October 1959 Popular Electronics
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Do you know what a
clip is? Chances are you would know one if you saw one, but you never knew what
it was called. This 1969 Popular Electronics magazine article, requested
by RF Cafe visitor Jan C., references a Fahnestock clip in the parts list for constructing
an easily tunable long-wire antenna. The simple circuit uses just a handful of components
for matching the high impedance antenna to a relatively low impedance coaxial cable
feeder. A flashlight bulb and a few turns of wire act as an RF sniffer to tune for
best match. A high quality ground is essential to the setup's operation so the author
describes using copper sulphate crystals or rock salt to treat the ground rod vicinity
for better conduction. It's a short article so go ahead and read it - if for no
other reason than to see what a
Fahnestock clip is.
The Novice 90 Antenna
Simple tuner makes long-wire antenna
effective on 40 and 80 meters
By Jay Stanley
Many a Novice ham has difficulty in "getting out" - and nine times out of ten the
trouble lies in failure to put power into the antenna. Fifteen watts of power actually
in the antenna will put out a reliable signal on the Novice bands.
Transferring power from transmitter to antenna can be tricky business, and this
is particularly true when you try to feed most ordinary long-wire antennas with
the typical pi network stage of a transmitter. In many cases, the antenna represents
a high-impedance load - and feeding it from the low-impedance output of the transmitter
makes for a big waste of precious power.
This problem is neatly sidestepped with the "Novice 90" antenna, which is designed
to be end-fed with a low-impedance line. Thus, the antenna is very simple to erect
and, even more important, you can adjust resonant length right in the operating
room. The adjustment is easily made using a 10-cent flashlight bulb which shows
you the point of maximum antenna current.
This current is the power being soaked up by the antenna.
Locate the antenna tuner for the shortest
possible ground wire while maintaining accessibility for tuning. A remote waterproofed
tuner installation is possible but this would make tuning more difficult.
C1-350·µµf. (or larger) midget TRF single-gang variable capacitor
J1-RCA type phono jack (or suitable coaxial cable connector)
L1-Six turns of B&W 2"-diameter Type 3900 coil stock
The "heart" of the antenna is a simple tuner, consisting of a TRF-type single-gang
tuning capacitor (C1) and coil L1. These parts are mounted on a convenient board
as shown in the diagram. Stand-off insulators support the coil and the antenna terminal.
Variable capacitor C1 and the Fahnestock clip for the ground connection are mounted
directly on the board. The RCA phono input jack J1 (a regular coax connector could
be used instead) is mounted on a small metal angle bracket screwed to the board.
Jack J1 connects to the coaxial cable jumper which runs to your transmitter output
The coil for the antenna tuner consists of six turns of No. 14 wire approximately
2" in diameter. Turns are spaced approximately 1/8" apart. Wind the coil yourself
or cut some turns from a piece of B & W 2"-diameter No. 14 wire coil stock (Type
The antenna itself is a 90' "L"-shaped length of wire. How much is horizontal
and how much is vertical is not particularly important: for example, 30' up to 60'
out is ideal. However, other combinations, such as 40' up and 50' out, will work
For best results, keep the ground lead under 10' in length, the shorter the better.
If it must be longer, subtract the length of the ground lead over 10' from the antenna
length in feet. For example, if the ground lead is 14', make the antenna 86' instead
You can build an efficient ground as shown in the diagram. Use a standard TV
ground rod (the longer the better) and then improve the conducting characteristics
by chemically treating the ground nearby. Copper sulphate crystals are excellent,
as is rock salt. Ordinary table salt will work well also, but of course is more
expensive. Dump in the chemicals, soak down the area with a garden hose, and you
will have a ground far more efficient than the usual water pipe ground. The latter
should be used only as a last resort and cannot be expected to work as well.
In a typical station layout, the antenna tuner should be mounted alongside a
window sill. The ground should be just outside the window, close to the house. The
antenna tuner can be connected to the transmitter by any convenient length of 50-
or 52-ohm (approximately) coaxial cable.
First, attach a two-turn loop of wire to a No. 44 dial light bulb or a bulb from
a two-cell flashlight. The loop and the bulb provide an indicator for antenna current.
Then, connect the coaxial cable from the transmitter to the antenna tuner. Set the
capacitor on the antenna tuner approximately one-half "open."
Next, set your transmitter for 80 meters, and tune it following the manufacturer's
instructions. Load up the transmitter final by adjusting the antenna loading and
plate tuning capacitors in the transmitter. Now, couple the pickup loop and bulb
(as shown in the photograph) to the antenna coil, and adjust antenna tuning capacitor
C1 for maximum brightness. When you find this point, you have the antenna at resonance
and it is taking maximum power.
On 40 meters the adjustment is quite similar, although the resonance point is
usually very broad, as shown by the tuning loop indicator. On this band, set the
antenna tuner capacitor to as high a capacity as possible (plates almost closed)
where the tuning indicator is at maximum brilliance.
The last step is to adjust the transmitter tuning for proper load as indicated
by the milliammeter in the final of the transmitter. Don't make any big changes
in the antenna resonance adjustment already achieved, but check for maximum brilliance
of the bulb.
Posted January 6, 2023
(updated from original
post on 3/18/2013)