[Premium-Rx] Broad Bandwidth HF RX Antenna

[Geoff Fors]

Speaking of "broadband" antennas with a resistor in them - -

About 25 years ago there was a "broadband" HF transmitting antenna offered
in the pages of CQ and 73 Magazines.  It claimed to cover the 2-30 MHz
spectrum with flat VSWR and was basically just a dipole with a large white
center insulator.  At the time, I worked for a large California ham radio
distributor and we obtained a sample for evaluation.  The antenna seemed to
meet the manufacturer's claims except that received signals were rather
lackluster and our contacts reported our signal somewhat worse than on a
standard dipole.  We discovered that the DC resistance at the coax connector
measured 50 ohms, which made it pretty obvious what was going on.  We sliced
up the center insulator assembly with a bandsaw, but we couldn't see much
because it was completely potted in fiberglass epoxy resin.  There appeared
to be a great deal of strange circuitry inside on small PC boards, which
didn't make much sense, but because of the potting, we couldn't tell what
was going on.  We did find what appeared to be a large non-inductive
resistor.

I later found out that the ARRL had one in their lab for pre-advertising
evaluation.  At the time, ARRL had a policy of not accepting advertising
from manufacturers whose products did not pass their lab tests, and I think
they still do.  They had sent the center insulator section out to be x-rayed
and had discovered that there was nothing inside it except a large 50 Ohm
resistor wired across the two terminals.  The circuit boards we had seen
were just scrap boards thrown into the mold to deceive people who might try
to take it apart.  I seem to recall that the lab ran the x-ray in QST some
months later without mentioning the name of the manufacturer.  The company's
ads were rejected, and we never did carry the product.


Geoff Fors
Monterey CA