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Inv Vee for all bands with only one link?


#1

I am thinking of building an inv Vee, cut for 80m(low end of the band–) and 40m, making it fan-like.
80m legs should cover 30, 17 and 12
40m legs should cover 15
That leaves one link for 20m
Anyone have any tips or thoughts?


#2

Like you say to me give it a whirl :smile:
Karl


#3

I think you’ll struggle - both getting it to resonate without an ATU and speading out a fan dipole on a summit due to windage and landscape restrictions. Better to build a link dipole in my opinion and just connect the sections you need as you go from band to band. It works for me.

73 Phil


#4

There is another possible advantage in a single linked dipole - when on the higher bands, the ends of the dipole are further from the ground than they might be in a “fan” arrangement, which should make it a bit less lossy…

For home station it could be a very neat idea, given a bit more height.

73 Adrian


#5

You could try an OCFD antenna for 40-10m bands think the measurements are 44ft and 22ft. For the 80m you could swap the 22ft leg for a 88ft length or build it with a link to join a 66ft length of wire on when needed on a suitable summit.
I used a G Whip 20-6m OCFD antenna a few times portable from a summit and was happy with the performance, it also worked well on 2m that was a bonus. I am currently building a 80-6m with the measurements above and a 4-1 current balun, the only problem is I don’t have the garden or an antenna analyser to test it prior to using it from a summit so will rely on T1 atu for help.
Using DX UL wire along with 8 meters of RG174 with 10 turns on a ferrite rod for a line isolator and a g whip mini balun the total wieght is .59kg, hope to try it out next week.

73 Graeme


#6

Hi
In practice a 7MHz dipole is not long enough to achieve 3/2 wave resonance on 21 MHz, it is closer to 22 MHz on its third harmonic, due to the end effect for the 7 MHz dipole being multiplied by 3, making it too short for 21 MHz. You would get a better match if you have a short linkable section for 15m. Similarly the 3.5MHz dipole is resonant on its 3rd harmonic well above 10.5, more like 11MHz. So an extension or an ATU is required to get a reasonable match for both 21 and 10 MHz.

I have used a fan dipole 40/20 for SOTA and the advantage of the second dipole is that it provides another two directions of guying and the pole is quite stable. It takes longer to set up (untangle) than a linked dipole but it is great to be able to just switch bands at the radio and keep operating.

73 Andrew VK1DA/VK2UH


#7

If you have a link dipole for 30/40m you can add some loops of wire at the links to extend the legs for 15m.

Link closed = 40m
Link open = 30m
Loop added at link = 15m


#8

I have played quite a bit with fan dipoles,

http://www.moosedata.com/g6wrw/hfdipole.pdf

You would need a tuner for it to cover 30/17/15/12m with less efficiency than resonant antennas for those bands. I’ve managed to load mine to work on 160m.

Carolyn


#9

Thanks for all input.
I will have to think about it for a while, cos I like bandhopping for S2S.
I don´t have enough space to try 80m ant at home, but with kind neighbours I can get 40m at home.


#10

This variation of the W3DZZ might be worth considering:

http://www.dxing.eu/w3dzz.html


#11

Look at http://www.i1wqrlinkradio.com/antype/ch10/chiave234.htm
[http://www.i1wqrlinkradio.com/antype/ch10/chiave234.htm][1]

[1]: DU1ANV antenna


#12

Hi,

You should just use 300 ohm ribbon and an ATU with a balanced input. Then your 40 m dipole or one extended by up to 2 m each side will tune up pretty well on all bands.

If you have an unbalanced ATU then a 1:1 current choke and/or a 4:1 current balun will solve that. The ribbon winds up nicely if you provide it with it’s own spool - one used for builders twine is ideal.

There is no way a simple dipole will match 50 ohms on all those bands and ditto for two dipoles - unless you add a lot of loss and that’s the last thing you need for QRP in a declining sun spot cycle.

73
Ron VK3AFW