>I noticed while mobile this weekend on 20M, that the signal levels in
>and around town are much lower than out over the open highway. I have
>noticed also near the ocean signal levels are better even the upper
>bands on HF. Has anyone look at the shielding effect of all the
>overhear wiring that typically runs around town ala. cable, power,
>I know that there are some vhf/uhf models around but nothing on HF.
>And how high above that cabling you would have to be in order for it
>to not effect things if you had a beam on a tower ?
>Just a thought. AA2T
It's a well documented fact that on low bands, ground conductivity
places a terribly important factor on signal levels. Chewing up the
ground for construction, roads, et. al. in a city or any other
environment lowers the ground conductivity, per the references I've
read. Undsiturbed soil in and around creek bottoms, marshes, especially
a salt marsh, make for better signals on HF, particularly low band
I'll relay, again an experiment I played with a VK3 on 40 CW. I've
posted it here before, but it's a fun story.
He had a sharply tuned loop antenna on his car! Said it attracted lots
of attention from the curioys, but it worked very well. He an I used to
talk frequently on 40CW at our sunrise when he was going home from work.
His home was inland a bit, but close to the ocean coast line for the
Pacific, and the road there wund out from Melbourne to that coastal
road, then past a cliff with a public boat ramp under it. The cliff
overloos the ocean.
On the way home from work on the road, one segment of it had concrete
and re-bar in it; another segment did not. He would often have to stop
and retune the loop going from the one to the other! Did it at traffic
lights, if I recall! He'd jump out and tweak it a red light I think!
You could see an actual difference between the re-bar road and the
As he drove along the coast line, he would be maybe S3 or so until he
would get to the bluff area where the road began to run along the blufff
overlooking the ocean. At that point his signal would rise two or three
S units! Then, he would go down the road to the public boat ramp. As
he approached the ocean, his signal would rise some more. He'd drive
the car down into the salt water, optimum tune the loop, and his signal
would be up at S9 on the meter, ofen more. As he backed out of the
water and moved back up the road to the bluff, his signal would go back
to what it was before he left it.
Fron there he had to turn down a side road to go home. As he drove the
mile or two back to his home site, his signal would fade down to S3,
often into the noise. We could communicate while he was in his
driveway, barely, at times. Of course he could go in and fire up the
fixed rig and do OK.
Now that's from S3 to S9 plus at times, just on the basis of aperature
effect and ground conductivity near salt water. And, no, I didn't,
don't have a calibrated microvolt-aware black helicopter receiver to
give you the precise signal levels. And no, because of the timing,
there really wasn't much effect of path decay from the sunrise at my
end which would have accounted for much of this.
We repeated this experiment a number of times. The results were the
same. In fact, somehere in my audio tapes, I have a tape recorded
session of it, buried deep in the box with the ones where I figured out
how to kill the woodpecker and get it out of 40 meters in the early
morning, plus the actual ID for the "V" beacon, which is/was RCQ45.
"V" is gone now, too, chuckle! But "P", "S" are still there chirping away
on 7038.8 and 7038.9, maybe "C" and "K" too, up there!
The effects of ground are less, I've seen on 40 than 80. Obviously, as
a low band fanatic, I'd be interested. Although I do not work 160, the
same is true there, with a side-bar comment. From what I have read,
there may be a somewhat different propagation scenario on 160 as you go
down toward the broadcast band, which changes the picture a little.
W8JI can tell us that here I suspect.
I don't work 20 and up. But I suspect that the effects of ground
conductivity decrease as the frequency goes up. Some of it, obviously,
has to be present there on 20.
Here where I live in Suth Central Texas, I'm a few DB better off than
just about 20 miles to the fault line that starts all the sand country
and pine trees of the Conroe, Livingston, Beaumont area in Texas. You
get into sand country and things get worse, but they are still bad here,
compared to the coastal plain in Texas, and worse than the black gumbo
up near Waco and in areas around Dallas which are pretty good.
Over forty years of this, and travelling around, comparing notes, my QTH
is down about 3 DB or so from these other better sites on low bands,
here in Texas. The overall path from either coast to me, is down at
least 10 DB, and I suspect maybe more, on average, from what the East
Coast folks see for Europe on low band, and the same is true for the
West Coast on Asian paths.
What you've seen is a beautiful example of why those with money that are
really concerned about ham radio .. move to places where it is easier to
win. It still the real-estate game, location, location, location. And
when you get down to that, add some more location.. chuckle!
The effect is well documented, especially when in the game you compete
with someone who has the keys to the kingdom right there on the ground!
--> Sleep well; OS2's still awake! ;)