beans_again?
1970s radio control heads t-shirt art
If you find an error, corrections are welcomed.
This started out as a project to make a t-shirt. The t-shirt maker required an Encapsulated Postscript (vector) file. This is a montage of cobbled together images. Some of the above was created from traced raster images from my photos. The knobs and shadows all had to be horsed with to get to this image. The virtual "Frequency 9" label is vector art.
At the top is the radio control head used by the operator to adjust settings. A twenty to thirty five pound box housing the electronics and tubes was mounted elsewhere in the vehicle and connected via a garden-hose-sized cable. The speaker and microphone are pasted below. These had maybe 3 tubes in their transmitter and everything else was transistors.
FREQUENCY 9 GE MASTR PROFESSIONAL UHF RADIO: At left is what's supposed to look like a 1975 Santa Clara County ambulance radio made by now-defunct General Electric Mobile Radio. It might be what you saw in a Fields, Palo Alto Ambulance, Bigleys, AAA, San Jose Ambulance, or the other companies whose names I can't recall. This was before paramedics. Everything was on one channel. If someone was bitten by a dog in Los Altos Hills, an ambulance in Gilroy, (at the other end of the county), could hear the dispatch. When an ambulance crew called the hospital to give report, everyone heard that, too. "Wheeler, Three Zero Six, inbound with a 57-year-old male, victim of a fall from a horse..." Radio users had to set the 1-2-3-4 switch to the correct setting for the geographic location of the ambulance. The ultra-high frequency (UHF) transmitter produced 60 watts. It was a basic, functional, single-channel system. Even in 1975, it was almost 24-hour, non-stop radio calls. Monday at 2am? There were people talking on the radio.
CALFIRE MOTOROLA SPECIAL PRODUCTS MOTRAC RADIO: In the 1970s, CalFire was known as CDF: California Division of Forestry. It was part of the Resources Agency. Like the Highway Patrol, they had radios custom built to match their growing, statewide system.
Their radios might be made by low bidders RCA, General Electric, or Motorola. The buttons, and names on them, looked the same regardless of who made the radio. They might be a different shaped button but they were labeled as here. Nowadays this is called "user interface." If you needed "District, Tone 4" you press the D button (District channel) and the 4 button (Tone 4) whether it was an RCA or Motorola radio. This was true until Midland microprocessor-based radios of the mid-1980s. "District" is now "Region."
I do not own this CDF Motrac or any other old CDF equipment. I may have had a MASTR Professional, or possibly a MASTR II, repair manual but these seem to have disappeared.
Both of these systems used an elderly technology called, "tone burst." I think the State tones were 1,800 Hertz, 1,950 Hertz, 2,100 Hertz, 2,250 Hertz, and 2,552 Hertz. Each mountaintop site listened for its assigned beep tone. If you selected 3, the radio would make a roughly 2-second, 2,100 Hertz beep every time you pressed the push-to-talk button. "[beeeeep] San Andreas, Chief Fourty Four Hundred responding." After an hour of busy radio traffic, your ears would be ringing with a 2,100 Hertz tone. Our engineers put a notch filter that knocked the ambulance network (Frequency 9) burst tone down to about one tenth of its original volume while having no effect on voice.
You may recognize the microphone and speaker on the CalFire radio at right. These were standard Motorola parts you'd see on television shows like Dragnet, Emergency, or Adam 12. Both the City and County of Los Angeles used a standard Motorola control head less complicated than the CalFire model shown.
By the way, the t-shirt came out perfectly.
The good thing about a legacy system is that you have one…
— Homer R. Wagner MD, Ph D
Please do not copy this image.
Journalism Grade Image.
Source: montage 5,200x2,700 TIF file.
1970s radio control heads t-shirt art
If you find an error, corrections are welcomed.
This started out as a project to make a t-shirt. The t-shirt maker required an Encapsulated Postscript (vector) file. This is a montage of cobbled together images. Some of the above was created from traced raster images from my photos. The knobs and shadows all had to be horsed with to get to this image. The virtual "Frequency 9" label is vector art.
At the top is the radio control head used by the operator to adjust settings. A twenty to thirty five pound box housing the electronics and tubes was mounted elsewhere in the vehicle and connected via a garden-hose-sized cable. The speaker and microphone are pasted below. These had maybe 3 tubes in their transmitter and everything else was transistors.
FREQUENCY 9 GE MASTR PROFESSIONAL UHF RADIO: At left is what's supposed to look like a 1975 Santa Clara County ambulance radio made by now-defunct General Electric Mobile Radio. It might be what you saw in a Fields, Palo Alto Ambulance, Bigleys, AAA, San Jose Ambulance, or the other companies whose names I can't recall. This was before paramedics. Everything was on one channel. If someone was bitten by a dog in Los Altos Hills, an ambulance in Gilroy, (at the other end of the county), could hear the dispatch. When an ambulance crew called the hospital to give report, everyone heard that, too. "Wheeler, Three Zero Six, inbound with a 57-year-old male, victim of a fall from a horse..." Radio users had to set the 1-2-3-4 switch to the correct setting for the geographic location of the ambulance. The ultra-high frequency (UHF) transmitter produced 60 watts. It was a basic, functional, single-channel system. Even in 1975, it was almost 24-hour, non-stop radio calls. Monday at 2am? There were people talking on the radio.
CALFIRE MOTOROLA SPECIAL PRODUCTS MOTRAC RADIO: In the 1970s, CalFire was known as CDF: California Division of Forestry. It was part of the Resources Agency. Like the Highway Patrol, they had radios custom built to match their growing, statewide system.
Their radios might be made by low bidders RCA, General Electric, or Motorola. The buttons, and names on them, looked the same regardless of who made the radio. They might be a different shaped button but they were labeled as here. Nowadays this is called "user interface." If you needed "District, Tone 4" you press the D button (District channel) and the 4 button (Tone 4) whether it was an RCA or Motorola radio. This was true until Midland microprocessor-based radios of the mid-1980s. "District" is now "Region."
I do not own this CDF Motrac or any other old CDF equipment. I may have had a MASTR Professional, or possibly a MASTR II, repair manual but these seem to have disappeared.
Both of these systems used an elderly technology called, "tone burst." I think the State tones were 1,800 Hertz, 1,950 Hertz, 2,100 Hertz, 2,250 Hertz, and 2,552 Hertz. Each mountaintop site listened for its assigned beep tone. If you selected 3, the radio would make a roughly 2-second, 2,100 Hertz beep every time you pressed the push-to-talk button. "[beeeeep] San Andreas, Chief Fourty Four Hundred responding." After an hour of busy radio traffic, your ears would be ringing with a 2,100 Hertz tone. Our engineers put a notch filter that knocked the ambulance network (Frequency 9) burst tone down to about one tenth of its original volume while having no effect on voice.
You may recognize the microphone and speaker on the CalFire radio at right. These were standard Motorola parts you'd see on television shows like Dragnet, Emergency, or Adam 12. Both the City and County of Los Angeles used a standard Motorola control head less complicated than the CalFire model shown.
By the way, the t-shirt came out perfectly.
The good thing about a legacy system is that you have one…
— Homer R. Wagner MD, Ph D
Please do not copy this image.
Journalism Grade Image.
Source: montage 5,200x2,700 TIF file.