[BC] Re: CONTINENTAL 10 KW AM'S TUBE TYPE

[Robert Meuser]

DHultsman5 at aol.com wrote:

> The 316 10 kW. which was the driver for the 317 50 kW. was a three cabinet 
> transmitter, Barry has a photo of the transmitters used as a driver at KRLA and 
> WDIA and a Canadian station.  I understood that CE also sold some of the 316's 
> as 10 kW's opnly in the US, Canaga and worldwide.  This was essentially part 
> of the Western Electric line after CE bought the Western Electric AM product 
> line.

A number went to the military. We had them in Germany (glass doors)along with 
314's (1KW) and basically the entire run of UHF TV transmitters. I believe all 
of the same generation.


> 
> The next was the 316B which as Rob Meuser stated was three 4CX5000A tetrodes 
> in parallel, screen modulated by 4 each 4-65A tubes in the ecreen circuit.  
> The 315B used only two tubes.

A very deadly TX

> 
> The next was the 316C which was two 4CX10,000 tubes in parallel operated in 
> linear mode, screen modulated by three 4CX250B tubes.  I know there was one at 
> WCFL and one at WLAC backing up their 317C's  I know of several of the 315C's, 
> Boston MA, WRR, Dallas, WMAK, Nashville


That's the one I was thinking of. I believe they called the modulation scheme 
'regulinear'


> 
> The next was sometime that Saintone was working on in 1968 when I was looking 
> at transmitters for KLIF's new 12 tower array.  They had a working prototype 
> 10 kW two-tube solid state transmitter.  They finally got it out about 1971 as 
> the 315F and 316F, using two 4CX10000's in the 5 kW and two 4CX15000's in the 
> 10 kW.  The tubes operated in a Doherity amplifier making it more efficient 
> than running in linear fashion as the two previous models.  The also set it up 
> so you essentially peaked the grids and dipped the plates which was the way 
> most class C plate modululated rigs tuned.
> 
> These two transmitters were the FIRST two-tube 5 and 10 kW AM transmitters 
> and predated the MW-5 from Gates and by several more years the MW-10 from Harris.


The 316F was the goal post Harris used for development of the DX line, 
especially the 50 kHz audio response the the excellent square wave performance 
that came with that. I went to Quincy a number of times to do comparative proofs 
between beta DX and my 316 Fs.

The problem with the 316F was the trade off between positive modulation and 
distortion performance. When you got near 125% positive the peak tube started to 
shift from AB1 to AB2 causing a large drop in drive impedance and thus requiring 
much more power from the exciter. You can see the positive peak on a scope 
flatten out on the exciter output. I have seen a few 316Fs modified to have a 
250 W SS TX as a replacement for the original 50W exciter to solve this problem. 
I know of one that took the sample TX output of a Motorola AM stereo exciter, 
applied a 500 W SS Linear and then drove the 4CX15000s. Fantastic stereo AND 
great positives. I also know of one and only one unit (un modified) that had 
nearly 50 db stereo separation, less than 1% distortion and could just barely 
make it past 125% mod, all at the same time.


R