[Elecraft] [OT] end-fed halfwave antennas

[Guy Olinger K2AV]

The EFHW antenna was not invented by anyone alive today. It is very
definitely a classic antenna. It's just a very efficient antenna that has
gone through periods of forgotten usefulness.

An end-fed 80m half wave L, or other "bent" form, is an antenna that has
been used successfully at least since 1957 when I first saw one as a 14
year old. The at-the-time 52 year old AM BC chief engineer who explained it
to me, alas, is long gone. He would be 111 today.  No one used center
loading coils back then. Puts the max current in the antenna on the loading
coil. If you couldn't make it long enough, you made it long as you could
and the difference got soaked up in the matching network.

Hams seem irresistibly drawn to antennas where "matching the antenna"
consists of connecting it directly to a piece of coax.

So it is that over the years, especially on 80m, many have shown up on the
air with amazingly inefficient antennas on 80m. They would check into 80m
traffic nets with really puny signals. Many of these weak signals were
excellently solved by going to an end-fed halfwave L fed with a matching
network (usually a tapped coil in parallel with a capacitor) against some
horrible ground. Grounds like a couple of buried bare wires running away
from a basement window, or even a ground rod, did not matter in series with
the end-feds' feed Z's in the 1000, 2000 ohm range and up.

The improvement in signal strength converting to the EFHWL was often
remarkable, as in two or three S units, or as said back then, "gone from a
peep to a pounder".

The EFHWL has never been popular because it always requires a matching
device *at the base of the wire*, and without some remote switching of taps
and/or cap value, only covered 50-100 kHz of the band in today's common SWR
limits. However back then that was often extended as rigs with tetrode tube
finals were far more tolerant of antenna Z. At QRP, particularly among the
SOTA and backpacker crowd, the EFHW is making a comeback.

If we ever get a good manufactured off-the-shelf *QRO* end-fed tuner, the
80m EFHWL will get popular and stay that way.

73, Guy


On Sat, Feb 11, 2017 at 7:59 PM, inventor61 . <inventor61 at gmail.com> wrote:

> My Elecraft rigs are connected to guyed, end-fed half wave vertical
> monopole antennas, one each on 30 meters and 40 meters.  I use
> tapped-L-parallel-C matching networks at the base of these antennas, which
> are ground mounted and insulated.
>
> They radiate at the horizon, or darned close to it, and don't need any
> inconvenient ground radial wires, or even a particularly low impedance
> earth.  To me, that fact alone was worth any other effort.
>
> I got inspiration for my antennas from similar designs used at the
> following addresses ... each have historical markers, incidentally ... if
> you are curious, you can use Google Maps to see them yourself:
>
> 764 Tylersville Road, Mason, Ohio
>
> 8068 Concord Road, Brentwood, Tennessee
>
> While the hams who designed and installed these antennas had bigger budgets
> than I do, they had the same goals.
>
> For portable use, if you can manage an overhead tree branch at a suitable
> height, only 60 feet of wire interrupted in the center with 47 microHenrys
> of L yielded a center-loaded EFHW I used *very* successfully on 80 meters.
> Again, no radials needed, a major consideration to me.  The feedpoint
> impedance was quite high, so the matching network I had to make was
> interesting but still do-able.
>
> Steve KZ1X/4
> K2 #771
> K3 #6081
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