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Re: [Amps] Amps] SB-220 update & gettering

To: <>, <>
Subject: Re: [Amps] Amps] SB-220 update & gettering
From: Catherine James <>
Reply-to: Catherine James <>
Date: Tue, 29 Nov 2016 01:16:23 +0000 (UTC)
List-post: <">>
John Lyles <> wrote:
> Good to hear you found the keying circuit issue and fixed that. Would 
> hate for that relay to only partially close while a kW of RF is trying to 
> come through the contacts.
**shudder**   Yes.  Fortunately I put no more than 5W of exciter power into it 
before finding and fixing that problem.

> You don't need to see cherry red with those tubes, but in high voltage 
> SSB setting you might see a dull orange on one or both tubes. 

I found that at full power, 1200-1300 watts CW, I get to a dull red/orange on 
the bottom half of the plates.
I won't be routinely running at that power output, however.  I'm aiming for 
800-900 watts CW and about
a kilowatt on SSB.  On 40 meters, about 60 watts drive and SSB plate voltage 
setting gives a kilowatt SSB PEP.

> If you are getting 1400 watts on 40, those tubes are fine and the vacuum 
> pressure
> is very good. I would recommend not worrying about getter activation, it is 
> apparently doing its job - FB.

I made more precise power measurements on 40 and 80 tonight.  In CW exciter 
mode, SSB switch
set to high power, 100 watts drive on 40 meters gives me 650 mA plate current, 
2800 volts plate, which
works out to about 1250 watts both on the meter and calculated (assuming 66% 
efficiency).  On 80
meters, I get 750 mA plate current and 2700 plate voltage, which works out to 
about 1300 watts.
And that does give me the dull orange glow!

> BTW, what sort of power do you see on 10 meters with that amplifier. This 
> starts to show the
> effects of losses  in the output network, and in the parasitic suppressors on 
> the anode connections.

On 10 meters, I took it up to 60 watts drive and got about 500 watts out.  At 
that point, the tubes were glowing brightly,
brighter than they did at 1300 watts on 40 meters, so I chose not to take it up 
any higher.  My guess is that it would
peak about 700 watts, maybe a tad higher.

I will seldom if ever operate on 10 with an amplifier.  Mostly I use one on 20, 
40, and 80 meters SSB for rag chewing,
on CW for DX, and I also operate on 30 meters without one.  Most of my domestic 
CW is at 50 watts, and if the bands
cooperate I don't need more. I don't find the high bands very useful at this 
point in the cycle, especially since I am not
retired and not home when the sun is up and the day bands are open.  My typical 
operating time is around 8 - 10 PM.

40 meters was awful tonight.  I worked two stations SSB, one near Dallas and 
one in Cincinnati area. Both were very
weak, especially the first one.  The TX station gave me a 55 report, despite 
the kilowatt into a good inverted vee up 50
feet or so. I could barely hear the Ohio station at all, despite low noise 
levels at my rural QTH.  This is about as bad as
I've seen conditions in the past 3 years!  But that's why I'm getting the 

> Does yours have the stock input tuning on each band? I 
> followed the techniques outlined by R. Measures years ago
> for mine, and  de-Q'd the input on each band with a different L/C value,
> and got better match across the bands than stock.

Mine has the Rick Measures anti-parasitic modifications with nichrome wire etc.
It came that way, so I didn't make any modifications there.  I have not made any
changes to the input tuning circuit.

> In such instances, one tube might have more anode color.

They both appear to show the same anode color at all times.

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