General – Page 55 – Engineering Radio

Upgrading National Weather Service Radio transmitter

If you have ever wondered about those ubiquitous NOAA all hazards radio (formerly National Weather Service radio) stations, wonder no more. These stations transmit on one of five frequencies in the 162 MHz band with power ranges between 250 and 1,000 watts. There are over 1,000 transmitters scattered throughout the country including outlying territories like American Samoa, Guam, Northern Marianas, Virgin Islands, and Puerto Rico.

The original 1958 plan was for these stations to transmit Aviation and Marine weather forecasts. The system was expanded for use by the general public in the early sixties. Since that time, it has been slowly expanding, with the most recent survey concluding that NOAA weather radio station can be received by 95% of the US population.

One of those stations in my neck of the woods is due for a transmitter upgrade. WXL-37 uses two Scientific Radio Systems SR-416P transmitters, as a main and a standby. The programming audio comes from the NWS office in Albany, New York, via TELCO line. The old transmitters are tube type made by in 1976. They are reliable transmitters, however, after 34 years of continuous use, they are getting a little tired. They are also big and bulky and since Scientific Radio Systems went out of business, not been supported.

This year, NOAA is replacing these transmitters with a Nautel NG1000. I have worked with Nautel’s military-grade transmitters before and found them to be extremely rugged. Those transmitters are what the original AMPFET design was based on. Nautel is not the only vendor that NOAA is using however, others include Armstrong Transmitters and Crown Broadcast.

Scientific Radio System SR416P transmitters — NOAA Scientific Radio Systems SR416P VHF transmitters

The Nautel NG1000 is a little thing, taking up about half an equipment rack with an outboard cavity filter and dummy load. There are two drawers, a controller an antenna switch, and a remote control. Each drawer is its own 1 KW transmitter. The GUI is on a laptop, which is what I prefer. If there must be some sort of computer-driven GUI, then make it removable, so that when lightning strikes the 1,000-foot steel lightning rod 25 feet away, it doesn’t get blown up. Each transmitter is connected to a 30 AMP 240 Volt breaker via a 4-prong twist lock plug.

Nautel NG1000 transmitter — Nautel NG1000 NOAA transmitter

The antenna for this station is near the middle of this 1,000-foot tower, thus the station gets excellent coverage with a TPO of 1,000 watts.

American Tower, Highland, NY — American Tower site, Highland, NY

On a related side note, the computer synthesized voices normally heard on NOAA stations took several years to evolve. Remember when this began back in the mid 1990’s with “Paul.” Several years later, “Craig” and “Donna” were introduced. Finally, “Tom,” is able to change voice inflections for emphasis. When I was in the Coast Guard, we did high seas synopsis and forecast on HF without aid of computers. At times, especially during typhoon season, it got a little busy in the weather broadcast position. There are advantages and disadvantages to both methods. Personally, I’d rather hear a human voice, especially in a crisis.

Downgrading AM stations

One of the AM stations around here that I am familiar with is considering a downgrade, which is to say reduce power and get rid of a directional antenna system in favor of a non-DA antenna. In this particular case, it makes sense, as the station can co-locate with another AM that is closer to the COL by a good distance. The coverage from the new site at reduced power looks to be a good fit. If this can be arraigned, the AM station in question would lose a multi-tower AM antenna system that is 50 years old and all the attendant headaches, expenses, and labor that goes with it.

five tower directional AM tower array in a tidal swamp

Many AM stations that are DA-2 or even DA should consider downgrading to a lower power level and getting rid of their DA system. Directional antenna systems on AM stations are maintenance nightmares. Unfortunately, in the ’50s, 60s, and 70s, it was often thought that adding power, and extra towers to an AM station would give them great swaths of extra coverage. Sometimes it worked out, sometimes it did not. Often what happened was some area was added, but in areas that were nulls toward protected stations, signal strengths went down. What the station ended up with was more towers, more maintenance, monitor points, a sample system, and more expense.

Taking an AM station in the other direction might actually make more sense. Go back to one tower non-directional 1 KW or whatever power can be used in the daytime. Time was when the FCC would only allow certain power levels; .5, 1, 5, 10, and 50 KW. Those were what a new station had to work with. No longer is that the case, any power level can be used so long as it meets interference contours and the city of license contour coverage requirements.

Presunrise authority is normally 500 watts and is available at 6 am, post-sunset authority varies but often a PSA extends the on-air time to 9 pm in the wintertime. For a local radio station, which is what all but the class A AM stations are destined to become, this will be adequate. For a losing station, it may be that, or turn in the license and sell the land to a developer.

Diplexing on another AM station’s tower closer to town is also a good way to get out of maintaining an expensive antenna array with diminishing income.

Something to think about.

Fireworks sychronized to music played over the radio!

In previous years, I have had the very pleasurable experience of setting up a fireworks show remote with music synchronized to our FM radio station. Ordinarily, I don’t go near a remote broadcast, however, this is one of the more intricate broadcasts requiring coordination between the studio, the remote site, and the fireworks barge anchored 300 yards offshore, out in the Hudson River. The fireworks company, Garden State Fireworks, are consummate professionals and produce a very well-choreographed show.

Giving them the synchronizing track on-site is not very hard, however, I was surprised to hear that not every radio station does that. In fact, one of our, ah, ehm, Clear Channel competitors from The big Metropolitan Center Nearby could not be bothered to do it for the 4th of July fireworks this summer and last summer too.

The synchronizing track is on the left channel of a CD that Garden State Fireworks created, it is 1200 baud FSK data, 8,N,1, so it is pretty robust.

I thought I would post on how I do it and why. First of all, for the how part, there are two options:

Play the music CD at the remote site and relay broadcast quality music back to the studio without any time delay. Hard to do even with an ISDN line.
Play the music CD at the studio and relay telephone quality audio for the firing track to the remote site from the studio. Have the remote site play the air signal over the local PA system.

Option number 2 is technically far easier than option number 1, although it takes a fair bit of coordination. Also, the sound reinforcement guy didn’t like the air signal idea because of the quality of the audio. That is a little nit-picky, especially given the fact that much of the music at the fireworks show will be drowned out by the fireworks explosions. In the end, he saw it my way.

Here is a list of equipment needed:

Telco auto answer coupler, such as the Indy Audio
Telco Hybrid, such as the Telos
If the announcer is at the fireworks site, a POTS CODEC such as a Comrex Matrix or blue box
Wireless microphone
Telephone set and cord with RJ-11 connector
Miscellaneous mic cables, power cords, etc
At the remote site, two pots lines from the local phone company, long distance service as required.

Here is the block diagram:

Note, this assumes no delay in the telco network, which under ordinary circumstances using the wired, not cellular network, there should not be any. The touchiest part of the whole thing is getting the stage coordinated with the studio during the transition to the remote broadcast. Once that is done, everything else just falls into place.

The firing computer is located onshore next to our broadcast booth. They send the signal out to the barge on a wireless LAN link.

That is the how part. Here is the why (the soundtrack is a little low):

That is from three years ago, but you get the idea.

Even though I don’t work for these people anymore, I asked if they needed help with the broadcast this year. “Nope, we got it, thanks.” I will be paying close attention.

How do you listen to streaming audio on an Android smart phone?

Update:There is a better way: www.engineeringradio.us/blog/2011/03/tunein-radio/

Ahh, since I posted about my android, a few readers have emailed me and would like to know. If you have tried to stream audio using a smartphone web browser, you have found out that it simply doesn’t work. The web browser is unable to decode the radio station stream because most of them are in AAC, AAC+, HeAACv1 or some other codec. At this point, most people give up on the idea and move on. I, on the other hand, determined that it should be doable.

First, I attempted to down load a few apps, but they either crashed or didn’t do what I wanted or weren’t in the right language, or something.

Clear Channel has something called iHeartRadio, which is a clearing house for mobile users that want to listen to Clear Channel radio streams on their iPhones. I don’t know, once you have heard one Kiss-FM station, you’ve heard them all as far as I am concerned. Most other Clear Channel programming is boring and uninspired.

What I finally ended up doing was going to Moodio and reading up on a few things. Here is a good step by step way to use Moodio to listen to radio station web streams on any mobile device.

Be aware that not all data plans are the same. ATT, Sprint, and others now cap data transfer and charge extra if a subscriber goes over. Know your plan.
On a regular computer, go to Moodio (http://www.yourmuze.fm/)
Set up a user account
Select from there list, the stations you want to listen to. They have many US stations as well as many from Europe. If the station you are looking for is not there, you can request that it be added.
Select the default data rate. Since I have unlimited data, I chose the highest rate for the best sounding audio. Others may want lower data rates so as not to exceed data caps.
Point your mobile device web browser to www.m.yourmuze.fm
Log into your account
The stations on your listen list will be displayed.

That is a lot of steps to take. Somebody has to be very into radio or a radio station to do something like that. A forward thinking radio station or group will be writing or paying somebody to write mobile streaming apps for their stream(s). A forward thinking radio station or group would then feature links to these apps prominently on their web pages. Very prominently if they are in a PPM market. Ahem, very prominently if they are in a PPM market.

That is what a forward thinking radio station would be doing…