Triode connecting pentode in RF use?

[NR5P]

Can a pentode be triode connected for rf plate modulated use and used as a triode?  Of course it's done with the 813 in class b audio and for a good reason since it's 0 bias and cheap.  I don't see it done for rf use, maybe because there aren't many advantages or maybe because there are other reasons?  The plus I can think of is simplicity for someone that wants to build a triode final amp.  There are some cheap Russion pentodes like the gk-71 that are cheap for the power output and I can't think of any triodes at that power level that are as cheap.  http://www.glowbugs.info/2009/12/gk-71-power-pentode.html

[Steve - K4HX]

Triode connected 813s have been used as RF linear amps.

[WQ9E]

Triode connected 813s have been used as RF linear amps.

The B&W amps (L-1001 and LPA-1) are fairly popular examples of this and seem to work pretty well.

[K0ARA]

Class C or Grounded Grid?

[NR5P]

class c

[WD5JKO]

Perhaps Nathan refers to a configuration that has the cathode common with the input and output, hence the term, "Common Cathode".

Quite coincidentally, I was researching this topic earlier today. The link shows two ways an old type 59 power pentode can be configured, and both be considered triode connected. The data sheet has plate curves for each triode configuration, and for pentode configuration.

http://www.r-type.org/pdfs/59.pdf

To the earlier post, grounded grid can be any class (A, B, C...) where this configuration has the grid in common with the input and output. A "common cathode" stage can also be any class (A, B, C..)

Jim
Wd5JKO

[w7fox]

4-400A, 4-1000A, 813, 807, 837 even some sweep tubes...seems pretty common.  They were always used in grounded grid but there is no reason they couldn't be used in common cathode.  Probably better to just use a triode.

[W2VW]

Knew a person with a "contest" amp with (4) 813s in parallel hi mu triode connected. It worked.

That Russian bottle most likely has fairly long grid leads and might not play well at upper hf.

[W2PFY]

That Russian bottle most likely has fairly long grid leads and might not play well at upper hf.

I have seen a six meter amp using an 813. They said it wasn't very efficient at that frequency but it was also very low in harmonics that would have caused TVI in the old days.

[WU2D]

Of course now you HAVE to neutralize.