A few months ago, a client called with an unusual problem. They were in the process of adding a new radio system to their dispatch operation.
 
Their radio tower was a few hundred feet from the 911 center and was connected via private telephone cable that we had engineered a number of years ago. The problem was they had run out of cable pairs in the telephone cable. Their growth over the last few years, as they had gone to county wide dispatch, had taken all future growth we had allowed in our planning.
 
The radio system was a simple simplex system with tone remote control. The cost estimate to add a new telephone cable was not in this year’s budget. The administrator came to us and asked what other alternatives do we have? The service shop had offered a number of high tech solutions including adding digital multiplexing to the cable to derive the needed circuit. This was also cost prohibitive. We offered to solve the problem for only a few hundred dollars plus our hourly fees.
 
In years past, the telephone company derived “phantom circuits” on physical copper cable pairs by the use of transformers (in telephone parlance, they are called repeat coils). This method is still a viable solution as it can give a third audio circuit for every 2 copper cable pairs and the use of six 600 ohm center tapped transformers which are still readily available.
 
We made up a drawing and an equipment list for the local radio shop to order and install. When it was completed we were able to take the new radio system and apply it to the phantom circuit that was derived and the system was made operational without the expense of additional cable or multiplex equipment.
 

 
The explanation of how this works is as follows:
 
Both wires of the circuit labeled Circuit A in Figure 1 become one conductor of the phantom circuit. As the current flow in these two wires is identical and in phase there is no voltage differential across the pairs and no audio is heard in the Circuit A audio circuit. The two pairs of the Circuit B audio circuit work in an identical manner. By taking the center taps of the two transformers and using them as the conductors for the phantom transformer, a third audio channel is derived that is not heard in either Circuit A or Circuit B audio paths. Note: it is necessary that the conductors themselves for each of the two side circuits must be within 2 ohms of each other and ideally below 0.5 ohm of each other. If this is not the case, the side circuit audio and phantom circuit audio will crosstalk.
 
There is even one more circuit that can be derived. By the addition of an additional set of transformers, connected between the center tap of the phantom transformer and ground, an additional audio circuit can be derived. This circuit is unbalanced and can be susceptible to audio hum, however, this circuit can be used as an intercom circuit between the radio equipment building and the dispatch center. This gives four separate voice circuits over 2 copper cable pairs and some inexpensive center tapped audio transformers.
 
A PDF version of this article is available for download in the White Papers section of this website. 
Copyright 2009 all rights reserved.

Recently, we were working with a customer that had new diesel generators installed at several sites.  We happened to meet the generator maintenance technician at one of the sites while doing other work. An interesting discussion ensued.  It turns out that the technician, in his instructions had been told to set the maintenance routine up so that the generator ran for 15 minutes once a week, under no load.

Generators are no different than an automobile when it comes to engine maintenance.  It’s common knowledge that the worst thing you can do to an automobile engine is to only run it for 15 or 20 minutes and then shut it off. This has to do with several items that affect an internal combustion engine.

First and foremost is the oil.  Oil oxidizes while sitting in the crankcase.  This causes acids to form and chemistry to change.  What removes these acids and normalizes the oil is heat and pressure over a minimum period of time.  15 minutes is not long enough to heat the oil and maintain that heat and pressure to remove the acids that form from the oil oxidation.

Oil and heat has a secondary affect on an engine.  Oil attaches and migrates into the pores of the metal. This limits rust and other contaminates from bonding to the metals of the engine.  The classic example of this is in the form of a cast iron skillet.  Anyone who cooks knows that a well seasoned cast iron skillet will not have food stick to it. The vegetable oil permeates the pores in the iron, thus not allowing things to stick. To maintain this, you must use the skillet regularly, get it hot and allow the cooking oils to penetrate into the iron. A skillet like this also will not rust, and will last for years.

Secondly, moisture affects an engine – particularly the exhaust system.  The engine needs to heat the exhaust system enough to boil all the water condensation out.  Have you ever noticed that during the winter your car exhaust has “smoke” coming out for some time after you start it, but it disappears once the engine gets hot? That’s the water vapor escaping as the system heats up.  A generator is no different, and the exhaust system is critical to proper operation of any gen-set.

It’s important to remember that the engine is only half of the generator.  The other half, the actual generator has its issues too.  It is also affected by moisture and heat.  That is why it’s very important to exercise the system under a load.  This allows the electrical portion of the generator also to come up to operating temperature.

Lastly, the NFPA has specific standards for testing.  The critical section is in NFPA 2010 Section 110, Chapter 8.  The maintenance routine is in Section 8.4. Specifically, Section 8.4.2:

“Diesel Generator sets in services shall be exercised at least once monthly for a minimum of 30 minutes, using one of the following methods:

(2)    Under operating temperature conditions and at not less than 30 percent of the EPS nameplate kW rating”

I will take issue here: I don’t believe that monthly testing is adequate.  In our industry, and for critical sites, weekly is required, with all the above criteria met.

There are several other standards dealing with standby generators, their installation and maintenance. Specifically, NFPA 70/NEC 701, which deals directly with “Critical Operations Power Systems” and the Joint Commission on Accreditation of Healthcare Organizations. I would recommend that if you have not reviewed these standards, that you do so.

I’ve been reading about this now for about 2 weeks, and frankly, I wanted to have more to talk about.  In this link to the National Weather Service, you can read the official announcement, and here is a nice article in the Wall Street Journal. Having lived in the St. Louis area for over 35 years, I’ve seen lots of floods.  Of course, the flooding in 1993 was the worst (so far).

So, why am I posting this? A couple of reasons;

First, I know that not everybody pays attention to the weather service, or the news for that matter, and I wanted to “spread the word” in my own way.

Second, I wanted to reinforce maintenance and systems preparedness.

Some of the things that I have come across in my experience that happens during flooding and chronic wet conditions can really create headaches. You really don’t want to be troubleshooting a communications issue while trying to dispatch sand trucks or trying to maintain a switching station.

Things to look for primarily are weatherproofing issues.  Some may be beyond your control.  Water creeps into telephone cables all the time. This can cause noise and cross talk in analog circuits, and can cause errors on T1 lines. While fiber is somewhat immune to the water, the electronics are not. Additionally, if the fiber handholds and electronics are under water, the circuits will fail.

Water also does interesting things to microwave paths. Water has a high reflection coefficient. This is why we design in diversity when paths travel over large bodies of water. These ties back to overall system design.

So, my question is, when was the last time you tested your hot standby systems? Have you recently busied out your T1 and accepted calls on your backup trunks? For that matter, when was the last time you tested your UPS on some of your smaller sites or non-generator systems?  Have you forced a ring direction switch on your fiber or ring microwave system?  If you are running a simulcast system, how does this affect the timing and the system retraining time? Are your people trained and experienced enough to notice and respond to equipment alarms appropriately?

For some of my customers, these items are standard operating procedure, but for some, the network is taken for granted.  Let’s not take things for granted.

When to check your nuts

OK, so a pithy headline can get anybody’s attention, but when it comes to tower maintenance, it really is about nuts and bolts.

Towers are like bridges – they all need maintenance, but unless they break or are visible, they tend to get neglected. Oh, sure, the big ones, the ones with lights and alarms get some attention, but when was the last time you checked the ones that don’t get painted or lit? Would you be worried if the nuts at the base of your tower were like the ones in this video??

OK – so, not fair; this was a new tower. BUT we discovered this during our final punch list.  This tower was lighted, and had all antennas installed.  In fact all the civil was completed.  We only needed to install electronics at the site.

However, this photo

is not of a new tower, but one that is up.  Notice the concrete? Over time, everything fatigues, even concrete and steel.  The forces of heating and cooling naturally work parts loose, and if not checked regularly, could lead to a major catastrophe. The crack in the concrete was found while adding antennas to this tower.  The crack leads right to one of the anchor bolts.  This is a serious repair.

As part of this post, I went out to Rohn, Sabre, and Valmont to try and find the recommended maintenance intervals and practice.  Unfortunately, my search of their respective web sites was not fruitful. I’m sure an email or phone call to them with the model number of your installation would get you quick results.

The point here is to make sure that you include tower inspections and routine maintenance in your budget.  I know things are tight from a fiscal perspective, but like your communications system, a minor failure can multiply, and over time become a real issue.  And we all know that it’s during the critical times that systems tend to break down.

I saw something today that I’ve seen so many times before that I really just don’t understand.  I walked into a tower site ran by a local Public Safety organization. The site itself was, from an external standpoint fairly nice. The tower, building and guys were well fenced, and access was excellent.  However, when we entered the small transmitter building, what we found was not quite what one would expect.  Expecting nice, albeit small equipment racks with equipment neatly stacked and arranged in such a manner as to display a professional and well thought out system, we found instead, 2 AC powered console base stations, and one 12 volt powered base station.  The console base stations were in cabinets and locked, a plus in my book, the other transmitter since it was substantially newer and 12 volt powered was sitting on a plywood shelf with the cheesy metal shelf brackets screwed into the wall.


Now don’t get me wrong.  I understand that sometimes economy trumps everything else. Especially when working with public dollars.  There always seems to be too much project at the end of the budget. The console base stations however, were not bolted to the floor. The grounding, coax and other infrastructure was neatly and professionally done. The 12 volt transmitter, even though on the shelf that it is, was neatly installed. Unfortunately, the location of this site is in a known earthquake zone.  One good shake, and as the rhyme goes, they all go tumbling down.


No, what really crumbles my cookies was what these AC base stations were plugged into. One would expect, at a minimum, a properly grounded commercial line interactive UPS, complete with alarming.  A quick note; I am NOT a DC power snob. While I do like DC power in certain applications, I do realize that AC power backup in the right situation(s) is appropriate, cost effective and reliable. But, when I walk into a Public Safety radio system site, I do not expect to see critical communications gear plugged into $150 UPS’s that someone picked up from the local office supply chain. The servers here at Praecom World Headquarters have better UPS on them than these radios.


I know the folks that installed and maintained the radios.  Again, they are fine competent radio people. But radio people are not power people. Public safety people are not radio OR power people. Radio dealers are in the business to sell radios, and in today’s competitive world, anywhere they can cut costs they will.


I’m not disparaging the UPS manufacturer either. These are fine units for an office environment or supporting a small single server.  I utilize a model very similar on the telephone system here in the office. The point I’m getting to is that it was the wrong application for the design.


You see, you have several dynamics all coming together that, if the moon and the stars are in proper alignment, something is going to go wrong. The site did have generator power, so hold time generally would not be a problem. The issue truly is that there lacks any visibility into the system. If the UPS were to fail, for any reason, AND the generator failed to start, all the poor dispatcher would know is that they were off the air. And these UPS’s do fail. Regularly, and when you least expect it.


As a comparison, also in this building is where the local RBOC has brought in a SONET terminal to drop out the circuits for the radios. The SONET terminal was in a small 19” rack, bolted to the floor. In a tray in the bottom of the rack was 4 nice 25 AH gel cell batteries and a float charger. The RBOC does have deeper pockets, but they also understand reliability and power. They have learned their lessons over 100 years of needing to provide service.


So the final advice is, whether you’re spending $250,000, $50,000 or $10,000 on a site take a little extra and design the power appropriately. A small commercial UPS and generator transfer panel is, in the grand scheme of things a small cost. And I guarantee you’ll sleep better at night. At a minimum, make sure you know what you’re asking for, and in the end, what you’re getting.

An excellent paper written by our Consultant Emeritus – Jay Underdown on Narrow Band implementation for Electric Cooperatives.

Sequachee Valley Electric Goes Digital

The Country’s First Digital Narrow-Band Radio Communications System in an Electric Co-op

Sequachee Valley Electric Cooperative is a 28,000-member co-op at the foothills of the Smokey Mountains in Tennessee. Its main office is in South Pittsburg, about 25 miles west of Chattanooga, close to the Alabama border.  With an average of 11 members per mile and 2,400 miles of power lines, and only 72 employees to cover its 4-county territory, responding to power outages is a real challenge.


Meeting this challenge demands a coordinated effort between members, the office, and the service technicians.  Because the Co-op must respond quickly to restoring and maintaining safe power services, a reliable radio communications system is crucial.  In the early 1990s the Co-op found that their low-band simplex radio system just wasn’t reliable anymore, and so the Co-op turned to an outside consultant for help in upgrading their communications systems.


In early 1993, the Co-op contracted with Spectrum Resources, Inc. (SRI), a communications consulting firm located in St. Charles, Missouri.  Jay Underdown, President of SRI, met with the managers at the Co-op to evaluate their communications needs.  Managers from all four offices of the Co-op – the main office in South Pittsburg, plus the district offices in Pikeville, Dunlap, and Tracy City – were involved in the meetings to assess their current needs and plan for future ones.  In June 1993 SRI prepared  an integrated telecommunications plan that includes SCADA, telephone upgrades, and fixed and mobile data communications.  The first phase of this plan was the implementation of a very-high-frequency (VHF) digital radio system.

Why choose a digital radio system?

Implementing a digital radio system was a bold undertaking for this medium-sized electric co-op.  No other co-op had done something this cutting-edge, so it was very much uncharted territory.  They couldn’t raise members’ rates, and thus had to contain costs carefully.  They also needed to move fairly quickly because the old equipment was not reliable, nor were replacement parts easily available.  In selecting a radio communications system, they were impressed with the many advantages of a digital radio system.


System design
SRI suggested a digital system based on impending changes at the Federal Communications Commission (FCC).  The FCC’s Refarming Report and Order and Further Notice of Proposed Rule Making (PR Docket # 92-235) was published in June 1995.  One of the purposes of the Refarming Report was to make more channels available in the VHF range.  The FCC did this by making the VHF channels half as wide as those that were in use (and thus doubling the availability); this is called narrow band operations.  The way in which the digital system modulates a signal is a definite advantage in narrow band operations, and thus digital radio systems are expected to become the standard in the next few years.


The new radio system makes more frequencies available to the Co-op.  With the old low-band simplex system, all four districts operated on the same frequency.  “If a storm came through and all four districts had a power outage at once, then all four district managers would be on the same frequency, talking to at least four different mobile units, trying to manage the situation.  It was difficult to make sure the right person got the right message,” notes Danny Kirkendoll, Director of Engineering at the Co-op.  Now, the South Pittsburg and the Tracy City district offices each have a dedicated repeater.  The Dunlap and Pikeville offices share a repeater.  However, all mobile units can access any repeater when necessary.  “This has helped us tremendously in managing situations better with less stress,” says Kirkendoll.  “We can communicate more clearly with the service technicians, which helps us reduce the time our members are without electricity.  This, of course, makes it safer not only for our technicians, but also for our members.”


Furthermore, moving to a VHF radio system meant that the Co-op could improve their coverage area. The low-band frequency they had been using is very susceptible to man-made forms of noise, such as vehicle ignition systems, power lines, and noise generated from electric motors and neon signs.  The new repeaters (see below), combined with the greater transmission capability of the VHF repeater signal, means that now they can communicate where they couldn’t do so before.   “We’re very pleased with the coverage we’re getting now,”  reports Bob Pickering, General Manager of the Co-op.


Privacy
Many people in this rural area have radio scanners to listen into police, ambulance, and other radio communications.  However, these scanners cannot receive the Co-op’s digital signal, and thus other people cannot listen in to Co-op radio communications.  “This is a great security feature,” says Kirkendoll, smiling.  “It gives our technicians more privacy in carrying out the repairs.  Plus, sometimes we have to communicate information about the members in order to make the repair.  With our digital system, other people can’t listen in, which also gives our members greater security.”


Quality of communications
“With digital radio, either the signal is picked up completely, or it’s not picked up at all,” explains Underdown.  “The only distortion happens when the signal isn’t strong enough; in this case you hear a ‘warble’ just as the signal fades, then the receiver squelches.”  Given the size and the rocky terrain of the territory they cover, the Co-op’s service technicians were used to hearing static when they were out of range of the old stations.  “With the digital system, there’s no static whatsoever,” says Kirkendoll.  In fact, this has been one of the biggest changes that the service technicians have noticed.


“We don’t have to strain to make out words in a message,” notes Kirkendoll.  “Now if a technician is not picking up the signal, he or she will move to a location where the signal is obviously clear.”  And their new equipment and repeater locations have significantly expanded the coverage area, so that there are now fewer areas where signals cannot be received.  Again, the ability to communicate clearly increases safety not only for the service technicians, but also for the members.


Voice and data transmissions
A digital system enables its users to mix voice and data.  This capability has many advantages for future upgrades.  For example, putting mobile data computers in the service trucks would give the technicians remote access to the main database.  This would enable technicians to double-check addresses, quickly retrieve information about past problems at a customer’s site, check pertinent customer data, and other advantages.  One of the Co-op’s goals is to build upon the recommendations of SRI and ultimately create a SCADA system.  “We wanted a good foundation for our future plans,” explains Tim Sallee, District Manager of the South Pittsburg office.  “The digital backbone will give us more flexibility in implementing other improvements.”


Another welcome aspect of the digital system is that, anytime a mobile or a base unit keys up, that unit number is displayed on everyone else’s units for quick identification.  And if a technician isn’t nearby the service vehicle when an emergency call comes in, then the office can signal the mobile units to turn on a hazard light or even honk the vehicle’s horn to get attention.  Furthermore, each district has portable radio units that can also be signaled to beep by the base units.  These portables are used by contractors, by employees walking the right-of-way, and by on-call supervisors, who can take the hand-held unit home and monitor situations in the evening.   “This type of signaling is not a unique feature of digital radio,” notes Underdown, “but it is a feature that is built into the digital system, and therefore it doesn’t cost anything extra.”

Equipment and training needs for the digital system

SRI’s plan called for three new digital VHF repeaters.  A new 240-foot tower at Suck Creek primarily serves the Marion County District.  This tower can ultimately be expanded to 380 feet for mounting microwave dishes.   A second, new 220-foot tower is located at Hobbs Hill, and primarily covers the area around Tracy City.  The Co-op also leases space on a commercial 280-foot tower northwest of Pikeville; this third repeater covers primarily the Pikeville and Dunlap areas.


All four district offices have a base control station, remote control consoles in the offices, mobile units in service vehicles, and a few portable radios.  Additionally, there is a second control base at the South Pittsburg office that gives general supervisory access to all three repeater stations.  The remotes look like telephones, and the voice analog signal is converted to a digital signal through a control panel bridge to the radio control base.


The radio equipment was selected from Motorola’s Astro product line, and the towers were manufactured by Pi-Rod.  The buildings at the antenna sites were manufactured by Fiber-Bond per SRI’s specifications to suit the Co-op’s needs (places to store materials and so forth).


The new state-of-the-art equipment is music to an engineer’s ears.  “So far with the new equipment I haven’t had any problems,” says Kirkendoll.  “With the old equipment, I was having problems every week.”  In particular, one of the old low-band stations was a magnet for lightning, being struck 2 or 3 times a year.  “SRI built in a tremendous amount of lightning protection at the towers,” notes Kirkendoll.  “I don’t think we’ll have any more problems with lightning now.”


Training has not been a problem either.  “The system is very easy to use,” says Sallee.  “We only spent an afternoon on training, and we all quickly learned what we need to know to operate the system.  The most difficult thing we’ve had to do is get used to the digital quality of the signal.  The voice quality takes some getting used to.”


The upgrade in the communications system, and ultimately in service to the members, has not cost the members anything.  “We haven’t had to raise the rates,” says Kirkendoll, “because Bob Pickering has very carefully managed our monies.”  The Co-op’s digital system went on the air in November 1996, and its implementation and functioning have been very satisfactory. Based on the Co-op’s experiences, their boldness in implementing the country’s first narrow-band radio systems in an electric co-op is indeed a sound investment for the future.


Motorola and Astro are trademarks of Motorola, Inc.

Pi-Rod is a trademark of Pi-Rod Corp.

Fiber-Bond is a trademark of Fiber-Bond Corp.

ã  1997 SPECTRUM RESOURCES, INC.