[AMRadio] Valiant carrier...

[John King]

My two cents worth!! I have always been taught in the broadcast business that 
70% efficiency for a Class C final amplifier was GREAT !! In the late 1950s, RCA 
developed a Class C circuit for its' broadcast transmitters that had  a tuned 
circuit in the cathode of the final tube tuned to the third harmonic of the 
fundamental frequency while the grid and final tank circuit were tuned to the 
fundamental. RCA claimed approximately 90% efficiency and touted the design of 
their transmitters to commercial broadcasters as a money saving feature because 
of the additional efficiency. That was an unusual RCA proprietary design and I 
don't think it ever commonly used in the industry. I can't be sure though. The 
problem with the circuit for hams was that as you changed the resonant freq of 
the grid and plate circuit, you also had to tune the cathode to the third 
harmoniuc of the fundamental.

I use an Apache that puts out 100 watts of carrier easily and with modulation 
peaks, my peak reading watt meter indicates approximately 300 watts output. I 
have been taught over my 53 years of hamming that one should expect about three 
times the pep from a properly tuned and modulated Class C transmitter.  
Hopefully, I am not too far off base with these comments. 73, John, K5PGW



----- Original Message ----
From: Jim Wilhite <w5jo at brightok.net>
To: Discussion of AM Radio in the Amateur Service <amradio at mailman.qth.net>
Sent: Wed, June 15, 2011 2:42:06 PM
Subject: Re: [AMRadio] Valiant carrier...

Rick, Johnson put ~600 volts on the plate of the Valiant and Viking 
series radios which is for Continuous Carrier operation.  Then with 330 
Ma. you get input of 198 watts and the best output I have ever seen from 
a Valiant is ~120 watts, which is about 60%.

The DX 100 radio has just two 6146s and gave the same power output. 
They put about 800 volts on the final which is Intermittent service.  I 
believe you will find that 70% figure is under certain circumstance you 
may not have in the Johnson, or for that matter in the Heath.

Jim/W5JO


----- Original Message ----- 



>I agree, 75% should be possible and I hope I'm able to get there.
> Rick / K5IAR
>
> From: amradio-bounces at mailman.qth.net
> [mailto:amradio-bounces at mailman.qth.net] On Behalf Of Ron Youvan
> Sent: Wednesday, June 15, 2011 2:25 PM
> To: Discussion of AM Radio in the Amateur Service
> Subject: Re: [AMRadio] Valiant carrier...
>
>   I don't know the Valiant, but 75% using class "C" should not be a
> problem, but 400 Watts PEP from three 6146s seems a bit of a stretch.
> I think you are going to need between 800 and 900 Volts on the plates 
> to
> maximize the power output to do it.
> -- 
>    Ron  KA4INM -
>

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