El 21-09-12 1:56, NM5K escribió:
On 9/19/2012 11:11 PM, ultravista wrote:


The IC-706 has two coaxial antenna ports and I am looking for antenna
suggestions for monitoring shortwave. I live in a house and have the
ability to string just about anything up.

Just about anything will work. Down to a simple random length of wire
stuck in the center conductor of the HF port, and draped around the
living area or yard.




A long wire from outside that goes directly to the receiver's
asymmetrical input will very likely provide sufficient signal for the
receiver. It may also receive lots of noise from indoor
electronic/electrical equipment. When external noise dominates,
further wire length increase will not help (excluding the very loooong
ones that operate in traveling wave mode).

If you have the possibility, use coaxial cable for the interior part
(75 or 50 Ohms). Don’t worry about mismatch, for reception you just
need sufficient signal.

Make sure you connect the braid of the exterior side of the coaxial
cable to a ground provision. This can be a ground stake, but every
large metallic structure can be used for that. You may add some common
mode choke (based on ferrite cores or rods) to further reduce the
effect of indoor generated noise.

If you live in a very low noise environment, using a 9:1 transformer
will give more signal and noise, given certain wire length. If
external noise already dominates, spending lots of money for a 9:1
transformer will not increase your S/N ratio.

Regarding the long wire or loop discussion; whether a loop is useful
or not depends on frequency band and local EM environment. You need to
try as you can't say beforehand what will work better.


--
Wim
PA3DJS
www.tetech.nl
Please remove abc first in case of PM