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Re: [TenTec] Centurion and AM

To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Subject: Re: [TenTec] Centurion and AM
From: "Tony Lelieveld" <va3dwi@gmail.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 3 Aug 2014 23:51:58 -0400
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
My first "home brew" 2 meter TX, in 1968, started with an FT-243 crystal in the 8 MHz range. Multiplied x3 x3 x2 put in the 144 MHz band. The final was, I believe a QQE 06-20 can't remember anymore, the North American equivalent of a 6360. The modulator was a dual triode 12AU7 or a 12AT7. The first triode was the mike audio amplifier and the second triode was in SERIES with the screen grid. By setting the bias as such that I had a carrier of about 8 Watt I could talk it up to max power, I believe around 15 Watt. If biased for no carrier, it would play havoc with the fast AGC at the receiving station RX, unless, he had an AGC with fast attack and slow release time as we use in SSB. It worked great with a low parts count and no big modulator.

Tony VE3DWI.

----- Original Message ----- From: "Bob McGraw - K4TAX" <RMcGraw@Blomand.net> To: "george fritkin" <georgefritkin@yahoo.com>; "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Sunday, August 03, 2014 3:45 PM
Subject: Re: [TenTec] Centurion and AM


The original DX-60 and versions there after are controlled carrier modulation. Thus they changed the voltage on the screen grid from some resting value, representing carrier with no modulation, to increasing the screen voltage to represent voice peaks. There were various timing constants involved that determined just how fast the screen voltage could rise and how slow it decayed. In effect there was no portion of the envelop that was negative modulation. If one observed the signal on a meter, average power detection, they would see the power increase with modulation and the station on the other end would see the S meter deflect upward.

True screen modulation is similar in some ways, however the method has the ability to control the screen voltage value from near zero volts representing 100% negative modulation to a positive value representing 100% positive modulation. In this case the actual carrier value does not change. Thus one observing the output on a average detection power meter would not see the power increase with modulation.

73
Bob, K4TAX


----- Original Message ----- From: "george fritkin via TenTec" <tentec@contesting.com>
To: <tentec@contesting.com>
Sent: Sunday, August 03, 2014 2:27 PM
Subject: Re: [TenTec] Centurion and AM


Isn&#39;t the original DX60 scheme really screen modulation.....some people call it controlled carrier

George, W6GF
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