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.

WISN night time allocation study
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
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
WISN antenna array

From the front of the transmitter building

WISN transmitter site, 1941
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
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
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.

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19 thoughts on “Milwaukee’s oldest radio station”

  1. I remember reading about a 12 tower somewhere in TX. Rumor has it that aircraft used to line up on approach to this array at night. Thanks for the pic.

  2. re KFXR – Is that array of 6×6 in two parallel lines designed that way in order to make the pattern just ridiculously narrow and directional? (I’m obviously no transmitter engineer, just an interested layman. I’m pretty good technically from the microphone to the transmitter, but once we hit the transmitter I’m almost completely out of understanding.)

    Is it directional along the axes of the row of towers?

    Even better, can someone recommend a book or website explaining the interaction of multiple towers?
    I always worked in FM and TV that were definitely not directional.

  3. @Spine, the KFXR pattern can be looked at here.

    Basically, it is aligned along 312 degrees true, i.e. northwest/southeast. The pattern shows a dog leg to the southwest, which makes me think the array is located northeast of town. Each tower in the array is phased positive or negative in relationship to the reference tower, which looks to be tower #1. That is how the pattern is developed.

    Looks like it was a bear to proof, I hope the Dallas radio market was worth all that trouble.

  4. The entire WISN property was fenced in, although I can’t say if it was at the time it was built. The fence still stands, enclosing the apartment/condo complex now on the site.

    Fencing surrounds the land containing the current 9 towers.

  5. When I started at WISN in March of 1966 as a kid just out of high school and a freshman engineering student, the BT-5E had been cold for about 6 months. It used an 892R in the final PA with a couple of 891R’s in the Class B modulator. A very straight-forward rig that was extremely reliable I was told. Not pictured was the RCA BT-1DA which was the previous full-time transmitter relegated to standby use. The BT-5E was sold to a station in Hawaii I believe and the BT-1DA was scrapped. The building pictured remained as the AM studio until 1969. The towers were taken down in 1968. The building was razed for a housing development in 1971.

  6. I forgot to mention that they had a Construction Permit for 25 kW nights which would have necessitated 3 more towers to the west. This CP was renewed several times, and the idea was finally scrapped. It would have narrowed the main lobe at 0 degrees True North too much to be worth the expense. At the time, WDGY (Minneapolis) and WCAR (Detroit) were high-power co-channel stations requiring protection. WISN was in about the middle longitude line of these other stations. The antenna array was designed by A. Earl Cullum, Inwood Post Office, Dallas, Texas.

  7. Thanks Paul. I’ll bet the math on that is interesting.

    Anyone with any ideas for the second question? (Even better, can someone recommend a book or website explaining the interaction of multiple towers?)

  8. Jack Layton’s book on AM band directional antennas is designed for the layman broadcast technician and is pretty simple. A more detailed theory and mathematical treatment can be found in The Radio Engineer’s Handbook, by F.E. Terman (1940’s), and the NAB Engineering Handbook published in the 1960’s and ’70’s. Above 4 towers, the computer becomes helpful doing the “busy work” of the design mathematics and analysis.
    In the United States, I believe 12 towers is the maximum number that has ever been considered or constructed. Beyond that, the law of diminishing returns comes into the equation.

  9. We’re trying to reconstruct the WISN with WJJD interference situation, and “what if” situation on achievable power levels if WISN had never moved to 1130 over on Radio Info. Do you have the actual parameters, tower layout, tower field ratios, tower phases, etc, that you could post here? I assume that all towers are .26 wavelength/94 degrees, and the theoretical RMS is 192 mV/m per kW at one mile. We could probably figure it out approximately from the nulls shown above. We like reverse engineering things, but we don’t have enough transform data to do it exactly. It looks like the NS tower spacing is around 90 degrees and the EW tower spacing is more than 180 degrees, maybe 200-225?

  10. This is all the information that I have. Your assumptions about tower heights and theoretical non-DA RMS is correct. However, I would say your estimates of spacing are off, just by looking at the pictures. If the towers are .26 wavelength at 1150 KHz, they would be about 205 feet tall give or take a few feet. From the picture above, which is the only thing I have to go by, it look to me that the N-S spacing is much less than 90 degrees, perhaps something like 45, the E-W tower spacing is greater than 180 degrees, but it is difficult to say how much.

  11. Since we’re looking at an angle somewhere close to 30 degrees, and the towers are 93.6 degrees, I would say 46.8/cos(30)=54.04 degrees. You are correct that they are much closer than 90 degrees. They get a lot of pattern gain with that spacing if the two tower component phase produces a two tower cardioid/kidney shaped pattern. The near half wave produces a two tower pattern loss.

    The phase relationship is shown by the Lissajous figures on the oscilloscope. For those who are too young to have used this arcane method, the Wikipedia article is pretty good.

  12. I’m in the process of reverse engineering the pattern. From the interference calculations, I plotted out about half the pattern. I looked at null symmetry and have so far concluded that the array is oriented at about 20 degrees true. It looks like two nulls coincide at about 245 degrees, so there are five nulls. There are two from the short dimension component of the parallelogram/rectangle and four from the longer dimension component which are symmetrical around the 110/290 degree axis, but asymmetric around the 20/200 degree axis.

  13. Well, I’m up to the point where I can feed the data into some software to check out whtether this is close or not, but it’s on a computer I rarely use lately. Here’s the Heights, Azimuths, Spacings, Field Ratios, and Phases I calculated so far.

    1 93.6, 0, 0, 1.0, 0
    2 93.6, 200, 54, 0.9, 142
    3 93.6, 290, 223, 0.9, 22
    4 93.6, 276.4, 229,4, 0.81 164

    It will be interesting to see if this turns out anywhere close to the calculated values. We have the day and night RMS also, which determines the pattern size, 192 mV/m at one mile. This is close to the nondirectional efficiency of a 93.6 degree tower with losses taken into account. The gain and loss of the two parallelogram components either cancel out or are compensated by an SLR if the pattern is too efficient to meet the requirements. If that were the case, the power would be less than 5000 under today’s rules.

  14. That is interesting, I wonder if any readers are former employees of WISN and could chime in on this. Seems about right to me and is close to what the loop current picture shows.

  15. According to the Wisconsin Radio History Call Letter page, WISN was at 5001 S. 60th St. in Greenfield.

  16. FWIW, Farnsworth Peak, just outside of Salt Lake City, Utah still has two engineers on site 24/7 to manage the 20+ stations in the facility.

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