[BC] Wireless Internet Installation on AM Tower

[RichardBJohnson at comcast.net]

Well you did not give much information. However, you need to get your 100-baseT network wire across the base insulator without shorting anything out, and you need to keep the tower's RF out of your network. I'm assuming that you have a base insulator and that your tower is not shunt-fed or a folded unipole.

First off, I would say you could not do it except with a big expensive custom coil of copper tubing within which you run your Ethernet cable. However, if you are an experimenter at heart, you might be able to pull it off using the characteristic of a 1/2-wave transmission line. Such a line, if shorted, will look like an open circuit at its end. Connecting an open circuit to your antenna should not do anything harmful.

Let us suppose you ran a piece of electrical conduit (EMT) from your transmitter building, a fixed distance above your ground system, out to the tower, then ran it up a tower face on insulators. You permanently bond the conduit to the ground-system where it enters the building. There should be some length of conduit where, if it were shorted to the tower, it would not make a spark. That is the point at which you bond the conduit to the tower. You could measure your antenna parameters and verify that you truly found the correct place and you did not affect the feed-point impedance. Once you have the conduit installed, you simply feed your network wire through the conduit. You need to make sure that rain does not get into the conduit, etc., but the system should work. I did this once to put a ham antenna on a 5 kW AM tower --I ran coax inside the conduit.

However, you do not want to buy a bunch of conduit for an experiment that might not work. Therefore, just use some wire, the cheapest wire you can find (aluminum electric-fence wire), for an initial experiment. The idea being to run the wire, with its starting end grounded, over the exact same path that the conduit would run. You can use some sticks of wood for temporary insulators where it runs up the tower. You drill holes in both ends and use plastic tie-wraps to secure everything.

Cheers,
Richard B. Johnson
Book: http://www.AbominableFirebug.com/

----- Original Message -----
From: "Carl Fletcher" <carlf at radiooneindiana.com>

To the Brain Trust:

Does anyone have any methods / thoughts on how I could install a Motorola Canopy radio using power over Ethernet on an AM tower ?  The install is for a wireless Internet provider.  Thanks in advance for any advice.