[Amps] Amps Digest, Vol 167, Issue 38

[Gary Smith]

Fwiw, I have noted the higher frequency I run my Ameritron AL-82 
(roughly same amp as a SB-220) the dull red in the 3-500's turn towards 
white.

Gary...wa6fgi


On 11/29/2016 9:00 AM, amps-request at contesting.com wrote:
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> Today's Topics:
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>     1. SB-220 update & gettering (Jim Thomson)
>
>
> ----------------------------------------------------------------------
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> Message: 1
> Date: Tue, 29 Nov 2016 08:02:28 -0800
> From: "Jim Thomson" <jim.thom at telus.net>
> To: <amps at contesting.com>
> Subject: [Amps] SB-220 update & gettering
> Message-ID: <B21DDC1926004CABA51FDB54AAC41623 at JimPC>
> Content-Type: text/plain;	charset="iso-8859-1"
>
> Date: Tue, 29 Nov 2016 01:16:23 +0000 (UTC)
> From: Catherine James <catherine.james at att.net>
> To: <amps at contesting.com>,  <jtml at vla.com>
> Subject: Re: [Amps] Amps] SB-220 update & gettering
>
>
> 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.
>
> ##  I would be careful about running an SB-220 at 1300 watts out on CW.  It only has a 500 va xfmr in it.  Operate
> it in the CW low B+ position  at aprx 650 watts out.  The sb-220 was designed around the old rules, like  650 out on cw
> and 1200 w pep out on ssb.
>
> ##  The LC ratios in the SB-220 tuned input are not optimum, the Q is way too low.  The C1 + C2 caps need to be much
> larger, and the coil needs to be smaller.
>
> Jim  VE7RF
>
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> End of Amps Digest, Vol 167, Issue 38
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