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

1296 MHz Antenna for SOTA?

I’ve just found that my 23cm yagi fits into the packaging from a commercial “white stick” colinear. In this case Watson, though I think other makers use simillar display sleeves.
This adds almost no weight, and makes it much easier to carry without snagging on things.
I spent some time pondering how to make a carry bag for it, then noticed this sleeve rolled up on a shelf in the shack :o)

To all who are interested in 23cm antennas

Here is my latest addition to my collection of homebrew 23cm yagi antennas.

I have constructed an ‘all brass’ robust 6el yagi for SOTA. This DL6WU design employs a gamma match. I used VK5DJ’s ‘Yagi Calculator’ software to determine each element length and spacing. Element lengths are within 0.01 mm, while element spacings are within 0.5 mm.

Gamma match - variable piston capacitor

Element and boom details courtesy of VK5DJ

5 Likes

Somewhat cruder, the key is to reduce the losses by making the transverter part of the antenna. There is <300mm cable from the transverter to the Driven Element (DE).

The antenna is 4.7mm Al Rod and the DE is brass tube. The boom is 15mm water pipe and if you use a 4.5mm drill the interference fit will hold the elements in place. I only had a 5mm drill to hand so hold the elements with cable ties. The DE is held in place with a modified pipe clip.

The whole bundle will sit on the top of a fishing pole at 4-5m AGL. With 10 elements the beamwidth of the antenna it wide enough to make alignment not too critical. It can be mounted horizontal or vertical with a minimum of effort.

The transverter is a SG-Labs box powered by 8 or 9 lithium AA cells. It has worked well over a 136km path using FM. 880m >> 200m ASL.

73 de Andrew G4VFL

2 Likes

Hi Andrew

Pleasing to see others experimenting with homebrew design and construction. Achieving the first QSO on a hombrew 23cm antenna provides immense self satisfaction. I bet you are proud of your efforts, well done :slight_smile:

73, Andrew VK1AD

Construction of a homebrew 23cm HB9CV. :slight_smile:

73 Andrew VK1AD

Andy

Finally got around to making a Bi-Quad for 23cm.

73 Andrew VK1AD

7 Likes

That’s really pretty and so much neater than mine.

What did you use as the two standoffs?

Hi Barry

Two 32 mm lengths of plastic sprinkler riser tube. Each end is secured by a cable tie. The whole antenna assembly is quite rigid.

Andrew

Hej Andrew,

what are the dimensions of the reflector? What’s the scale, cm? Have you already tested the bi-quad against another antenna?
I’m asking because I’ve just built a 23 cm bi-quad with a 240 x 160 mm reflector. It’ll get hard to fit a bigger reflector in my rucksack.

Ahoi
Pom

Hi Pom

The reflector is 231 x 116 mm. Yesterday I tested the Bi-Quad against my homebrew 6el yagi. The Bi-Quad had 1 S-point over the 6el yagi. I will carry the Bi-Quad in my hand, but only for summits where I’m not scrub bashing through dense aussie scrub.

Construction notes and test details at my SOTA blog. This post demonstrates the bush scrub I’m dealing with. Wade’s recent video demos the antenna in action.

73, Andrew VK1AD

1 Like

Thanks, Andrew. This makes me quite optimistic. I thought my reflector might be a bit small since all biquad plans I found online have bigger reflectors. So I built the biquad from the scrap box just to test if the reflector is big enough to perform well. I wrapped hard paper in aluminium foil and mounted the biquad on it. I didn’t want to spent the money for a copper-plated pcb which equals a container of Lindener Spezial without knowing if the concept will work. :wink:
I think I’ll order the pcb.

Ahoi
Pom

Hi Pom and anyone else interested in 1296 MHz

See photos. This morning from summit VK2/ST-006 South Black Range I worked four SOTA chasers on 1296.150 using the Bi-Quad antenna, I qualified on 1296 MHz :slight_smile: The summit is heavily timbered with eucalypt trees, other obstructions include large Granite Tors. Best contact through the aussie scrub was with Matt VK1MA/2 along a 70 km signal path. Even better I worked Chris VK2DO in grid QF54CH due East on the south coast of NSW at a distance of 66 km. That’s 66 km as the crow flies.

1296 MHz Contacts:
VK1MA/2 S2S VK2/ST-005 - 70 km
VK2DO/p - 66 km
VK1KW - 53 km
VK1RX - 40 km, however we didn’t have a direct signal path. The signal from Al’s QTH first went due west (I was 40 km east of Al’s QTH) for a reflection off the Brindabella Ranges. The secondary signal path was close to 84 km.

Bi-Quad and 23cm transverter mounted at the top plate of a 1.4 metre tripod beaming west for a S2S contact with Matt VK1MA/2 on VK2/ST-005, Al VK1RX and Rob VK1KW. BTW, the purple antenna is a 3el 2m yagi for 144.200 SSB.

The signal path view to VK2DO as seen by the antenna

Beaming east for VK2DO

73 Andrew VK1AD

2 Likes

I wonder if vertical polarisation works better because of all the tree trunks?

Hi Andrew, interesting that you decided to operate towards the bottom part of the AZ - I normally operate on the top adjacent to the large boulder. Presumably you were trying to maximise path opportunities?

I think the next time I activate South Black Range that I will take a ladder up there with me so that I can safely get up onto the boulder and activate from there. No major benefit on HF, but should improve opportunities on VHF and higher.

Matt
VK1MA

I would expect absorption and scattering to be greater with the tree material parallel with the electric field. I no longer have access to the neat little kit that we used to teach this sort of thing.

As I recall the students all assumed that our parallel wire grid acted as a cage to keep the waves in rather than warming up as an absorber. Perhaps someone is still teaching this and can give a proper experimental answer.

73,
Rod

PS lovely piece of work that wood based Yagi antenna Andrew illustrated; no idea which Andrew or where I found that, so commenting here,

Thanks Rod for the feedback, yep I had lots of fun fabricating the yagi. Link to my blog below.

Cheers, Andrew VK1AD ex (VK1NAM)

Hi Matt, that’s right, I was looking for a break in the trees. I set up about 7 vertical metres below the top boulder. The 25 metre AZ is halfway down the trail before exiting on to North Black Fire Trail. Loads of vertical space to find the best signal path out of the scrub.

Andrew

Thank you for the link, Andrew. I will get out some tools and have a go.
73,
Rod

She’s not much of a beauty but wears all the copper well. :wink:

Ahoi
Pom

5 Likes