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:
Category Archives: Ham Radio - Page 2
The first test ;)
Posted by Damien Gardner
on December 12, 2010
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Multi-band dipole
Posted by Damien Gardner
on December 4, 2010
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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’. This is comprised of three dipoles, in a ‘fan’ layout. As explained here, I have so far built the centre insulator.
Center Insulator:
Now to run two lengths of copper wire up the sides (1.0mm mains cable should do nicely? 🙂 ), build an ugly-balun on the bottom, and measure out the cable lengths for the dipole.. The top run (40m band) will be 3mm stainless steel 7×7, as it’ll be carrying the weight. The lower two (or maybe three?! 😉 ) 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 😉 ) |
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!
Posted by Damien Gardner
on November 17, 2010
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So the TEV, as good as it is, really doesn’t cut it for 40m 🙁
So it’s time to string up a dipole!
Of course, it’s not that simple 😉 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’.. 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 🙂
Relocated the TEV-1 AGAIN
Posted by Damien Gardner
on November 16, 2010
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Been having absolute hell getting much reception at all on 40m.. After shoving the TEV-1 specs into an antenna analyser, I realised the installation instructions from te manufacturer are simply *wrong*. I’m not sure why they say to use a 4:1 balun (I threw that away after the first day), or to get it ‘as high above ground as possible’.. but analysis shows that *sitting on the ground*, it has a VSWR of 10:1.. Sitting 3m above ground, that jumps just a little bit.. – to 129611:1!@#! Yeah, that’d be why I’m not hearing much 😉
So the TEV-1 is now down off the big 8m mast, and will go up behind the shed again, at roof level with three grounded radials below it, as soon as I get new bolts from TET-Emtron.
Oh, yeah, I again had the privilege of being the only person to ever have the screws disappear from their TEV-1! I find it slightly surprising that I’m the only person to ever shove their TEV-1 up in the air (like the instructions say 😉 ), although maybe I’m just the only person on the coast doing it 🙂
Either way, all good, they offered to send me replacement elements if I wasn’t able to separate them (8hr in lanolin bath sorted that out!), and are sending me bolts to replace the screws, so it shouldn’t come apart again 🙂
Rain Sucks!
Posted by Damien Gardner
on January 3, 2010
1 comment
Wow, 20 metres was alive as anything last night.. Now I’m sitting here with it pouring rain outside, and not hearing a thing on 20 metres! Well except one New Caledonia station who I’m not managing to reply to!