VHF/UHF radio and telephone voice switch systems - UK Vintage Radio Repair and Restoration Discussion Forum

Sparks · 10th Apr 2018, 1:23 pm

By the above, I mean the network of headsets/microphones, frequency selectors, transmitters and receivers and phone lines, such as those used in Emergency Services control rooms, Coastguard and Air Traffic Control towers.

Does anyone know if the operator's voice, via the headset/handset microphone, is connected directly to the radio/phone or does it go through some sort of processing first ? In most cases noise-cancelling microphones are used which takes care of ambient clutter but I wondered if any other adjustments or enhancements are made such as bass, treble and amplification ?

I know the previous vintage system used at Leeds Bradford Airport used a device called a VOGAD to ensure a constant output from the controller's microphone.

Thankyou.

Radio Wrangler · 10th Apr 2018, 3:56 pm

Voice Operated Gain Adjusting Device.

Just a straight gain compressor. Redifon did their own with long strings of diodes as variable resistors (GK203 manual)

Plessey did some VOGAD devices in their SL600 radio IC family.

(The Hitch-Hiker's Guide to the Galaxy has this to say about Vogads.....)

David

Dave Moll · 10th Apr 2018, 4:18 pm

Quote:

Originally Posted by Radio Wrangler

Voice Operated Gain Adjusting Device...

(The Hitch-Hiker's Guide to the Galaxy has this to say about Vogads.....)

David

Perhaps it should have been "Voice Operated Gain Obliterating Noise" then.

Sparks · 10th Apr 2018, 4:49 pm

Back in the day, the Leeds Bradford controllers used headsets with NC magnetic microphones, as opposed to moving coil or electret types. Plug one of these into a normal cassette recorder for a test and the output is very clear, if a little quiet, and quite treble-heavy. However, when connected via a matching in-line amplifier, the result is noticeably superior. Maybe the VOGAD performed this same function.

10th Apr 2018, 1:23 pm	#1
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 598	VHF/UHF radio and telephone voice switch systems By the above, I mean the network of headsets/microphones, frequency selectors, transmitters and receivers and phone lines, such as those used in Emergency Services control rooms, Coastguard and Air Traffic Control towers. Does anyone know if the operator's voice, via the headset/handset microphone, is connected directly to the radio/phone or does it go through some sort of processing first ? In most cases noise-cancelling microphones are used which takes care of ambient clutter but I wondered if any other adjustments or enhancements are made such as bass, treble and amplification ? I know the previous vintage system used at Leeds Bradford Airport used a device called a VOGAD to ensure a constant output from the controller's microphone. Thankyou.

10th Apr 2018, 3:56 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,903	Re: VHF/UHF radio and telephone voice switch systems Voice Operated Gain Adjusting Device. Just a straight gain compressor. Redifon did their own with long strings of diodes as variable resistors (GK203 manual) Plessey did some VOGAD devices in their SL600 radio IC family. (The Hitch-Hiker's Guide to the Galaxy has this to say about Vogads.....) David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

10th Apr 2018, 4:49 pm	#4
Sparks Heptode Join Date: Oct 2006 Location: Leeds, West Yorkshire, UK. Posts: 598	Re: VHF/UHF radio and telephone voice switch systems Back in the day, the Leeds Bradford controllers used headsets with NC magnetic microphones, as opposed to moving coil or electret types. Plug one of these into a normal cassette recorder for a test and the output is very clear, if a little quiet, and quite treble-heavy. However, when connected via a matching in-line amplifier, the result is noticeably superior. Maybe the VOGAD performed this same function.