I'd like some advise from the group regarding planning a microwave hop at a weather radar site.
The owner of the radar is a tenant of the site owned by another party. It is a C band 5.4ghz radar operating at 250W output / 630W erp according to the license. It occupies the top of the tower at 37m elevation atop a 330m peak.
We can construct at the 30m level or the 25m level with excellent LOS to our two coordinate sites. There is an existing single 6Ghz microwave with a 6 ft dish and high performance ring used by the same tenant, but they have not returned inquiries yet on how well their link works with respect to the radar and possible interference.
I'm suspecting I need to plan for licensed 10ghz or 11ghz operation with a similar strategy using high gain dishes with high performance rings to (1) reject noise from the radar, and (2) avoid interfering with their link on a similar azimuth as one leg of our proposed hop. However, my customer wants to explore using the public safety unlicensed 4.9ghz band to reduce costs if possible.
Any thoughts or caveats about microwave near a radar are appreciated. Thank you.
microwave at a radar site
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Re: microwave at a radar site
Software is available that can help map terrain with Fresnel zones and path loss.
I am not sure about the unlicensed part of the 4.9 Ghz band, I was under the assumption that this band was strictly licensed and unavailable for commercial/private use.
RadioWaves makes a nice dish with high gain and low radiation near the dish edges to prevent 'spillover' as it were.
They are in the same ballpark figure as the Andrew variety and perform just as well.
Point to point should be a snap, what is the link margin?
How much are they TXing with?
Is this going to be a full/semi-duplex mount?
If mounting 10 meters below or more, there should be no interaction between the dishes, there should be ample rejection in the vertical plane to overcome any intermod that may be generated.
Deep dishes help greatly with this, as the sidelobes prevent radiation near the dish edges, so usually there are no rings used.
Aiming these are fun, you need two people(one at each end) and in direct radio or phone contact to align the az/el of the mount.
What distances are you planning to use these for?
Individual gain on each dish will be required for link budget analysis so you will know how much power to use in each direction,especially in nasty weather.
Any peaks in between that you need to work through?
This is where a good terrain mapping software comes ino play, or you could get GEO maps from USGS and map fresnel zones over your projected path, and calculate path loss in each direction for your link budget.
A 20 mile path at 5 Ghz, and 15dB dishes at both ends should work easily with less than 20 watts feeding the antennas, probably less, but link margins are always first in mind.
I am not sure about the unlicensed part of the 4.9 Ghz band, I was under the assumption that this band was strictly licensed and unavailable for commercial/private use.
RadioWaves makes a nice dish with high gain and low radiation near the dish edges to prevent 'spillover' as it were.
They are in the same ballpark figure as the Andrew variety and perform just as well.
Point to point should be a snap, what is the link margin?
How much are they TXing with?
Is this going to be a full/semi-duplex mount?
If mounting 10 meters below or more, there should be no interaction between the dishes, there should be ample rejection in the vertical plane to overcome any intermod that may be generated.
Deep dishes help greatly with this, as the sidelobes prevent radiation near the dish edges, so usually there are no rings used.
Aiming these are fun, you need two people(one at each end) and in direct radio or phone contact to align the az/el of the mount.
What distances are you planning to use these for?
Individual gain on each dish will be required for link budget analysis so you will know how much power to use in each direction,especially in nasty weather.
Any peaks in between that you need to work through?
This is where a good terrain mapping software comes ino play, or you could get GEO maps from USGS and map fresnel zones over your projected path, and calculate path loss in each direction for your link budget.
A 20 mile path at 5 Ghz, and 15dB dishes at both ends should work easily with less than 20 watts feeding the antennas, probably less, but link margins are always first in mind.
Re: microwave at a radar site
There's a chunk of 4.9 reserved for public safety. You just have to coordinate with APCO. One hop is 20 miles, and the other is 12 miles. But, there is only 9 degrees between the azimuths. So, I'll have to synchronize them as well as put rings on the dishes. I may put them on separate legs to help cut side lobe energy down. I haven't worked up the link budget yet. But, an IM study has already been put on the table for discussion. I'm trying to decide if Canopy / Cambium is up for the task, or if we need Harris or MNI with better filtering in this environment. 650W ERP is a lot of local energy to deal with.
Re: microwave at a radar site
I have a 1 Megawatt ERP radar at 120' elevation about 400' away from my main tower. I have 7 GHz. dishes at 500' and 700' on the main tower. Before that I had 2 GHz. dishes at the same elevations. The major problem I have with the microwaves is temperature inversions, I've never seen any interference from the radar, but I use class A high performance antennas (Andrew) and MRC radios. The 7 GHz. receivers have channel filters installed as part of their factory configuration (I didn't pay extra for them, they came from the factory that way). This link is 26+ miles and is constantly monitored (its our program stream). I also have duplexed transmitters on each of the receive antennas (2 or more channels seperation)and they work quite well.
Re: microwave at a radar site
(cough) 1MW! And you are in the near field. I'll be directly below in the null at a much lower power level. I prolly don't have much to be worried about. Thanks.
Re: microwave at a radar site
mruwave wrote:I have a 1 Megawatt ERP radar at 120' elevation about 400' away from my main tower. I have 7 GHz. dishes at 500' and 700' on the main tower. Before that I had 2 GHz. dishes at the same elevations. The major problem I have with the microwaves is temperature inversions, I've never seen any interference from the radar, but I use class A high performance antennas (Andrew) and MRC radios. The 7 GHz. receivers have channel filters installed as part of their factory configuration (I didn't pay extra for them, they came from the factory that way). This link is 26+ miles and is constantly monitored (its our program stream). I also have duplexed transmitters on each of the receive antennas (2 or more channels seperation)and they work quite well.
Time to dig out the NARDA alert monitor for that site!