[Amps] Thoughts after a weekend with my SB-200 during CQWW SSB

[jeremy-ca]

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 at bellsouth.net>
To: "Amps" <Amps at 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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