[Elecraft] Comparing continuously loaded and other short vertical ants

[Ron D'Eau Claire]

Absolutely!  It's not "rocket science" to get a ground impedance down
below 100 ohms, but there are a lot of Hams trying to use a "ground
coupled" affair with a piece of metal capacitively connected to the
earth (including anyone going "mobile"!) or the guy with a wire to a
ground stake, or the guy on the second floor with the only "ground"
being the mains ground or perhaps a bit of wire tossed on the floor. 

These grounds can be in the hundreds of ohms. 

A sign of the state of r-f grounds for many ops is the number who have
trouble with r-f feedback, especially when feeding a high-impedance
antenna like an end-fed wire near 1/2 wave long. If they had good r-f
grounds, such feedback would be nonexistent. Having been one of those
ops for many years working from upper floors of a building or in other
limited circumstances, sometimes a good r-f ground seems like an
impossible dream! 

And yes, matching circuit losses can be VERY high, especially with the
commercial ATUs manufactured today. The common "T" match as sold by MFJ
and others are especially bad. They work very well under certain
conditions and have very high losses in others. They do a good job
"tweaking" the match of a nominal 50 ohm antenna system to keep the SWR
below 2:1 at the rig. Although they will handle very high and low
impedances as well, the ATU losses can reach 7 dB or more, especially
with low impedances on the low frequency bands where we are most likely
to have such antennas. An interesting web site offers a T-match
simulator in which you can plug in the numbers and see the calculated
attenuation displayed instantly. Go to
http://fermi.la.asu.edu/w9cf/tuner/tuner.html

The L-network used by Elecraft is inherently better on paper. It'd be
interesting to know how good the KAT2 and KAT100 are at their impedance
limits.

Ron AC7AC
K2 # 1289


The only point I would add is that my measurements indicate that 100
ohms of ground resistance is not typical.  With only 16 radials that are
approximately 1/2 the length of the vertical radiating element, ground
losses are about 13 ohms, i.e. the input Z of a 1/4 wl vertical is
nearly exactly 50 ohms.  The Z with a perfect ground would be about 37
ohms, so the difference of 13 ohms is ground losses.  This is only about
1.3 dB of loss due to near field ground.
Dave
AB9CA