One way shingles
 

"bilou" wrote in message
...

"Ralph Mowery" wrote in message
m...
It rained and now he can not hear me, but I can hear him fine on either
rig
Hi
Either his receiver is dead or it is suffering interference.

Now that is an idea I have not explored.

A six meter repeater was just put on the air about 5 miles from him and
sometimes there is a power pole that generates enough noise at the repeater
site it desenses the repeater receiver. We are working with the power
people now.
We do not hear it on the repeater, but an AM receiver pickes it up very
well.

I am sure it is not this noise as it is too far away, but he may have a
local source that is causing a problem.

One way shingles
 

"Ben" wrote in message ...
The usual cause when this happens to me is an frequency offset in either
my in rig or the other operators. Are you sure that your rig isn't set
accidently to some type of TX shift. There are two rigs at the other end
and none of them can hear you.


Now the shingles have dried out we can hear each other on all the radios and
antennas. I know nothing has changed as the radios need to be programmed by
computer and I have the cable.

The distance is just under 10 miles so we should be almost radio line of
sight. The land between us is rolling hils. Going from about 600 feet at
the lowest to 900 feet at the highest.

One way shingles
 

"Ralph Mowery" napisa³ w wiadomo¶ci
m...
Not that it maters but another ham and myself have been licensed for 40
years.

He built another antenna , so he has two antennas and rigs. A Midland
and GE comercial unit that puts out 40 watts each. I check the
sensitivity on a HP 8924C and they both seemed to be as good as a Midland
I was using.

It rained and now he can not hear me, but I can hear him fine on either
rig and antenna of his

Do you think we have discovered one way shingles ???

Yes. Water is able to damp completly the weak yours waves.
His waves are emitted close to the wet shingles and are damped a little
only.
S*

One way shingles
 

Back when the Michigan State Police used 40 MHz, at some posts static levels
would become so high as to reduce range to almost nothing. Some say it was
precipitation noise (as is common with aircraft) and some people believe it
had another cause. It seemed to be weather related.

On 6 meters, with an AM circuit I had for years with my father, I have heard
discharge noise that starts with a sequence of pops and progresses to a
steady roar that occasionally would abruptly stop. (about 100 km path with
yagi antennas at both ends)

My guess is it was due to local, enhanced noise. Effects may have been
suppressed due to the nature of FM and its mode of squelching. 73,
Mac N8TT

"Ralph Mowery" wrote in message
m...


"Ben" wrote in message ...
The usual cause when this happens to me is an frequency offset in either
my in rig or the other operators. Are you sure that your rig isn't set
accidently to some type of TX shift. There are two rigs at the other end
and none of them can hear you.


Now the shingles have dried out we can hear each other on all the radios and
antennas. I know nothing has changed as the radios need to be programmed by
computer and I have the cable.

The distance is just under 10 miles so we should be almost radio line of
sight. The land between us is rolling hils. Going from about 600 feet at
the lowest to 900 feet at the highest.



J. C. Mc Laughlin
Michigan U.S.A.
Home:

One way shingles
 

On 10/8/2012 8:56 PM, J. C. Mc Laughlin wrote:
Back when the Michigan State Police used 40 MHz, at some posts static
levels would become so high as to reduce range to almost nothing. Some
say it was precipitation noise (as is common with aircraft) and some
people believe it had another cause. It seemed to be weather related.

On 6 meters, with an AM circuit I had for years with my father, I have
heard discharge noise that starts with a sequence of pops and progresses
to a steady roar that occasionally would abruptly stop. (about 100 km
path with yagi antennas at both ends)

My guess is it was due to local, enhanced noise. Effects may have been
suppressed due to the nature of FM and its mode of squelching. 73, Mac N8TT


That noise sequence is exactly what I hear when I see a corn snow squall
come through my property in the winter. I have actually watched the wind
blown snow come closer and closer while the HF radio noise increases
until all signals are wiped out, then when the back edge of the squall
passes the antenna, all is quiet, again.

I live at 2800 ft in the Central Oregon desert. The antenna is either a
ground mounted 5BTV with 40 radials, or a 160 meter horizontal loop at
35 ft.

Paul, KD7HB

One way shingles
 

On Wed, 19 Sep 2012 10:12:09 -0400, "Ralph Mowery"
wrote:

Do you think we have discovered one way shingles ???

Nope. You've discovered Fresnel zone diffraction, multipath
cancellation, and frequency selective fading. Congratulations.

Anyone else seen anything like this ?

Not on 6 meters, put plenty at 900MHz and up. Basically, if you have
more than one path between endpoints, and the path lengths differ by
1/2 wavelength, you'll get cancellation. It's easy enough to detect
the problem by simply moving 1/2 wavelength toward or away from the
other endpoint and see if the signal levels change significantly. If
you can't do that, change frequency by the largest amount possible.

Also, if you live 15 miles apart, with antennas at about 15ft off the
ground, you're below the horizon. That means you're relying on knife
edge diffraction to communicate. That works, but is not reliable as
almost any metal object near the knife edge can send the signal off
into the wrong direction. At 6 meters, things like swaying wet trees
can do that. If the signals are NOT stable and tend to move around in
the wind, this might be the problem.

One way paths are possible. It's not the path. It's the antennas.
The basic assumption is that the antenna pattern is the same in xmit
and receive. That's a fair working assumption but not always true.
Different side lobes of an antenna can have a slightly different phase
shifts. If the two multipath signals arrive via the main lobe and a
side lobe in receive, and the side lobe moves slightly in transmit,
it's possible to achieve cancellation only in one direction.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

One way shingles
 

On Thu, 20 Sep 2012 11:45:52 -0400, "Ralph Mowery"
wrote:

I am sure it is not this noise as it is too far away, but he may have a
local source that is causing a problem.

If the 6 meter receiver has a noise blanker, he could be hearing so
much noise that the receiver acts like there's nothing to hear.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558