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ANTENNA for 4m band (SOTA)


#1

I have a 4m band in my kx3 module. please plan the antenna for 4m band for field activation. I would like to try ssb on horizontal. TNK


#2

For a small light portable antenna where 4m portable activation is allowed (it’s not allowed in Germany) take a look at building a Moxon antenna.
It’s solid when assembled and quite light with some gain (roughly the gain between a 2 and 3 element yagi). I don’t know of any commercially built 4 metre Moxons though (only for 2m & 6m from Par antennas in the US).

73 Ed.

UPDATE: correcting myself - I have just found that Wimo in Germany do a dual-band Moxon for 6m & 4m the 5070MOX at €150. It’s described on this page: http://www.wimo.de/antenna-6m_e.html the fifth antenna down.
If you’d like a Yagi, the sixth antenna down is the DK7ZB tri-bander (6,4,2m) €121 and the seventh antenna down are two OWA antennas covering 4m & 6m for €239 (5/4 element) & €312 (6/5 element) respectively.

The Moxon is probably a better antenna for portable use though.


#3

I am watching, rather too big for SOTA


#4

A single band 4m moxon, if you chose to build one can be taken apart easily and doesn’t take up much room.

This one is made of garden canes and wire:
http://www.70mhz.org/moxon.htm

Or design your own here: http://tippete.net/cgi-bin/moxgen.pl

Ed.


#5

A 4m link in your linked dipole?

I’m sure many will laugh etc but depending upon your expectations is may work well enough.


#6

Hi Compton, using a simple dipole element at 70Mhz would bring some other interesting properties. The antenna will be above 1/2 wavelength high and so would not be an NVIS antenna and would probably exhibit some directional capabilities. I suspect that the performance would not be fantastic though - but if Leszek already has a linked dipole it might be worth trying. Better than no antenna or a rubber duck antenna in any case.

Ed.


#7

If we had a 4m allocation in VK, I would construct a half-wave vertical coaxial dipole, also know as a Flower Pot Antenna. Very easy to construct.

Save your money by building your own antenna.

73 Andrew VK1AD

P.S. As an axample take a look at my 2m coaxial dipole antenna.


#8

It’s easy to rig a 3 ele Yagi for 2m SOTA activating. It’s a little more involved to rig a 5ele for 2M with wind loads etc. A 3 ele Yagi for 4m is bigger than a 2m 5 ele Yagi and immediately is a bit awkward and a 4m 5ele is quite a serious undertaking for SOTA.

Make a simple rotatable dipole out of long telescopic antennas. It will be viable for S2S operation with other relatively local SOTA stations and viable for local SP stations. The best time to operate is now when there is a strong chance of sporadic E on the band. As the returning polarisation for SpE is random, a vertical would work as well as a horizontal antenna, but the ability to steer the beam gives a horizontal antenna an edge for simple contacts.


#9

Hi Andrew,
Leszek said he wanted a horizontal polarised antenna.

73 Ed.


#10

On 50 MHz, I often use my coax-fed 10 MHz half-wave dipole. It functions as five half waves on 50 MHz and loads up very well. I have worked all over Europe and the Middle East with it.

I have not tried it yet, but by the same logic a 10 MHz half-wave dipole should also work on 70 Mhz as seven half waves. Any HF dipole will work on odd multiples of its fundamental resonant frequency and will present a suitably low impedance at the feed point. Hence, a 7 MHz half wave dipole works very nicely on 21 MHz (three half-waves).

73,
Walt (G3NYY)


#11

can you devote your time and calculate parameters for a coaxial dipole for 4m band?


#12

Not too hard…


#13

Hi Leszek

I will build a coax prototype and mail it to you. :slight_smile:

What frequency do you use? Or what is the EU band allocation?

73 Andrew VK1AD


#14

[super thx. call frequency in Poland 70.200 ssb . I will work only here for SOTA only 3w(KX3module)
Leszek sq9mdf


#15

A delta quad may be compact enough but I’m not aware of a 4m version. Sandpiper do one for 2m which I’ll be buying when funds allow

Sandpiper Delta Quad


#16

Build a Slim Jim from ribbon feeder.


#17

Leszek originally said he wanted an antenna to operate in horizontal polarisation, that seems to have been changed now - therefore a J-Pole antenna would be another simple antenna that could be used but like the slim-jim and the vertical coaxial dipole, they’re not horizontally polarised.

I suppose he could hang the coax dipole from Andrew horizontally though.

Ed.


#18

Extremely easy to deploy a Slim Jim vertical or horizontal. Mine is circular for most of it’s time… and I can make that left or right on request.


#19

As noted, a dipole or Slim Jim constructed so that you can use horizontal or vertical. Next up would be a delta loop, there are some simple plans online for a portable one.
You should be OK with the first, so long as there are other operators to work.


#20

I need something tested. I do not have time for rehearsals and experiments. I will do the antenna myself, which has already worked