Steps to the Son of Mod Bob . . .

I have three aluminum elements up for the Mod Bob and will take down the center element:

I already have a coax cable running from the Array Solutions switch you see to the left that goes all the way to that far element.

The outside elements have the wire attached and it comes down to the center via a cool resin plastic (DXE) guy ring. I have figured out how I can solder the two wires using what is essentially a “bow and arrow” technique:

The two outer elements already are “leaning in” a bit from when I made the wires taught and brought them down to the center balanced feed. I can get on my tall ladder and pull and clip the wires in a way that keeps the bend on those elements. I will solder them and let the two elements “snap back” to where they want to be – which is straight up and down. If there is a little center sag – so be it. If there is more than I’d like, all I have to do is loosen up the clamps on one of the elements and just twist the element around. At the top of each element I have three wire ties for strain relief, and the wire has a very secure lug ring which is crimped, soldered and covered in Alumox – so its very strong and will stay electrically and mechanically connected.

Worst case – I can just loosen one element and just lower it until I can connect the two wires and solder and then add liquid electrical tape. So, the steps:

  1. Take down center support and get the two wires connected and soldered. The BT1500A and its box needs to be set aside – I will re-use the box and sell the BT1500A
  2. Run a new long control cable out to the far element
  3. Set the u.RAT remote tuner at the base in the box and wire up the control line
  4. In the future – the old control line that goes to the (now removed) center element will be used for the other element – where it will switch the grounded loop line in and out just by supplying 12v that is switched from the shack. Since my main goal and priority is 160M, I will only worry about that first. I might just use the Inverted U as the 160M antenna – I might not run a
    parallel line that is an Inverted L. Here is the difference:
    I think trying to add the Inverted L wire in parallel is a negative because the pattern is not much better and the added weight and complexity is simply not worth such little improvement
  5. Test the u.RAT on all bands and tweak where need be. I will see if maybe I can have a single inductor installed where the only moving part that I need is the variable capacitor. That would be superb if I can pull it off. This is because I don’t like how long it takes to move the roller inductor – it is always slower than the variable cap. I also would like it even more if I could use the Comet vacuum variable capacitor instead of the air variable cap. In fact, if I could just use a variable capacitor and a fixed inductor, I might just use an analog rotary encoder and then I could sell the BT1500A and the extra KPOD that I have. Then my control box would be two switches and a rotary encoder. The remote is a single stepper motor on one side and a relay on the other. Very simple and very reliable.
  6. Re-run the center control line to the northernmost element in preparation for adding the relay to switch in the grounded loop wire. Until I actually have the relay in place, I will use an alligator jumper when I am testing tuning on 80M. Because John says that I should expect 70 ohms on 80M:
    I think this might bode well for just having to use a variable capacitor and a fixed inductor

I can’t package the u.RAT up until I perform these experiments. This will no doubt take the longest amount of time, and it means it will be a full day job. I think impedance on all four bands will be in the range – mainly because of the grounded loops 70 ohms. I know with the Mod Bob – 80M was much higher impedance than the other bands, and that’s why the Palstar 1500A was required. I’m quite sure this solution all the way around will be better and easier too.


3 Comments on “Steps to the Son of Mod Bob . . .

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