microwave path testing?

[FMROB]

Does anyone have experience with testing microwave paths with two large weather balloons. What kind equipment do you use to verify the ballons or radios will see each other.

Is there a specific kit or manufacturer that makes these kits?

Thanks, Rob

[sethcwilliams]

You'll probably have to throw out a lot more info to get an answer to this one. I don't deal with aerostats, but a few obvious questions that hit me....

Are we talking true microwave, directional antennas point-to-point vs omni-antenna radio links? (seems like a serious "pain in the engineering" feat to accomplish a directional shot from baloon to baloon)

What type of circuit? (T-1/E-1, 802.standard, etc...)

Distance between antennas?

Frequency? (Ku, K, KA-band 12-40 Ghz, etc) Hope it's not the 30 ish range, better hope the wind doesn't blow the wrong way...

[FMROB]

Ok, sorry about that. It was more a general question. Here is some further info.

4.9 GHz band
either Moto PTP or carlson wireless Trailblazer systems
both will be connectorized and use parabolic dishes
Ultimately it will be a T1 circuit with a channel bank and E & M modules or use the internal mux in the carlson.
Distance is no more than 10 miles
Most will be line of site
The ones that I question are our two near line of site applications

Hope this helps more. There is one specific hop that the PTP planner says will work with 99% reliabilty, but it is close to the tree tops. So I had heard about ballon tests, just have never seen or done one.

- Rob

[sethcwilliams]

That's my fault, man. I didn't mean to come across like a smarta**.

[sethcwilliams]

I think I'm tracking now, I missunderstood in the first place. I think you're talking about using baloons to test a proposed path for a microwave shot? Sorry man, I've never seen that one. Our microwave engineer does plots and path projections in a certain software program and usually delivers those reports my way before I process the frequency assignment.

Sound like it might just be GPS sureveying equipment, similar to what GIS guys might use for plotting topographical data, etc. I could see that giving a three deminsional path projection

I thought you meant using baloons as an antenna point of presence. I was going to offer your microwave guy a job, that would be pretty impressive.

[FMROB]

Sorry about the, but that is funny. I could see that the lack of info could lead to a crazy thing. I to would like to have a job like that. LOL

But, you are correct. I heard of someone using weather balloons to test path propogation. Instead of using a tower ladder or JLG lift at both sides, they have a weather balloon with a rope with visual markers on it, lets say maybe every 25 feet.They raise the two balloons, one at each location to see if they see each other.

This is what I am thinking. I just don't know what they are using to tet the RF. I don't think the the balloons will carry any type of weight. I guess the best that you could do would be raise a balloon on one side at the propesd height of the antenna, and go up in a bucket on the other side with field glasses to see if you can see it. Doesn't sound to technical though.

- Rob

[sethcwilliams]

Good thing is, you really won't have to verify the RF. Using the licensed 4.9 Ghz public safety band, Moto and Carlson both advertise their point-to-point equipment with ranges >100 miles (in theory of course). If you moved into the unlicensed band, your distance would be a fraction of that. With 4.9 Ghz you'll be alotted the apropriate power output authorization to cover your distance. All they really need to verify is LOS and no possible EMI generator in between (high voltage power lines are my achilles heel in this otherwise dry, flat POS desert).

[mruwave]

Any good supplier should have the ability to give you a case study on each of your planned links. Most will do it for free just to get a chance to bid on the equipment and installation. Some are extremely reliable and some are speculation. If they won't give you a printout, they're probably just speculating.

Go to

http://awapps.commscope.com/downloads/p ... fault.aspx

download their 'Powertools' (freeware) CD and use the Andrew Microwave System Planner to get a good idea of your path reliability. It can be a bit obtuse to use but its pretty darn accurate.

- Jim

[escomm]

I've had the ACES team plot expected paths, all they need are geo coordinates and elevation of the antenna

[Jim202]

You don't want to use a microwave path that is close to the tree tops. In a few years you will
be trying to figure out why your loosing the path at times. The trees grow and get taller. The
taller trees mean less path clearance.

The balloon test is not that good these days for a 10 mile path. There is just too much haze in
the air to be able to see that good. If you insist, I would use a red balloon or even a black one.
Your chances of seeing a white one are probably real slim. Even with a high powered scope, my
bet is you can't see that far. The balloon is probably too small to be seen over a 10 mile path.

You might consider trying to wait until a heavy rain goes through at night and then try early in
the morning. Be at the east end and put the balloon at the west end. Use the clear air and the
sun to help your efforts.

A second method would be to use a high powered hand spot light. Climb the tower to the antenna
height and point the spot light towards the distant tower. Do as the old timers did using the sun and
a mirror. Try flashing the path. This is where you take the high intensity light and wave it back and
forth towards the distant end. Make sure the distant end has a good set of binoculars. Also make
sure you both have a radio that you can talk back and forth on to tell each other what to do. As
you might gather, this test is best done when the sun isn't up. Like at sun rise or sun set times.

It probably would save you a bunch of effort if a computer generated path profile was done. At least
this way you knew if you even had a chance to make a path between the 2 locations and how high
up the antennas needed to be to clear everything. It will also provide the exact direction to face.

Jim

Ok, sorry about that. It was more a general question. Here is some further info.

4.9 GHz band
either Moto PTP or carlson wireless Trailblazer systems
both will be connectorized and use parabolic dishes
Ultimately it will be a T1 circuit with a channel bank and E & M modules or use the internal mux in the carlson.
Distance is no more than 10 miles
Most will be line of site
The ones that I question are our two near line of site applications

Hope this helps more. There is one specific hop that the PTP planner says will work with 99% reliabilty, but it is close to the tree tops. So I had heard about ballon tests, just have never seen or done one.

- Rob

[wa6jbd]

The only balloon test I've ever seen involves a single balloon, and requires that the other end of the path have LOS for an observer. The balloon at the far end is raised until the observer can see it, and the length of line required to get the balloon high enough is recorded. There's no easy or practical way of performing this test with balloons on both ends of the path. This is not an RF test at all, it's strictly a visual observation of the balloon.

In the case of a path requiring towers on both ends to see the far end of the path, you're best bet is to hire a surveyor who specializes in laying out microwave paths. They will ome up with a suitable elevation for the antennas on each end, and if directed to, can allow for tree growth, etc. Relying on software tools alone can be dangerous. The terrain resolution is 3 seconds or more, and I've seen plenty of cases where the software says there's a path, when reality says there's a piece of rock in the way. Of course, now they're selling systems that claim non-LOS ability. Did they tell you how slow the throughput will step to make the path work?

99% availability is really pretty crappy for a microwave path. Have you calculated how many seconds of down time you'll see per year?

[ai4ui]

If this system is going on existing towers, make sure you know exactly where the towers really are. I was involved in a project that included a microwave link a few years back. When the crew put up the antennas they wouldn't link. As it turned out, the coordinates for the towers (errected in the mid 1970's) were wrong. They had to go and GPS the towers to get the direction right. One of the towers was off by nearly 1/2 mile.