[Amps] power limiting in 8410 amps?

[Jim Thomson]

Message: 2
Date: Fri, 2 Nov 2018 18:35:30 +0000 (UTC)
From: Russ Williams <hrd998cc at yahoo.com>
To: Amps at contesting.com, Steve Bookout <steve at nr4m.com>
Subject: Re: [Amps] power limiting in 8410 amps?

< Steve.? I would thrilled to get 1200 watts out of my L4B with 40 watts drive . 

<Russ KW6T

##   40 watts to drive an L4B to  1200 watts.... not gonna happen anytime soon, not with
2500 vdc under load..and  800 ma plate current.   I get 1290w pep out of my  4 x L4Bs 
on 80m, with calibrated watt meters..and abt  100w pep  drive.  

## The best you can do with the L4B, is to toss the grid chokes and grid caps..and directly bond
the 3 x grid pins to the chassis.   Then install  10 x 1N5408 diodes  in series...for bias.   Drakes  scheme
of   operating the pair of  3-500Zs  with no bias..and  220-230 ma of idle current is  fubar..ditto with
the pair of  50 watt, 50 k bleeders  in the outboard  L4PS   B+  supply..not required.   Drakes scheme
of using +  130 vdc  for cut off bias on RX is more fubar.... a  50 k ohm  @  3 watt  mof is ample for that
job,  just rewire  the  center pole of the  3PDT  TR relay to shunt out the  50 K on TX. 

Then the L4PS runs stone cold.   With grids bonded directly to chassis, the amp is easier to drive, typ
20-25 watts  LESS drive required..... but some of that gets negated by adding the 7 vdc of bias. 

Jim   VE7RF