[Collins] 30L-1 vs 30S-1

[Dr. Gerald N. Johnson]

Yoiks. I was thinking 125 watts, probabaly the data sheet rated power 
for a pair in class B. Generally with linears there's about 50% 
efficiency so the available RF power out is about the same as the 
available plate dissipation. The 30S-1 has 1 KW plate dissipation and 
the manual rates it at 1 KW PEP output. The 30L-1 manual doesn't show 
output, but limits the input to 1 KW PEP so the output would tend to be 
about 500 watts PEP, still driving the tubes way beyond their rating for 
intermittent service and even further beyond their Continuous Commercial 
Service dissipation rating of 45 watts per tube. So the Collins rating 
dissipates about twice the tube manual (RCA TT-5) which means the plates 
probably glow a bit. Its a wonder the glass doesn't get soft like some 
over driven sweep tubes had been known to do and then the vacuum pulls 
the soft glass into be against the tube plate. Using sweep tubes for SSB 
linears brought a new era to ham radio where the intermod products were 
a lot greater than the Collins 32S transmitter standard.

Or the RCA rating was very conservative allowing those antique tubes to 
survive that much abuse.

Usually when a tube or gang of tubes is worked very hard to intermod 
products are significantly increased. The 30S-1 manual specifies 
intermod products, the 30L-1 manual does not.

So for the original post, the 30L-1 puts out no more than half the 
output power of the 30S-1 and probably with considerably more splatter 
from over working the tubes.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.

On 12/10/2015 10:22 PM, Glen Zook wrote:
> The 30L-1 definitely does NOT have 500-watts of plate dissipation!
>
>
> The 811A is rated at 65-watts of plate dissipation and, having 4-tubes,
> the 30L-1 has a total plate dissipation of 260-watts!
>
>
> Collins definitely pushed the envelope with the 811A. Art Collins
> reportedly worked with RCA and their 811A tubes and got permission to
> push the tubes. The rated input power for the 30L-1 on CW was 1000-watts
> NOT to exceed 30-seconds key down time. The rated input power for the
> 30L-1 on SSB is also 1000-watts continuous service. However, the FCC
> equivalent power rating for SSB is only 20% which makes the average
> plate dissipation somewhat lower than on CW. As such, the continuous
> rating for SSB as opposed to 30-seconds maximum key down with a 50% duty
> cycle for CW.
>
> Glen, K9STH
> Technical Adviser CCA
>
> website: http://k9sth.net
>
>
>
> On Thursday, December 10, 2015 4:34 PM, Dr. Gerald N. Johnson
> <geraldj at netins.net> wrote:
>
>
>
>
> On 12/10/2015 3:24 PM, Jim Isbell, W5JAI wrote:
>  > What can the 30S do that the 30L cant?
>  > ______________________________________________________________
>  >
> At least 1500 watts from the S1 with a KW of plate dissipation with a
> tube designed in the 1950s where a linear is often barely 50% efficient
> vs a tough KW pep input from the L1 with only 500 watts of plate
> dissipation in tubes designed in about 1937. Basically a conservative
> design vs a ham style living on the edge design in the 30L1. I noticed
> in the catalogs from the 60 when power was limited to 1 KW input, that
> both had the same ratings but the S1 showed low intermod values and the
> L1 didn't mention them. To acheive that conservative design the S1 does
> take up a lot more space. And I think the S1 can run RTTY at full power
> which could fry the L1 quickly.
>
> 73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.
>
>
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