Dont waste your money on another fan. Remove that one, clean and lube and it
will be fine for another 30+ years.
If you plan RTTY keep the output down to around 300-400W. A muffin fan on
top to draw out the heat will help.
Real contesters wear headphones.
Carl
KM1H
----- Original Message -----
From: "W5CPT" <w5cpt@bellsouth.net>
To: "Amps" <Amps@contesting.com>
Sent: Monday, October 29, 2007 10:26 PM
Subject: [Amps] Thoughts after a weekend with my SB-200 during CQWW SSB
> Here are some thoughts after a weekend using the SB-200 during CQWW SSB.
>
>
>
> Firstly I will never get over the difference it made. I started with the
> amp in standby (I built my rig to amp interface and included a bypass
> switch in it rather than in the amp itself) thinking that I would only use
> it if NECESSARY. When the first station I called did not answer after 3
> tries I tuned it up and flipped the switch. BANG, he came back to me on
> the first call with the amp. I tried the same thing a few more times with
> exactly the same result so the amp stayed in the contest till the end. I
> will have to upgrade the TV cabling as the bride says it puts lines in the
> TV and makes the picture BLOOM sometimes. I think an S-Video cable from
> the satellite box to the TV should cure that and I had been planning to do
> that anyway.
>
>
>
> The amp is really tolerant during tuning. The TUNE control has WAY more
> effect on the output than the LOAD control does. In fact, while I have not
> gone through and built a TUNE/LOAD chart for the different bands I would
> be willing to wager the LOAD control is always between 4 & 7. The peaks
> are rather sharp with very little gained after the first tune up on a
> frequency. I am using an old Heathkit HM-102 as an output meter, so I
> really don't know how much power it really is putting out. I will borrow a
> Bird and run a calibration between them to see how close the HM-102 is, (I
> am not counting on it, but it is a good relative reading of power).
>
>
>
> To tune the amp, I am running into a cantenna and putting the radio in
> RTTY and using the TX button to key the radio and amp. The GRID CURRENT
> rarely gets over mid scale requiring me to turn down the power. I am
> running about 50 to 70 watts during tune. I did crank the radio back up to
> 100 watts when I noticed that the GRID CURRENT (I leave the meter switch
> in that position since I think it is the greatest indicator of how I can
> damage the amp) was barely moving during SSB TX. I imagine that would not
> be true for CW and RTTY. During tuning I watch the HM-102 for max and the
> GRID CURRENT for max center of meter scale.
>
>
>
> I resorted to using a headset for the contest as the fan is noisy. Not
> really bad, but annoying enough to want to block it out when trying to dig
> my callsign out of the noise and the pile up. Harbach sells a
> replacement. Should I get one of those or would a muffin type fan be
> better and quieter? I might consider two muffins, one top and one on
> bottom to get the air flow without the noise.
>
>
>
> Since I am going to open up the amp should I consider changing the RCA
> jack input to an SO-239? I have a RCA to SO-239 adapter into an L
> connector to feed the RF to the amp. I do not use ALC since two hams
> whose opinion I respect have said it is not necessary. One went so far as
> to say ALC stands for "Automatically Limits Contacts". Also there is no
> adjustment for the ALC on the SB-200 so the set up with my IC-756 would be
> problematic.
>
>
>
> As always I invite comments, suggestions and answers to my questions are
> always welcome.
>
>
>
> Clint - W5CPT
>
>
>
>
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>
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