The 16 channel bi-directional STL

As a part of our studio build-out in Walton, we had to install a high-capacity STL system between the studio and transmitter site. Basically, there are five radio stations associated with this studio and the satellite dish and receivers are going to be located at the transmitter site.

The audio over IP gear is getting really sophisticated and better yet, more reliable.  For this application, we are using a Cambium networks (Motorola Canopy) PTP-250 radio set and a pair of Wheatstone IP88 blades on either site.  Since there is quite a bit of networked gear at the transmitter site, the IP88s will live on their own VLAN.  The PTP-250s will pass spanning tree protocol, rapid spanning tree protocol, 802.1Q, and other layer two traffic.

The Wheatsone IP88A blades are the heart of the system.  Not only do they pass 16 channels of audio, we can also pass 8 logic closures bi-directionally.  This is key because we are shipping satellite audio and contact closures back from the transmitter site.  The IP88A setup is fairly easy, once the IP address is entered.  The web GUI is used for the rest of the configurations including making the connections between units.

Pair of Wheatstone IP88A AoIP interfaces
Pair of Wheatstone IP88A AoIP interfaces

The switches are managed units.  The switchports need to be set up via command line to pass VLAN traffic.  There is an appendix in the IP88 manual that outlines how to do this with various managed switches.  This is the most important step for drop-out free audio.  The switchports that connect to the two radios are set up as trunk ports using either VTP or 802.1Q.

Cambium PTP-250 5.8 GHz out door units
Cambium PTP-250 5.8 GHz out door units

The PTP-250 radios were already on hand, new in the box.  They are built really well and look like they should not break in a year or so.  These particular units are connectorized, therefore an external antenna was needed.  There are many such antennas, this system ended up with an RF Engineering & Energy 5150-5850 MHz dual-polarized parabolic dish with RADOMES.  RADOMES are necessary to prevent ice or snow build up in the winter.

RF Engineering & Energy 5150-5850 MHz dual polarized parabolic dish with LMR400 jumpers
RF Engineering & Energy 5150-5850 MHz dual polarized parabolic dish with LMR400 jumpers
STL link dish installed
STL link dish installed
1 1/2 inch EMT going from TOC to roof
1 1/2 inch EMT going from TOC to roof

Since the path is only 3.37 miles (5.43 kilometers), I set them up with a 40 MHz wide channel.  This is a rural, small-town setting.  When I looked at the 5.8 GHz band on a spectrum analyzer, it looks fairly uncongested.  These are MIMO single or dual payload selectable.  I will try them as single payload units since the path is short and the band is uncongested.  This should keep the throughput high.

Studio to transmitter site LAN extension
Studio to transmitter site LAN extension

The PTP-250s use POE injectors in mounted in the rack rooms.  CAT5e shielded cable with the proper connectors properly applied is a must for lighting protection.  The PTP-250 units came with Cambium PTP-LPU lightning protectors.  I also installed Polyphaser AL-L8XM-MA type N surge suppressors on each RF port of each PTP-250.

Emergency Communications

In this modern day and age, we take electronic communication for granted. Imagine being plunged into a world where there are no phones, cellphones, internet, email, television, or even radio. Back in the day when I served aboard ships, we called that being underway.

Way, way back in the late 1980s and early 1990s, those that served at sea were at the mercy of the Fleet Post Office.  I will say, the FPO did a very good job routing the mail to the appropriate place, however, sometimes weeks or even a month would go by without mail.  When the mail finally did arrive, it all smelled the same.  Everyone’s wife or girlfriend put some sort of scent on the outgoing, but since those letters mingled tightly packed in the same bag for weeks, often in hot humid tropical Pacific air, those scents blended together and became the Westpac Mail Smell, which permeated everything, even the letters from my father.

What will happen if people can’t sign on to Facebook?

Fortune favors the prepared.

Communications loss in ordinary circumstances

Loss of utility company power, phone service, and internet service can happen at any time for a variety of reasons.  The worst case scenario will occur when such loss is coupled with a natural disaster, which is often a major disruption of normal life.  Loss of information, especially at critical moments, can make a bad situation much worse.  In a situation where all normal means of communication are not functioning, something will fill that void, most likely the rumor mill.  That could be bad.

For information gathering, there are many options.  A good AM/FM shortwave radio is a decent start.  I would recommend a quality shortwave radio that has AM/USB/LSB options.  During run-of-the-mill storms and power outages, many radio stations will remain on the air with emergency generators.  The key is to figure out which stations are staffed and offer good timely information.  NOAA all hazards radio can be a good source of weather information, however, their transmitters can remain off the air for weeks or months at times.

One might ask “Isn’t this overkill or alarmist?”  I suppose that depends.  In the December 2007 ice storm, we had no power for seven days. In the aftermath of several major Northeast hurricanes and winter storms, some people had no power for more than two weeks.  Not only no power but no cable, phone or internet either.  In situations like that, having some form of connection to the outside world can make a big difference.

Communications loss in less-than-ordinary situations

Other situations and scenarios may require more effort.  Prolonged information shortages could be triggered by any number of national or global situations.  Shortwave receivers are not only for listening to international broadcast stations but also for tuning into amateur radio (AKA “Ham”) frequencies as well.  Amateur radio is often used for emergency communications on a local and national and international level by governments and the Red Cross when other systems are out.  National and international communications are often heard on the HF band; 3-30 MHz.  The Amateur radio primary emergency voice nets are:

  • 3791.0 USB VOICE PRIMARY International, DX, and Emergency/Disaster Relief
  • 5371.5 USB EMERGENCY Emergency/Disaster Relief
  • 5403.5 USB EMERGENCY Emergency/Disaster Relief
  • 7185.5 USB VOICE PRIMARY International/Regional and Emergency/Disaster Relief
  • 14346.0 USB VOICE PRIMARY International/Regional and Emergency/Disaster Relief
  • 18117.5 USB VOICE PRIMARY International/Regional and Emergency/Disaster Relief
  • 21432.5 USB VOICE PRIMARY International/Regional and Emergency/Disaster Relief
  • 24932.0 USB VOICE PRIMARY International/Regional and Emergency/Disaster Relief
  • 28312.5 USB VOICE PRIMARY International/Regional and Emergency/Disaster Relief

These are voice channels from the ALE website. If there is no traffic on these frequencies, tune around a little bit.  In addition to voice nets, the amateurs also use something called ALE, which stands for automatic link establishment.  This is a data system that can be decoded on a listen-only basis with a computer and some free software, for those so inclined.

For local amateur communications, 2-meter and 70-cm repeaters are often pressed into service.  For those, a VHF/UHF scanner is required.  Get a trunking scanner for 800 MHz police/fire dispatch as well.  Make sure that all radios can operate on 12 volts DC.  For this application, the size of the solar panel and the battery is moderate, as receivers do not use much current.

Another option is a wide-band USB radio for a laptop computer like a WinRadio WR-G315e.  These devices can be powered by the USB outlet on the computer while the computer itself is charged with a solar panel.  For this route, some research on laptop solar chargers is needed.  The DC power requirements vary from laptop to laptop, so I can only offer general advice here.

With any receiver, a good antenna will greatly improve performance.  If there is room for an outdoor antenna, any length of wire strung up in a tree, away from power lines will work well.  For indoor setups, some type of receiving loop will work best.

Prolonged loss of communications in extraordinary circumstances

For longer-term situations, gaining access to vital information and communications may become more problematic.  First of all, electronic communications require electricity.  Long-term disruptions to the electrical distribution system could occur by either natural or man-made events.  When those events happen, those that are prepared will be in a better position to survive if not thrive.  Things like ad hoc computer networks and amateur radio can facilitate two-way communications.  In order to use amateur radio, one needs to get a license first.  This is a pretty easy thing to do and most other amateur radio operators won’t talk to you without a valid call sign.  Not only will they not talk to you, but they will also likely track you down and report you to the FCC.  That is the nature of the hobby, like it or don’t.

Amateur radio setups can be very simple and not terribly expensive.  A used HF radio can be purchased on eBay for a moderate sum.  A simple multiband vertical antenna will serve general purposes.  For those that are interested in HF Link, a newer radio will work better.

Wireless ad hoc computer networks can be set up to establish a quasi-internet over a moderate-sized area.  WiFi WAN networks can be locally established using 900 MHz, 2.4 GHz, 5.8 GHz, and 24 GHz license-free channels.  Depending on the frequency, those links can be used for point-to-point medium to long-haul links, or to establish local links to laptops and wireless devices:

  • 900 MHz: lower speed data rates, long haul, good to moderate building and vegetation penetration
  • 2.4 GHz: Limited channel availability, high atmospheric absorption, moderate speeds, low vegetation, and building penetration
  • 5.8 GHz: High number of channels available, potential interference issue with TDWR radar systems, moderate to high speeds, line of sight only
  • 24 GHz: Large bandwidth, high speed, point-to-point backhaul, line of sight only

Once the information is obtained, distribution to the greater public becomes a problem.  A very simple webserver (Apache, Nginx) with a lightweight, simple index page containing vital information, news, weather, etc can be set up on a laptop and all HTTP traffic is directed to the default index page.  This type of setup could be run off of a battery charged by a solar panel.  The issue here would be obtaining the information to put on the web page.

North Adams Tower update II

Work continues on rebuilding the North Adams tower after the collapse of March 2014.  Over last winter, a new tower was erected.  This is a fairly substantial tower.

New North Adams tower on ground
New North Adams tower on the ground
North Adams new tower erected
North Adams new tower erected

In the interim, a new Shively 6810 four bay half wave spaced antenna was ordered. This antenna will be combined for two stations, WUPE-FM and WNNI using a Shively 2630-2-06 branched combiner. The 70 foot utility pole next to the building will be retained as a backup facility for both stations. The Shively Antenna went up in stages.

New WUPE-FM and WNNI Shively 6810 antenna
New WUPE-FM and WNNI Shively 6810 antenna
Tower climbers rigging tower for new antenna
Tower climbers rigging tower for new antenna

Prescott Tower from Rutland Vermont was on site to do the tower work. They were the primary contractor for installing the new tower and did a really nice job of it.

New North Adams tower ice bridges to various shelters
New North Adams tower ice bridges to various shelters
Hanging the top two bays of new antenna
Hanging the top two bays of the new antenna
Lift of bottom two bays and first tuning section
Lift of bottom two bays and first tuning section
Securing bottom section and bolting bays together
Securing the bottom section and bolting bays together

After that, there were twenty feet of rigid line, another tuning section, then the 1 5/8 inch heliax into the transmitter room. The antenna was tuned and the load looks very good. We are waiting for the electrician to finish wiring up the new racks and we will move both stations into their new home.

Pittsfield Massachusetts’ newest “Metro-Station” 103.3, W277CJ

We have been poking away at this one for the last year or so.  It seems that the previous owners of Berkshire Broadcasting had filed for a translator to rebroadcast WNMB, (100.1 WUPE-FM) North Adams in downtown Pittsfield, during the great translator rush of 2003.  When the CP showed up in the mail last March, the current owners were quite surprised.

After looking at the Construction Permit, we made some modifications;

  • Moved the transmitter location from 100 North Street to 1 West Street (Crowne Plaza Hotel) which is the tallest building in Pittsfield.  Antenna AGL is 44 meters (145 feet).
  • Changed the rebroadcasting station from WUPE-FM, North Adams to WUPE-AM Pittsfield
  • Changed the antenna to non-directional
  • Changed the ERP from 48 watts to 100 watts

We were able to make those antenna and power changes because we changed the parent station to the local AM station, WUPE, 1,110 KHz.  The previous power/pattern was submitted to keep the translator signal within the 60 dBu contour of the FM station in North Adams.

This, I feel, is the best use for an AM to FM translator.  WUPE-AM is a class D station with no nighttime service.  Adding a nighttime service greatly increases the station’s value to the community.  While the 100 Watt translator does not cover nearly as much as the 5,000-watt AM station, the transmitter location is right in the center of Pittsfield, so coverage of the population center is excellent.

The view from the top of the Crowne Plaza is quite spectacular.  I am pretty sure I will have a lot of transmitter maintenance to do right about the middle of October.

W277CJ 60 dBu contour
W277CJ 60 dBu contour

The installation is fairly straightforward:

W277CJ installation, roof of Crowne Plaza, Pittsfield, MA
W277CJ installation, roof of Crowne Plaza, Pittsfield, MA
W277CJ transmitter in outdoor enclosure
W277CJ transmitter in an outdoor enclosure

The outdoor enclosure is a DDB POD-16DXC which is rather nice, it comes with rack rails and a thermostatically controlled fan.

W277CJ Shively 6812B antenna
W277CJ Shively 6812B antenna

The antenna is a Shively 6812B with RADOMES. The transmitter is a BW Broadcast TX600v2.  I really like these transmitters, they are well-designed and rugged.  We have yet to have a single failure of one of these units in the field.

The station ERP is 100 watts, so a small bit of calculating is required to arrive at the proper station TPO.  I find it easier to make all these calculations in the decibels per milliwatt (dBm) unit domain, then convert them back to watts.  Thus, the ERP is 100 watts or 50 dBm.  The antenna has a gain of -3.4 dBm.  We used 25 feet of LMR-400, which at 103.3 MHz, has a loss of -0.26 dBm.  The total losses are -3.66 dBm, making the necessary TPO 53.66 dBm, 232.27 watts, or rounding down to 232 watts.