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PolyPhasor lightning protection

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duckfan98

Guest
Okay, newbie question here.... are these as simple as they seem? Simply plug one end of antenna into it, the other end into a pigtail in the back RF out of your transmitter?

Is anything else required? Our antenna / transmitter has no lightning protection (other than antenna DC grounded to tower ofcourse), so need to do something before lighting season starts around here.
 
Gotta ground them to the same copper strap everything else in the station is grounded to.

If you don't ground them, they won't work.
 
I'm assuming this is an FM station.

1. Depending on the number of thirsty neighbors with bolt cutters & other similar implements, you want to tie the tower base to the transmitter, equipment rack, and to the breaker panel with either copper strap (preferred) or a couple of runs of #6 (or thicker) copper wire. Sometimes you can slip the strap under the breaker panel, sometimes easier to connect a few short pieces of bare #10 from the ground connections in the box to the strap.

Bond everything together. Ideally should be silver soldered, however, getting some brass bolts and nuts & binding the strap to equipment racks at several points is better than having it unconnected. Plumber's solder, rosin and a torch can be used to tie larger pieces of strap together.

Your local electrical supply shop will have clamps for ground rods as well as something that could be clamped to a tower leg. Sandpaper off any paint to get a good connection, then spray paint over the completed connection. If it's a big tower, you need to make connections to each "leg" and join the strap or wire to the main ground strap.

Copper strap: Georgia Copper (http://www.gacopper.com/) has reasonable prices, a 50' roll of 3" medium thickness strap will run around $200.

Roofing tar spread over the strap or insulated wire will discourage the copper thieves.

2. At the base of the tower, if you can, sink a couple of ground rods. Depending on the geography of your site, you may also want sink a few more rods on the path from the tower to the transmitter building.

3. The polyphasor can then be bolted directly to the copper strap--closer to the tower the better. A good point is where the cable(s) come in the building--again, depending on your geography, you may want to run the main strap in at ground level, but then run a piece of strap up the inside wall to where the cables come in. That would be a good place to mount your polyphasor. Again, be sure to tightly bond the short piece of strap to the bigger run at ground level--fold the shorter piece over the bigger, mechanically tie it together with some brass bolts, then silver solder or even use plumber's solder with lots of rosin & a torch.

4. RF Specialties and other supply houses have grounding kits for most size coax cables from 1/2" on up. These have a basket type clamp that folds over the outside shield of the coax, and a pigtail with a lug for grounding You carefully cut off the black insulation with a sharp knife, put the clamp over the bare copper, then use the black butyl coax seal and good black tape to water proof. This would be done where the coax leaves the base of the tower, the ground lug can usually be clamped to the tower with a ground clamp like you would use on a ground rod. Sandpaper the paint off the tower leg, put the clamp on, then use coax seal and tape or paint for weather protection.

5. Surge Suppression: Best to have some kind of surge suppressor mounted either on the panel box, or on the feed to your transmission equipment. Inexpensive "whole house" unit for typical 100 amp panel is the Leviton 51110-1, which you can find for around $50--there are many designs, price goes up from there. I like to mount them in the panel box on separate breakers (220 device)--they will short out if you get a big "hit" from lightning strikes coming in the power line.

There are a million and one ways to do lightning protection, but anything is always better than nothing, and you can start with a simple system and keep adding to it.
 
TomT said:
5. Surge Suppression: Best to have some kind of surge suppressor mounted either on the panel box, or on the feed to your transmission equipment. Inexpensive "whole house" unit for typical 100 amp panel is the Leviton 51110-1, which you can find for around $50--there are many designs, price goes up from there. I like to mount them in the panel box on separate breakers (220 device)--they will short out if you get a big "hit" from lightning strikes coming in the power line.
Other school of thought is that lightning has multiple pulses...the first pulse pops the breaker and the next 5 pulses pop everything else. If I have a good quality surge protector ($800+ for single phase/$1100+ for 3 phase--Lightning Protection Corp makes good ones) hooked across the mains via a non fused disconnect switch, this method has worked well for me over the years.
 
Dont forget other copper lines coming into your transmitter hut. Like telephone, internet, cable, sat dish feedlines, etc. Polyphaser and others sell supression items for all of these. And as mentions many times, all of these need to be grounded to the main station ground.

Here is a shameless plug for Nautel if you happen to be using one of their low power transmitters. Spend the money and buy their suppression kit option. Power, RF, control lines all route through it before they enter the transmitter.
 
I believe PolyPhasor has some white papers on their site...or, maybe still part of their catalog you can ask for.

Many, many sites use their stuff, including lots of cell phone and LMR sites.
The biggest thing they tell you is, get a good sized copper entry panel between the sky and the inside equipment. The polyphasor units fit in the holes in the panel, and literally divert the lightning charge, with the big copper plate blocking it from getting indoors.
A good grounding system, with everything tied to one ground point is essential.
 
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