Ham Radio – interests wading

I have been active in Amateur Radio on and off for over 43 years.  Things have changed quite a bit since I started.  I remember the days before the Internet where I would listen for hours to other ham radio operators talking about their projects, describing various circuits and enjoying other ham’s conversations.

I was always learning something and getting involved with interesting conversations.  Today it’s different. You don’t have as much on the technical side.  Some conversations make me cringe, either too political or religious, or just plain bad behavior.   There are always weekend contest which interfere with my enjoyment of the hobby.   I am not very  interested  in participating in contests and have found that contesters  are getting more rude through the years with no concern other than making a contest contact.

The digital modes seem like the are now driven by total automation. I used to enjoy the low powered modes that kept the bandwidth small. It seems like FT8 has taken over most of the digital modes now.  In my opinion,  FT8 is a joke with people running higher and higher power to make contacts; where is the fun in that?

I still enjoy a CW conversation now and then, but when your noise level is at S9 due to all the lousy electronics in your neighborhood, and the band conditions are terrible, it’s a bit turn off.

So it’s time to shift hobbies and if anyone knows me, they know I have plenty.  I’ll be sharing some astronomy projects as well as my learning process regarding astro imaging.  I’ve done CCD imaging back in the mid 90’s with a Cookbook Camera.  But, the current technology is amazing.

73, for now.

SB-200 Modifications

The Heathkit SB-200 amplifier has been around for years and many are still in use.

I rebuilt my Heathkit SB-200 that I obtain from e-bay.  This one was in bad shape but the price was right.  It was dropped, bad tubes, and definitely been used.  I slowly rebuilt the amp and got it fully functional. Initially I rebuilt the power supply using  Harbach Electronics PM-200 Replacement Power Supply Module. Refer to their website.

I came across a web site,  http://www.xs4all.nl/~pa0fri/Linairs/SB200/sb200eng.htm, which PA0FRI explains in detail on how to modify the sb200. I went ahead and modified my SB-200 according to his website and followed most of his recommendations. The following items are what I wanted to accomplish with these modifications:

  • Tube Protection. Fuse the high voltage to reduce catastrophic failures.
  • Soft Start to limit the primary in-rush of current and slow the rise of anode voltage. This protects the filaments and rectifier diodes and permits the use of a lower current primary fuse.
  • Stability
  • Change amplifier key to support modern radios.
  • Reduced filament voltage. On my SB-200,  I had almost 7 Volts on the Filaments.  I ended up using a loop of 18 gauge Teflon wire to drop the voltage until the filament voltage was in an acceptable range.
  • ALC Adjustments is now easily adjusted.  This is nice when I use it with my Drake transmitter which I can easily overdrive.  The amplifier is very stable and is well protected.
  • Faster QSK Operation.  I  wanted a faster transmit/receive transition, by  updating  the input and output relays did the trick.
SB-200Modified Amplifier

SB-200 Modified, Schematic Diagram

These modifications are based upon PA0FRI’s modifications.  I give him all the credit. I am impressed with the stability of the amp and have not had any issues.  Please refer to his  website: http://www.xs4all.nl/~pa0fri/Linairs/SB200/sb200eng.htm,

The modified SB-200 schematic diagram is shown below.  This uses a “Key-All” circuit board for keying the amplifier. This board may still be available from Jackson Press.  I also incorporated a “soft-start” from Harbach Electronics.

Here is the meter switch wafer detail.  This needs to be modified per the schematic above.

Input/antenna relay uses a reed relay for the input and a VAC relay for the output side. I had to had a 24V power supply for these relays since the original used 117V.

SB-200 Modified Amplifier Gallery: