Antenna

[G0KTD]

lantern 4 side's of 6 loops

lantern vertical polar diagram side A 017-1.jpg (57.57 KiB) Viewed 785 times

Polar plot of lantern antenna GB3NQ

top view final.jpg (58.23 KiB) Viewed 785 times

Hi all have been building Flat plate antenna's for Digilite portable use from G8GML, in conjunction with the artical in the CQ-TV 234
as in Cornwall we have a hilly county and alot of granite which adsorbs RF a great deal we have done 30 miles or so the one that
have been made so far on 1bay of 6 loops gain of 16 dbd and 2bay of 6 loops gain of 19 dbd others have made 4bay of 6 loop 22 dbd.
I have made 1bay and 2 bay version and all work well on analog and digital at the moment I have a 2 bay of 6 loops for my system.it works
fine power split-er of of Ebay Chinese manufacturer SWR 1.1to1
Normal size is 1bay 150x 600mm, mine are 1bay 230 x600mm 2bay 500x600mm.

[G0KTD]

1bay of 6 loops

PHOT0104-1.JPG (74.86 KiB) Viewed 782 times

This is the 1 Bay 6 loops I have for Portable use Tuned to 1249 for TX now making one for 1316 for RX
The feed point pic not that clear will take another later.

[g4bbh]

Interesting to see your aerial. I have been using one with quad diamond shaped loops but never got a good match with 6 loops per bay and have considered making one to the CQ-TV design. Have you used all dimensions as per the CQ-TV article? Have you had a chance to estimate the gain and bandwidth?
I won't comment too much on the Chinese power splitter. Suffice it to say the one I have is of poor construction and it gets very warm if I run it at 10W. A 1/4 wave line splitter is far superior. I have some Mini-Circuits splitters which work very well on receive but are not suitable for transmitting more than a few milliwatts.
Dick G4BBH

[G0KTD]

Hello Dick the feed point for the 6 loop antenna was designed by G3wkf as in the Batc CQ-TV 234 you can see the feed arrangement and up through the center is the Copper Balun which is 60mm long and is clamped to the screen of the coax this gives the necessary impedance to the 6 loops and the Trombone effect of the brass tube's is their so to adjust the loops in and out for the best SWR for the Freq you require all the other measurement are as the original Author.
as for the Chinese power splitter it has given no problems.

[KenW6HHC]

Hi G0KTD,

The Panel-Antenna appears to be a very interesting antenna for 23 cm.
I do have a few "conceptual" questions that perhaps you can clear-up?

1) if two 6-loop-arrays are positioned side-by-side on a flat screen, are the two arrays fed in-phase? That is: the coax splitter just "transforms" the two 50-ohm arrays back to a 50 ohm feed coax?

2) Is there a gain advantage (over question 1 above) to position the two 6-loop-arrays "front-and-back"...sort of one-half of your latern construction?

3) in your latern antenna construction, are the two east-west arrays fed in-phase or 180 degrees out-of-phase?

4) Finally, in the latern construction, what is the spacing between the opposing "east array" and the "west-array"?

Many thanks...de Ken W6HHC

[G0KTD]

Hi Ken this is what I think what you ask for

1. Yes the 2 set would be fed in phase and the power splitter is 50 ohm to 50 ohm
2. This I have not tried (I take it one plate 6 loop on the front and 6 loops on the back)
3. All in phase
4. All in a 8” square and 24” long 200mm X 200mm
5. The plate is 6” X 24” but we all measure in mm on this so 150mm X 600mm
6. The spacing from 6 loop elements to the plate is 30 mm and the feed point
7. This is not my design it has been taken from CQ-TV 182 G8GML and the follow up by G3WKF in the CQ-TV 234 articles’ the only difference is the feed arrangement as the G3wkf model
8. In the 4 plate lantern there is a power splitter for the four in the centre and fed coaxial is equal in length to the splitter
9. The 6 loop elements are made in a jig and insulated at the crossover point, this is necessary to get this part correct and the brass tub used in the feed point is to adjust the elements in and out to adjust the SWR for the frequency you require then solder when it is set.
10. the gain figures as by G8GML
11. 1bay 6 loops .Gain 16 dBd
12. 2bay 6 loops .Gain 19 dBd
13. 4bay 6 loops .Gain 22 dBd
14. 8bay 6 loops .Gain 25 dBd
15. Hope this all helps
Keith G0KTD

[KenW6HHC]

Hi Keith G0KTD,

Yes...your answers help very much.

You wrote..."2. This I have not tried (I take it one plate 6 loop on the front and 6 loops on the back)"
What I was thinking originally was just two of the plates in the latern separated by 8 inches (as in your contruction...say plate-B and plate-D in the GB3NQ polar plot). I was originally wondering if there was a gain effect due to phasing between the two separated arrays. But I now realize that the screens act as a ground plane and prevents the two arrays from interacting like a 2-element beam. So, as I see it now, if I had a two-plate array as I was envisioning, one plate would beam to the east and the opposite plate would beam to the west.

I do like 4-plate latern approach you are using...a very nice gain omni-directional antenna.

Many thanks...de Ken W6HHC

[G0KTD]

Ken
2. that is right I have not tried 6 loops on the front and back of plate as the fed point would make it difficult to do
and I think it is unnecessary to do.
Lantern type is quite light to make as a group of us have done for our local repeater we have one for RX and Now one for
TX as here in Cornwall the Hilly nature of the countryside require this approach and the Granite seems to soak up RF.
I get into the repeater with 18 watts about 5 miles away from the repeater but I am under the hill close in so it is difficult
to get in I have a 36 ele beam can RX with it but not able to get in with that but with the flat plate no problems.

Keith G0KTD