Jay, the people whose advice you're following are simply wrong. There is no
series resonance in the SB-220 plate choke that would affect performance or
cause damage in either the 18 or 24 MHz band. That is true of some other older
amplifiers, but not this one.
I suspect I could make your SB-220 arc at either the tuning capacitor or the
bandswitch (depends on the era in which your SB-220 was built) simply by
running the loading much too light, or by causing a fault in the antenna.
Both these topics have been discussed several times on this reflector.
The correct amount of loading is not a matter of "belief." It has to do with
loading for maximum output (at whatever plate voltage) and then adding a little
bit of additional loading if you are concerned about optimizing IMD performance.
73, Pete
At 05:45 PM 3/3/2007, you wrote:
>Pete -
>
>You loss the bet. There was never an issue with of
>arcing in my SB-220. The advise came from a number of
>SB-220/221 users when I asked the same question.
>
>The reason given to me was that damage to the filament
>choke could occur when used on 17m and 12m running
>full power.
>
>Since the output is quite sufficient in the CW/Tune
>position, use under SSB never entered my mind.
>
>I have no problem with loading the amp "heavy" in the
>CW/Tune position. I don't believe in "Light" loading.
>
>73,
>Jay/AF2C
>
>
>
>--- Pete Smith <n4zr@contesting.com> wrote:
>
>> I don't think that is correct either, Bob - I use my
>> SB-220 on 12 and 17 in the SSB position all the
>> time. I'd be willing to bet that this advice is
>> based on having arced the tuning capacitor a time or
>> two while finding the right setting with the loading
>> too light.
>>
>>
>> >Use LV position, and why is that Jay? I would
>> agree to get within a
>> >reasonable setting with LV and pop her over to
>> SSB... But why do you say
>> >stay with LV?
>> >
>> >BOB DD
>> >
>> >-----Original Message-----
>> >From: amps-bounces@contesting.com
>> [mailto:amps-bounces@contesting.com] On
>> >Behalf Of Jay Musikar
>> >Sent: Saturday, March 03, 2007 1:33 PM
>> >To: Win; Amps@contesting.com
>> >Subject: Re: [Amps] Loading SB-220
>> >
>> >GA Win -
>> >
>> >1. Loading on the WARC Bands must be done in the
>> >CW/Tune Position.
>> >
>> >2. Do not operate the amplifier in the SSB position
>> on
>> >the WARC Bands.
>> >
>> >3. 17m
>> >Band Switch - 15m
>> >Tune - Top of the 40m markings
>> >Load - 4.0
>> >
>> >4. 12m
>> >Band Switch - 10m
>> >Tune - 20m (just left or CCW)
>> >Load - 4.0
>> >
>> >The are a number of variation on which Band Switch
>> >Position to use and relative Tune and Load
>> settings.
>> >
>> >In either case DO NOT use the SSB postion (HV).
>> >
>> >Good Luck es 73,
>> >
>> >Jay/AF2C
>> >
>> >--- Win <w0lz@winlyn.us> wrote:
>> >
>> >> Can someone comment on loading the SB-221 up on
>> 18
>> >> and 24 MHz. using the
>> >> existing band selections. Will the input Z
>> change
>> >> much? Which band switch
>> >> positions to use for each band? At the moment I
>> am
>> >> really only interested
>> >> in 18 MHz. As conditions get better, I will
>> >> probably become interested in
>> >> 24 MHz.
>> >>
>> >> Thank you in advance.
>> >>
>> >> Win, W0LZ
>> >
>> >
>> >
>> >
>>
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>
>
>
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