Paul, As I mentioned earlier, the ARRL assumptions about ladderline loss are very optimistic. It's easy to do a calculation based on the RF resistance of the gauge of wire used in ladderline to show
Dave, A good summary - but can I just pick you up on one minor issue: the configuration required for the L-network does *not* depend on whether the load impedance is higher or lower than the required
Stan, I have had exchanges with G0KSC about errors on that page where he describes the Pawsey Stub, as you will see from his recent additional note in red. In particular: 1) It is *not* the different
I have some modelled examples on my web site which illustrate the effect Jim is talking about. Take a look at the section "Why reactive chokes are undesirable" on this page: http://www.karinya.net/g3
Rudy Severn's work showed that for a given total length of copper, more short radials - as opposed to fewer long ones - was the better option. He also found some supporting evidence for the old "Ham
Jim, Agreed! If folk would look carefully at the Brown/Lewis/Epstein paper they would see that it's not so different from Rudy Severn's work. Figure 30 in their paper plots received field strength ag
I would expect it to be. With ground radial fields of these sorts of dimensions you are primarily affecting the Near Field efficiency, not the elevation angle. To substantially affect the elevation a
Grant, The 1:1 choke at the ladderline/coax junction will impede conducted CM current from flowing back along the outside of the coax sheath. That will drive equal and opposite leg currents in the la
The problem is that the moment we attach a feedline to the feedpoint we have the potential for unbalancing the currents because there's another path for the antenna CM current to take. It's very inst
You can have a dipole where each leg is equal length has an identical impedance to ground, and yet still have unequal currents. Picture such a "perfect" dipole fed with coax. The outside surface of t
The problem is, I don't know how to get power to a dipole without using a feedline ;) So the potential for imbalance is always there in a practical system. Steve G3TXQ _______________________________
For me, distortion of the radiation pattern of a simple dipole or loop is the very least problem that CM currents can cause. Much more significant is the potential for RFI, and increased noise levels
Pete, Yes, I've used them in my shack for the last couple of years or so, and now use them exclusively. As you would expect, they are every bit as easy to fit as a compression N-type. So far I haven'
Photograph, here, for anyone who's not familiar with them: http://www.karinya.net/g3txq/temp/pl259.jpg Steve G3TXQ _______________________________________________ ____________________________________
John, In what I would call the "classic" version of the G5RV the ladderline section needs to be an electrical half-wave on 20m - that usually works out at just over 30ft, not the 20ft you are using.
Be aware that if you're tempted to use the G5RV on a band where the VSWR(50) is high, the 1:1 balun windings may need to withstand some quite high voltages. For example, on 30m at 1400W the voltage b
Here are a couple of simple calculations based on EZNEC predictions of the impedance at the end of the G5RV ladderline - where the 1:1 balun operates: 40m: Z = 27-j78 At the 1500W level, I = 7.5A rms
Apologies - I don't avidly read US band plans and power limits ;) So, try 1500W on 10m instead: peak voltage = 2.88kV 73, Steve G3TXQ _______________________________________________ _________________
John, As you realise, adding a choke to the G5RV is not primarily about improving the match or saving dB - it's about stopping the ladderline, and more importantly the coax, from becoming part of the
I don't know where this "ham myth" comes from that the original G5RV was just a 20m antenna! Varney's original article published in the RSGB Bulletin, July 1958, is entitled "An Effective Multiband A