Sometimes I want to chase. At home, I have a horizontal deltaloop 80m. It’s great on the lower bands but mediocre above 20m. I wanted a beam antenna, not so big, not so expensive and multiband. After looking at the designs, I went for hexbeam. The commercial models are way too expensive for what I do, and because I like to build things more than using them, I decided to make one “from scraps”.
This thread will be a journal. Since I’m only starting the project.
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1. Construction of the antenna
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The base plate will be an aluminium frying pan. 0€ from the junkpile.
Deciding between making a simple mast or buying a telescopic mast, not sure yet. A telescopic mast would be much handier for antenna setup and maintenance. Crafting such a mast seems a bit tricky, and since I don’t have the tools for it, I’m afraid it might not be worth it financially because galvanized pipes are sold in 6m long and it’s also usually quite hard to find pipes fitting tightly in each other.
Making the rotator from a 12V DC gate motor I had in my junk pile. I’m already working on the software for it, as it will be controlled via an ESP32.
This weekend, I’m crafting a center post. It turns out that I couldn’t find an easy way to make it very neat and fully enclosed as I wanted, so I had to follow the approach used by other homebrew hexbeams, with the coax on the outside. I’m aware of the negative impact water can have if it gets into the coax. Most builders use liquid tape to seal their coax.
However, perhaps organizing all the connections to face downward would be enough to prevent water from running in? Still afraid of capillarity though …
Now I need to make a good choke balun an attach it at the top of the center post. Then check it with vna, hoping that all those “arrangements” do not ruin the impedance of the feed line.
Where did you procure the PP clamps? I’ve been trying to figure what to use for a collapsible mini-hex using fiberglass segmented tent poles and haven’t been able to find a decent source stateside. Using an old pan as a construction base is a great idea and I may need to use that for my build since I still haven’t decided on my center support!
You will find the PP clamps in any hydraulic shop since they are made initially to hold hydraulic hoses. I bought mine here.
In the US I don’t know but a quick google search give me many websites like https://theclampcompany.com , you could also try local farming / tractors stores ?
Yes it’s an idea. I could also fit the whole center post in a PVC pipe, whith holes for the wires to go through.
I’ve been working on the software part of the rotator lately.
So what do we have here ?
ESP32 as the main controller
IBT2 Hbridge motor driver
12 V motor, I believe it’s from a car wipers, I soldered a bike gear, it will transmit the rotation to the mast via chain.
Optical rotary encoder with a rubber wheel (it will be positioned against the mast, not against the gear, the display in the video is for developpement only)
How does it work
The ESP32 is running a small web server with a simple page. I have an azimuthal map and a 30° rotating sector showing the main lobe direction of the hexbeam. When I click “rotate,” a command is sent to the H-bridge to run the motor clockwise or counterclockwise at the desired speed. The mast rotates accordingly. While rotating, the mast turns the rubber wheel of the optical encoder, which reports the position to the ESP32. The ESP32 then updates the angle on the webpage, rotating the sector on the map.
What’s missing at the moment is a way to save the angle, even when the power goes off. Currently, the beam’s angle is lost if the ESP restarts. I’m still unsure about the best method to address this, but I see two possibilities:
Saving the angle in the non-volatile memory of the ESP32.
Adding a hardware “calibration” switch, such as a limit switch, aligned to azimuth 0°, combined with a small bump on the mast corresponding to the front of the antenna. When the bump triggers the switch, the angle is reset to 0 in the ESP.
It looks like the Stauff 109.5a-PP-H or 109.5a-PP are some of the closer matches. Unfortunately I’m only finding it from the direct US distributor with $15 minimum shipping. Some other distributors list it but don’t have stock.
I guess the adventure of finding something locally will be needed since shipping is more than the product! Reminds me of why some of these parts look familiar, but I didn’t buy them last year. Oh, also none of these specify the mounting hardware spec; presumably because they want you to buy their pre-kitted packages. Alas.
I’m not sure what you need as “mountaing hardware spec”, but in the technical details sections, you can see all the details: here and there.
It’s always a problem with online shopping, and it’s getting worse and worse as shipping costs have been dramatically increasing over the years. I just ordered some toroids and ended up paying around €22 in shipping costs for items worth only €5. Since it was so expensive, I padded my order with all kinds of gear that I’m sure I’ll never find elsewhere, let alone in a local store. Sometimes, it’s just easier to pay and have it delivered to your mailbox than to waste an entire day driving, burning fuel, and visiting hardware stores that usually have a very limited selection.
I was more concerned about the recommended hardware size/thread and dimensions for acceptable sized washers to avoid the mounting plate cost/complexity. Otherwise it’s off to fiddle with hardware until I get something that fits. Unfortunately just part of off-label use, I think.
Very true on the potential advantage of shipping and its real cost. Unfortunately my limited mechanical (versus electrical/electronics) supply needs make the hit on these parts higher.
I used A2 stainless steel bolts, 6mm diameter, 50mm long. They are too long but I can cut them if necessary. Now if I had more choice, I would use round bolts with Allen heads, like this:
I don’t think there will be a lot of constraints on the clamps, so I didn’t put metal plates on them.
Washers, well if you want them in the hole, between the bolt head and the clamp, you will need very small washers. I didn’t use any since my classic large head bolts were judged enough to no damage the clamp.
You have a bunch of other options than an incremental encoder. Don’t forget that as well as azimuth, you may also want to know how many turns of windup are in your coax. i.e. you want (say) 3*360°
magnetic absolute rotary encoder IC. This is probably the best solution given weather resistance and cost. (lots of modules on AliX)
A normal non-360° pot geared to N turns of the mast. Since you can’t wind-up the coax anyway, this is not a limitation. A 10 turn pot is obviously less limiting and a better choice.
A pair of ordinary pots driven by a cam ≅ 90° to each other
a pair of 360° pots at 90° (or sin-cos potentiometer)
A small analog video camera imaging a disc/cylinder with the angle printed on it. e.g. a car backing camera. No microprocessor, H bridge etc. Simple reversing switch for the motor.
It was my first idea. But from what I understood, I would have to put the magnet at the butt of the mast, meaning the mast would have to “fly” above the module. Not very convenient for my setup.
I needed something where I could get the angle from the side of the mast.
I don’t understand what you mean by “pot” in your other propositions.
I think I could address the calibration of the antenna + the turning limitation with the same set of limiting switches. Maybe limiting the turning to -180 / + 180°, with two switches like in this schematic, viewed from above:
Gear or toothed belt or pulley+string+tension spring (string is wrapped 3 turns around the mast and pulley), off to one side.
If the magnet pulley is 5x the diameter of the mast, then you get ±2.5turns absolute position
Potentiometer = variable resistor
e.g if you couple a 10 turn pot 1:2 to the mast (i.e. pot pulley = 1/2 diameter of mast), you have ± 2.5 turns of absolute position from an ADC input
By the way, you should take the side load with bearings and let the pot float. Potentiometers don’t last very long if you are pulling the shaft sideways at all.
Oh gosh yes, that’s a very good idea. Just get the value of the resistance with a simple analogread and boom I have the value of the angle at all time. This solution is very robust and easy to implement! Thank you.
It’s not done yet. I don’t know how strong it has to be. Also I don’t have the mast yet. I’m waiting for the genius to strike me but it’s not happening. I will end up buying a commercial aluminium telescopic mast, 280€ for 9.5m, 65mm bottom diameter to 40mm upper diameter. With some guy lines it should make it.
Because I can’t solder aluminium I made the center piece in metal, and the center post is tightly fitted on a metal tube which is soldered to a metal plate. Same for the lower part. A metal tube will be soldered to the metal plate and the mast will fit inside.
I might add 3 reinforcement legs (orange in the picture) to make sure the pan will not tilt on the mast in case of wind.
C’est pas plus mal que si c’était pire 
