[Amps] sb-220 non uniform grid current ??

[Dan Sawyer]

Thanks,

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??

Dan


R. Measures wrote:

>With 700 - 800mA key-down on the CW tap, what is the grid-I?  Tnx.  
>
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>>All,
>>
>>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.
>>
>>Thanks,
>>Dan
>>
>>
>>
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