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Ethernet and AM transmitter near by

D

darklife

What is the general procedure and cable type to use for ethernet near by an AM installation?

I am currently using Cat5 unshielded and it's giving me all sorts of trouble no matter where I place the cable or how far away I can get it from the transmitter gear.
The studio computers are able to access the internet just fine on unmodulated carrier but as soon as music is played over the air the ethernet access slows down to a damn near halt. The louder the modulation the slower the internet access. Full 100% modulation completely takes down ethernet access.

This is nothing more than a simple setup where we run an ethernet cable 50 feet from the local router to the studio computer. WIFI access through the router is completely unaltered by the high RF exposure, however the ethernet cable run seems to pick it up like an antenna and demodulate it causing the whole internet stream to fail.

I was thinking Cat7 would be the way to go because it's shielded pairs rather than the whole bundle being shielded on the outside.
Not sure if Cat7 is backwards compatible with Cat5 though is it?
Or would Cat6a cure the problem?

This is a low power AM station so we don't have to worry much about RFI with other devices. The ethernet connection seems to be the only real issue.

I am thinking of just connecting the router directly to the computer and just extending the phone line (it's ADSL) to it, instead of the long ethernet connection. Not sure if that would help any. The modulation doesn't seem to be getting into the phone line at all so maybe that could work?

Thanks for any input.
 
I've not had that much of an issue, even at a 5kw am I cared for in the past which was using old cat5, not cat5e and poor terminations at that, held up fine in the RF.

At my day job, I have wireless network equipment on the tower with a 1kw am no problem, using double shielded cat6 which has a full braided shield on the tower with proper ground kits every 30 ft, have had 0 trouble with that one since installed.
 
First, be sure your RF is radiating from the antennae and not from the phasers due to a problem with vswr.

Route the Cat Cable through grounded conduit.
 
I should have put more emphasis on this being ADSL (high speed internet over phoneline)

After looking up why it effected only the download speed and not the upload speed I came across some information that ADSL uses the same frequencies as AM radio. Go figure.
Using WIFI through our router I am able to use the full speed of the service, but using a direct Cat5 ethernet from the router to the computer is when the problem comes in.

Today I am going to try just moving the router right next to the computer and using a very short ethernet connection to see if that helps.
It doesn't seem to be getting into the phone lines as much as it is the Cat5 cable.
I will get back to you all on the progress.
 
Had a DSL at a 5kW AM that barely worked. Switched to Comcast and have 50 down and 20 up with no problems.

I would ground it everywhere possible and use shielded cable for starters. Do you have a building ground system that's tied in with the main (antenna) ground?

But, even with 6" copper strap everywhere the DSL didn't want to work right when on day power. If you have cable internet that may be the way to go.
 
I live in Atlanta across from an AM antenna farm. There are five AM radio stations across the street from me. When we first moved here in 2000 I called BellSouth for DSL. This was a brand new complex and we were the first residents. My DSL would stop working at about 9AM and start again at around 4:30 in the afternoon. I got all the way up to a VP engineer at Bellsouth and we trouble shooted this for three months. He wanted to know what was causing the problem because other in the same complex were having the issue.

Long story short, I found out that ADSL frequencies start at 1000khz. One of the stations across the street is at 1190khz. It is at critical hours power of 2.5 KW and then goes to 24KW. So, they would go to full power two hours after sunrise and then drop two hours before sunset. While at full power they DSL would not work.

What kept throwing us off is one of the stations is WQXI-AM at 790khz. That station was bleeding into everything. Phone lines, fire alarms... I could even hear it in my dial-up modem before I connected the phone line. So, the BellSouth engineer and I were so focused on 790 being the problem, that we never thought to consider the other stations.

Twelve years later, BellSouth never solved the problems and nobody in this complex can get BellSouth DSL. Every telephone in the complex must have an RF filter on it. Also, every line has another RF filter. The fire alarm speakers have RF filters. DSL and AM radio are not friends.
 
But both Barry and WNTI's stories suggest the RFI is getting into the phone company's stuff and not the Ethernet.

Honestly, I've never heard of Ethernet getting RFI to the point that it stops working. The shorter cable would be the first thing I'd try.
 
Kage Michaels said:
I should have put more emphasis on this being ADSL
Click to expand...
As you noted, the DSL frequencies and the AM band overlap. I have never been able to use DSL at 5-10 kw AM transmitter sites where the transmitter shack is right at the tower base, only cable internet connections or dialup. I had another site where the studios (and transmitter) were over 1/4 wave from the towers, but were well uphill from the towers - same problem.
 
DSL and AM do not get along, especially if your AM is running any kind of power.

Any filter designed to kill RF on the phone line will also kill the DSL signal.
 
....But those little DSL filters DO work great at getting the AM out of phone lines!! Hang on to those!
 
WNTIRadio said:
....But those little DSL filters DO work great at getting the AM out of phone lines!!
Click to expand...

Even better are brute-force Z100B1 filters developed by Bell Labs for Western Electric for the use of Baby Bell techs battling POTS interference near AM transmitter sites. They were later marketed under the AT&T brand, and are now available as Westek Z100 filters:

http://www.westek.com/Z100-Filter-pr-16424.html
 
Ground everything including the DSL modem (ground the ring of the power supply to the station ground).

Minimize the equipment. I use a Westell 6000 DSL modem/router as my router.

Run shielded cat 5 everywhere. Ground the cat 5 shields to station ground. I run everything through a Linksys rackmount 24 port switch that has grounded jacks.
Solder all connections and try to run shielded wire from the POTS underground to the DSL modem (as short as possible).
Run ALL modem wires through ferrite beads two turns (I get mine from scrapping old computer switching power supplies).

I have DSL at my transmitter and it runs pretty reliably because of these. It didn't run at all before. I also have Towerstream wireless T1 service for my PCM STL. It also runs through the switch.
 
I did all that, bonded it to the copper strap which is in every room in the building (studios/tx are co located) which is bonded to the ground system and it only worked marginally after that. If it rained it got worse. Winter was worse too. Got rid of the DSL and went with Cable, bonded the shields to the ground system and get 50mbps down and 33mbps up. Same price too.

IF you can get cable, go that route. Just easier in the long run and also happens to be a lot faster too.

I've got those Z100 filters all over the place, even with everything grounded. The problem is the cheap phones will pick up the AM if there isn't a filter on them. And the bigger problem is that even the expensive phone systems are "cheap phones" on the inside when it comes to shielding and grounding.
 
I put 4 of them in series after the DSL modem because I don't want DSL products intermodulating with weak AM signals
I want to receive. All the phone lines branch after the 4 DSL filters.

I also did not want to hear any vestige of the DSL hiss on my phones.

Only donwside is I can no longer use the telephone dial finger stop as an antenna for a crystal radio.

Once upon a time, the telephone dial finger stop was the best ever antenna for a kid's xtal set.

It also seems to stop any residual audio of my pt 15 AM 1620 khz on the phones, which was
audible but barely before the filters were installed.

A sweep of the house with a little AM radio near phone wiring showed a large drop in DSL noise on weak signals,
placing the radio near a phone or ph wiring showed the noise was still there, just not radiating significantly.

I don't see much noise of etheret itself on weak signals, but admit pickup within a high rf environment is
the OPPOSITE side of the problem.

I want fiber optic as soon as possible for so many reasons, mostly because of rouge rf from coax design/implementation,
which I will avoid at all costs.
 
We are running a T1 into a 20 KW daytime, 2 KW night time AM site. 50 ft of cat 5 from the Telco interface to a conventional router switch then to a Davicom remote control, Comrex Access unit carrying the stations audio and an on line computer. No problems at all. conventional cat 5 cable everywhere with runs of 50ft max. after the switch. This is a new site I built 4 years ago with particualr attention to the ground system in the 4 tower antenna field, the building in the middle of it, the transmitters and the phasor. Not doing anything special with the cat 5 distribution inside the building. I suspect keeping the RF ground system clean, the cat 5 runs short and using common sense hookups makes a difference. I would not try this with a cheap switch or bargan cable. At a Mt. FM site I do use sheilded Cat 5 for runs longer than a few ft. but we have 7 High power FM's and a few two way and microwave links at that location.
 
The CAT5 has inherent RF proofing with its twists and common mode rejection built in. It's a balanced system, Ethernet, with two wires for transmit and two for receive.

The frequencies used run up to 350MHz for a 100MB lan.
 
If wireless connections to the Router work in your RF environment, why not make every connection wireless?
USB wireless devices are cheap.
 
WiFi is okay as long as it's not mission critical data. I wouldn't dare run an automation system using WiFi!!

If it's the sales-mutants computers or the reception desk, no big deal for WiFi.
 
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