Single Yagi: modified DK7ZB 7-Element design5 (28 Ohm,11 dBd gain). Also can be used stand alone. + 2 Yagis form a horizontal layer by introducing a spacingstructure also made out of fiberglass segments
Theoretical overall gain: 17 dBd
Collapsed length is less than 120 cm
Antenna structure weight: 3.3 kg
Can be supported by fiberglass mast (I use lower 8segments of a Spiderbeam 12 m HD fiberglass mast,weight is then appx. 3 kg)
Still lightweight and small enough to pack and to carry thewhole structure on a mountain top.
The design principle is based on my old 6-Element design which i already described here:
Maybe this is not an antenna for “every day use” but more for contesting and DX!
@OK1CDJ Ondra,
Looking forward to see you building it with 3D-printed parts
I think you will find lots of things to improve!
Congratulations Martin, I love antenna building and this is… impressive!!
Thanks for sharing all details and the excellent video. Real engineering there.
Please let us know how it works in practice and the long distance contacts you get with that.
This is fantastic Martin!
What next, 80m portable 3 ele?
Great work, very nicely written instructions, inspiration.
Let us know how you get on using it.
73
Tim
G4YTD
Thank you all for your feedback. Good feeling to see that all the work is of interest to you and the amateur radio community.
I must admit that I’m also devoted to big antenna structures like Armin and Ignacio Maybe this was also the main reason for me to build this antenna. Ok 6 dB of extra gain compared to a single Yagi is also not to bad …
EME is also something I want to try asap. At the moment I’m preparing two additional “layers”. This will result in an 4x2x7 Element and I will attach it to a 18 m aluminium mast. This most probably will happen within the next weeks. Pictures and documentation will follow. I will not carry this on a mountain top… Hmm, but if you were a group of 3 to 4 people … this would also be possible.
With this I want to try EME. But I will have to spend some time on an LNA and maybe PA before.
I did not think about doing EME from a summit yet. EME S2S would be cool But I i first have to learn CW. SSB will not be possible …
Missing eleveation control is also a problem for EME. I’m thinking about a electrical elevation control for the 4x2 group. But that is a topic for the future …
Tim, I think the Spiderbeam concepts will more likely lead to your 80m 3 element beam
I want to move up in frequency for my next antenna projects. I’m thinking about a lightweight 23 cm group for the mountains …
Great looking antennas. Whether justified in terms of additional contacts for SOTA is something you will need to assess in due course.
If you look at the EME path loss etc and calculate your required antenna gain and transmit power, you find there is a lot needed. There is a calculator on the website of VK3UM (SK) which helps you calculate gain and tx power, also the tolerable feedline loss and mast head preamp noise figure. CW requires a lot of power AND a lot of antenna. JT65 type modes require less.
I was one of the ops at VK9NA at Norfolk Island 9 years ago, we had a 300w amp and a 19 element yagi, on JT65. To give you an idea. Our reports received were generally between -15 and -25, meaning S:N of -25 db. A very few of the stronger stations I thought I would be able to copy as CW signals, they were at about -10 to -15 as indicated by WSJT. We never made any CW contacts - the main aim was to work as many as possible. In about 14 days we made about 120 contacts, on 2m EME. We made other contacts on other vhf and uhf bands to Australia and New Zealand.
EME is an addiction much more serious than SOTA! And is expensive!
Martin, it’s possible to do EME with quite small antennas and power now if you use JTx modes. CW is harder (whether you speak CW or not) and SSB still needs some substantial uplink signal.
Thank you, Andrew and Andy for sharing your experiences on EME! I know that this will result in a completely new story for me with lots of effort and patience required.
My antenna is not really intended for SOTA. For SOTA I would recommend to go for the small single 6 - Element design. When I use bigger structures on a mountain top, I usually also bivouac there. The advantage is that you have more time and you most probly do not offend other people with your crazy antenna structure. The moutains are quite crowded here in southern bavaria …
Yesterday we mounted my 2H x 4V x 7 Element VHF yagi array the first time.
Support is a 18m Spiderbeam aluminium mast.
It will not get any bigger any more, I promise
So you have launched a massive construction. Unfortunately not very suitable for everyday use …
I would be interested to know where the problem areas were:
How did it go with the adaptation (wiring)?
Where are the difficult mechanical points?
What could you prepare?
How did it go with the construction? - How many helpers were involved?
no, not intended for everyday use, but for fieldday and contests.
Setup time is roughly 2-3 hours with 3-4 persons.
Main problem ist not to forget anything regarding fixing or wiring because you can’t access the parts any more when they are up in the air. At the first setup, I forgot a loop in the feedline to allow for mast rotation at the lower guyrope bearing and we forgot to connect a yagi So you have to stick to a plan and you have to double check everything.
Wiring / Feedline are 2 x 1:4 coaxial dividers and one 1:2 divider (2x75Ohm Sat cable for the ld/4 part).
Hmm, difficult mechanical point… Don’t get a mess with the small support guy ropes for the fiberglass construction. Alinging all layers in one row …
There are for sure some things to improove. I’m not sure yet, if everything is fine with the electrical part of the antenne. Some testing about pattern/gain has to be conducted to be sure.
Yesterday we made a second try at a fieldday but the qth was absolutely no place for VHF A mountain valley. So hardly no qso possible … even with reflections … maybe also because of the very low elevation angle. So all energy into the woods but nothing to the mountain tops. But as I said, I’m still not 100 percent confident on the electrical function …
Maybe this was also the main reason for me to build this antenna. Ok 6 dB of extra gain compared to a single Yagi is also not to bad …
