[Amps] power limiting in 8410 amps?
Jim
jimw7ry at gmail.com
Sun Nov 4 21:49:18 EST 2018
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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