[GreenKeys] History of modems

[73131.3073 at compuserve.com]

Duncan -

Do you recognize a TH-5 in this photo? This is a TU that I built out of one of them. The circuit was the W5BGP TU that was published in CQ magazine back in the 60s I believe. It worked fairly well although the electronic keyer was a little 'weak' I felt like. The front panel was fixed up to look like a Galaxy V which is the rig I had back then. One item that was missing from this design was a low pass filter after the detector. I traded it off and have always regretted it!


73,

Tim Swarthout
WA5QEG













-----Original Message-----
From: Duncan Brown <duncanancy at earthlink.net>
To: greenkeys <greenkeys at mailman.qth.net>
Sent: Thu, Nov 7, 2013 8:46 pm
Subject: Re: [GreenKeys] History of modems


          
    It is often hard to pinpoint the "first" of anything, but the for    the "first" modem, I always think of the US Signal Corps' TH-5/TG:
    
    
    
    This was the Signal Corps' first tactical (came with a water-proof    cover) modem and probably the first mass-produced modem. Not    designed for civilian telephone lines but used with 2-wire (simplex)    or 4-wire (full duplex) field-phone circuits. Designed c1950 for    60/100 wpm teletypewriter circuits and so operated at 42 & 75    bps/baud. Two-tone AFSK: 1275 & 1325 Hz. Uses 15 tubes, mostly    12AU7s & 12AX7s, and weighs about 18 pounds. Contains two 20ma    loops - one for RX & one for TX. Contract date is 1951 &    first manual date is 1952.  A solid-state version, the TH-22/TG came    out about 1967. It was the same size and didn't weigh any less. The    TH-5 operator's manual was updated in 1983, so it was apparently    still being used then.
    
    Duncan
    K2OEQ
    USASA 31J
    
    
    
On 06-Nov-13 12:06, Jim Haynes wrote:
    
    
      
http://www.techradar.com/us/news/internet/getting-connected-a-history-of-modems-657479      
      
      jhhaynes at earthlink dot net      
      ______________________________________________________________      
    
    
  



	
		
												
		
			
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