[AMRadio] TH vs TL


W2INR w2inr at amfone.net
Sat Feb 23 15:56:37 EST 2008


The only differences will be drive and bias voltages. The performance 
will be the same once dialed in.



G

Brett Gazdzinski wrote:
> I don't think you will see any difference at all.
>
> I used both as modulators, with the same results, and use 811 and 812
> triodes in the push pull rig with the same results also.
>
> Theoretically, the higher bias tubes work better in class C
> but you cant hear or see any difference.
>
> Brett
> N2DTS
>
> ----- Original Message ----- From: "Barrie Smith" <barrie at centric.net>
> To: "Discussion of AM Radio" <amradio at mailman.qth.net>
> Sent: Saturday, February 23, 2008 1:41 PM
> Subject: [AMRadio] TH vs TL
>
>
> I'm curious as to the difference in RF performance between the TH (as 
> in 250TH) and the TL (as in 250TL)  versions of older triode tubes.
>
> Looking through the Eimac spec sheets for various old, glass triodes, 
> the only real difference appears to be that the TL versions require 
> higher grid bias in class C RF service.
>
> I've used the TH versions of several of the older tubes a good number 
> of times over a many year period, but I've only used the TL types in 
> modulator service.  However, if there is no real difference in RF 
> performance between the two in class C, I'm tempted to.
>
> 73, Barrie, W7ALW
>
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