Category: Construction

I have had a few emails now from people asking for STL files to print themselves some of the wire guides I have used on my disguised cobweb or my 20m wire moxon. So I have uploaded 3D printed wire guides for moxon or cobweb antennas in various different sizes for free download.

I have no idea what size tubes other people are using so I have made a set that covers poles from 7mm diameter up to 25mm diameter in 1mm increments. continue reading

Like many hams, when there is a lot of wind about outside I have to check on how the mast is doing. One thing I did not like was the way the wind rocks the beam back and forth on the rotator. I figured this cannot be good long term of the gears, especially as they seem to be mostly plastic. (Unverified)
When you have something like a 20m moxon up the play back and forth looks quite dramatic. So here I am sharing my YBB boom tether system idea.

For a couple of years now I have had a small arm attached to the stub mast and I guyed that down but it was very short and even with a lot of tension the boom still moved about in bigger winds. Also was quite a lot of  sideways downforce on the rotator (I don’t have a cage).

So in the design and build of my new 20/15/10m tri-band 2 ele beam I incorporated a tethering system on the boom itself at each end to have more effect and balance the side loading to the rotator.

This has proven to be very successful, keeping the boom practically motionless while the 20m moxon element dances all over the place. So I thought I would share it as an idea for others, especially those with a christmas tree stack of beams. I always retract the mast when not on the air, but I know others also retract their masts when high winds are due, and this could help then.

This is the mast retracted to about gutter level and the beam tethered. The left hand tether point is close to the 20m driven because the balance point of the beam is to the left of the 10m driven so it was a small contribution to try and reduce the imbalance on the mounting point.

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This may not seem that radio related but an arbor press is a very useful tool, even if it is not used that often. Most recently I have used it to press in my YBB washers into Stauff clamps for an antenna build. I’m tuning it up in order to use a 5 inch vice based brake press set to do some sheet metal folding, mostly as I don’t actually own a vice to use the brake press set in but also because if I did I would only have a couple of inches of throat to bend whereas the arbor press will give me about 5 inches. These are great tools and not expensive but out of the box they don’t feel or work that great so I decided it needed a simple tune-up.

I actually bought an arbor press because I could get what I really wanted which was a lever press RS (Radio Spares) used to sell. If you have one of these in good condition, I need it!!

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This was another Covid lockdown project in 2020 to enable me to do some over the air audio checks with locals and maybe give some points away in contests to the locals (my QTH is very poor for VHF/UHF). I wanted something small I could put in the attic. I figured a simple DK7ZB dual band 2m/70cm yagi in the loft with a single feeder would be ideal.

on this page:
https://www.qsl.net/dk7zb/Duoband/4+5_2m-70cm.htm

Martin DK7ZB describes his design for a single feed dual band yagi with 4 elements on 2m and 5 elements on 70cms on a compact 1m long boom.

I already have my element cutting jig  (see here) so cutting the elements was easy enough as usual. I went for the 8mm elements to make it nice and light.

To assemble it I decided I would 3D print not just the dipole box but also the element mounts themselves. The beauty of this over commonly used mounts like the Stauff clamps (see here) is I could design in a feature to ensure the elements are nice and perpendicular to the boom. I also don’t like drilling my tubular elements. For a start it weakens them and also adds a place for inaccuracies to creep in.

So this was my design for the element mount:

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So many commercial and home brew constructors use Stauff type clamps for attaching yagi elements to the boom but I have until now avoided these because I hate the huge bolt holes that are typically at least 6.5mm in diameter which is sloppy even on a grossly overkill M6 bolt. Of course these clamps were not designed for making antennas but are extremely useful as they come in pretty much every tube diameter there is. So after many builds avoiding these clamps I decided to come up with a way to use them that would satisfy my exacting standards. One night instead of being able to sleep I came up with the YBB washer.

Usually instead I have been making my own elements mounts in some way or other but I am building some HF beams and it’s just convenient to use off the shelf Stauff clamps so I decided I needed to do something about this issue. I recently assembled a commercial beam that had a tapped boom so next to no slop bolt to boom but you could move the element side to side about ±6 inches or more at the ends of a 50MHz element. I had to use a square to mount them: continue reading