ICE 180 a reasonably
professional matching unit
to minimizing noise pickup with an end fed antenna (Beverage,
longwire, inverted L, or vertical) is to feed it with coaxial
cable whose shield is well grounded.
Unfortunately, coaxial cable is a poor impedance match to a wire
antenna, except perhaps at a few special "resonant" frequencies.
A matching transformer at the base of the antenna can smooth out
the fluctuations in antenna system efficiency with frequency,
yielding an antenna system that works well enough for good reception
from longwave to the top of the shortwave range.
I've posted instructions for winding such a transformer several
times on rec.radio.shortwave. My homebuilt transformer works well.
However, after about the fifth time this summer that I left the
antenna cable plugged into my receiver by accident, I decided
I needed to improve my lightning protection to minimize the chance
of damage. After looking through catalogs, I decided to buy a
matching transformer with internal lightning protection.
is *very* solidly built. A barrier terminal strip is provided
for three different antenna inputs, allowing impedance transformation
ratios of 6:1, 9:1, and 12:1 to be chosen. These are labelled
as 300, 450, and 600 ohms for use with 50 ohm cable. A "UHF" type
coax connector is provided, along with a nice grounding stud for
grounding the case.
The unit appears to be hand made. The transformer itself is wound
on a two hole "balun core". There's a gas discharge tube across
the transformer secondary and a 3 kV capacitor between the secondary
and the central socket of the coaxial connector. The workmanship
inductance of the transformer drains static to ground. The
discharge tube clamps the voltage due to a sudden discharge. Most
of the energy in an electrostatic discharge is at low frequency
and below: the capacitor blocks this. This is worthwhile protection,
but not comprehensive enough to completely protect a sensitive
receiver: more protection is needed at the receiver end of the
cable. This is not a criticism: I don't believe that comprehensive
protection is possible in a single package.
is rated for use at frequencies of 1-30 MHz with 50 ohm cable.
I use 75 ohm cable in my system: this might be expected to reduce
the frequency range slightly.
To check it, I used the transmitter for a radio controlled boat
(at 27.145 MHz) and a local radio station (at 1.600 Mhz) as stable
(ground wave) reference signals.
I compared the 180, using its 9:1 input, with my homemade
9:1 transformer using the S meter on my Drake R8. The antenna
was a 17 m inverted L.
At 27.145 MHz, there was no detectable difference (<1dB) between
the two units.
At 1.600 MHz, my homebuilt transformer yielded a slightly stronger
signal (1-2 dB).
Nevertheless, the Model 180 has enough low frequency response
that I can easily hear the antenna's noise floor all the way down
to 100 kHz, so a "better" response would not, in fact, improve
short, I cannot find any fault in this unit.
At $32 it is
also the least expensive transformer of this type that I'm aware
of (unless you make your own).
products can be ordered on-line at the official
ICE web site Here you will find datasheets as well
as free publications on grounding and beverage antennas.
I have no connection with ICE except that I'm a satisfied customer.
published on Usenet's rec.radio.shortwave forum, September 1994,
updated in March 1998 and October 2003.