I have found Longer is always better for antennas;

I have found a Short co-ax lead -in cuts down Man made moise considerably;
I use the cheap, grey Radio Shack Co-ax

( Whatevers cheap, effective & around . .)


In article , "Arthur Harris"
writes:


"Zoltar" wrote:
I am acquiring a Sony icf-7600gr and want to put up a longwire aerial for
it- can some one advise on the specs viz wire length etc. also is it
necessary to run a coxial cable from the aerial to the radio and if so how
does one attach (both ends) ie is the shielding attached to the aerial as
wellas the centre core

Does the 7600 have a jack for an external antenna, and if so, what does it
look like?

You don't really have to use coaxial cable. In fact, a random wire (it's not
really a longwire) will not be a good match for coaxial cable unless a
matching transformer is used.

You can run a wire of any random length (25 to 50 feet) from the radio to
any convenient support (tree, pole, etc.) Keep it away from power lines, but
try to get it up high and away from sources of interference such as TVs and
computers. It can be run entirely indoors, but that will probably pick up
more noise and interference.

You may find that a longish wire will pick up so much signal that it will
overload your radio. That won't damage the radio, but will generate intermod
which will adversely affect reception.

If you don't have an external antenna jack, just clip the end of your wire
antenna to the telescoping whip. If signals are too strong, just wrap a
couple of turns of the (insulated) wire around the whip.

The antenna wire can be any convenient gauge that's strong enough
mechanically. It should be insulated anywhere it touches anything.

Some folks use a 9:1 matching transformer with their random wire. When
properly grounded, that type of system can reduce noise pickup. What matters
in shortwave radio reception is not so much signal strength, but signal to
noise ratio!

Art Harris N2AH

"Diverd4777" wrote:
I have found Longer is always better for antennas;

True in general. But some portables can't handle that much signal. I think
the original poster is in Europe (based the words "aerial" and "centre").
Europeans seem to have more problems with overload due to the abundance of
nearby transmitters.

I have found a Short co-ax lead -in cuts down Man made moise considerably;
I use the cheap, grey Radio Shack Co-ax

Agree with that!

Art Harris N2AH

Arthur Harris schrieb:

"Diverd4777" wrote:
I have found Longer is always better for antennas;

Until the natural noise floor is higher than the receiver's
sensitivity... Modern receivers can squeeze out even short antennas
pretty well - my AR7030 not only has a switchable +10dB preamp, but also
offers an impedance inverter (whatever that is) intended for telescopic
antennas but also useful for short wires.

True in general. But some portables can't handle that much signal. I think
the original poster is in Europe (based the words "aerial" and "centre").
Europeans seem to have more problems with overload due to the abundance of
nearby transmitters.

In fact, I've even experienced IM products when using the 7600G on the
whip alone. A few meters of extra wire like the AN-71 can be used, but
this has to be done carefully and with some antenna tuning /
preselection device, something also to be recommend when using the radio
on the whip alone (antenna tuning out of the box doesn't seem too great
in some ranges). (If an antenna is connected via a properly inserted
3.5mm plug, the maximum length will be higher since the receiver enables
some kind of attenuation then.) That's not an issue with the AOR, of
course, this should handle even nice big antennas (like, say, a 40 m
Delta Loop) well.

The OP, BTW, obviously seems to be from South Africa. Signal levels
should be a whole lot less critical there (unless one happens to live
next to a xmtr station, that is) - well, of course, everything is less
critical then Central Europe. As always, some experimenting will be
needed to figure out the optimum antenna length.

Stephan
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