The Answer to Ailing Copper

I don’t know how things are in your neck of the woods, but here in the Northeastern US, our old copper TELCO networks are on their way out.  This is a problem for broadcasters who still rely on POTS lines (Plain Old Telephone Service) for transmitter remote controls, studio hot lines, etc.  The vast majority of my transmitter site access is through dial up remote controls.  There are a few locations that have web based remote controls, but to be honest; the phone part of my smart phone still gets a lot of use.  There are several locations where the old copper is just failing outright and not through a lack of effort by the repair techs.  Generally, the copper pairs get wet and develop a loud hum, which makes the remote control unit either hang up or become unresponsive to touch tone commands.

The best course of action is to get some type of VOIP line installed.  Here is the rub; many transmitter sites are nowhere near a cable system.  Several times, I have contacted the cable company to see if they will provide a VOIP phone line at a certain site.  The response is usually; sure, we can do that!  However, it will cost  you (insert some ridiculous amount of money) to extend the cable to your transmitter site.

LAN extensions to the transmitter site are a useful for a number of reasons.  More and more transmitters are equipped with web interfaces as are processors, UPSs, transmitter remote controls, security cameras,  etc.  LAN extensions can also be used for backup audio in case of STL failure.  Finally,  an inexpensive ATA (Analog Telephone Adaptor) and DID line can replace a POTS line for a lot less money.  One example; has the following plans as of this writing:

Plan type Per month per DID number (USD) Incoming call rate (USD) per minute Outgoing call rate (USD) per minute
Per minute $0.85 $0.01 (USA) $0.009
Unlimited $4.25 $0.00 $0.009
Toll Free (800) $0.99 $0.019 $0.009

Any of those plans surely beats the standard TELCO rate of $40-50 per month per line.

Design criteria for a wireless LAN system needs to take into account bandwidth, latency and reliability.  Each VOIP phone call takes anywhere from 28-87 Kbps depending on the protocol being used.  If the wireless LAN is being used for other things such as back up STL service, access to various GUI’s, etc then the total bandwidth of all those services need to be considered as well.  Do not forget ethernet broadcast traffic such as DHCP requests, ARP, SMB, etc which can also take up a fair amount of bandwidth.

For LAN extensions, I have been using a variety of equipment.  The older Moseley 900 MHz LAN links still work, but are slow in general.  The Ubiquiti gear has proven to be both inexpensive yet reliable, a rarity to be sure.  There are several links to various transmitter sites running on various types of Ubiquiti gear, usually without problem.  One simply needs to remember to log into the web interface once in a while and make sure that both ends have all the firmware updates installed.  They are cheap enough that a couple of spares can be kept on the shelf.

The following diagram shows how I replaced all of the copper pots lines at various transmitter sites with VOIP:

Diagram of LAN extensions to various transmitter sites
Diagram of LAN extensions to various transmitter sites

List of equipment:

Nomenclature Amount Use New or used
Ubiquiti Rocket M5 3 AP and station units New
Ubiquiti AirMax 5G-2090 90 degree sector antenna 1 AP point to multi-point antenna New
Ubiquiti Rocket Dish 5G-30 2 Station antennas New
Ubiquiti ETH-SP-G2 3 Lightning protection New
Trastector ALPU PTP INJ 6 Lightning protection out door units New
Cambium PTP-250 2 Point to Point link Existing/Used
Motorola Canopy 900DA PCDD 1 AP point to multi point Existing/Used
Motorola Canopy 900DA PCDD 2 Station Existing/Used
Microwave Filter #18486 diplexer 3 Diplexer 900 MHz ISM band and 944-952 STL band Existing/Used
Cisco SPA122 ATA 9 Dial tone for remote controls New

The main studio location has the gateway to the outside world. This system is on a separate subnet from the automation and office networks. From that location a point-to-multipoint system connects to the three closest transmitter sites.  This setup uses the Ubiquiti Rocket M5’s with various antenna configurations.  Then, from one FM transmitter site, there is an existing 5.8 GHz path to another set of transmitter sites.  This uses Cambium PTP-250s.

The next hop rides on the STL system, using Motorola Canopy 900 MHz radios and Microwave Filter Company #18486 dilpexers.  These are long paths and the 900 MHz systems work well enough for this purpose.  The main cost savings comes from reusing the existing STL system antennas which negates the cost of tower crews to put up new antennas and or rent on the tower for another antenna.

There is a smaller sub system many miles away that is connected to the outside world through the cable company at the AM transmitter site.  Unfortunately, due to the distances between the main studio and those three stations, there was no line of site shots to these sites available on any frequency.

When installing the 5.8 GHz systems, I made sure to use the UV rated, shielded cable, shielded RJ-45 connectors and Lightning Protection Units (LPUs).  Short cuts taken when installing this equipment eventually come back in the form of downed links and radio heads destroyed by lightning.

Regardless, I was able to eliminate seven POTS phone lines plus extended dial tone service to two sites that previously did not have it before.  In addition to that, all of the transmitter sites now have Internet access, which can be useful for other reasons.  All in all, the cost savings is about $310.00 per month or $3,720.00 per year.

8 thoughts on “The Answer to Ailing Copper”

  1. Speaking as a WISP operator in southeastern Indiana (and broadcast engineer), Ubiquiti AC radios will give you better performance over the long run. Plus you can move your STL audio off the legacy 950 MHz STL paths over to the IP path.


  2. Great idea Paul. Looks like something I have seen before. That makes all the difference having IP connectivity at remote sites.

  3. I’ve set up two STL links with MFC diplexers…one a 18 mile 900 Mhz link using Mikrotik Metal 9 radios, and a 16 mile 7 GHz TV STL using Ubiquity Bullet M5’s. Both have worked well. The 900MHz link replaced a phone line that the phone company cancelled due to its own billing stupidity, and refused to light back up. We converted them to IP remote control.

    Paul, have you found a favorite ATA, and do you need to change codecs or other settings on those ATA’s to get touch-tones to pass reliably? At the day job, we sometimes have to haggle with the cable co’s to get the VoIP settings to work with the closed-captioner’s modems.

  4. DHCP, ARP and RTSP data overhead can all be carefully eliminated by thoughtful network planning. No reason to have DHCP active if every address is static, no reason to have spanning tree overhead if you only have one link and no possibilities of loops, etc… every bit counts in these cases, and adds latency.

    little time with Wireshark & NMap and you can find out ALL the junk you are needlessly blasting point to point.

  5. I have been using a couple of Ubiquity M5 units over a 2 mile hop in the Florida Keys for about 5 years and they have worked well, even surviving Hurricane Irma. Since the satellite receiver was located at the transmitter site (it didn’t survive Irma) I have four channels of audio and a slew of contact closures going in both directions. Both Comrex and the much less expensive Barix units provide both closures and serial data.

    The run I have in the Palm Beach area, also using Ubiquity M5’s, is around 11 miles. One bit of caution in the lightening capital of the US is to make sure one has lots of protection. After lightening took out the transmitter units twice I have added protection on the tower at the dish in addition to where the Cat6 enter the equipment rack.

    My only problem with the Ubiquity units is the total lack of support. If you have a question or problem you are on your own.

  6. While IP connectivity to the remote control is great, there are many more single points of failure in the path to the remote control.
    I like the dial out POTS at the transmitter site for it’s robust nature. When you loose a link to the remote control you are stuck until you can get to the site.
    Of course you can automate some routines such as switching transmitters etc. I like the idea of remote controls that have both dial out and IP connectivity. Also the ability to have multiple remote controls that can interact together (such as the Audemat remote) can allow you to automate between separate main and aux transmitter sites.
    Also being notified of alarms by text or email doesn’t offer the ability to instantly control the remote control like dial out with voice reporting and DTMF does.
    I’ve been able to get the alarm call and switch transmitters to get the station back on the air all while driving down the highway. Using blue tooth and the DTMF buttons on the phone interface of my car’s Garmin GPS.

  7. Gregg; I’m retired now, but when we did VoIP in 2006 we used Multitech ATA modems. We used them for 4-wire intercom connections for a news bureau. Multitech had models that did more than one line in a rackmount configuration with FXO/FXS interfaces. The Multitech are now end of life, but the C7 made by Mediatrix looks very similar. We didn’t use the Multitech for POTS as our Nortel phone switch had built-in VoIP.

    Here’s a bit more of the story. Note the use of 5.8 GHz and HD video over IP.

  8. Scott, you are correct, the AC radios would give greater bandwidth.

    Gregg, for this I used Cisco SPA 122 ATA’s. I have found most inexpensive Cisco or similar ATAs will to the job nicely.

    Don, my experience with Ubiquiti support is limited. The one time I did contact them, they told me to do a factory reset then upload the latest firmware. That actually worked. I have dealt with other completely dead radio issues by tossing the defective unit in the garbage and buying a new radio. That has not happened very often, thankfully.

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