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Antenna Coupler.
,STRIPPED
Fig. 3. A ntenna configuratio n u sing stripped
RG·81U.
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RG-8' '''
in 6-inch sq uares as shown in Fig. I. It was
about 32 feet high and proved quite effective
on 75 when worked against ground as a
quarter wave vertical. The second and final
antenna was made from old RG8/ U coaxial
cab le with the outer braid remo ved. Since
the stripped RG-8/U did not lend itself to a
square configuration, the antenna was made
in a series of loops as shown in Fig. 3. With
the dimensions shown, the antenna resonated
at 2150 kHz against ground.
This was a little high for the frequency of
interest (1990 kHz) and would have req uired
making the antenna about four feet longer.
Since I was out of lumber as well as energy,
I decided to use a simple series tuned antenna
coupler as shown in Fig. 4. The coupler
was also satisfactory for tuning to the 1900­
1925 kHz segment of the band. The simplest
way to adjust the antenna system is to "grid
dip" the tuner to the operating frequency
and then use the transmitter pi network to
load the transm itter in the normal manner.
I had no luck loading the transmitter " pi"
network directly into the antenna because
the antenna impedance was too low for the
"pi" network-about 30 ohms as measured
on an antennascope. No attempt was made
to feed the antenna with a transmission line,
since the antenna base and ground were bo th
located right outside the shack window.
This antenna, like all quarter wave antennas
req uires a good ground system. Radials, of
course, would be best if you have the space
and the energy to install them. I used three
eight-foot ground rods in conjunction with
three water pipe ground connections, all t ied
together. The antenna curre nt was the same
whether a half wave or quarter wave antenna
was used, so I assumed that the ground system
was fairly efficient.
As for results obtained wit h this antenna,
I have had neither the desire nor the a mb i­
tion to opera te odd hours and check the antenna
on some rea l DX. However, tests run
with stations 250 miles or so out in dicate a
two S-unit gain at times over a low horizontal
antenna. Strangely enough, stations closer
in (40 miles or less) favor the horizontal
L
e'
1 -" ", , ,
, ,
:5Z' \APPAOll.
Fig. 5 . Inverted " L " co nf igu ration .
antenna by two S-units or so. Excellent reports
have also been received when working
Idaho and Wyoming stations from this QTII
with 50 watts input.
For those amateurs who think 60 feet or
so is still too high for an antenna, I suggest
an inverted "L" configuration as shown in
Fig . 5. The antenna is, in effect, a 1/8 wave
vertical with a 1/8 wave horizontal wire added
. It has given a good ac count of itself as an
all around 160 meter antenna both for DX
and local work and is only 32 feet high.
No ma tter which antenna type yo u decide
to build, you will be sure to have a conversation
piece-on the roof, that is.
...W6FPO
' 0 '
MAY 1969 7 1