Modify SB-200 for 6 meter

[SM7CLM]

Does anyone know how to modify a SB-200 amplifire, so it will work on 6meter ??
73
SM7CLM
Lennart

[WB2WIK]

Although some have done this, I wouldn't recommend it. SB-220 or AL80A/B is a much better, easier and more stable 6m modification.

Always better to use tubes actually rated for the operating frequency (or preferably much higher).

[SM7CLM]

I also have a SB-1000, is that easier to modify
sm7clm

[WA6MHZ]

The SB-1000 is a much preferred unit to mod to 6. It is easy and, with a single 3-500Z, will put out about as much output as the SB-200 would. Just change out the tank circuit for one resonant for 6, and mod the input circuit, and U are good to go! I wish I had a SB-1000 myself to do that job!

[WB2WIK]

I also have a SB-1000, is that easier to modify
sm7clm

I agree, much easier. The SB-1000 is very similar to an Ameritron AL-80 series amp. The 3-500Z will run 800W PEP output on six meters. I've modified two AL-80Bs for 50 MHz and they both worked perfectly.

[SM7CLM]

Thank you Steven,
I just met the right guy, who knows how to modify my SB-1000! Yes?
I am ready for some instructions..! Please....
By the way,,, what a great picture of you and your daughters.
73
Lennart /sm7clm

[WB2WIK]

Thank you Steven,
I just met the right guy, who knows how to modify my SB-1000! Yes?
I am ready for some instructions..! Please....
By the way,,, what a great picture of you and your daughters.
73
Lennart /sm7clm

I can send you complete instructions for the AL-80B 6m mod on Monday when I can access my office, where the file is kept.

The component designations will be different for an SB-1000 but the circuits are quite close.

If you have a 5-30 pF 5kV vacuum variable capacitor available, the conversion is quite easy. A small value air-spaced capacitor can work, but it's a lot trickier as many won't really work at 50 MHz (some will). The vacuum variable takes all the experimenting and guesswork out of the job.

[SM7CLM]

Please do, Steven...
I will be very thankful, if you will send me the instructions!
I do not have the variable capacitor, but I will put an add in and see what to find!??
You made my day..
73
Lennart

[WB2WIK]

Please do, Steven...
I will be very thankful, if you will send me the instructions!
I do not have the variable capacitor, but I will put an add in and see what to find!??
You made my day..
73
Lennart

You'll have the detailed instructions on Monday.

Look for a 30 to 50 pF "maximum capacitance" variable cap, 5kV or 7.5kV; these are available in 3-30 and 5-50 pF, and maybe some similar capacitance ranges. What you need is something with very small minimum C, as to achieve a reasonable plate tank Q on 50 MHz with a 3-500Z or similar tube you're really only using about 6-10 pF of plate tuning capacitance in most cases. You can go slightly higher on the "C" and smaller on the "L" to still achieve resonance, but it makes tuning trickier and more critical. I like "smooth and easy" tuning which is easy to accomplish.

You can re-use the original plate TUNE capacitor as the new LOAD capacitor for six meters, it's almost perfect for that and with its fairly wide spacing, it will never arc.

73

Steve WB2WIK

[WB2WIK]

SM7CLM: Conversion instructions sent to your e-mail address this morning.

73 Steve WB2WIK