Category Archives: Custom Antennas

Dipole up :)

Well yes, the TEV-1 sucks as ever, so I finally got my bum into gear and sorted out stringing up the 40m dipole.. Center is hanging from a tree in the back corner of our yard. One element comes back towards the house, strung up to a 6m pole conveniently stuck down between some formwork in the retaining wall at the side of the house (Pleasantly surprised to find a sturdy mounting point so easy without bolts required!).. The other element took a bit of work – trimming a bunch of dead branches from trees in the park behind our property, but finally (and after using the aforementioned 6m pole to get a pull-rope into the top of one of the trees, much to the amusement of the lady next door putting out her washing) it’s up and it’s all quite easy to take up and down if I want to finish the ‘fan’ part of the dipole build..

We’ll see how it works, I may just get off my butt and pull the buddipole out of its bag where it lives in the back of the Pajero, and set that up instead of having all the other stuff strung up permanently.. we’ll see ๐Ÿ™‚

So far it’s working GREAT on 40m – put it up as it had been at the old house, and was getting a solid 1.2:1 SWR, so that’s good enough for me for now ๐Ÿ™‚

Dipole center balun up, and west-side element strung into the park!
East-side element is up :)

The first test ;)

First test is to simply build a 40m dipole. Aka, ensure that the centre is built correctly..

Dipole center+Balun is completed, and ready to go:

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Completed dipole centre with feedline connected up, and end cap in place

Multi-band dipole

With the two 8m tall masts erected on each side of our yard, it’s time to build the dipole!

Because I don’t like doing things by halves, I’m building a ‘multi-band fan dipole’. ย This is comprised of three dipoles, in a ‘fan’ layout. ย As explained here, I have so far built the centre insulator.

Center Insulator:

The 'center insulator' for my tri-band fan dipole

Now to run two lengths of copper wire up the sides (1.0mm mains cable should do nicely? ๐Ÿ™‚ ), build an ugly-balun on the bottom, and measure out the cable lengths for the dipole.. ย The top run (40m band) will be 3mm stainless steel 7×7, as it’ll be carrying the weight. ย The lower two (or maybe three?! ๐Ÿ˜‰ ) runs will be simple speaker wire.

Wire lengths should be:

Band Centre Freq Wire Length Notes
40m (+15m) 7.100Mhz + 21.3Mhz 20.28m (4% short) (I’m not interested in the upper 200khz of the band, as I don’t do CW)
20m 14.15Mhz 10.61m
10m 28.5Mhz 5.263m (note, using 28.5 rather than 29, as I am more interested in digital modes than anything else. And 2Mhz bandwidth is probably hoping for too much ๐Ÿ˜‰ )

Note: this *was* originally calculated with a 30m dipole as well, but after modelling it, that was quite horrid.. (swr of 38 on 30m)

Building a new Antenna!

So the TEV, as good as it is, really doesn’t cut it for 40m ๐Ÿ™

So it’s time to string up a dipole!

Of course, it’s not that simple ๐Ÿ˜‰ ย I figure if I’m going to the effort of putting up support masts (using 6.5m lengths of 20mm MD gal tube (5mm wall), mounted to the fence posts each side of the yard), and running rope, cable, etc.. then I may as well ‘do it right’.. ย So I’m budiling a Multiband Dipole! It looks pretty good, so we’ll see how it works – the poles are on order (BJH don’t keep 20mm medium-duty pipe in stock, so it should be arriving friday..), I’m currently building the centre separator (18″ high, as I want to make it four-band to include 10m as well..), plus figuring out how to run the wires for the dipole.. I have a 100m role of light fig-8 speaker cable here, so I’m figuring I’ll just split that (giving me 200m), and then make the top run of the fan actually out of light rope, with the dipole wire tethered to it.. – then the other (shorter) wire runs should be ok to hang under that.. – we’ll see how they go, we can always replace with rope later on..

Photos to follow ๐Ÿ™‚