[Amps] 813 efficiency

[Eddy Swynar]

On 2013-02-22, at 11:14 AM, Jim Thomson wrote:

> 
> 
> ##  eddy, toss the books. Spend 5 mins with the GM3SEK  PI  software instead.  The L PI is the ticket,  but it can take many variations.   With higher amounts of L in the plate lead  ( anywhere b4 the tune cap)
> you require less L  in the main 10m coil..and vice versa.   You can see that effect right away in the software.    There is NO reason to have to switch that coil out of the circuit, why bother ?

Because the tuning on the lower bands was radically altered with it in, far & away removed from quoted "text book specs" for a pair of 813s in GG...

> 
> ##  and why would you want to switch the coil in the plate lead at the plate caps ?    You shoulda just put the coil  AFTER the plate block caps, and b4 the tune cap.    Then it wouldn’t have any B+ on your switching contacts.
> The way you have done it, you have both B+ and RF voltage on it.   When driven full bore, the anode..and your mercury relay contacts...will have almost twice the key down B+ voltage on it.   The RF in the tank circuit
> is AC.   And AC will back feed through the plate block caps... and onto the anode..and eveything in its path. 

Makes sense---good idea. Guess I shoulda considered that before incorporating the scheme...as I recall, I simply copied the methodology used in the ARRL literature...

> 
> ##  remove your popsicle stick, mercury relay, etc... and toss em.    Insert your L coil  between plate block caps and tune cap.   If no room insert in plate lead.    Toss any parasitic suppressor,  the amp doesn’t
> need it on any band. 

No---I don't think so. The thing works well enough for me now, as it is...why fix it, if it ain't broke, right...?!   :o)

~73~ de Eddy VE3CUI - VE3XZ