[Amps] power limiting in 8410 amps?

[Jim]

The Drake L4B only need 2-4 diodes for bias. The less ZSAC the harder it 
is to drive.

73

Jim W7RY



On 11/3/2018 12:25 PM, Jim Thomson wrote:
> 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
>
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