K8AC’s wonderful balanced antenna tuner with stepper motors and controller
K8AC Control unit
One of the coolest projects you can do in ham radio is automate an “analog” or manual antenna tuner. I just bought the Palstar BT-1500A, which is a balanced tuner, and I fully expect that it will be great on 160 – 30M with the “Mod Bob” antenna that I wrote about in an earlier blog post. In fact, for 160, I can bypass the BT-1500A completely if I want, but that would require as much work to come up with a safe switching scheme than just using the tuner in line and probably having the L and C set to pretty much zero in both places.
WD4ED also has a set of videos on his project that looks really close to what I would need. If all I could do is set memories for the stepper motor locations, then I’d be set. I’m not too concerned about making the control part fully automatic – just to make sure the remote stepper motors go to their right positions. The reason I don’t need it to be “perfectly” automated is because my SPE Expert 1.3K-FA just needs < 3:1 SWR, which would be easy to do with some memories that I could manually click on ion the shack on the PC. Maybe I’ll tie into the K3 band control line later.
Anyway, there are so many variations on this project with videos and circuits and other hams to contact and get some pointers from.
Last summer I started a project that ended up almost lasting a year – I feel like I took a real “trip around the universe” trying to find the best / lowest noise / highest RDF 160M receive antenna system, and that was a huge success.
This time I expect that this will be a bit more straight forward. What’s cool – I can mount the BT-1500A at the base of the antenna and use my AA-30 to first check to see if just manually I can get the antenna to be < 3:1 SWR on as many bands as I can from 160 – 30M, and maybe I will really luck out – but I expect that something will need to be tuned. Maybe it will be really easy and I can set the roller inductor in one position and then have one stepper motor on the capacitor.
Ed, WD4ED went this route and explains in his video that he went this route because he smoked one of the high power LC based remote tuners (like the MFJ), and his concern has been my concern because I have smoked a remote switch before. This is mainly because the voltage can be in the several KV range when tuning and when off the mark – and also you just don’t know exactly what a remote auto tuner is doing. When I used to use the Palstar AT2K in the shack with my ACOM 1500, I never had any doubt what was going on and that my rig and amp were being operated correctly. I avoided amp faults by being really careful.
The Mod Bob is a balanced fed antenna, so it requires this different kind of tuner – the BT-1500A.
I’m excited that I have such a cool project because on the air – conditions have just been poor, although I did hear W1AW on 160M last night better than its been for a while, and for the first time in several weeks heard a ZS on the long path on 40M this morning.
The “summer project” is a great way to compensate for crummy conditions. I used to assume summer is no good for the low bands, but last summer I proved that is not exactly true. However, having less daylight means it gets harder to DX on the lowbands and still get sleep!
Caveat: I have no lightning. That makes a huge difference.
I have a theory that we really are going to experience better low band conditions “just around the corner” because 160M is so long over due for an improvement. But as always, DX-ing takes a lot of patience – especially on 160M.