On 9/22/2012 10:11 PM, Channel Jumper wrote:


I think it is more then obvious that you do not know what you are
talking about when it comes to antenna's.

Talking about pot=kettle=black... :/


The key to any antenna is LOCATION / LOCATION / LOCATION....

I don't think the guy is going to move so he can have the
optimum location to string up a wire..


If you are in a crappy location, it is not going to work well...

That would generally apply to any antenna installed in that
location. But for what he wants to do, which is merely listen
to the HF bands, almost anything is going to do reasonably well.
One poster had a point about possible shack noise, but not all
homes are huge noise sources. I remember as a SWL, I often ran
simple random wires, merely stuck in the center conductor, and
had perfectly acceptable results. If shack noise rears it's ugly
head, then it's time to consider other options.
But it's quite possible that shack noise will not be a huge issue.
You never know until you try it.

If you are in a good location, the B & W 90 will out talk your Carolina
Windom or any other long wire antenna, due to the fact that antenna
tuners reduce the amount of power applied and they do not physically
tune the antenna, just the coax to the antenna. The only tuners that
works is the ones that are placed directly at the feed point of the
antenna, not something inside of the shack...

That's silly.. Do you think that matching at the feed point
ensures no loss? Better think again..
It would be quite possible for a shack tuned system to show
less loss than the B&W, if designed right, and one used the
very least inductance needed to get an acceptable match.


The B&W 90 on 20 meters acts kind of like a beam antenna, which exhibits
some forward gain - due to the nature of it's construction.
The one wire acts like a reflector while the other wire acts like a
driven element.

It most certainly does not.. It acts like an appx 3 wave long folded
dipole..


On 40 meters it still acts like a 1.5 wave antenna and on 80 meters it
acts like a Dipole antenna...

Well, almost.. It's a bit short on 80, and with the resister at the
feed point to match it, it would never be as good as the full size coax
fed dipoles I run. Ever.
Mine require no matching whatsoever. Zero, nada, zip..


On 160 meters - if you wanted to be all that you could be - it would
need to be 80' or more } depending upon terrain } off the ground to get
in the right place for it to be at optimum height...
It also depends upon the ground {earth } underneath the antenna...
Wet / swampy earth is always better then rocky dry soil....

Even 80 feet is fairly low for a 160m dipole, but this is not a strong
issue being as he only wants to receive.


You have to realize what arrival angle the DX signals come in at and the
fact that there is two signals you are receiving, both the direct path {
good} and the reflection off the earth { bad} at Gb before reaching our
station location..

How are you going to receive a space or ground wave from a DX station?


Unless you compared the two antenna's at the same location at the same
time, at the same height within one hour of each other, there is no way
for sure for you to comment about which antenna works best...

Can't really argue with that.. But it is fairly easy to predict..


10 - 40 meters band equals about 19.9 meters of height mininum / needed
to get optimal angle.

But what is the optimum angle? It's going to vary, depending on the
path. And each band would need a different height to be optimum at a
certain angle. It's not worth worrying about in his case, unless he
wants to chase his tail.


20 meters likes about 32 meters of height, heights between 15 and 32
meters - { 50 - 105 feet are about as good as you can get} for anything
between 6 meters and 160 meters....

Sure.. Almost anything is going to work at 96 feet in the air..
But it's overkill for what he wants to do, which is merely receive.


Most people just puts their wire antenna in a tree about 40' high or
strings it up between two towers and calls it good enough.
The problem is - there is a null on the ends of the antenna and the path
that the signal uses isn't always a straight line...

This is going to be the case no matter how high it is. I bet the
nulls would actually be more pronounced the higher you installed it.
Not that it's something worth worrying about for general receive use..
He's still going to receive signals in the null directions. They just
might be down a tad vs the favored directions.
The pattern off a dipole that long would likely be like an "X".


The problem is - with a 160 meter antenna, this is hard to accomplish,
hence it is easier to use a vertical antenna for 80 and 160 meters - but
is very expensive to use a base tuner and a 80 / 160 meter vertical
antenna - which must be supported by some type of tower in most
locations.

Huh?? Why would base feeding a 160m vertical be expensive?
It's never cost me much money.. :/


The wind would damage it quickly and its survival rate would be poor
without some type of support...

At the same time, my antenna is mounted 20' off the ground between two
houses, and a jib boom mounted on the back of my house, fed with 40' of
cheap Radio Shack coax and it still talks well in most directions.

As would about anything else installed at the same location..


I can hear north / south / east / west with a antenna that is aimed east
and west and sometimes when the Maritime Mobile net or the YL network
needs a relay station, I can relay between two signals - where they are
using some type of beam antenna for the monitoring station and the
person trying to check in either has a beam with a poor signal or a
G5RV...
And I never run more then 100 watts!

I'll alert CNN.. :\


Even when they are running 1000 watts - my signal still is better then
most peoples signals on 20 and 40 meters....

It would be even better if I replaced your antenna with one of mine..

If I really need some help, I just turn on the processor and it has
enough compression that I can get through, even when there is a pile
up...

Brute force can help.. At the expense of audio quality.. :|

On 9/23/2012 6:33 PM, NM5K wrote:
On 9/22/2012 10:11 PM, Channel Jumper wrote:



Large snip.

Well said.

tom
K0TAR

On Thu, 20 Sep 2012 04:11:29 +0000, ultravista
wrote:


I recently acquired an Icom IC-706MKII radio. My plan, before I get my
license and begin transmitting, is to use the radio for a general
coverage and shortwave receiving.

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.

Looking for recommendations for a great all-around shortwave antenna
that will connect to the coaxial port.

A random length of wire strung around your yard, and coming to the
central connector of your coax plug, will probably give you more
stations than you know what to do with.

If you want to get fancier, MFJ makes an inexpensive random wire tuner
(#16010) that you can peak for maximum signal strength. This is
something you could also use when you get your license and are ready
to transmit.

You could also build a random length dipole, and feed it with coax,
connecting the center conductor to one leg, and the braid to the other
leg.

Lots of options here. Start simple.

bob
k5qwg