Got bored this morning so I built me a multi-balun out of the loose junk I had.
This is the next antenna I'm building. The only piece I need is the variable cap. I plan on making the frame from PVC that fits in my tripod and making it remote tune-able
I'm grabbing this now as we all know how the life expectancy of a tripod website. Remember geocities,
----------------------------->8 Clipped from website 8<-----------------------------
UPDATE: Math from 66Pacific which I will try first before committing to the original design I found. I'll make a second loop to get me 80m and if it fails then build another 40m and sell it as such.
Antenna efficiency: 36% (-4.4 dB below 100%)
Antenna bandwidth: 15.4 kHz
Tuning Capacitance: 122 pF
Capacitor voltage: 2,912 volts RMS
Resonant circulating current: 15.6 A
Radiation resistance: 0.074 ohms
Loss Resistance: 0.132 ohms
Inductance: 4.25 microhenrys
Inductive Reactance: 187 ohms
Quality Factor (Q): 454
Distributed capacity: 16 pF
Antenna "circumference": 20 feet
|Side length: 2.50 feet|
Antenna diameter: 6.0 feet
Well I revisited the inverted v dipole I had previously made and with the help of a couple of calculators came up with an off center feed dipole. But this time instead of cutting my wire to the length required I started from the terminals of the 4:1 jetstream balun to the receiving part of the dogbone. One element 23' 2" 3/8 and the other element 46' 3" 5/8 and holy smokes what a difference. 40m, 20m and 10m I get 1:1 SWRs. Which really doesn't mean much as my can-o-dummy gets 1:1. I haven't had a chance to test it's range. Nor have I plotted it in MMANA. This was just an impulse brain fart. But I calculated 1/3 wave for 7.074 and doubled that for the other side. Before that I was trying to find a happy middle between digital and phone, but that's a difference of 3 feet from end to end. And neither side feeling the joy of resonance. So since I do more digital I sided with the lengths for digital modes. I may fire up the smelter furnace and do some lost PLA casting to make an octopus antenna using ham stix this summer for my next project.
There are probably cheaper ways of doing this, but I had these parts on hand.
- 2 section of fence top rail
- 1 antenna mounting bracket
- 1 little pulley
- 1 make shift hanger for the top to hold the pulley
- All the above can be substituted with a tall tree or a pair of them, or more for even kewler antennas.
- 66 feet of 14 THHN Stranded wire or anything really. You could use nylon coated wire rope. Just factor in the velocity spec which may be a foot in one direction of the other. I already had a 500 foot spool, and I didn't use any of that. I took all the short pieces I had and soldered them all together to make a pair of 33's. Don't run your hand down these bad boys.
- And the magic of it all is a Jetstream 4:1 Balun that keeps it all happy. Calum M0MCX has a nifty SWR calculator for excel to dial it in.
That's pretty much it. Mine is up 6.5m in the middle and 3m on each end. You will need a tuner with it. Should be close to 1:1 on 40m though. If you had two 51 foot lines and 30-34 foot of ladder line you'd have a G5RV or two 25.5 foot pieces and 15-17 feet of ladder a G5RV Junior. Neither of the last two require a balun. Ugly balun yes or a bunch of ferrite beads as you can almost see in the picture by the balun.