Palstar BT1500A (semi) Automation

WD4ED’s stepper tuning project

I have three antennas – two that are resonant – a home brewed 20M 2 element yagi and a 2 element 40M phased vertical array. They both work great with the new SPE Expert 1.3K FA full power solid state amplifier that I just received a few days ago. Here is another video on a great home brewed Arduino based auto tuner:

The non resonant antenna that I have (that requires a tuner for multi band use) is my “Mod – Bob” 3 element vertical array.

Its resonant on 160, but I also want to use it on 80 and 30M, an on those two bands, the SWR is way too high for my new amplifier. Here is a video of my test setup at the base of the center element of the Mod Bob:

The Rig Experts AA-30 shows the Mod Bob as resonant on 160M, and really no where else. Luckily, with the same switch settings on the Palstar BT1500A (> 50 ohms and Low C), the only thing that needs to be done is to power the tuner up (which activates a relay inside), and then tune the L and C front panel controls. This means a 12V DC control line with whatever USB command line wires would make for an easy project – perfect for 2 stepper motors to control the BT1500A. Here are the plots once I manually tuned the two controls for 160, 80 and 30M:

160M at the BT1500A

80M at the BT1500A

30M at the BT1500A

My goal will be to control the stepper motors using a program that has memories. One click of a mouse and the tuning controls move for 160, 80 and 30M.

I don’t see any need to also tie it into the K3’s RS-232 band data line – but maybe I will do that later. For now I have emailed Ed, WD4ED, who no doubt can give me a parts list for this project since he did the exact same thing.

One good thing I found in the SPE Expert 1.3K FA manual is that I will have to disable the ATU in the amplifier when I use this remote tuner. That is easy because its menu configurable – when I switch to 160, 80 or 30M, the amplifier will automatically bypass the ATU.

I think what I need is:

  • Two stepper motors, perhaps bipolar (?)
  • An Arduino board (I have one already)
  • Two stepper motor drivers
  • Anything else?

I’ll first just play with the Arduino and other boards and whatnot in the shack. I’m guessing the voltage for the stepper motors will be 12V, and not sure if the Arduino board and drivers will stay in the shack? Hopefully all I will need are voltage lines for the Palstar and control lines for the two stepper motors. I already have an 8 wire heavy duty rotor control cable run from the shack to the Mod Bob – so this could be a fun and easy project.

While the bands are in the dumper – I at least have a very fun and worthwhile “summer project” – just like last year!






Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: