"bpnjensen" wrote in message
ps.com...
On Oct 1, 3:09 pm, "Dale Parfitt" wrote:
wrote in message

ps.com...
In the RFI/EMI world the maximum length
of grounding conductors has been found
to be 1/20 of a wavelength. Conductors
longer then 1/20 of a wavelength become
effective unintentional radiators. It is true
that we consider a 1/4 wavelength to be
the most effective and desirable length.
But significant radiation does occur from
even cables as short as 1/20 WL.

A 1/4 wavelength long ground wire is the WORST possible length. A 1/4
wavelength line acts as an impedance inverter (just as in transmission
line). So the low Z at the ground rod gets transformed to a hi Z at the
radio- making the ground totally ineffective.

Dale W4OP

Hi, Dale. On your SW insulated wire antennas, do you then recommend
using a ground at all, or just go with the ungrounded cable-to-wire
junction?

I am seriously thinking about getting two of these gems and phasing
them, if I can make the geometry work on my constricted lot...if I
don't have to ground them, I'd be way ahead of the game for other
reasons. If grounding is better, would separate ground rods be
appropriate?

Thanks!
Bruce Jensen

Hi Bruce,
I copied this from the FAQ portion of our site:
What is the best grounding arrangement for the EF-SWL?

Unfortunately, there is no one answer. That is why we have provided separate
grounds on the matchbox. Lug 1 is the ground end of the antenna side of the
transformer while #2 is ground for the coaxial shield. Depending on the
source of noise, it may be advantageous to: 1. Leave the factory shorting
strap in place and attach either lug to a suitable RF ground at the antenna.
2. Remove the strap and ground only lug 1 at the antenna site. Then, the
receiver may be grounded or left ungrounded- whichever results in lower
noise.

So, there is no single answer, but some sort of short ground for the
matchbox will yield less noise than no ground. With no ground at all, the
outside of the coaxial shield is free to conduct noise.
Please note, that we have had to suspend all amateur/SWL mfg for October
while we deal with an unprecedented level of military and aerospace work.
Thanks for your patience.

73,

--
Dale W4OP
for PAR Electronics, Inc.