AM – Page 25 – Engineering Radio

AM HD update and other ideas

Looks like the AM HD Radio™ juggernaut continues… To sink under its own technical faults that is. According to the list the number of AM stations running IBOC in the US is now down to 233 stations from a high water mark of 290 or so. That represents a total of just 4.8% (233 IBOC/4782 Total stations) of all US AM radio stations. On a related note, Bob Savage of WYSL 1040, Rochester, NY has a good idea:

I’ve always said – if you want to see surprising new life in the AM band, s**t-can the stupid irrelevant NRSC pre-emphasis filter and allow stations to run to 15 kHz during daylight hours and 10 kHz nighttime. Mandate C-QUAM in all receiver and receiver devices.

It will sound better than HD, be more robust, and cause far fewer problems. Plus it wouldn’t obsolete a single radio out there, while making a whole bunch of them sound a whole bunch better.

It is so simple in concept, so easy to implement, with almost no expense to AM stations. Again, Mr. Savage:

Most software-based processors have com ports which can be addressed by a remote control system like Sine Systems, so when the power gets reduced at evening pattern change, the bandpass can be changed at the same time…..vice-versa at sunup. No biggie.

For older setups a simple outboard relay and rolloff network could accomplish the same thing. It’s a little more complex but again, not a big deal.

Wow. Facepalm.

Wish somebody had thought of that a few years ago, it might have saved several million dollars and we’d have a different AM band today.

There are a few shoehorned AM stations around here that might be adversely affected by 15 KHz daytime bandwidth, but those are few and far between. By and large, most stations are spaced correctly where this could really work and work well. It certainly would not generate the chaos that AM HD Radio™ has.

Milwaukee’s oldest radio station

WISN 1130 AM has been on the air since 1922, although not always with those call letters. In an interesting twist, the license was granted to the local newspaper, the Wisconsin News, and the Milwaukee School of Engineering. Initially, both entities were programming the station, however, by about 1925, the newspaper was responsible for programming and the engineering school was responsible for technical operations.

In 1941, the station increased power from 1,000 watts to 5,000 watts and added nighttime service. This is a series of pictures from that time period.

Back in 1941, nighttime interference was taken seriously. The nighttime allocation study (on 1150 KHz, WISN’s former frequency) includes co-channel stations in the US, Canada, Cuba, and Mexico.

The array consisted of four Blaw-Knox self-supporting towers in a rectangle. Notice the lack of fencing, warning signs, and the like around the towers.

From the front of the transmitter building

The site looks well designed, no doubt manned during operation, which at the time would likely be 6 am to midnight except under special circumstances. Most of these old transmitter sites had full kitchens, bathrooms, and occasionally a bunk room. The transmitter operators where required to have 1st telephone licenses from the FCC. There is only one manned transmitter site in the US that I know about; Mount Mansfield, VT. There, WCAX, WPTZ, WETK, and VPR have their transmitters.

The WISN RCA BT5E transmitter looks huge for that power level. Back in the day when AM was king, these units were designed to stay on the air, no matter what. I don’t know too much about this model transmitter, but if it is like other RCA/GE models from the same era, it has redundant everything.

Old school antenna monitor. I have never seen one of these in operation, however, as I understand it, the scope was used to compare the phase relationship of each tower against the reference tower.

These pictures are of the WISN 1150 array was it was in 1941. Since then, the station has changed frequencies to 1130 KHz and increased power to 50,000 watts daytime/10,000 watts night time. The daytime array consists of six towers and the night time array has nine towers, all of which are 90 degrees.

Special thanks to John A. for sending these pictures along.

The mechanical tower light flasher

This is a Hughey Phillips mechanical tower light flasher that has been in service since 1960. Basically, it is a motor connected to a cam that rocks a mercury relay back and forth. These were standard technology for tower lights from the 1930s through about 1970 or a little later. They were very reliable, we still have some with a “pancake motor” in use on some of our towers. They were very robust and immune to lightning damage, RF interference, and other problems. The only maintenance that I can think of is lubricating the motor bearings. Eventually, however, they do wear out. Cold weather seems to take its toll, often causing the motor to stop.

Hughey and Phillips mechanical tower light flasher

This particular unit is mounted inside the tuning house for the far tower (north tower) at the WGHQ antenna array. It has finally reached the end of it’s existence; the motor bearings are shot and it has gotten stuck in both the on and off position this year causing the FAA to be notified of the malfunction.

Today, I am replacing it with a solid-state flasher (SSAC B-KON FS155-30RF). Solid-state flasher units have been known to malfunction in high RF fields, such as AM towers. To cure that, the manufacturer has built-in 0.01 uf bypass capacitors, hence the “RF” suffix. Older units did not have built-in bypass caps, so external 0.1 uf bypass capacitors were normally installed on units mounted to AM towers. While I was working on this, I turned the transmitter down to 500 watts, no need to get any RF burns.

Naturally, this has to happen after there is two feet of snow on the ground. Also, it should be noted that this is the furthest tower away from the transmitter building. Now where did I put those snow shoes? Never mind, it has been very cold and the ground is frozen solid, I’ll take the truck… This is good because I will have all the tools, drills, nuts, and bolts without having to walk back and forth several times in the snow.

Hughey Phillips mechanical beacon flasher

I removed the motor and mercury-filled relay. I’ll have to figure out how to dispose of the relay. I then drilled a mounting hole through the base of the old flasher housing and bolted the solid-state relay to it. This is required because the solid-state relay needs a pretty good heat sink.

Turn everything back on and: Ta-da! All works normally, the tower beacon is flashing away up there. Time to leave.

Pull forward about 2 feet to turn around and CRUNCH! The truck goes through the ice of a hidden stream. Any attempt to move only makes it worse:

Put in a phone call to the one guy I know that can get me out. About an hour later he shows up with chains, a shovel, and a come-a-long. We attach the come-a-long to the fence support post and pull the truck out backward 1/2 inch at a time. It took us about an hour and a half to get it all the way out so I could drive it back across the field. I’d have taken some pictures, but my guy; was a little grumpy.

I won’t do that again.

Still, I did the job I came to do, so it was a good day after all.

FCC seeks comments on Traver’s Information Stations (TIS)

Another one of those things that might work could possibly provide some service to travelers, but often falls short. Very similar to EAS, the government officials nominally in charge of the system have no idea of broadcasting. The Rhode Island TIS on I-95 had an endless loop proclaiming “This is the Rhode Island Department of Transportation Travelers Information System.” While that was welcome information, in a snowstorm, something about road conditions or perhaps the weather forecast might have been more appreciated. According to the FCC website, that was WPTJ441 on 1630 KHz with a power of 10 watts. The transmitter is located at the I-95 rest area on the Rhode Island/Connecticut state border.

The FCC is seeking comments on the current TIS in NPRM 10-203:

We solicit comment on whether to modify the existing rules governing the licensing and operation of Travelers’ Information Stations (TIS) to expand the scope of permitted operations. Since the inception of TIS in 1977, the Commission has authorized TIS operations to permit Public Safety Pool eligible entities to transmit noncommercial travel-related information to motorists on a localized basis. However, certain parties and licensees have sought to expand the scope of TIS operations in order to transmit more general alerts and public safety-related information to the public, including non-motorists. By initiating this proceeding, we grant petitions for rulemaking filed by Highway Information Systems, Inc. (HIS) and the American Associations of State Highway and Transportation Officials (AASHTO) requesting the commencement of a proceeding to amend the TIS rules. We deny the petition for declaratory ruling regarding TIS filed by the American Association of Information Radio Operators (AAIRO), but incorporate the issues raised in AAIRO’s petition into this rulemaking proceeding

The TIS as specified in the 1977 RO docket 20509 FCC 77-414 is outdated for the most part. The current rules, 47 CFR 90.242 give pretty specific requirements including things TIS stations are not allowed to retransmit, like NOAA weather forecasts. In one section of the NPRM, it is noted with the currently specified facilities, the average vehicle traveling the speed limit will transit the TIS coverage area in 90 to 120 seconds. For the above station, I found it was listenable for about 5 minutes, from the time I saw the sign next to the transmitter until it faded out, which works out to be about five and a half miles.

One alternate possibility is something like a carrier current station or a leaky coax setup buried in the median. Something like that might have more reliable coverage along the highway without blanketing the general area with a broadcast signal.

Again, in Rhode Island, drivers have the option of calling 511 on their cellphone, provided it is a hands-free cellphone. My only comment about that is when there is a major traffic jam and everyone is dialing 511 to get information, the cellular network will get congested quickly. Having a broadcast outlet for people to listen to on their car radios would be a more effective way to transmit information to the masses. As to what information a driver might want; here are a few suggestions:

Up-to-date traffic information including alternate routing instructions in case of a major tie-up.
Up-to-date weather information including roadway surface conditions and possible lodging locations
Up-to-date construction project information including alternate routing instructions for both car and truck traffic
When there are no traveling issues, other general information about rest stops, hospitals, tourist attractions, etc.

The most important thing is the information is up to date and relevant to a traveler.