Gary, K4FMK wrote:
"Do the same in the vertical plane also."

Never had a minor lobe identification problem.

Never improved over the bubble-level set of vertical elevation angle on
long paths either, but I always tried.

I had always calculated my path gains and losses, and my best received
carrier power was very nearly always within a db of my calculations. If
not, I had a problem. Fortunately, that was very rare.

Best regards, Richard Harrison, KB5WZI

(Richard Harrison) wrote:
Gary, K4FMK wrote:
"Do the same in the vertical plane also."

Never had a minor lobe identification problem.

Never improved over the bubble-level set of vertical elevation angle on
long paths either, but I always tried.

I had always calculated my path gains and losses, and my best received
carrier power was very nearly always within a db of my calculations. If
not, I had a problem. Fortunately, that was very rare.

Best regards, Richard Harrison, KB5WZI

Did you actually do very many?

The reason I ask is that there are other factors, and you
*can't* calculate them, and in some cases you can't even
adjust for them.

The best example that I know of was a TV microwave repeater that
was put in north of Tucson for a link between Tucson and Phoenix
back in the 1960's. This thing was located 50 miles from town,
at 8500 foot on a mountain top. They had a 50 foot tower
installed on a concrete base that cost $50,000 (think about that
in today's money!). And when all was said and done, they turned
it on, and it worked great!

But somebody had the smart idea to see what happens if they
slide the dish down the tower to see if the signal would
improve. It did!

So they positioned it vertically on the tower for best signal
strength. About 7 feet off the ground... :-)

(And darned if a few years later a build up of rhime ice on the
43 feet of tower above the dish didn't fall down and bend that
dish into a pile of ruble too.)

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

Floyd Davidson wrote:
"Did you actually do very many?"

I`ve done single-hops, several-hop systems, and transcontinental
systems. I`ve done them on-shore, off-shore, and in a multi-hop loop
system on-shore and off-shore. I`ve done several systems with paths
sandwiched between tall buildings. I`ve done 960 radio, 2-GHz, and 6-GHz
systems. I`ve done space-diversity systems, hot-standby, and unprotected
systems. I`ve done solid-state systems, vacuum-tube systems, etc., etc.

I have no reason to say anything which is untrue. Floyd knows of an
anomalous hop in the desert. The path suffers reflections, else it would
not have great variation of signal with height. I know of many anomalous
systems, but I never built one. All of mine worked as designed.

Best regards, Richard Harrison, KB5WZI

(Richard Harrison) wrote:
Floyd Davidson wrote:
"Did you actually do very many?"

I`ve done single-hops, several-hop systems, and transcontinental
systems. I`ve done them on-shore, off-shore, and in a multi-hop loop
system on-shore and off-shore. I`ve done several systems with paths
sandwiched between tall buildings. I`ve done 960 radio, 2-GHz, and 6-GHz
systems. I`ve done space-diversity systems, hot-standby, and unprotected
systems. I`ve done solid-state systems, vacuum-tube systems, etc., etc.

I have no reason to say anything which is untrue. Floyd knows of an
anomalous hop in the desert. The path suffers reflections, else it would
not have great variation of signal with height. I know of many anomalous
systems, but I never built one. All of mine worked as designed.

As I pointed out, that was the most _interesting_ example that I
know of.

However, you've just stated something that I can't quite get my
arms around. "All of mine worked as designed." is stated as if
the "anomalous systems" that have a path which "suffers
reflections" are somehow not common, or not well designed, or
not normal.

Yet you mentioned "on shore" and "off shore" each twice above,
and I'm having a real difficult time thinking you've ever
designed a microwave shot across tidal waters without having
"reflections" which could not specifically be calculated. And
there is simply no way that it "worked as designed" unless you
mean you just allowed for a large enough fudge factor to account
for signal swings from day to day. The original claim that they
*all* came in within 1 dB is just hilarious.

My bet is that you have hung around and do know how these paths
function over time, and I'll bet you just exaggerated a little,
that's all.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

Floyd Davidson wrote:
"---I`ll bet you just exagerated a little, that`s all."

Too many hours of daylight on Floyd are taking their toll.

Everything you work with is known. precisely, including path attenuation
under normal propagation conditions. Normally, you don`t have a path
grazing at a highly reflective point. Your path survey discloses path
detractions and you adjust for the possibility of distructive
interference. You may opt for a high / low antenna placement for the
path ends, diversity, more clearance, shorter paths, and brute-force
fade margins. The high / low option lets you move the reflection point
and the reflection. Long microwave systems must have huge fade margins
anyway due to noise buildup from individual path contributions. A
receiver not too much below the overload signal point is a very quiet
receiver and contributes almost no noise to a system.

When the path design is right, the as-built numbers are almost exactly
as calculated, whether you believe it or not.

Best regards, Richard Harrison, KB5WZI

(Richard Harrison) wrote:
Floyd Davidson wrote:
"---I`ll bet you just exagerated a little, that`s all."

Too many hours of daylight on Floyd are taking their toll.

Look like you need some daylight.

Everything you work with is known. precisely, including path attenuation
under normal propagation conditions. Normally, you don`t have a path
grazing at a highly reflective point. Your path survey discloses path
detractions and you adjust for the possibility of distructive
interference. You may opt for a high / low antenna placement for the
path ends, diversity, more clearance, shorter paths, and brute-force
fade margins. The high / low option lets you move the reflection point
and the reflection. Long microwave systems must have huge fade margins
anyway due to noise buildup from individual path contributions. A
receiver not too much below the overload signal point is a very quiet
receiver and contributes almost no noise to a system.

When the path design is right, the as-built numbers are almost exactly
as calculated, whether you believe it or not.

Lets see, now you are saying that you go out and *measure* the
path, rather than calculate it.

And of course you measure it, *every* *single* *time*, on a day
when you *know* whether it is giving you the best path, the
worst path, or some specific point in between.

Richard you can cut the bull**** out. I've been measuring
microwave paths for 40 years. You don't calculate them to
within 1 dB. You might find out what that is after measuring it
on a regular basis for a year. (I've done *continous* path
measurements of several paths for over a year, and on two for
10 years.)

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

Floyd Davidson wrote:
"Richard you can cut the bull**** out."

Floyd claims to have measured microwave paths for 40 years. I`ve been
doing it since 1960, so that`s about as long.

I`ve made repeated measurements over a number of years on the same
repeaters. During normal propagation, which is by far most of the time,
path loss like other system losses is very constant.

Of course there are periods of anomalous propagation. It depends on
location, season, and time of day. It`s worse when the atmosphere is
stagnant.

I`m sure that marginal paths with insufficient clearance and other
problems may have propagation which comes and goes. I`ve seen some, but
I haven`t built any like that.

Best regards, Richard Harrison, KB5WZI

Floyd Davidson wrote:
"This thing (TV microwave relay station) was located 50 miles from town
at 8500 foot up on a mountain top. They had a 50 foot tower (at the TV
studios I suppose)----they turned it on and it worked great."

So, if it wasn`t broke, why did they fix it?

Floyd also wrote:
"But somebody had the smart idea to see what happens if they slide the
dish down the tower to see if the signal would improve. It did!."

I wasn`t there, so I can only speculate, but I might have not been
surprised by those results.

On a 50-mile path with plenty of mid-path clearance, propagation is
similar to communications with a satellite. One difference at the
Arizona latitude is the vertical angle the dish path makes with the
Earth. The low angle the dish on the terrestrial path makes with the
Earth, makes it vulnerable to reflections from the Earth. The higher the
dish is placed, the more vulnerable it becomes. That`s a reason to go
high / low on a reflective path, and not high/high. (Low/low won`t make
the trip on most long paths due to Earth curvature).

Best regards, Richard Harrison, KB5WZI

(Richard Harrison) wrote:
Floyd Davidson wrote:
"This thing (TV microwave relay station) was located 50 miles from town
at 8500 foot up on a mountain top. They had a 50 foot tower (at the TV
studios I suppose)----they turned it on and it worked great."

So, if it wasn`t broke, why did they fix it?

Floyd also wrote:
"But somebody had the smart idea to see what happens if they slide the
dish down the tower to see if the signal would improve. It did!."

I wasn`t there, so I can only speculate, but I might have not been
surprised by those results.

On a 50-mile path with plenty of mid-path clearance, propagation is
similar to communications with a satellite. One difference at the
Arizona latitude is the vertical angle the dish path makes with the
Earth. The low angle the dish on the terrestrial path makes with the
Earth, makes it vulnerable to reflections from the Earth. The higher the
dish is placed, the more vulnerable it becomes. That`s a reason to go
high / low on a reflective path, and not high/high. (Low/low won`t make
the trip on most long paths due to Earth curvature).

A 50 foot tower on top of an 8400' mountain. What are you
talking about high/low etc etc. I wasn't there when the
decision was made to put it on a 50 foot tower, and neither you
nor I have any idea why that was done. Perhaps the topo maps
were wrong, and some obstacle they assumed was there didn't
actually exist. Perhaps the engineer made a mistake. I don't
know and you don't know. But, you don't suppose the engineer
knew exactly what he was doing, eh???

A 40 foot change in elevation suggests there simply were no
obstacles, so one has to wonder what the 50 foot tower was
supposed to accomplish... other than allow a range of adjustment
to find the best point for signal strength. Because this was
not a 50 mile shot, it was much closer to 100 miles and no doubt
they were very interested in optimizing the signal strength.
With no obstacles, not even earth bulge, calculating reflections
isn't so easy... unless you move the antenna vertically to find
the right position.

But, it doesn't emulate "a satellite" shot even in the slightest.
Or, not for real satellite shots at least.

E.g., the look angle for a geosynchronous satellite here is only
10-12 degrees or less depending on where the satellite is. I
don't agree at all that a 50 mile microwave path with no
obstacles is approaching similarity to a satellite shot! Some
satellite links have *less* clearance.

Of course, your exposure to satellites might not be that great.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

Floyd Davidson wrote:
"But, it doesn`t emulate "a satellite" shot in the slightest."

A satellite is a microwave repeater in the sky which is usually not
susceptible to earth reflections.

Terrestrial microwave paths are often designed to minimize earth
reflection.

Reason is, on a long path, the lengths of the direct ray and the Earth
reflected ray are almost the same. Reflection reverses the phase of the
reflected ray so that the reflected ray detracts from the direct ray
when they combine at the receiver. They arrive out-of-phase, at least at
some antenna altitudes.

The phase of the signal undergoes 180-degrees of phase change as we
examine the signal either forward or backwards from the plane of the
signal. That is to say, the phase of the signal is a function of
distance along the path. When a second signal source is created by Earth
reflection on the path, the combination of the direct and reflected rays
produces strata of stronger and weaker signal intensities as altitude
changes. No reflected signal, no significant variation of signal with
altitude, given sufficient path clearance. This is a worthwhile design
goal.

No matter which end of the TV relay path was varied to produce a
significant signal strength change, the attenuation at the higher
elevation was probably caused by an Earth reflection. Another reflecting
surface near the microwave path could have been the reflector. I`ve seen
that in the city canyons I`ve had to squeeze signals through. But on
most paths, the Earth is the most likely reflector.

Best regards, Richard Harrison, KB5WZI