Jim - the 20ft height of your vertical is obviously an advantage. Lest anyone misunderstands me: I'm not saying the dipole is always better than the vertical - I'm trying to highlight the dangers of
Dennis, EZNEC modelling certainly doesn't confirm what you are saying. I just modelled a 40m horizontal half-wave 33ft above average ground - the optimum take-off angle was 66 degrees. Then I modelle
Denny, Do you have a specific Cebik article in mind? I'm pretty familiar with his work and I just re-read his 5-part article on modelling 160m verticals, but I can't immediately see anything that sug
Denny, I've spent some more time wading through LB's pages, but I'm struggling to find anything that suggests he thinks the modelling might not be valid. The most pertinent page "Horizontal vs.Vertic
Nope - the current will be much higher in an electrically short antenna. What matters is not its high reactance - that will get tuned out by the matching circuitry - but the low radiation resistance
Martin, with respect this is completely wrong. Take a simple example of a shortened dipole that's only a quarter-wavelength overall length. It has a feedpoint impedance of about 13-j750. If this ante
To further illustrate what is happening here, I took my "quarter-wave" dipole example, matched it with a simple L network at 30 MHz (series 4.1uH inductor and shunt 180pF capacitor) and looked at the
Dave, I don't know of any programme that will calculate the voltages and currents - I just did it the "hard way" with Smith Chart and a pocket calculator :) If you simply want to see what sort of com
Apologies - that was the local link on my PC! The Tuner simulator is at: http://fermi.la.asu.edu/w9cf/tuner/tuner.html 73, Steve G3TXQ _______________________________________________ ________________
Jim, Nope! [13-j750] is the equivalent SERIES representation of the feedpoint impedance, so the same 8.7 Amps flows through the resistive part AND the reactive part; there is no 500 Amps flowing anyw
Bud, There's no mystery - the other 860 Watts gets dissipated in the 2.4 Ohms loading coil loss resistance and the 4 Ohms Ground loss assumed by HI-Q. The maths all hangs together: Efficiency = Rrad/
Martin, I'm happy we can agree, and draw a line under this. I only joined the discussion to challenge your original statement that: "This all assumes you're talking about a full size dipole. If your
John, No, an inverted L doesn't need to be resonant. Increasing the total length raises the radiation resistance, and that may help the efficiency if you have a "less than perfect" ground system. How
Not even that! EZNEC says 0.04dB going from #14 to #6 on a 20m dipole. 73, Steve G3TXQ _______________________________________________ _______________________________________________ TowerTalk mailin
Mike, So 0.08dB going from #14 to 2". Not sure about the accuracy when dealing with such small numbers. More significant is the increase in bandwidth caused by the thicker conductors. The improvement
Dan, I'm using lots of segments - 10 times as many as the EZNEC Conservative Auto Segmentation. Lossless Average Gain is 0.00dB Convergence testing - doubling the number of segments makes no differen
Worst case impedance looks to be on 12m where the losses in 125ft of RG213 would be 6.3dB Steve G3TXQ _______________________________________________ _______________________________________________ T
Should have said that the matched loss, using the tuner at the feedpoint, would have been 1.2dB. So, tuner in the shack is worse by about 5dB Steve G3TXQ _____________________________________________
Jim, I very nearly sent off my 350 dollars to get the 12dB, but then I realised I'd have trouble matching to the cage dipole. To quote their web site: "The cage antenna has 1/6th of the radiation res
That just illustrates how silly some of this stuff can get! An increase in power from 80W to 500W is about 8dB. That would show up as just over 1 S-unit on a meter calibrated at 6dB/S-unit. 5 S-units