1970s Radio Studio Project

1970s radio studio

The 1970s were a great time for FM radio. As the dominant form of music entertainment of the time, working in FM was a great gig. This page brings it all back with a museum-quality studio straight from the '70s. This project evolved over time. But first some background.

Back in the day, I worked in radio in Northern California at an AM/FM station as Chief Engineer. It was a very good opportunity for me, since the owners at the time wanted the AM facility rebuilt and a new FM station put on the air. Even more important, they were willing to spend the money to do it right. It was a great experience. We had a very nice facility that served the community for many years.

Fast-forward four decades. In a chance visit to eBay one day I saw a Gates Executive Audio Console available for sale. We had one of those consoles at the station in the 70s. It came to pass that I purchased the console and rebuilt it. Then I went looking for other elements of the studio that I built back in the 70s. And that let me to a rather complete duplication of the FM studio I fondly remember from 40 years ago. And it all works!

the 70s radio studio

The center piece of the studio is a Gates Executive Audio Console. The studio in laid out in the usual U-shape, with a short return section at the rear. The return can function as an interview position.


overall view of the studio

The studio occupies space in a working office. As such, space is somewhat limited and desk elements need to share functions. Very little attention has been paid to acoustics, since live recording is not currently done. Practical options exist for improving the acoustics, such as area carpets on the floor, movable baffles, and acoustic treatments of various types.


input source equipment

Input sources, in addition to a Shure SM7B microphone and SM58 microphone, include three Harris Criterion 90 cart machines. One is a record/play and the other two are play-only. There are two turntables, both Harris CB1201, with Shure M232 tone arms and Shure M4407 cartridges. Two reel-to-reel tape decks are included, an Ampex AG-440 pro machine and an Ampex 1455 consumer product.


close-up of turntables

The turntables are in excellent condition. The Shure tone arms and cartridges are new-old-stock (NOS). A new felt pad is used on each platter to facilitate slip-cueing.


console installed at Studio Two

All input sources are grouped on the right side of the console, which is helpful for right-handed operators. (Regrettably, no so much for left-handed operators...)


audio processing gear

A compact rack houses all of the audio processing gear, which includes a Harris MSP100 tri-band audio processor, CBS Audimax 4400 gain controller, and CBS Volumax 4100 limiter. A TFT 760 Emergency Broadcast System (EBS) generator/decoder is also present. The top unit, a TFT 763 modulation monitor, provides confidence readings for the operator. A 40 W vacuum tube amplifier (on the left) is used to drive the two Electro-Voice Sentry 100A monitor speakers.


monitoring and terminal gear

Twin racks are included for monitoring and terminal functions. On the right side the the photo, TT-type, RG-45-type, and XLR patch pays are provided. A Gentner SPH-3 phone patch can be seen below the patch bay. The top card frame houses program distribution amplifiers and the headphone amplifier. The bottom card frame houses input conditioning boards, a tone generator, and "cue/dim" controller. The "cue/dim" controller, when enabled, automatically decreases the volume of the monitor speakers when program sources are being cued. On the left side (from top to bottom) are a TFT 7601 transmitter remote control, TFT 724 stereo monitor, and TFT 730 SCA monitor.


transmission equipment rack Collins exciter

The transmission gear is housed separately in a 7-ft rack. The transmission rack is fed through Cat-5e wiring from the studio to the shop, which also serves as a transmission point. On the right, a Collins 310Z-2 FM exciter can be seen. The exciter includes a stereo generator card. A second TFT modulation monitor is included in the rack, along with STL and RPU gear. Patch bays allow for reconfiguring the equipment as needed. The TFT 7601 is connected to the controller in the studio and can be used to energize or de-energize the exciter, effectively serving as the transmitter on/off control.


The full compliment of studio and transmission gear is as follows:

  • Gates Executive Audio Console. See the Gates Restoration page for available downloads.
  • Shure SM7B microphone connected to Channel 1 (operator position).
  • Shure SM58 microphone connected to Channel 2 (guest position).
  • Two Harris CB1201 turntables with Shure M232 tone arms and Shure M4407 cartridges.
  • Harris Criterion 90 cart machines; two playback, one record/playback.
  • Ampex AG-440 reel-to-reel audio recorder.
  • Ampex 1455 reel-to-reel audio recorder.
  • Gentner SPH-3 hybrid phone patch.
  • Digital audio workstation with Digigram VX222-V2 sound card. (The sound card is in a dedicated server; it links the 1970s hardware with current ways of accessing audio programming.)
  • AudioSource AM/FM tuner.
  • WhitakerAudio 40 W Stereo Power Amplifier.
  • Electro-Voice Sentry 100A studio monitor speakers.
  • M-Audio powered speakers for external cue monitoring.
  • AKG K240 headphones.
  • Harris MSP100 audio processor (for the stereo program chain). A spare MSP100 is located in the AG-440 equipment rack.
  • CBS Audimax 4400 level controller (for the SCA channel or stereo program backup). An updated User Manual is available for download.
  • CBS Volumax 4110 peak limiter (for the SCA channel or stereo program backup).
  • Audio Logic SC215 dual-channel equalizer.
  • Audio Accessories 96 point Type TT patchbay, with custom interface panel for peripheral equipment.
  • Four Samson S-MAX MCD2 Pro 2-Channel Passive PC Direct Box, used for interfacing consumer equipment with the Executive audio console.
  • LINKCOMM 24-bay shielded RJ45 patch panel. Two are used; one is for telco interface at the studio and the other is for telco interface at the transmission point.
  • XLR patch panel for mic-level sources.
  • TFT 760 EBS monitor/generator.
  • Moseley SCG-3 stereo generator.
  • Moseley SCG-8 SCA generator.
  • Moseley PCL-505 STL transmitter. Two are used, one at 455 MHz and the other at 950 MHz.
  • Moseley PCL-505 STL receiver. Two are used, one at 455 MHz and the other at 950 MHz.
  • Rockwell/Collins 310Z-2 FM exciter with stereo generator option. An updated User Manual is available for download.
  • TFT 763 FM modulation monitor with TFT 765A FM preselector (studio). A replacement trim piece is available for download. This Adobe Illustrator file may be used for other TFT monitors by modifying the file. Self-adhesive printed trim pieces may be produced by FastSigns or similar vendors.
  • TFT 763 FM modulation monitor with TFT 764 FM preselector (transmitter).
  • TFT 724 stereo modulation monitor.
  • TFT 730A SCA modulation monitor.
  • TFT 7601-C transmitter remote control (studio).
  • TFT 7601-R transmitter remote control (transmitter)
  • ADC 48 point 0.25-in patch bay.
  • Marti RPT-15 remote broadcast transmitter.
  • Marti CR-10 remote broadcast receiver.
  • Shure M-67 four-channel remote mixer.
  • Electro-Voice 635A interview microphone.
studio equipment rackAmpex AG-550 reel-to-reel tape deck

To round-out the vintage studio it seemed appropriate (and even necessary) to add some vintage vinyl. The current record library numbers about 100 albums, mostly 1960s and 70s rock, with some country included. A random search on eBay yielded the American Top 40 box set that aired on October 20, 1983. The four-record package includes the rundown sheet, which lists that week's "Hits From Coast to Coast." While a few years outside of the "70s era," it is nonetheless a cool piece of radio history.

Another piece of radio history that I was pleased to find on eBay was a 5-record set of the Drake-Chenault History of Rock and Roll series that aired in the early 1980s. Cool stuff. I remember listening to the series when I was (much) younger.

Most of the albums in my slowly-growing collection were purchased from used record stores. Fortunately, there are several stores in the San Francisco Bay Area (where I live) with a wide selection of artists. Most are in good shape overall, some in very good condition. I have also purchased new pressings that are re-releases of classic albums on 180 gram "ultra-analog" discs. They sound spectacular.

In a bit of irony, most of the records that I have collected so far are albums that I owned back in the day. In fact, there are some that I have purchased four times: first as an LP in the 60s, second as a CD in the 80s, third as an MP3 in the 2000s, and fourth, now, as an LP (again). Like many baby boomers, I let my LP collection go away when CDs came out. That was a bad call. I have resolved to not buy the same album a fifth time!

The revival of interest in vinyl records is most encouraging. Some artists are releasing new albums on vinyl as well as downloadable files. The Vinyl Snob website has an interesting podcast on "Record Store Day" that is worth a listen.

AT40 album set

overall view of the studio

All of the hardware in the studio works and with the Collins exciter operating into a dummy load, the modulation monitors pick up enough energy to operate from an off-air sample. So, it is a complete FM radio station from microphone to transmitter (albeit a very low power station).

Through web searches and other means, I have been able to collect printed manuals for all equipment in the studio. Documentation, of course, is essential for proper operation and maintenance. If you are having trouble locating a manual for the equipment listed above, let me know. I may be able to help.

The studio is an ongoing project. Most work has been completed, however, refinements are planned. A recent addition was an Ampex AG-440 reel-to-reel recorder. It was a big project as the unit purchased on eBay was in rough condition. The restoration project is documented on the Ampex AG-440 Restoration page.

For several years I have been looking for an FM transmitter to round-out the 70s radio studio collection. I would love to find a Rockwell Collins 831G-2; that's the type I put on the air in 1979. There are several problems with collecting this transmitter, however. First, it is big and heavy. Second, it requires an ac power service of 208 V 3-phase 4-wire-wye. Third, while I have found such transmitters on eBay, shipping is a major challenge. I had a line on a smaller 2.5 kW Collins rig, but somebody bought it while I figured out how to ship the thing. I haven't given up.

I have been asked (by family members) what's the end game for the 1970s radio studio? I haven't thought that far ahead, and besides I'm having too much fun building the studio. In any event, I see two options at some point in the future: 1) sell it to a collector, or 2) donate the whole thing to a museum. Probably that. Stay tuned...