As is often the case when doing studio wiring, some type of work light is needed, especially when working inside studio furniture. Having a good work light makes it easier to see wire colors and usually means fewer mistakes, thus the installation work goes faster. I remember being questioned by the CFO of the last company I worked for when making purchases like this in the past:
CFO “Fifty-nine dollars for a work light? Did we really need that?”
Myself: “Yes.”
CFO:
Myself:
CFO: “Uh, care to expound on that at all?”
Myself: “No.”
The studio I was working in yesterday didn’t even have its overhead lights installed yet, so work lights were a must.
Normally, some type of halogen or incandescent light is used. The downside to these types of work lights is excess heat, especially inside studio furniture cabinets. I have often felt like the side of my face was getting sunburned when working in close quarters with one of these units.
Fortunately, we bought this light:
LED work lightLED work light
Say or think what you will about global warming, environmentalists and so on. The high-efficiency LED light works very well and kept me from boiling when punching down wires. As with most LED lights, it has a high blue content, which most people find a little harsh. I like this light temperature for detail wiring work. It has an internal battery plus a plug-in wall wart for recharging and using as a wired light.
Not that I have any loyalty to that particular brand, but the light worked very well. I am not sure how durable it is, it seems a little light duty. That being said, I’d recommend it.
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.
WISN night time allocation study
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.
WISN night time allocation ma
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.
WISN antenna array
From the front of the transmitter building
WISN transmitter site, 1941
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.
WISN RCA BT-5E transmitter, 1941
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.
RCA AM antenna monitor
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.
Update: What? Nothing Happened! Something I think any radio engineer can appreciate, the incoming magnetic field from the flare was not polarized for maximum effect. According to NOAA Space Weather Prediction Center, the incoming particles were parallel to the earth’s magnetic field, and thus blocked. In order for storms to have major effects, they need to be cross-polarized with the earth’s magnetic field. Learn something new every day.
On February 15 at 01:50 UTC, a massive flare erupted from the sun. Classified as an X2.2 storm, it is the largest since December 2006. The 2006 storm disrupted GPS, and some satellite signals and caused 950 mHz STLs to burp occasionally. With all of the cellphone systems synced to GPS, not to mention things like HD Radio exciters, it could be an interesting day. Or not. Already, some reports are trickling in from southern China of communications disruptions.
Feb 15 0150 UTC solar flare
According to NOAA Space Weather, there is a 45% chance of geomagnetic activity starting on Thursday, February 17th. It is noted that Geomagnetic storms reaching the G1 level and radio blackouts reaching the R1 level are to be expected. Mid to high-level latitudes may see extensive aurora borealis, which will be visible in spite of the full moon.
All of the programming elements, all of the engineering equipment and practices, all of the creative process, the music, the talk, the commercials, everything that goes out over the air should reach as many ears as possible. That is the business of radio. The quality of the sound and the listening experience is often lost in the process.
Unfortunately, a large segment of the population has been conditioned to accept the relatively low quality of .mp3 and other digital files delivered via computers and smartphones. There is some hope however; when exposed to good-sounding audio, most people respond favorably, or are in fact, amazed that music can sound that good.
There are few fundamentals as important as sounding good. Buying the latest Frank Foti creation and hitting preset #10 is all well and good, but what is it that you are really doing?
There was a time when the FCC required a full audio proof every year. That meant dragging the audio test equipment out and running a full sweep of tones through the entire transmission system, usually late at night. It was a great pain, however, it was also a good exercise in basic physics. Understanding pre-emphasis and de-emphasis curves, how an STL system can add distortion and overshoot, how clean (distortion-wise) the output of the console is, how clean the transmitter modulator is, how to correct for base frequency tilt and high-frequency ringing, all of those are basic tenants of broadcast engineering. Mostly today, those things are taken for granted or ignored.
Audio frequency vs. wavelength chart
Every ear is different and responds to sound slightly differently. The frequencies and SPLs given here are averages, some people have hearing that can go far above or below average, however, they are an anomaly.
Understanding audio is a good start. Audio is also known as sound pressure waves. A speaker system generates areas or waves of lower and high pressure in the atmosphere. The size of these waves depends on the frequency of vibration and the energy behind the vibrations. Like radio, audio travels in a wave outward from its source, decreasing in density as a function of the area covered. It is a logarithmic decay.
The human ear is optimized for hearing in the mid-range band around 3 KHz, slightly higher for women and lower for men. This is because the ear canal is a 1/4 wavelength resonant at those frequencies. Mid range is most associated with the human voice and the perceived loudness of program material.
Bass frequencies contain a lot of energy due to the longer wavelengths. This energy is often transmitted into structural members without adding too much to the listening experience due to a sharp roll-off starting around 100 Hz. Too much base energy in radio programming can sap loudness by reducing the midrange and high-frequency energy from the modulated product.
High frequencies offer directivity, as in left right stereo separation. Too much high frequency sounds shrill and can adversely affect female listeners, as they are more sensitive to high-end audio because of smaller ear canals and tympanic membranes.
Processing programming material is a highly subjective matter. I am a minimalist, I think that too much processing is self-defeating. I have listened to a few radio stations that have given me a headache after 10 minutes or so. Overly processed audio sounds splashy, contrived, and fake with unnatural sounds and separation. A good idea is to understand each station’s processing goals. A hip-hop or CHR station obviously is looking for something different than a classical music station.
For the non-engineer, there are three main effects of processing; equalization, compression (AKA gain reduction), and expansion. Then there are other things like phase rotation, pre-emphasis or de-emphasis, limiting, clipping, and harmonics.
EQ is a matter of taste, although it can be used to overcome some non-uniformity in STL paths. Compression is a way to bring up quiet passages and increase sound density or loudness. Multi-band compression is all the rage, it allows each of the four bands to react differently to program material, which can really make things sound differently than they were recorded. Miss-adjusting a multi-band compressor can make audio really sound bad. Compression is dictated not only by the amount of gain reduction but also by the ratio, attack, and release times. Limiting is relative to compression, but acts only on the highest peaks. A certain amount of limiting is good as it acts to keep programming levels constant. Clipping is a last resort method for keeping errant peaks from affecting modulation levels. Expansion is often used on microphones and is a poor substitute for a well built quiet studio. Expansion often adds swishing effects to microphones.
I may break down the effects of compression and EQ in a separate post. The effects of odd and even order audio harmonics could easily fill a book.
