Paul Thurst – Page 148 – Engineering Radio

It’s cold enough to…

Cause the STL receiver to unlock. A quick peak at the thermometer this morning showed -12° F outside. Meanwhile, out on the island, the WICC TFT STL receiver decided that it was just too cold to continue and gave up the ghost. Weak sister. This created quite a bit of hiss on the WICC signal until about 11 AM, when the program director finally called me to tell me of the situation.

Via remote control, we switched over to the backup analog ~~8 KHz~~ 15 KHz TELCO line, which sounds fine, given the talk radio program material.

Unfortunately, vehicle access to the transmitter site is now gone. I have the option of taking the Bridgeport harbor master boat over to the dock and walking .9 miles, or driving to the Long Beach parking lot and walking 1.3 miles in order to repair it. This will likely be tomorrow, as the weather is supposed to be better, 36°F and light snow. Well, it is what I get paid to do.

Regarding the analog 8 KHz TELCO line, that is an anomaly. These analog circuits where used to wire the country together, once delivering all of the network programming to affiliate stations before the widespread use of satellites. They require unloaded dry pairs and normally have an equalizer on the Z (far) end. Nowadays everything is digital, try and find a tech to repair one of these circuits when it goes down. Fortunately, this is a short distance circuit.

Medium Wave List

This is an excellent data base of LW and MW worldwide: www.mwlist.org

According to the website:

This is a radio station database of all Longwave (LW), Medium wave (MW) and Tropical bands stations worldwide. You can browse frequency and location lists, search for stations, and get technical information. If you register, you can use a online logbook, create bandscans, and provide update information to the database editors. This is a free, open and non-commercial hobby project which depends on the cooperation of many individuals.

For LW/MW DXer’s this is a good information source.

The Tandy TRS-80 Model 4D computer

File under: You can find the darnest things at the transmitter site. Near as I can tell, this computer dates from about 1985 or so, it looks remarkably like my Apple IIe of the same vintage. We used an earlier model TRS-80 in high school, that model had a cassette deck as the data storage device. These have 5 1/4 inch floppy disks. I used my Apple IIe as a gloried type writer, mostly for college papers. I did manage to write some basic programs, no doubt copied from somewhere else.

For the day though, saving something for later editing, even to a floppy drive, was an order of magnitude over the single spaced type written page.

There are actually two of these computers, serial numbers 7086 and 7128. I have no idea whether they work. I’d donate them to a museum if there were one that was interested. Otherwise, they may sit in the corner for another twenty years or so.

Center of Box, AMC-8

Satellite dishes have been a part of radio station technical equipment for years. I am surprised at the number of broadcast engineers that do not consider center of box when aiming dishes. As dishes get larger and focal points get smaller, center of box aiming is not a nice thing to do, it is a necessary thing to do. The latest generation of satellite receivers, (AKA XDS) have a somewhat less than lively RF front end, they require higher E/B than the previous generation Starguide receivers to stay locked.

For years, the majority of commercial radio networks were carried on AMC-8 or its predecessors living at 139° W. On the East Coast, particularly in the Northeast, that makes aiming points relatively low to the horizon, anywhere between 8-10° elevation.

3.2 meter comtech dish — 3.2 meter COMTECH satellite dish

This all means that precise aiming the satellite receive dish is critical for satisfactory performance. SES Americom owns AMC-8 and thus they have a web page about all of their satellites and important operating information. SES Center of box for AMC-8 is available in one-month blocks, which makes scheduling the aiming chore fairly easy.

I have always used a spectrum analyzer through a 3 dB splitter to look at the 950 MHz LNB output. This aiming setup allows the best combination of Azimuth/Elevation/polarization. Using the satellite receiver to confirm and maintain signal lock, peak the waveform that the receiver is locked to. It is pretty crowded up there, so there will be lots of signals on the spectrum analyzer trace.

It is a pain in the rear end to lug all that equipment out to the satellite dish, especially if it is on the roof. That is why it only need be done once; the right way the first time.

Any shortcuts will likely lead to those annoying chirps and dropouts or complete loss programming, particularly when the weather turns bad.