[AMPS] 4-1000A Project

[Phil (VA3UX)]

At 06:02 PM 4/3/2001 -0500, you wrote:
>
>Why do you need a good bandswitch to prevent arcing at high voltages?
>
>The band switch should come AFTER the DC blocking cap.  Therefore, as long
>as it can handle the circulating currents present in the tank, the plate
>voltage should make no difference.
>

Huh ?  Say what ?  

Gee, could it be that the peak RF voltage is related to the DC plate voltage ?

>If you have a design that is not DC blocked (not sure why you'd want to do
>that), then I agree.  But with a proper design, it should not matter.
>
>Also, no offense to Mike, W1NR, below, but I suspect his power numbers as
>well.  All my experience and actually data in the books shows that the
>4-1000A does not put out 1800 W from 100 W in at 4400 Volts.  Perhaps he's
>got an extremely hot tube, but that is not the norm.
>

I don't suspect Mike's numbers at all.  I do suspect your data (and perhaps
your "experience").  I have Eimac's bulletin (# AS-1) right here : with Ep
= 4000V and 105 watts drive it is spec'd for 1870 watts. At Ep = 5000V and
70 watts drive it's spec'd for 1900 W out.  Both cathode driven.

>Most ham power meters are not at all accurate at mid-scale power readings.
>

They aren't accurate at any position of the scale to much better than 10%.

Phil
>73,
>
>Jon
>NA9D
>
>
>on 4/3/01 5:48 PM, DF3KV@aol.com at DF3KV@aol.com wrote:
>
>> That is exactly my experience wirth QB5/1750 or the russian aquivalent.
>> 12-13db of gain are quite normal with 4,5 to 5 KV on the Plates in
>> GG zero bias configuration.
>> With higher voltages you need a very good bandswitch to prevent arcing.
>> 
>> 73, Peter 
>> 
>> 
>> 
>> 
>> My 4-1000A amp will get 1800W key down output with 4400V full load
>> on the plate and 100W drive.  At 5000V things start to arc all over
>> the place.  It is very happy with 70W drive for 1500W output and 4400V
>> full load plate voltage.  Tube is "new old stock", not a BC pull.
>> 
>> Mike, W1NR 
>
>
>-------------------------------------
>Jon Ogden
>NA9D (ex: KE9NA)
>
>Member:  ARRL, AMSAT, DXCC, NRA
>
>http://www.qsl.net/ke9na
>
>"A life lived in fear is a life half lived."
>
>
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>
>


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