[Amps] sb-220 non uniform grid current ??
elowell at maine.rr.com
Thu Feb 26 07:00:35 EST 2004
Why are you not using a dummy load?
----- Original Message -----
From: "Dan Sawyer" <dansawyer at earthlink.net>
To: "R. Measures" <r at somis.org>
Cc: "amps" <amps at contesting.com>
Sent: Wednesday, February 25, 2004 11:25 AM
Subject: Re: [Amps] sb-220 non uniform grid current ??
> The following data was collected from an antenna with an SWR of about 1.5.
> Plate ma Grid ma
> 100 0
> 120 10
> 140 20
> 160 30
> 180 40
> 200 50
> 300 100
> 600 150
> These were obtained by carefully increasing the drive and incrementally
> tuning first load and then tune. These appear to be good results.
> Attempts to tune directly have to be approached very slowly and
> carefully. Is it possible the high grid current readings are a result of
> poor tuning skill on my part??
> R. Measures wrote:
> >With 700 - 800mA key-down on the CW tap, what is the grid-I? Tnx.
> >>I have an sb-220 with non-uniform grid current. With low to medium drive
> >>grid current is linear (or apparently close to it) with plate current
> >>(minus about 100 ma base) and output power. However if input drive
> >>exceeds the medium level of 25 to 30 watts grid current starts to hockey
> >>stick "high". It is not a digital switch; but a very steep response.
> >>The components in the bias and grid meter side of the circuit have been
> >>checked in circuit. The grid bias coil has been replaced with an 1/8
> >>watt 33 Ohm resister.
> >>Amps mailing list
> >>Amps at contesting.com
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> Amps at contesting.com
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