PROBLEMS with DC switches at or near FM tower locations

[gilljr]

I personally have not mounted on a FM site but operate on a few AM sites. Depending on the tower configuration I have used Ferrities and Lighting Chokes.

I am planning adding to an existing installation on an AM tower.
1. AM Radio broadcast is off of lines running outside parallel to the tower about 4'.
2. Mounted 2/3 of the way up the tower.
3. Currently use ferrites at the base of the tower and the top of the tower to filter out unwanted frequency.
4. 48VDC Power
5. To breakup the signal and minimize the energy being transferred to my cable I am using grounding clamps every 15ft up the tower on a shielded cable (Without the ground the ferrites shatter and the cable melts).
6. All ethernet runs are shielded and less than 10ft in length.
7. Equipment excluding radios include a Cambium CMM4, 48 to 24VDC down converter, and various DC PoE injectors.

I wanted to install a WS-12-250DC up the tower to power some p-to-p radios and not have to mount more PoE injectors. Should I wait for a new product?

The only real issue I have had at AM sites is the occasional GPS antenna burning up which I have not had happen enough to determine the cause.

Gilbert

[sirhc]

I personally have not mounted on a FM site but operate on a few AM sites. Depending on the tower configuration I have used Ferrities and Lighting Chokes.

I am planning adding to an existing installation on an AM tower.
1. AM Radio broadcast is off of lines running outside parallel to the tower about 4'.
2. Mounted 2/3 of the way up the tower.
3. Currently use ferrites at the base of the tower and the top of the tower to filter out unwanted frequency.
4. 48VDC Power
5. To breakup the signal and minimize the energy being transferred to my cable I am using grounding clamps every 15ft up the tower on a shielded cable (Without the ground the ferrites shatter and the cable melts).
6. All ethernet runs are shielded and less than 10ft in length.
7. Equipment excluding radios include a Cambium CMM4, 48 to 24VDC down converter, and various DC PoE injectors.

I wanted to install a WS-12-250DC up the tower to power some p-to-p radios and not have to mount more PoE injectors. Should I wait for a new product?

The only real issue I have had at AM sites is the occasional GPS antenna burning up which I have not had happen enough to determine the cause.

Gilbert

All of the current issues are with FM sites so who knows?

AM and FM are vastly different frequencies.

You could have no problems or it might be worse.

Right now we are addressing reported FM issues.

If you try it let us know.

[cwachs]

This is beginning to turn into an FM interference discussion and that interests me as well. I have two Cambium ePMP 1000's (GPS) on a tower with FM (and FM on towers all around it). We are on the hill with all the primary broadcast (FM and TV) towers. I don't think we have AM up here. My cable runs are 100' - no way to really fix that. However, they are carrier class shielded cables and go through surge protection at the bottom and well grounded.

One of my ePMPs is perfectly happy with a 1000Mb link and no errors. The other keeps negotiating a 100Mb to 1000Mb and generates errors - though not constantly.

I originally thought bad ends but after fixing them, figure this is FM interference. I bought a bunch of ferrites to clamp on the cable top and bottom. My question is, how many are you putting on? I've heard some people (on Ubiquiti's site) state they put a dozen on each end of the cable. My plan was to put 6 in a row at each end but I don't know the general practice here.

[wifi442]

Very interesting stuff.

Chris, I am still running the inverter with the AC switches at my noisy FM site. I apologize for not getting back up there to try the I2C cables as I have been extremely busy with a few new sites that have gone up (With DC switches that are running great!) The AC Switches + Inverter setup has been working so well at the FM site I have decided to leave it that way for now anyway as it has already proven itself.

Keep me posted as you get closer to a solution. If you need to test anymore hardware, I can always run it up there.

For what it's worth I am running a WS-6-Mini 50 feet up on the tower in the plastic box and there is a 1500 watt FM array on the other side of the tower (about 10 feet away) and the tower next door is pumping 25,000 watts FM out and the WS-6 has been rock solid!

J

[markec]

Hi all.

We are having the same issues with FW 1.3.8 and latest 1.3.9rc! Switches are: WS-24-400A (2 pcs). They have same problems. ususally they occur when we change PoE status of ports. Is there ny progress on mentiones issues?


Regards,
Marko

[sirhc]

Hi all.

We are having the same issues with FW 1.3.8 and latest 1.3.9rc! Switches are: WS-24-400A (2 pcs). They have same problems. usually they occur when we change PoE status of ports. Is there any progress on mentioned issues?


Regards,
Marko

What same issue, please describe issue.

[MrBook]

"None of our AC switches are affected by FM Broadcast towers, just the WS-8-250-DC and WS-12-250-DC"

We are having issues with an installation of a couple of WS - 6 - MINI's mounted on a 400' FM Tower. I'm not sure if it's related to the issues reported here or not. We have a WS-8-250 AC on the ground. Ports 1 & 2 have 48VH enabled to power the 2 MINI's on the tower which are about 200' up and a 230' cable run. The ground switch also powers a Rocket M5 backhaul about 180' up the tower. The link between the WS-8-250-AC and the MINI's and the Backhaul is rock solid, never an issue. 6 MINI #1 in turn powers 2 Rocket M2's and a RBMetal9hpn another 120' (320' AGL) up the tower. 6 MINI #2 powers 3 Rocket M5's 150' (350' AGL) up the tower.

The problem we are having is the Rockets on the tower consistently revert to 10 M-F ethernet speed. A port bounce or running a cable diagnostic test ALWAYS restores the ethernet speed to 100 M-F. I set the ports to bounce every morning at 4:00 A.M. but I often find it back down to 10 M-F during the day and have to run the diagnostics to restore it to 100 M-F. The Cable is shielded Primus Cat5e. We were planning on swapping he cable but that involves getting the FM station to turn down their power while we're on the tower and of course weather so we haven't gotten to it yet. After seeing this thread, I'm wondering if it could be a related issue?

[sirhc]

After seeing this thread, I'm wondering if it could be a related issue?

No, your problem is the same issue people have had with Ethernet on FM towers for many years.

The problem with DC switches on FM towers is an I2C bus issue.

[MrBook]

Any idea what to do for my issue? I thought I saw something eluding to installing the 802.3af adapters.

[sirhc]

Any idea what to do for my issue? I thought I saw something eluding to installing the 802.3af adapters.

If you are referring to Ethernet communications on FM towers this has been an issue with WISPs for many years.

The normal battle plan was has been using better shielded cables and in some cases putting the cable in metal conduits.

This issue has nothing to do with the switch design nor is it related to the I2C issue on our DC models with FM towers....well it is related in the sense that FM uses 80 to 108 Mhz and Ethernet uses the 100BaseT/Cat 5 clock rate of 125 MHz rate, but since more data is transmitted at the same time, the transfer rate is higher. The math is quite simple: 125 MHz x 2 bits per signal (i.e., per wire pair) x 4 signals per time = 1.000 Mbps.

And since FM is transmitted at a very HIGH EIRP to carry NLOS great distances the side band splash at these sites wipes out the Ethernet modulation and often forces errors and causes it to step down or not work at all.

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