[R-390] Why 6DC6?

[Roy Morgan]

At 03:42 PM 9/6/02 +0000, Philip B Atchley wrote: ....
>Yes, I do have some 6BZ6 tubes here and two separate identical Marconi
>signal generators but I really don't have all the test fixtures and
>additional equipment to run a total analysis comparing both tubes


Phil,

The ARRL handbook tells how to build a "hybrid signal combiner". It appears 
pretty simple (one toroid, a few resistors, connectors and a box.)  I plan 
to build one when I can.

>  to get optimum results one would have to adjust the
>cathode bias, screen resistors etc to get a fair comparison of tubes and
>I don't feel like cutting into my R-390A (that would be blasphemy).

I have an RF deck from a "junker" radio that I expect to do such 
experimenting with.  HSN carried an article or series of them using 
frame-grid tubes in  the first RF and  some mixer stages.  Changes to the 
circuits were involved.  Greatly improved intermodulation and
"overload"  performance, and much lower noise were claimed.  Others have 
since reported that the improvements were not worth the effort.

PS:
Who can explain in simple terms what "third order intercept" means??

Roy

- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
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