I’ve seen a few forum references to power lines causing interference, and I was wondering if anyone could clarify the type of lines and recommendations.
Are we talking about:
1) High tension power lines (ie what feeds a substation)?
2) General overhead distribution lines (ie in some neighborhoods)?
3) Post transformer feeds to the house itself (ie 220V service lines)?
I can see where 1) would cause problems. If 2) is a problem, moving to another location on the house doesn’t seem like it would do anything if you still have to point to the same AP and you need to shoot over the power lines at the road.
What are the ramifications of number 3 (home feed)? I wasn’t aware of suggestions to avoid power lines when we put up a mast to hold a 900MHz SM for a private pt-to-pt link. The mast is at the same end of the house where the overhead power comes to the home. The SM is over 30 ft above the power line, and facing over 90 away from it. That is, the overhead line comes in from the side and over 30 ft below the SM. The network feed coming down the mast would come within about 5 ft of the power line at one point, but we are talking just the 150 amp service feed here, not the higher voltage lines ahead of the transformer.
The home feed power line would not be in the Fresnel zone at all.
Is that still a potential source of problems?
Doug
dhandy wrote:
Are we talking about:
1) High tension power lines (ie what feeds a substation)?
Doug
Most of my 900 customers are past 5 miles so I won't even try. Even if I can get a link, it likeley will be a flaky connection. If I has one within 2-3 miles looking though High Tension, I might try it.
dhandy wrote:
2) General overhead distribution lines (ie in some neighborhoods)?
Doug
Over, under OK. Through is a no go (at 10 miles). As you get closer your ability to get through the interference improves. I have not tried it closer.
I had one where the power lines were about 100' from the house. From the roof I was looking right through the lines - could not get a link to stay consistent. Moved to the ground a it hooked right up. This was at 10 miles with perfect LOS.
dhandy wrote:
3) Post transformer feeds to the house itself (ie 220V service lines)?
Doug
Had a problem at 2 miles where a 5.7 and a 2.4 would not connect looking through the feed to the house. Changed to a 900 and it's been fine since.
It would seem that a 60Hz power line would not affect a 900MHz signal. The only thing I can think of is that we are transmitting such low power that the harmonics off the power lines are enough to disrupt the link. A standard distribution power line can be between 3.3kV and 25kV so you can get a high number of harmonics away from 60Hz and still have alot of energy relative to our little radios.
Jerry,
Thanks for the response. It sounds like the power lines are not likely to be part of my equation. There are no high tension lines, I’m shooting probably 30’ over the regular distribution lines along the road, and the home feed isn’t in the signal path at all. Total SM to AP distance is 1.34 miles, and distance from SM to the road is probably 150’ or so. The house is uphill from the road, and the SM is on a 50’ mast so I’m probably 30’ above the power lines at a distance of 150’.
Sound reasonable?
My connection is still way more unstable since upgrading to 7.3.6; I’m hoping v8 may improve that when released. (I hope that is soon though.) I’ll also try adding another 8’ to one of the mast heights, but we haven’t had an opportunity to schedule that yet.
Doug
you are not going to have a substantial problems with power lines.
Are you running 7.3.6 in software mode? After we migrated to the Advantage radios and they were running is software the performance was worse than before the upgrade. We migrated everything to hardware and now everything runs much much better.
Jerry,
Jerry Richardson wrote: you are not going to have a substantial problems with power lines.
Thanks for the confirmation. That was my interpretation, but I’m new at this.
Jerry Richardson wrote: Are you running 7.3.6 in software mode?
No, with hardware scheduling. My ping times went from 32ms down to 9-11ms except of course when the SM goes IDLE, which seemingly happens about as soon as you start passing data. I can sometimes finish a single link test of 2 secs, but rarely do two in a row without dropping the session.
Which naturally makes the connection rather fruitless.
When the AP and SM are about 7000 feet apart, how much effect will a little bit of sway have? I’m mounted on masts about 50’ high using the integrated antennas, and when the wind blows can get some sway that I’d consider minor. However, my sessions drop even when it is completely calm outside and with no sway to my knowledge.
At 7000 feet apart, can mast sway have some effect? The sessions page is still showing the jitter values as typically 3-4.
And the same masts and guy lines were in place while on the older releases with software scheduling, where I didn’t drop near as often.
Doug
while your on the electrical subject i can tell you something not to do.
if you ever mount anything on a light pole do not connect the surge protector to the copper ground wire stapled down the side of the pole.
I was going to try to take a short cut and after trying to link to the sm i could not. long story short that copper ground wire attaches to the nuetral at the top of the pole then the ac hot wires wrapped around it going to the transformer basically was injecting ac ripple in to my network.
so spend a couple of bucks and get a ground rod :0
kmeadows
kmeadows,
kmeadows wrote: so spend a couple of bucks and get a ground rod :0
My ground lead goes down the mast (not a power pole) and then ties directly to the ground rod buried by the electrical service entrance. That is, I share the ground rod used with the home electrical and phone service.
Not that I’m adverse to installing my own – it was both conviently located plus I thought using the same ground rod was actually preferable from an electrical standpoint of keeping them at the same potential.
Doug