history – Engineering Radio

W2XMN Alpine, New Jersey

This historic site is where Edwin Armstrong continued developing FM radio starting in 1936 after his fallout with David Sarnoff of RCA. There is an active experimental station on 42.8 MHz, WA2XMN. It is usually on the air to commemorate Armstrong’s FM demonstration to the FCC, which happened on 17 June 1936.

Last Thursday, June 19th, I had a very enjoyable afternoon at SBE Chapter 15’s annual summer barbecue. Over the years, I have probably passed by hundreds of times, often thinking, someday I’d love to see what is there. I can say, I was not disappointed.

The site was constructed in 1936, after Edwin Armstrong was asked to remove his FM equipment from the Empire State Building by RCA. At that time, RCA was more interested in TV development and thought that FM had little place in broadcasting. Boy, were they wrong.

Armstrong had this 400 foot tower built and used this building as his test bed. Broadcasting on two frequencies; W2XMN on 42.8 (later 44.1) and W2XEA on 92.1 MHz (later KE2XCC on 93.1 MHz) with power of 50 KW.

W2XMN building, Edwin Armstrong’s laboratory

Today, the WA2XMN broadcasts are produced by a replica GE BT-1-B phastron transmitter built by Steve Hemphill, with a power output of 250 watts. Unfortunately, there is a large hill between that site and my house, so I cannot hear it very well from my radio room. However, during the broadcast, there were several reception reports from around the area, including out on the eastern end of Long Island.

WA2XMN transmitter on 48.2 MHz, Alpine, NJ

The story of FM and Edwin Armstrong is a mixed tale. He was a professor of Electrical Engineering at Columbia University in New York. A creative engineer, having several patents to his name including regenerative receiver, super hetrodyne receiver, wide band FM, and early FM radar, he had a close relationship with David Sarnoff, the president of RCA. Unfortunately, that relationship soured over patent infringement lawsuits and Armstrong eventually committed suicide in 1954.

After which, the site ownership went to Columbia University. It sat, mostly unused, until it was purchased by the current owner (K2 Communications) for use as a land mobile transmitter site. Thankfully, they knew what they had and preserved the historical features. They are currently working on turning the W2XMN building into a museum.

Columbia University has an extensive archive of information about Edwin Armstrong. More information can be found here: Alpine NJ, Alpine, NJ Part II, Closing of Station KE2XCC

There is also this excellent article in the Short Wave Listening Post: WA2XMN revives Armstrong’s Legacy with 90th Anniversary Broadcast

If you have the time, This Week In Radio Tech (TWiRT) has a Youtube Video: Armstrong FM at Alpine (it is about an hour long).

I always recommend, for those interested in the history of FM broadcasting; Empire of the Air by Tom Lewis.

And a final thought; there is nothing in this job that is worth your life. Suicide is a permanent solution to a temporary problem. Most engineers I know (myself included) are introverts. We tend to take responsibility for things which do not really belong to us. One of the things that I learned, over time, is to enforce boundaries. It can be difficult to do with the electronic connectivity today; the ability for people to interrupt your life via text, email or phone call. Sometimes those things are important, but too often, not. When this happens, use your words. Respectfully tell the other person that you will deal with it during business hours. If that doesn’t work, remember; there are many, many open positions for broadcast engineers these days.

The Alford Antenna

I have been doing a bit of work in this building recently.

5th Avenue Lobby, Empire State Building, New York, NY

Therefore, when I saw the opportunity to acquire a piece of NYC radio history, I took it. The SBE Ennes Workshops are designed to bring affordable education to the Broadcast Engineering community. One major problem in the Broadcast Engineering field is the aging workforce. Any resource that can spur interest by younger people is important. Named after Harold E. Ennes, the Ennes Educational Foundation Trust funds scholarships, workshops, seminars, and helps underwrite the costs of producing text books. Making a donation by bidding on an element of the Alford antenna was an easy decision.

The Alford antenna was manufactured and installed in 1965 on the 102 story observation deck of the Empire State Building. It was designed by Andrew Alford, an electrical engineer, who designed antennas for ILS and VOR aviation navigation systems. It is the first purpose build combined FM master antenna system in the world. Both the antenna and combiner system were novel ideas at the time.

The master antenna was becoming a necessity because the spire and tower on top of the Empire State building had become over crowded with FM and TV antennas. In the 1931, RCA/NBC leased the 85th floor of the ESB for their development laboratory.

Circa 1936, RCA television transmitter on 85th floor, from the Early Television Museum

Once both services became commercial, the FCC forced RCA/NBC to allow other FM and TV stations to locate on the building.

According to the IEEE paper written about it, the idea of a master antenna came about in 1959. It was not until the mid 1960’s that the first three stations agreed to the idea.

The requirements for the new antenna included:

1) System should accept the output of seventeen different FM station transmitters at a power level of 10 kW each.
2) The antenna should radiate an essentially omnidirectional signal in both horizontal and vertical polarizations in approximately equal amounts.
3) The antenna gain and multiplexer losses should be such that each station can achieve an ERP of approximately 5.5 kW in both polarizations (the maximum power presently authorized by the FCC for that height above ground and that location).
4) The antenna system should be well matched over the entire frequency band from at least 92 to 108 MHz and preferably from 88to 108 MHz.
5) The external portions of the antenna should be deiced.
6) System VSWR should be 1.1 or less at each station’s input over a 200 kHz band centered at each station’s carrier frequency.
7) Isolation between antenna and other antennas on building should be at least 40 dB.
8) Isolation between FM transmitters connected to the system should be at least 40 dB for adjacent FM carrier frequencies and at least 36 dB for non-adjacent FM carrier frequencies.
9) The frequency-phase characteristic of the system as measured at each station’s input should be linear within ±50 throughout a 200 kHz band centered at each station’s carrier frequency.
10) System should allow for any number of stations to participate at the beginning and should allow for additional stations to be added from time to time as required up to a maximum of seventeen in any arbitrary order of carrier frequencies.

IEEE TRANSACTIONS ON BROADCASTING, VOL. BC-13, NO. 3, JULY 1967, The Empire State Building Master FM Antenna.

That article is an interesting read.

This is one of 32 elements of that antenna. It was in position 10L, according to the name plate. Date of manufacture was 7-65. It is 81.28 x 139.7 x 13.9 cm (32 x 55 x 5.5 inches) and weighs about 45 KG (100 lbs). The RF input is 1 5/8 inch EIA flange, located in the middle of the mounting plate.

Of course, the covers had to come off so I could see what was inside. The antenna is cast from non-magnetic (AKA stainless) steel. The elements were installed with the covers down, as they are not water proof and have weep holes to allow condensation to drain out of the element.

Inside contains the resistance heating element. Interestingly, the return wire for the element is tied to ground and does not have an insulated path to neutral. Each return wire was burned open, meaning that at least this antenna element had no heaters. In the northeast, that will certainly lead to problems.

I wonder if that was one of the reasons to replace it with a new master antenna. Other reasons would be that newer antennas have better circular polarization, more even signal pattern giving better reception, better gain characteristics, better combining systems with more isolation and the ability to pass HD Radio side bands, etc.

No doubt, this antenna section will end up in my radio room, but I am still working on how I will display this interesting piece.

WSM Nashville, Tennessee

We recently went on vacation in Tennessee, which is a great state. Most of the time was spent hiking around various state parks, investigating interesting places, or eating at various restaurants. I highly recommend the state parks, there are many and they are all good. All of that being said, I could not resist the temptation to swing by WSM on the way back to the airport. I am happy I did.

Historical Marker, WSM Brentwood, Tennesee

The site is right off of I-65 and easy to get to. There is a public dog park that is behind it, which is a convenient place to park.

WSM Blaw-Knox tower, transmitter building

The Blaw-Knox tower is impressive. The site is well-maintained overall.

WSM tower base, transmitter building and Aux tower

The main tower is fed with open wire transmission line. The aux tower is off the right. It was nice to stop and walk around the site taking pictures. The Brentwood Police Department even stopped by and welcomed us to the neighborhood.

WSM open wire transmission line, looks like 450 ohms

It is always interesting to stop by some of these more famous stations. It would be nice if more sites were recognized as historical places, given the role that radio played in 20th-century US society. Both of my parents grew up during the Great Depression. According to their stories; life was tough, it was a struggle to feed the family and pay rent, but they did have a radio in the living room which was switched on every night after dinner.

A few pictures

Some things I have been working on lately:

Finishing up a transmitter site rehab. The BE FM20T is nearly 20 years old. The BE FM2C transmitters are new. There is also a rack of new fiber equipment and CODECs. This site has good utilization; there are three stations on one tower with a shared STL antenna and generator.

Energy Onix ECO-6 tube-type transmitter. One of Bernie’s better designs; a grounded grid tube with a solid-state driver section. This one needed some fans replaced and a new tube.

AM transmitter site. Looks like these vines have not been cut in a couple of years.

I wonder how much the guy tensions have changed…

Noticed this after some particularly strong thunderstorms

The reason why you do not use a POTS line phone during a thunderstorm.

I took a tour of the USS Slater, a museum ship in Albany, NY. The museum has painstakingly restored the ship to its WWII configuration. The main transmitter is the RCA TBL-8 seen in the left/center of this picture. This unit put out 200 to 400 watts CW or 150 watts AM phone. During the hostilities, it was turned off as allied ships observed radio silence unless they were sinking (and sometimes even then).

A little ChiFi tube type RIAA phone preamp. — A little ChiFi tube-type RIAA phone preamp.

I have been fooling around with this little 6AK5 preamp. I find it works very well and sounds better than the built-in phone preamp on my Kenwood VR-309. The FU-29 tube amp did not come with a phone preamp.

This is a short video clip of an audio processor at one of our transmitter sites. The fancy lights around the control knob are designed for the program director. They are saying “Buy me… Buy me…”