HD radio – Page 3 – Engineering Radio

All Digital AM?

I have been reading, with interest, the saga of HD Radio on the AM (AKA Medium Wave) band. First question; if it goes all digital, will we still call it AM? Of course, there are other questions and concerns:

The proprietary nature of HD Radio, AKA MA3 or NRSC-5D as they are now calling it, is problematic. Xperi, the latest patent owner, currently (their word) has agreed to waive licensing fees for AM station owners who install their system. Is this a limited-time deal for early adopters or in perpetuity for all stations?
The NRSC-5D tests on WWFD, Fredrick, Maryland are hopeful, but as I pointed out before, it is one station with a well-functioning antenna system. Many AM antenna systems are defective either in design or due to deterioration. Is the FCC going to start policing the AM band again to cure these self-inflicted wounds?
Of course, the NAB wants zero oversight on the entire adventure. Under their proposal, small ownership AM stations would have a difficult time remediating interference issues from all digital co-channel stations by eliminating any required notification period, as proposed by the SBE.
The NAB also wants to nix a 1 Hz carrier frequency requirement, which would help with both the analog and digital interference issue, saying it would be too expensive. I disagree. In this day of universal GPS timekeeping, it would be easy to implement this on all modern transmitters, especially if they were already installing an HD Radio exciter.
Denis Jackson’s Radio World Article states that reliable coverage can be had out to 0.1 mV/m. This seems very, very optimistic given that ambient electrical noise (non-broadcast related) on the AM band is at very high levels and still climbing. Further, once the all-digital conversion starts, more and more co-channel digital interference will happen, likely cutting down that contour to a great extent. It works now but may not work later. These types of statements seem naive or perhaps disingenuous. Again, WWFD is one digital signal in a vast ocean of analog carriers.

While I am skeptical of some of the statements made in various articles and comments before the FCC, I do believe that converting the Medium Frequency band to all digital will have benefits. The BBC DRM tests carried out in 2007 (The Plymouth DRM long term trial) show that digital on MF can work. DRM has been implemented in various countries with good results.

Getting rid of the hybrid IBOC/Analog is a step in the right direction.

My concerns are the small owners who are still making a go of it on AM. Those guys still doing community radio and serving the public interest. If they choose to wait, are they going to get buried under a digital dog pile and then have to pay the full license fee later? Something like that might be the end for them.

HD Radio in and of itself is not the panacea for the AM band. Other things have to happen to make it work right. The SBE speaks extensively about ambient noise on the MF band. They are entirely correct. In addition, there are many, many AM stations that do not have compliant antenna systems. There are stations operating a DA-2 system full-time on the night pattern. There are stations operating a DA-2 full-time on the daytime pattern and power. There are stations that are supposed to turn off at night, which stay on 24/7. There are stations not reducing power to nighttime levels. The list goes on. Simply putting digital carriers on everything will not reduce station-to-station interference, especially at night.

I am cautiously hopeful that the FCC will look into the ambient noise problem, which simply cannot be over-emphasized. They would also need to re-invigorating the Enforcement Bureau. Since they closed down most of their field offices, it has been kind of a free-for-all out here.

GatesAir FLX-40 one year in

I was at the WEBE transmitter site recently and took the time to look over the transmitter we installed last year:

GatesAir FLX-40 transmitter, WEBE Bridgeport, CT

Overall, I would say that this transmitter has been very reliable. We had to install a UPS for the exciter and HD Radio exporter, but that is not a big deal. During the first power outage, the exciter went dark first. It took longer for the transmitter controller board to lose power, in the interim the controller turned the transmitter power all the way up. When the generator came online 10 seconds later, the transmitter returned to operation at 41.5 KW. This, in turn, caused one of the other field engineers to freak out and nearly lose his mind (stay away from the brown acid, FYI).

I installed the UPS a few days later.

WEBE TPO 35.3 KW with HD Radio carriers on

The transmitter power output is 35.3 KW, which is getting into the semi-serious range. The reflected power goes up when it gets warm out and goes down in colder weather. Over the winter, it was running about 50 watts. Even at 138 watts, that represents 0.004% reflected power. The TPO forward goes to the 6 bay, 1/2 wave spaced antenna side mounted, 470 feet (143 meters) AGL. The station covers pretty well.

WEBE Pump station, pump is running 2/3 speed and fans are running at about 1/2 speed

Overall, I would give the liquid cooling system an A grade. The transmitter still dumps a fair amount of heat into the room from the RF combiners and PA power supplies. Most of the heat, however, ends up outdoors. Previously, we had two Bard 5-ton AC units running almost full-time. Now, only one AC unit cycles on and off except for the hottest days of the year. The outside temperature when this picture was taken was 81 degrees F (27.2 C).

Next year, we will have to send a sample of the coolant to be analyzed.

I have had good experiences with the GatesAir FLX/FAX series transmitters. I would recommend this to a friend.

Status of AM revitalization

It has been about five years since the AM revitalization initiative was first proposed by the FCC and about five years since the first rules changes took place. Those rules changes included:

FM translators for AM stations
Allowing stations to use MDCL (Modulation Dependent Carrier Level)
Changing some of the antenna radiation efficiencies requirements
Changing some of the allowable interference towards other stations requirements
Loosening some rules regarding proofs, MOM, nighttime coverage over the city of license, etc

Things that were not addressed:

Receiver quality and technical advances
Ambient noise levels on Medium Frequency (among other) bands
HD Radio or any other digital modulation scheme

Things that were discussed then changed subsequently as a separate initiative:

The main studio rule, which was eliminated for all broadcasting stations

What has been the net effect of these changes? Has any of this revitalized AM radio? The net effect has been approximately more of the same. There have been many stations that have applied for and received licenses for FM translators. Those stations, in most cases that I am aware of, receive some benefit of extra revenue because of this. Stations with carrier power levels of 10-50 KW have taken advantage of MDCL technology to save some money on their electric bill. Nothing wrong with that.

For stations that use a directional antenna, proofs of performance and other DA matters with the FCC have become slightly easier. Medium Frequency (MF) directional antennas are very large, require a lot of land, are expensive to build, license, and maintain. I know of several stations which have downgraded from a class B station with a directional antenna to a class D station with a single tower and greatly reduced nighttime power. Those downgraded stations certainly benefit from an FM translator.

I have heard from more than one AM station owner who says after four years, they are going to “turn in their AM license and just keep the FM.” I am sure that they are not informed regarding translator rules. Perhaps, however, the FCC will allow this in the future; a sort of back-door commercial low-power FM station classification.

The AM band zenith occurred in November of 1991 when there were 4990 licensed AM stations in the United States. As of June 30, 2018, the total stands at 4633. That is a decline of 357 stations. There are currently 90 AM stations listed as silent. That represents a decline of approximately 9 percent or less than 1/2 of one percent per year.

The last number of AM stations actually transmitting HD Radio that I found was approximately 110, which differs from the iBiquity (and FCC) number of 240. The FCC database includes stations that are currently dark or stations that were transmitting HD Radio at one time but have since turned it off. Either way, it is a small percentage of licensed stations. As of this time, AM HD Radio appears to be a non-starter. In other parts of the world, Medium Frequency DRM seems to be doing well. The difference seems to be that the DRM operation is all digital and the digital carriers have a much higher power level than that of the hybrid AM HD Radio being used here.

Of those 4633 standard broadcast stations, approximately 260 belong to iHeart radio, Cumulus owns approximately 120 and Townsquare owns approximately 80. That accounts for 460 stations. The remaining 4000 or so stations currently on the air are owned by medium-sized corporations or individual owners. The reason for the distinction; I have noticed that large corporate owners tend to concentrate resources and effort on those licenses that will make the best return, e.g. FM stations. Of course, there are a few exceptions to that trend, often in major markets.

Of those 4000 or so remaining AM stations, most seem to be treading water. They are making enough money to stay on the air. There are a few AM stations that are doing remarkably well. Those are the ones with primarily local content. The vast majority of AM stations are running some type of syndicated talk. News/talk and sports radio are the two most common formats. Conservative news/talk seems to be the bread and butter. Liberal news talk has been tried, but none have succeeded.

Last May, the Supreme Court overturned the Professional and Amateur Sports Protection Act of 1992. That federal law prevented gambling on outcomes of professional and college sports games. With the overturn of that rule, individual states can now legalize sports betting. It will be interesting to see what states allow legalized sports gambling and whether that has any effect on the various sports radio formats. I can see where individuals and odds makers may want to get good inside information regarding team dynamics and so on. The sports network that can furnish such information may be in a good position to carve out a niche.

Music can and does sound good on AM when it is done correctly. There is a great misconception that AM fidelity is poor. That is not necessarily so. There are a good many AM receivers these days that have much better bandwidth than the previous generation receivers. I am noticing that car radios in particular sound much better. Yes, there are still problems with electrical noise and nighttime interference. There are still technological improvements that can be made for analog AM on the receiver side.

In summary; the revitalization efforts have benefited some AM stations in some areas. The truth is, that many AM stations have been let go for so long that there is no saving them. Other AM stations that are still viable are making a go of it. In nautical terms; there is six feet of water in the hold, the pumps are working and the ship is not sinking… for now.

Speaking of Radio…

I was talking to a friend from Russia about history, my job, and various other things that are going on in my life. I received this reply, which I thought was interesting on a number of levels:

I’m glad we are on the same page about the era of the ‘cold war’. We were interested in your life even more than you in ours. We had almost no sources of information except for ‘The morning star’ which is a newspaper of the Communist party of Great Britain. The Voice of America and the Liberty (or Freedom, I have no clue because for us it was ‘RADIO SVOBODA’) were extremely hard to tune on. All foreign broadcasts were jammed. So to listen to the station you should maximize the volume up to the limit which was dangerous. Soviet houses are not at all soundproof and your neighbors could easily rat on you. Since that time I’d been dreaming of a small radio with could receive a clear signal from abroad. Of course we have the Internet broadcasting now but they often use old recording instead of live air and the signal depends on your data carrier. You should be online, you should have an app and unlimited data on your contract, your phone should be charged all the time. Too many conditions. Unfortunately a lot of foreign sites are banned here and the trend is to make this number bigger and bigger.

I find that perspective interesting. We take for granted our ability to listen to information and listen to different points of view, even those we don’t agree with. There are still trouble spots in the world and some people are not as fortunate. It is very easy to block internet traffic and there are several countries that currently block access to some or all of the internet, for the safety of their citizens, no doubt. Ideas are dangerous.

VOA/RFE transmitter site, Biblis Germany. Photographer: Armin Kübelbeck, CC-BY-SA, Wikimedia Commons

In the last ten to fifteen years, many large government shortwave broadcasters have reduced or eliminated their programming favoring an internet distribution model. This is a mistake. It is very difficult to successfully jam terrestrial radio broadcasts. Shortwave Facilities are expensive to develop and maintain, there is no doubt about that. However, as the Chief Engineer from Radio Australia (ABC) once told me “HF will get through when nothing else will.” Ironically, ABC has eliminated its HF service on January 31, 2017.

It seems to me that a sort of “Shortwave Lite” version of broadcasting might be the answer. Use more efficient transmitters with lower power levels closer in to the target areas. Such transmitters could be coupled to rotatable log periodic antennas to target several listening areas with one system, thus greatly reducing the number of towers and land required. Solid-state transmitters with a power of 10-50 KW are much, much more efficient than their tube-type brethren.

DRM30 (Digital Radio Mondiale) has not gained widespread use in the MF and HF bands. Like its HD Radio counterpart, the lack of receivers seems to be one of the adoption issues. As of 2017, there are only four DRM30-capable receivers for sale not counting software plug-ins for various SDRs. That is a shame because my experience with DRM30 reception has been pretty good. I have used a WinRadio G303i with DRM plug-in, which set me back $40.00 for the license key (hint for those nice folks at the DRM consortium; licensing fees tend to quash widespread interest and adoption).

CFRX, Toronto coverage map, average HF propagation conditions

Finally, I have advocated before and still advocate for some type of domestic shortwave service. Right now, I am listening to CFRX Toronto on 6070 KHz. That station has a transmitter power output of 1 KW into a 117-degree tower (approximately 50 feet tall) using a modified Armstrong X1000B AM transmitter netting a 15-32 µV received signal strength some 300 miles away. That is a listenable signal, especially if there is no other source of information available. The average approximate coverage area for that station is 280,000 square miles (725,000 square kilometers). That is a fairly low overhead operation for a fairly large coverage area. Perhaps existing licensed shortwave broadcasters should be allowed to operate such facilities in domestic service.

The point is before we pull the plug on the last shortwave transmitter, we should carefully consider what we are giving up.