you know what a Fahnestock clip is? Chances are you would know one if you saw one, but you never knew what it was
called. This 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.
October 1959 Popular Electronics
of Contents]People old and young enjoy waxing nostalgic about and learning some of the history of early electronics.
Popular Electronics was published from October 1954 through April 1985. All copyrights are hereby acknowledged.
See all articles from
The Novice 90 AntennaSimple 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.
Simple tuner makes long-wire antenna effective on 40 and 80 meters
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
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
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 terminal.
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 3900).
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 as well.
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 of 90'.
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
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.