on 4/3/01 8:47 PM, Phil (VA3UX) at phil@vaxxine.com wrote:
> 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 ?
Yeah, I wrote it in a hurry and wasn't thinking clearly. You are absolutely
correct. Call me a loser. I know some here will. Let me be the first to
say it: Hoof and Mouth disease affects humans.
>
>> 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.
I understand what Eimac's numbers say. Believe me, I tried for them when
building my amp. I've never seen that kind of gain. I've asked others who
have built 4-1000A's as well and they haven't either. I will say the tube
has a lot more gain at lower frequencies. On 80M, I can drive mine with
about 50 Watts to legal limit. On 15M where I am least efficient, my drive
is nearly 100 W.
Are there more efficient tank circuits than mine? Probably. That's why I
suggested folks not use the B&W coil/switch combination as the coil
inductances aren't anywhere near what is needed in the 4-1K.
>
>> 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%.
They are especially inaccurate at mid scale. I just did some rough
calibration and comparison on mine as I replaced a meter movement. At the
low end and high end of the meter, the accuracy was much better between
meters than at mid scale. Just an observation.
73,
Jon
NA9D
-------------------------------------
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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