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1296 MHz Antenna for SOTA?


#21

VK2JDS is great to have at the other end of a 23cm activation. He’s in a few of my logs on 23cm. I give him credit for 95% of the QSO. He’s also really good at remotely fault finding your gear as I found out last week end when on Mt Walker.
Plus he enjoys it!
Compton


#22

#23

Hi all

Activated Livingstone Hill VK2/SM-093 (6 points) today on 23 cm 1296.150 SSB. Al VK1RX/2 activated ‘The Peak’ VK2/SM-068 (8 points) 78 km south at 180 degrees also on 1296.150 SSB. Both Al and I were using SG-Lab’s 2.5 watt 23cm transverter. Al’s antenna is the delivered HB9CV 2el yagi while my antenna is a homebrew 23 cm 12el yagi. Signal reports between Al and I were 5-9+ each way.

Both Al and I qualified our respective summits on 23 cm, stations worked; Rob VK1KW 61 km, Ian VK1BG 56 km, Rod VK2TWR 90 km and Matt VK1MA 61 km. Al was ~140 km south of Canberra, not bad for 2.5 watts and a 2el yagi.

On 2m 144.2 USB additional VHF DX Net stations were Mat VK1MT 35 km and Steve VK2NSS 86 km both north of Livingstone Hill.

Qualifying a VK summit on 23 cm is a great challenge and comes with immense personal satisfaction when four unique contacts are made. :smile:

VK1AD 23 cm station, temperature is 3 degrees C, wind is a cold north-westerly at 20 km/h.

Yagi heading 180 degrees south to work Al 78 km over the horizon.

23cm and 2m/70cm yagi antennas

Al VK1RX 23 cm station at The Peak VK2/SM-068 140 km south of Canberra. 23 cm transverter and antenna are both mounted to the tripod pan head. Note the rocks to prevent the tripod from blowing over in the strong wind. Photo courtesy of Al VK1RX.

73 Andrew VK1AD


#24

Can you please point me to the design/dimentions for this antenna?

Stewart GM0GTU


#25

The double quad design came from Bert Modderman’s site. http://www.pe1rki.com/quad.html

I’ve built both 23 and 13cms versions and they work well.

Beware! Don’t go browsing his excellent website or you’ll waste hours looking at all the groovy stuff he has for sale. :grin:


#26

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)


#27

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


#28

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


#29

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


#30

Construction of a homebrew 23cm HB9CV. :slight_smile:

73 Andrew VK1AD


#31

Andy

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

73 Andrew VK1AD


#32

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


#33

What did you use as the two standoffs?


#34

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


#35

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


#36

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


#37

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


#38

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


#39

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


#40

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