Radio Equipment

[rboltz]

Did the radios require the 100 amp alternator or could they be run on a truck with the regular 60 amp unit.

If equipped with a ratt rig or other communications shelter, the 100 amp kit was installed. Not required for just a single VHF radio.

[kwai]

Would there be any other reason to install the 100 amp kit besides the comm shelter?

I have a couple of trucks that have the cut-outs for the 100 amp rig. Be interesting to know what they might have been used for.

[rboltz]

Would there be any other reason to install the 100 amp kit besides the comm shelter?

I have a couple of trucks that have the cut-outs for the 100 amp rig. Be interesting to know what they might have been used for.

Non that I know of but strange things went on. There were all kinds of shelters, just like today, that had telephone switching, fire control (arty), and the like but I can't think of why any would need the 100 amp set up other then the ratt. The ratt draws about 45 amps during transmit and I run mine with the 60 amp alternator but you need some RPM's to keep up long term. The 100 amp systems we had would do OK at high idle. I'm transmitting short voice segments so no impact but if you run the TTY and need the inverters, the load climbs to 60 amps real fast. We ran some long message tapes in the signal corp so we might transmit for 20 min. at a time.

[kwai]

Ok. What are RATT and RTTY abbreviations for. Your site doesn't say and I didn't quickly find an answer on google.

[randyscycle]

Ron, you're gonna get questions fired at you rapidly now......

One question I have is with a unit drawing up to 60 AMPS to power it, what was it actually radiating in terms of watts? I've seen some linear amplifiers for CB stuff that pull around 6-8 amps and they tend to boost output wattage like mad.

I'll get in line behind everyone else for an answer now.

[rboltz]

Ok. What are RATT and RTTY abbreviations for. Your site doesn't say and I didn't quickly find an answer on google.

RATT and RTTY is "Radio Teletype" TTY is Teletype" a RATT RIG was and still is an Army slang term for a "Radio Teletype Shelter"

[rboltz]

Ron, you're gonna get questions fired at you rapidly now......

One question I have is with a unit drawing up to 60 AMPS to power it, what was it actually radiating in terms of watts? I've seen some linear amplifiers for CB stuff that pull around 6-8 amps and they tend to boost output wattage like mad.

I'll get in line behind everyone else for an answer now.

The older AN/GRC-46 sets were 100 watts but were AM for voice and FSK for RTTY. They used dynamotors to generate the voltages needed for the transmitter (some later models tried solid state power supplies but these were troublesome). All tube sets. Lots of loss in conversion. The T-195 transmitter in there needed 100 amps surge to get the dynamotors started and 60 amps to transmit. Add in the rotary inverters for the TTY gear and 24 volts for the old tube modulator and demodulator and you were way up there.

The later AN/GRC-142 and 122 sets were 400 watts Single Sideband and AFSK for TTY. They are mostly but not completely solid state. The high voltage inverters for the amplifier are all solid state and much more efficient. Low inrush. Plus SSB is more efficient, you don't waste power on the AM carrier or the lower sideband so the current varies with your speech.

The quick answer!

[randyscycle]

Interesting stuff! Now one more......heh, heh......


Did that stuff tend to propagate at night like regular AM stations do? A 50K Watt AM station during the day has to throttle back to say 2K at night. Of course I am sure the communications were encrypted somehow, but that seems like a fair amount of AM power.

[rboltz]

Interesting stuff! Now one more......heh, heh......


Did that stuff tend to propagate at night like regular AM stations do? A 50K Watt AM station during the day has to throttle back to say 2K at night. Of course I am sure the communications were encrypted somehow, but that seems like a fair amount of AM power.

How far you transmit is dependent on conditions, atmospheric, night/day, terrain, and frequency used. Generally speaking, we relied on ground wave for point to point communications and selected a frequency related to the distance we needed to communicate. This is for the HF band, 2-30Mhz. At night, or even daytime if the conditions are right, you can transmit for great distances on some frequencies. I have worked the UK, and Germany sitting in my shelter with just the 15' whip during the day. In my Army era, reliable long range communications went by microwave stations set up in 2-1/2 ton comm centers.

VHF vehicle sets like the RT-68 series and the RT-524 were generally line of sight and used mostly for convoy communications, vehicle to vehicle. The PRC series are portable and used in tactical situations for squad to squad and squad to command areas and could also talk to the vehicles.

[randyscycle]

That clarifies things!

I didn't realize though that this stuff was line-of-sight. I always tend to think of FM (88-108 Mhz) that way, but never think of lower band the same. Again, and I may be comparing apples and oranges, but AM bounces off the ionosphere and that changes after sunset, wouldn't these sets do the same?

The reason I am curious by the way, is that it would seem that in a tactical situation these communications would have been easier to intercept if the enemy had the proper frequencies. Sort of like the guys who DX shortwave broadcasts.