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SB-221 10 / 15 Meter Upgrade - Heathkit sb-220 10m - install ?

Discussion in 'Amateur Radio Amplifiers' started by N0OHL, Dec 13, 2019.

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  1. N0OHL

    N0OHL Ham Member QRZ Page

    Getting ready to add 10m and 15m to my newly acquired SB-221. After looking at sb-220 and sb-221 manuals it looks fairly straight forward, but thought I better ask if there was an upgrade instruction sheet for this modification. I understand Heathkit did offer this upgrade to the SB-221 - so was hoping there might be an install sheet(instructions) out there somewhere?
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    SB-221 already covers 15m. You mean 12m.
     
  3. W1QJ

    W1QJ Ham Member QRZ Page

    Heathkit offered a special kit with all the necessary parts needed, along with instructions to add 10 meters to the SB-221. Unless you find an original kit that has all that material (highly unlikely) you are in the dark on the adding everything individually that are the exact parts. There are a couple of caveats when going about "piecing" together the necessary parts. First and foremost, the kit that was sold for adding 10 meters to the 221 was intended to be used at the time of the original build and not after the fact. When you consider that you need to remove both the band switch and the input switch and change them, as well as adding a 15 and 10 meter coil, it is quite a bit of work and is time consuming to say the least. Most hams opt to simply purchase an entire "L" chassis removed in tact from an SB-220 and just install it in the 221. It is probably the easiest thing to do. Replacing the the band and input switch is no easy task. You should also be aware that pin 1 and 7 on the input switch were reversed between the 220 and the 221. That right there would drive you nuts if you didn't know that going inot doing it either way.
     
  4. WL7PM

    WL7PM Ham Member QRZ Page

    If I were going to mod a 220, it wouldn't be for 10 meters... I'd want to get it to run 160 meters, There's a band for a pair of 3-500's
     
  5. W1QJ

    W1QJ Ham Member QRZ Page

    Any 160 meter mod for the SB-220 would be somewhat of a compromise much like adding 6 meters along with the other bands on a 220. A compromise. Quite a few modified SB-220 for 160 fell into my hands and in most cases they were failures or caused failures as far as I could tell. Although some have done a good job at adding 160, the successes are few and far between. I can tell you from experience that it would be much easier and better in the long run to just get just about any junker amp and make it a mono band 160 meter amp. It will play better than any add on mod. With the right recipe a mono band 160 amp is a one day job. Of course if you have to engineer it from scratch it would take longer.
     
  6. WL7PM

    WL7PM Ham Member QRZ Page

    I have a couple solar cycles experience with 160 and 10 meters, but admit to being VERY new to QRO.
    Finding great utility for Kilowattage on 160 meters, and zero need for same on 10.
    .
    Would you consider the SB220 a reasonable candidate for a 160 meter MONOBander, or do you still think a different " Pair of Glass" superior ?
     
  7. W1QJ

    W1QJ Ham Member QRZ Page

    =
    The SB-220 should make an excellent 1500 watts pep SSB 160 meter amp. Will probably run just shy of that on CW as well. For DXing purposes it should hold up at the output. Probably not at contest level duty cycles however. As a mono band amp the efficiency will go through the roof compared to an add on band. I tried the exact same thing with an SB-200 and the results were totally flooring. Did a mono band 160 on a Clipperton L and at 46 pounds it does full legal without exceeding plate current. Last one was an AL-1500 as a mono band 160 45w=1500w
     
  8. N0OHL

    N0OHL Ham Member QRZ Page


    Thanks for the tips -- I will watch for the Input Switch difference --- Still hoping someone may have the old Upgrade Instruction sheet that you mentioned.
     
  9. W1QJ

    W1QJ Ham Member QRZ Page

    The instruction sheet isn't really necessary. Once you have accumulated all the needed parts all you need to do is go to the SB-220 schematic and follow it. Just remember that when you rewire the new input switch and add the 15 and 10 meter coils that you account for the pin1 and 7 flip. Basically all that means is that the input caps and the tube side caps on the input coils are flipped on the SB-221 so when wiring the new switch and the additional 15 and 10 meter coils you make a decision on how you will compensate for the previously wired SB-221. You can either tap the coil you have which is easy or obtain an already tapped coil. Based on what you will spend locating the needed parts and the time you will spend, it is probably easier to obtain an SB-220 "L" chassis network and do a simple mechanical swap with only a couple of solder joints. If you decide to go that route you can contact me off list and I can fix you up with a network.
     
    KD2ACO likes this.

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