
A Resistive choke will *always* reduce CM currents; a Reactive choke may not. Here's an extract from an EMC handbook: "For high frequency applications, ferrites should be viewed as frequency dependen
Rob, No, it doesn't annoy me; and I apologise if I have given offence by pressing the point too much. It's just that I find a disappointing lack of understanding within the ham community about the pr
Factor in an uncertainty of up to 5% to allow for variations in wire velocity factor, further uncertainties due to the environment (ground conditions etc), and plain errors because he has assumed tha
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 _____________________________________________
"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, I seem to recall reading somewhere that the term NVIS dates from the Vietnam war; I'll see if I can find a reference. 73, Steve G3TXQ _______________________________________________ TenTec mai
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
Jerry, Following extracted from a discussion on the Yahoo NVIS discussion group: "I believe George Hagn was the first to use the term, "near vertical incidence skywave" in 1967 and Sol Pearlman at Ft
OK - just so there are no disputes in 100 years about where the term originated and by whom ........ I'm going to re-design my antenna system to provide strong signals at the low take-off angles need
OK - for the benefit of history, and so that my obituary is accurate, it was invented at 2130hrs GMT on 4th January 2011 in the small UK village of Milton Malsor ;) 73, Steve G3TXQ __________________
The Compass is nearer - about 100 yards; if we made it the Greyhound I'd have to stagger 150 yards to get home ;) 73, Steve G3TXQ _______________________________________________ TenTec mailing list T
I presume the "wink" indicates that is a joke ! The only thing that would improve the elevation pattern would be improved ground conditions in the Fresnel Zone where the ground reflections are taking