Who has time to troubleshoot?

The model for Radio Engineering these days is such that one engineer is covering multiple stations in various locations. At the very least, this person has a full (if not overflowing) plate. Thus, when something breaks, the procedure very often is; to pull the suspected module or board, call the manufacturer and order a replacement. That works as long as the manufacturer supports the model in question or has parts. As we all have learned by now, replacement parts are subject to the global supply chain, which is tenuous.

Then there is the question of AM transmitters. Is it worth it to replace an AM transmitter these days? I suggest it would depend on the market and revenue. In some cases, yes. In other cases, keeping the older equipment running makes more sense.

Troubleshooting is becoming a bit of a lost art. In addition to the time it takes, we tend to be unfocused and obsessed with rapid gratification, ready for the next social media post. What is lacking is the ability to take apart the layers of a problem, accept our initial analysis may be flawed, move beyond those assumptions, and work until the issue is solved. Troubleshooting is often like a crime scene investigation. There are several logical steps;

  • Assess the current situation; take steps to ensure it is safe to proceed. Remove all power from the transmitter and don’t work on failed transmission equipment during thunderstorms
  • Gather evidence; look for fault indicators, alarms, automated log entries, burned components, abnormal meter readings, etc
  • Check external factors; power failures, lightning or storm damage, excessive heat, moisture, etc
  • Check internal factors; aged components, bad cables or connectors, improperly seated boards or components, and obvious signs of damage
  • Work from one side of the issue to the other
  • Check the maintenance logs (if there are any) to see if this problem has occurred before and what was the fix
  • Use available resources; troubleshooting guides provided in equipment manuals, factory support, and available test equipment
  • If a failed component is found, make sure that it is the problem and not a symptom of something else

Here is a good example of a recent troubleshooting evolution; I went to change over to transmitter #2 and these fault lights appeared:

DX-50 transmitter, faulted, no power output

The conversion error on the A/D converter indicates why the transmitter power output is zero.

The first step; secure the transmitter, remove all power, etc. Next, consult the book!

The Harris DX-50 manual gives good troubleshooting guidance. This transmitter was manufactured on March 22, 1990. It has been a reliable unit, to date. Section K.4 Analog to Digital Converter (A34) of the manual suggests loss of audio clock frequency sample due to the following;

  • Loose connection with the carrier frequency sample cable coming from the RF drive splitter (A15)
  • Bad or missing jumper connections on P-10, frequency divider section
  • Bad U-29 (74HC161, 4 bit binary counter, only in use if the carrier frequency is above 820 KHz, Not Applicable)
  • Bad U-12 (74HC14, Schmitt trigger)
  • Bad CR13 or 14 (1N914)

Fortunately, there was a working DX-50 about 15 feet away, so I was able to make some measurements at various places on the A/D converter board.

On the working transmitter (DX-50-1), at the RF sample input (input of R83) on the A/D converter board, I see a nice strong sine wave, on frequency:

WABC carrier from RF drive splitter to A/D converter board
WABC carrier frequency

Second, I measured the logic pulses on TP-6, as described in the manual. Those look good.

On the non-working transmitter, I made the same measurements and found a fuzzy sine wave way off frequency on the input of R83. The logic pulses on TP-6 were normal.

Definitely lost the RF sample. Since the transmitter is 32 years old, I suspected the cable (#92, RG-188 coax) between the RF drive splitter and the A/D converter had gone bad. Perhaps rubbed though on a rough metal edge or something like that. Several checks with a Fluke DVM showed that there were no shorts to ground or internal conductor shorts. End-to-end check on both the shield and inner conductor proved good. So, not the cable…

I then went on a bit of a wild goose chase suspecting the output from the oscillator to be low or the drive regulator power supply was defective. The drive level going into the PA was close to normal but slightly lower than the previous maintenance log entry. Also, drivers 8A and 8B were both on, which is not normal and made me suspect the drive regulator.

I made a call to GatesAir and spoke with a factory rep, who had me swap out the A/D converter, oscillator, driver power supply regulator board, and the buffer amp/pre-driver module between the working and non-working transmitter (while the low power aux was on the air). With the working transmitter close by, I was able to confirm that these boards or modules were not the cause.

Finally, I went back to the RF drive splitter and use my camera to take a picture:

DX-50 RF drive splitter (A15) J-17, board side

There is a 6-pin connector on the underside of the board (J-17). Pin 2 (from the right) is the center conductor and pin 1 is the shield of the cable going to the A/D converter board. Upon closer examination, the solder joint on pin 2 is suspect. I re-heated this connection with a soldering iron and viola, the transmitter started working again.

WABC DX-50-2, returned to service

The extenuating circumstances; the air conditioning at this site was slowly failing and that part of the transmitter was subjected to heat cycling several times. More recently the HVAC system was in the process of being replaced, of course, on one of the hottest days of the year. This pulled a lot of warm, humid air into the room. Also, as this is transmitter #2, it was not in regular use until recently (we began a procedure for operating on alternating transmitters for two-week periods).

All of this work took place over the course of two and a half days or so. That would be a lot of time for the module swap guys who tend to move on to the next outage quickly. On the other hand, buying a new 50 KW AM transmitter is an expensive proposition these days and there are very long lead times on some of these units. Being persistent and focused paid off in the end.

Filters for Over The Air Television

Many people are surprised that OTA TV (Over The Air Television) is still a thing. I am here to say that there are lots of TV stations still broadcasting. OTA is alive and well, especially around big cities. To wit; I noticed this older TV antenna on the roof of a transmitter building in Lodi, NJ. Being curious, I connected an ATSC 1.0 TV to the antenna lead in the kitchen. One scan captured 62 TV channels and sub-channels OTA in the NYC market.

Somewhat aged TV/FM antenna pointed at Manhattan

That site is 10 miles northwest of the Empire State Building.

I also noted that the satellite dishes on site have had Terrestrial Interference (TI) filters on the LNB’s for many years. Recently, 5G filters were installed as well. Thus, I added a 5G/LTE filter made by Channel Master (part number CM-3201) to the TV antenna splitter. A rescan captured 79 channels. Interesting.

I began ordering TV receiver filters and testing them with my network analyzer. There are many different units made by different manufacturers. The smaller, cheaper units do not have as good performance as the larger, more expensive ones. Go figure.

Here are a few sweeps of various filters:

Channel Master CM-3201 5G/LTE filter. Cut off 608 MHz
Silicon Dust USA LTE LPF-608M. Cut off 608 MHz
Phillips LTE-5G. Cut off 616 MHz

There is also an FM band-stop (Channel Master CM-3202), which is effective for blocking out 87 to 113 MHz.

Channel Master CM-3202 FM band-stop

Sometimes I get questions from non-technical readers, thus for the uninitiated; these sweeps are return loss. The higher the line on the right-hand graph, the less signal will get through the filter. A flat line at 0dB means that little or no signal is getting through on those frequencies.

These filters are helpful, especially with inexpensive consumer-grade TV receivers. If you live near an FM transmitter site, then an FM band-stop filter may help, especially with the low and high-band VHF stations. If you live anywhere near a cell site (and most of us do) then a 5G/LTE filter will likely help.

Happy cord cutting!

A little bit of catching up…

I regret not having enough time for writing these days. There are a number of reasons for this. Firstly, much of what I do running my business is mundane and not worth noting. For example; today I am going over work reports and reconciling the bank account. Necessary, but about as exciting as watching the grass grow or reading about drying paint.

However, the rest of the time I have been working on various projects around the northeast, to wit:

In Boston, I took part in converting an LPTV station to ATSC 3.0. That was interesting and I am enjoying the TV work.

WCRN-LD exciter GUI
Boris Johnson resigns, also one of the first ATSC 3.0 images transmitted OTA in Boston, MA

In Syracuse, we had to lower a TV transmitter from the 23rd floor to the 22nd floor on the outside of the building. The transmitter itself became marooned because an electrical conduit for an alarm system was installed restricting the size of the stairwell.

Carefully lowering a 2KW UHF TV transmitter, State Tower Building, Syracuse, NY
Transmitter re-assembled and on the air

Fortunately, we hired a moving company to do this. I am pretty sure that our insurance does not cover damages from transmitters falling 22 stories.

In NYC, I installed two FLX-40 transmitters for GatesAir.

WXBK FLX-40 transmitters, Rutherford, NJ
FLX-40 Heat Exchangers
“Do you see over yonder, friend Sancho, thirty or forty hulking giants? I intend to do battle with them and slay them.” “Take care, sir, those over there are not giants but buildings on the island of Manhattan.”

In Kingston, NY a used BE AM1A (along with a coax switch and dummy load) was installed at WKNY.

Slightly used BE AM1A installed as backup at WKNY, Kingston, NY
7/8 inch coax switch and 2.5 KW oil cooled test load suspended from the ceiling

It is nice that this station has a decent backup transmitter to buttress the aging, yet very reliable Nautel ND-1.

Even though it is a short drive away, I had never visited the 1969 Woodstock Music and Art Fair site in Bethel, NY. It was interesting and being sort of an audiophile, I enjoyed this exhibit in particular:

Your author, standing in front of a “Woodstock Bin.”
Back of high-frequency horns

From the display:

This speaker stack sat on scaffolding high in the air… festival sound engineer Bill Hanley custom-built eight speaker cabinets for Woodstock, amplifying music and stage announcements across the large festival site… Afterward, the design would be known in the industry as the “Woodstock Bin.”

Bethal Woods Performing Arts center Museum, August 10, 2022

The high-frequency horns used Electrovoice diaphragm S/A compression drivers. I don’t know which driver was used for the bins.

Site of Woodstock ’69 stage, looking up into the field
Looking down from the field to the stage area. Person(s) for scale.

I am also writing articles for Radio Guide, I hope that you are enjoying them!

The State of Media in Russia

I read with interest the Radio World Article: Why reviving Shortwave is a non-starter. The main premise of the article is that reviving Shortwave broadcasting to Russia is just wishful thinking. Since I am still in contact with persons in Russia, I figured I would attempt to ask them what they thought about it (without putting them at risk, of course).

The short answer; the opinion by Daniel Robinson and Keith Perron is correct. Shortwave is a non-starter in Russia. I asked a series of questions of my Russian friends and received the following answers:

Question: Do Russians own AM/FM radios?

Answer: Yes, especially those with cars. Most listening to analog AM or FM radio is done in cars and sometimes at work wearing headphones.

Question: How about Shortwave or Longwave sets?

Answer: Amateur radio operators and some hobbyists may own these radios, but not the general population.

Question: Are there any left over shortwave sets from Soviet times/the cold war period?

Answer: Not likely, and if there are, they probably don’t work. Soviet equipment was not high quality.

Question: What about listening to the radio at home?

Answer: Not very many people do this. Most people watch TV while at home or stream movies.

Question: Where do most people get their news?

Answer: The state media TV services (Russia-1 or Channel-1). A few people may stream news from overseas, although this is getting harder and harder to do. Anyone who does this will likely use a VPN.

Question: How many people can find, download, install and configure a VPN?

Answer: Mostly young people will do this, but it is getting harder to find VPN apps. They are getting removed from on line sources and people are afraid to install them on their mobile devices in case they have interactions with the police. Approximately 10% might be using a VPN.

Question: Could Russia disconnect the internet completely from the rest of the world?

Answer: Yes, but it would be difficult. The internet in Russia was not designed to do this the same way as say North Korea or the Great Firewall of China. There are many physical connections out of the country and not everything is well documented. It is much more likely that they will block, censor and track users rather than completely disconnect.

Question: Are there any sources of outside information available in Russia right now?

Answer: For those that are searching for it, yes but likely not for much longer.

Question: If Radio Free Europe/Radio Liberty where available on AM/FM or Shortwave, would people listen to it?

Answer: No one cares. Unlike during Soviet times, no one really cares about western news or opinion. Things changed in 2014 with the first set of western sanctions. The cultural ministry (Roskomnadzor) began blocking access to internet sites they deemed detrimental. There were few independent media voices left. With the 2016 US election and anti-Russia investigations, most Russians believe that the west is turned against them. The news, as presented on Russia-1 is believed as truth.

As a radio professional, I believe in the medium including HF broadcasting. The point of my Russian friends; even if the programs were directly receivable via radio (of any type), most Russian people would ignore them. It is not a technical matter of getting programming to them. It is more a perception problem, brought on by years of propaganda and negative press from the west. If shortwave had been reinstated in 2007 when the first signs of censorship began to appear in Russia, things might be different. Instead, no one seemed to notice or care.

HF broadcasting, like all radio services, can be effective when nothing else works. Much of the VOA’s HF service is targeted to Africa and Cuba, two places that do not have a high percentage of internet users. It is very expensive to build and operate. To revive HF, it will need to get smaller and less expensive. DRM (Digital Radio Mondial) shows promise in this regard, but there is a dearth of available receivers (a quick search on Amazon nets zero usable results). Instead of trying to burn holes through the ionosphere with giant 500 KW AM modulated transmitters coupled to huge antennas with +20 dB gain or more, smaller digitally modulated transmitters with simpler antennas could net the same or better results. If these systems were placed closer to the intended target audience, so much the better.

Clearly, the world has changed. It is time to re-examine (and perhaps update) some of this old technology for 21st century use. Whatever happens, there are no short, quick, or easy answers. It took decades of time and a momentous effort to bring western ideas to the communist block. This was all undone in a few years by budget cuts.