AM – Page 22 – Engineering Radio

Troubles at the Tower

Troubles at the AM tower; I don’t know why, it won’t switch power.
Over the phone I can tell, the program director’s day is not going very well.
Press the “day” button but there is no kerchunk, the directional coupler shows the load is junk.
Out into the big field, I go to find the problem quickly and fix it just so.
The wind is cold, the snow is deep, I think of the contract terms I must keep.
Reaching the tuning house, take out the keys, lock, do not be frozen, please.
Once inside, there I find, no big surprise, the mice have been a working this pre-sunrise.
A nest they have build in a most inconvenient place, in the back of the phasor wiring chase.
Oh, the wires they have chewed, the circuit’s destroyed, all for the lack of mousetraps deployed.
As I reach in to clean out the mess, the smell of mouse makes me gag, I confess.
The fuses are blown, the contactor is jammed, perhaps, if I am lucky, I can move it by hand.
A large screwdriver strategically employed, I pry up slowly, further damage to avoid.
The bar thunks up, the contacts engage, the transmitter is ready to apply amperage.
Call on the cell phone, tell them it’s fixed, stand back and watch the base current meter, transfixed.
Then; Up it goes! Wonderful radio frequency current flows!
I clean up, lock the door, lock the gate, carrying bad news the owner will hate.
The damage is grave, the repair bill is steep, if a good relationship with the FCC you desire to keep.
Business is off, the accounts are low, is this really necessary, he wants to know.
The terms of the license are your obligation to keep, getting caught out of tolerance will not be cheap.
Looking forlorn, the owner says in disgust, it is only the AM, but fix it if you must.
Happy as a lark, with a song in my heart, I dig though the manual and order the part.
Time to go home, eat breakfast, brush teeth, take a shower. I have another client to see before the noon hour.

Dedicated to all those who have been there, done that and the breed of RF men and broadcast engineers who are slowly fading away.

WNAW North Adams

Originally signed on as WMNB in 1947, it is a Class C AM station on 1230 KHz, one of thousands in the country. Initially, it had a power of 250 watts, upgrading at various times to its current power of 1,000 watts.

WNAW-WUPE-FM, North Adams, Ma circa 2012

What is different about this station is the studio building. It is located in its original place on Curran Highway on the south side of North Adams. The studio is a late Art Deco design, complete with a small glass atrium in the lobby. Like many older radio stations, this installation was built on a raised floor. The walls and doors are all well constructed for maximum sound attenuation. The doors are large, heavy, and solid wood.

WNAW news room, formerly the performance studio — WNAW newsroom, formerly the performance studio

Inside, the original studios are laid out with a control room, a broadcast studio and a live performance room. At one time, the live performance room had a grand piano. Several times per week, live music shows were broadcast on the station. There was a large newsroom, and a big corner office for the General Manager and sales managers.

WNAW studio, looking into the control room. Back in the day, the announcer, whose only concern was announcing, worked in a separate studio from the engineer on duty, who worked console in the control room. The audio level limiting consisted of turning down the level on the console if the announcer started speaking loudly. They often communicated with each other with hand signs through the windows.

At the time that WMNB was signed on, the Adams/North Adams Massachusetts area was in the heart of the northeast manufacturing belt. Sprauge had a capacitor plant in Adams, GE was making plastics in Pittsfield, There were many textile mills still in operation and so on. The population was predominantly working middle class.

Obviously, the console has been changed since those days. The current console is a Audio Arts R-60. This serves as the control room for WNAW and WUPE-FM. The programming for WUPE-FM comes from Pittsfield on a T-1 line. From here, it is relayed to the transmitter site on a 950 MHz STL. WNAW transmitter is located about 2/10 of a mile south of the studio building on Curran Highway. It consists of a skirted self supporting tower with a Gates 1 solid state transmitter.

Equipment racks containing the T-1 equipment, modulation monitors and STLs. Note the very old Moseley TRC-15 remote controls. We have been unwiring these at the transmitter sites and disconnecting the TELCO lines. The transmitter sites now have Sine Systems dial up remote controls.

In 1961, WMNB-FM (now WUPE-FM) signed on the air from a tower north east of downtown, off of Mohawk Trail (MA route 2). It broadcast on 100.1 MHz with an ERP of 1,000 watts using a Gates FM1B transmitter.

WNAW continues on today as a community based radio station and is well liked and supported.

The 90th anniversary of…

Many of the US’s earliest commercial radio stations are celebrating their 90th anniversary of broadcasting this year. I’ve seen announcements for WOR, WGY, and a few others.

It is fun to go back and look at the old pictures of those stations during the golden age of AM radio. If nothing else, it reminds us of what used to be and will likely never be seen again. Stations like WGY employed hundreds of people in their hay day; actors, musicians, announcers, news people, salespeople, support staff, engineers, etc. These days, WGY likely employs less than ten, certainly not more than twenty directly.

There are a few stations bucking that trend, but very few.

So here is to what once was and happy birthday to the hollowed-out shells of their former selves.

Update: WINE WRKI transmitter site move

I have been spending my days in Brookfield, Connecticut, dragging transmitters around and reconnecting them in various ways. The WRKI-FM WINE-AM transmitter site is finally moving into the “new” transmitter building at the base of the tower. Today, we moved WINE.

WINE was first signed on in 1963 on 940 KHz from a 170-degree non-directional tower on top of a pretty high hill. That same tower serves as the antenna support for WRKI, which signed on in 1957. The station runs 680 watts daytime, however since it is non-directional, it has some pretty serious power reductions at night. The post-sunset power drops in two steps, 450 watts for the first hour, then 189 watts for the second hour, followed by 4 watts nighttime.

The 4-watt nighttime signal goes about 2-4 miles before it becomes unlistenable. The Post Sun Set Authority (PSSA) allows the station to stay on the air with at least some coverage up to about 6:46 pm in the winter time and 10 pm in the summer, which is better than nothing.

The problem is, the Harris MW-1A transmitter goes down to 250 watts and no lower. In order to make the nighttime power, the station switches to a dissipation network to burn off 246 watts of RF, at 50% percent AC-RF efficiency, which just ends up being a waste of power. Further, the station engineers have been ignoring the PSSA because there are too many steps and it was easier to just switch to night power at sunset.

What we decided to do instead, was install a small low power night time transmitter, a Radio Systems TR-6000. The MW1A can then be set to use the low power level for the first step of the PSSA, then switch the dissipation network in for the second step of the PSSA, and finally switch in the night transmitter at the proper time.

Harris MW1A AM transmitter, WINE 940 KHz, Brookfield, Ct

This is the Harris transmitter, new Circa 1981, which was cleaned up and moved into the new transmitter building.

WINE Parallel dissipation network and dummy load

The dissipation network. This will have to be reconfigured for the proper power levels, once the night transmitter is installed. The dissipation network is on the right, a dummy load is on the left. The two large RF contactors switch the dissipation network in and out, or select which transmitter is feeding the antenna/dummy load. This is the really, really old school way of doing it. Most transmitters manufactured after 1990 or so can run at any power level, making a dissipation network unnecessary.

Before re-installing the dissipation network/dummy load, we lined the enclosure with copper mesh. I don’t want that thing interfering with any of the other equipment nearby, which would be the STL receivers, satellite receivers, or Town of Brookfield police dispatch radios.

Schematically, it looks like this:

WINE 940 KHz Brookfield, CT night time dissipation network

This is the picture behind the transmitters, which shows the coaxial cable feed through ports and the dissipation network on the wall.

WINE WRKI transmitter room, behind the transmitters

It is a work in progress, so forgive the mess.