Other SOTA sites: SOTAwatch | SOTA Home | Database | Video | Photos | Shop | Mapping | FAQs | Facebook | Contact SOTA

Portable antennas


#1

Hi all

I’m now quite happy with my portable 2m antennas (a 3 el yagi and a j-pole mounted in a length of pvc tube) but I wish to try activating hill tops with hf.

I already have a FT-817 and a LDG Z-11Pro tuner so the questions are. What, from your own experience, are the most efficient designs? As I will be mainly looking at activating 80m would a single band dipole be best or should I look at a doublet/G5RV for multi-band operation? Has anyone had experience with the Super Antennas MP-1 vertical?

Carolyn (G6WRW)


#2

In reply to G6WRW:

I would recommend a linked dipole. I made one and John GW4BVE made an almost identical one. When I made a second one I followed John’s sizes and needed no adjustment (probably because I used the same gauge wire). There will no doubt be some who will dispute it but a resonant antenna will always outperform a none resonant one with a tuner. If you do only 80m a straight dipole cut for your preferred spot frequency would be best IMHO.




Best regards Steve GW7AAV


#3

In reply to GW7AAV:
I totaly agree with Steve a dipole for the band or a linken dipole, this is what I use and is easy to make, set up and quick to QSY. Also light to carry. I used the dipole calculator on the web site at http://www.burtonarc.co.uk
and the inverted V sizes. Hope this helps.

73 Dave G0AOD


#4

In reply to G0AOD:
I have been messing about with LF antennas for SOTA and have found a problem with dipoles.

The problem is that in SOTA you get CW activity at about 3.55 MHz, and SSB at about 3.666 MHz and 3.726 MHz. Solid state PAs have high SWR protection that reduces output as the SWR increases and shuts them down at an SWR of about 2:1, and the bandwidth of a dipole between the 2:1 points is about 150 kHz. If you cut the dipole to favour 3.666 it will have an SWR of about 1.75:1 at 3.726 MHz (with the output already reducing) and about 2.2:1 at 3.55 MHz (with the PA shut down). It seems to me that you either have to use a tuner or physically change the length of the dipole to cover all three activity areas - or increase the bandwidth, perhaps by using a folded dipole, but then matching to the cable becomes a problem. Does anyone see a way around this?

73

Brian G8ADD


#5

In reply to G8ADD:

I would suggest maybe you cut the 80m dipole for 3.55 then fold the ends back so it is the right length for 3.726 and at this point fit your guy lines then you could also add a tape marker for 3.666. Now by folding back the ends and simply holding them in place with a rubber band you will find it tunes for either of the two favoured ssb areas of the band and for CW you simply let those folded back ends dangle. This is what we do when tuning a dipole before we cut it anyway so I know it works.

Hopefully I described this well enough.

Another way would be to put another link in for the CW bit.

Regards Steve GW7AAV


#6

Hi Dave Steve and Brian

I’m following this thread with interest.

The linked dipole does appear to be a good option so will try building one. The bandwidth on 80m is not an issue at the moment as my morse is very weak (which I’m working on though).

Any other options or suggestions are welcome

Carolyn


#7

In reply to GW7AAV:
Good idea, Steve, I really should have thought of that for myself!

I rejected the additional link as adding complication!

73

Brian G8ADD