5.665 Ghz cantenna

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m1cdq
Posts: 113
Joined: Thu Feb 28, 2019 4:28 pm

5.665 Ghz cantenna

Post by m1cdq » Sat Sep 18, 2021 11:51 am

I am having a little play in the workshop. I have made a few 23cms cantennas and the work very well.
So i decided to have a go at making a 5665mhz cantenna for ATV on the 5.6Ghz band.
The calculator i used is here https://www.wikarekare.org/Antenna/WaveguideCan.html

To solder the end on i used solder paste and a blowtorch. this made life easy. As the copper will dissipate a lot of the heat. I did the same attaching the SMA connector.

I intend to attach one to a sky dish. I will be making and 3d printing a holder so i can attach it to dish.
I don't know the gain of the cantenna on its own.( Ive heard figures from 4 to 12 dbi) I guess around 5 or 6 or once its attached to a dish. maybe one of the antenna gurus master of the dark arts of RF could let me know.
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G0NMY
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Re: 5.665 Ghz cantenna

Post by G0NMY » Sun Sep 19, 2021 2:36 pm

You would of been better using an ID of 35mm
As your highest resonant freq is below 5665MHz according to the data you posted.
It will work I guess, but will be a bit lossy, I'm not sure what your vswr will be like on 5665MHz.

Also one tip would be to use a pipecap on the end thus keeping any RF absorbing lead solder outside the waveguide.
Just a few tips as Microwave antennas are quite critical and can be very lossy if not tuned correctly
Cheers Mark G0NMY
   

   

http://www.g0nmy.blogspot.co.uk/

¡ʎɐqƎ ɟɟo pɹɐoqʎǝʞ ɐ ʎnq I ǝɯᴉʇ ʇsɐl ǝɥʇ sᴉ sᴉɥʇ

m1cdq
Posts: 113
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Re: 5.665 Ghz cantenna

Post by m1cdq » Sun Sep 19, 2021 8:20 pm

cheers for the advice Mark.
Im trying it out wiht what odds and ends i had in the workshop. I know lead solder is not the best to use. I did not have any silver solder at moment.
for copper pipe i had either external dia 0f 35mm or 42mm so i went with the slightly bigger than too small.
my other option for mkII is to build the same. but to slide another piece of 42mm copper tube split down its length inside to make the internal the right dia and to use silver solder and by placing a piece of copper on the end instead of an end cap i can get the distance from the reflector accurate

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G0NMY
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Re: 5.665 Ghz cantenna

Post by G0NMY » Mon Sep 20, 2021 2:21 am

The end cap doesnt have to be soldered all the way around, especially if you are putting it inside a plastic container to keep the weather out, just as long as it is a good flat fit, which it should be if the tubing is cut square
So you could create say 2 or 4 tabs to fold over the outside of the tubing and then solder them to keep it in place Or even use a jubilee clip.
Anyway your idea of tube inside tube should work if it comes out at 34 or 35mm ID.
Anyway its fun to try different materials and sizes Im sure you will come up with a suitable design.
Thats the fun of experimenting isnt it.
73 and let us know how you get on
   

   

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¡ʎɐqƎ ɟɟo pɹɐoqʎǝʞ ɐ ʎnq I ǝɯᴉʇ ʇsɐl ǝɥʇ sᴉ sᴉɥʇ

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PA3CRX
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Re: 5.665 Ghz cantenna

Post by PA3CRX » Mon Sep 20, 2021 7:11 am

For your specific cantenna you asked for the gain; in fact it is totally irrelevant.

The inside diameter of your tube is 0.74 Lambda; you can read about this in http://www.w1ghz.org/antbook/chap6-3.pdf Your design performs optimal in a deep dish. I do not know the f/D is of a Sky dish but if it is an offset dish it is over illuminated.

I have two canfeeds for the 6 cm band (with 39mm ID). One with an N-connector and one with an SMA connector. The dimensions are the same but one gave a very bad return loss. Two additional screws solved this but this shows that even when you build in accordance with some calculator, result could be very different. I use this canfeed with a dish with f/D 0.5.
It will work but likely not the optimum result that could be reached (likely a few dB’s less then optimum).
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About the bottom. It is probably not even needed to have a full bottom at all. With my C-band LNB I did some tests and the result of horizontal and vertical polarization looked very similar. This LNB contains two probes (one for each polarization) and it is of course not possible to have the distance from the probe to the bottom for both correct. So a rod is placed at the distance you would expect the bottom, parallel with the probe. For the other probe, this rod is not 'visible' (and the borrom performs as bottom).
C- band LNB.JPG
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In the coming issue of CQ-TV you find my article about illumination of dishes :)

Just my thoughts,
Chris PA3CRX

m1cdq
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Joined: Thu Feb 28, 2019 4:28 pm

Re: 5.665 Ghz cantenna

Post by m1cdq » Wed Sep 22, 2021 12:50 pm

cheers for that chris. your simple explanation of the rod system for H/V makes sense.

thanks for the info.

its nice when the "daft will it work path" matches up with the "educated already done it path"
just spent 2 hours in IKEA lighting department looking for "suitable dishes" on by way back home after a short break.
nothing found but replenished my meatball supply

now to start deep dish hunting

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PA3CRX
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Re: 5.665 Ghz cantenna

Post by PA3CRX » Wed Sep 22, 2021 8:06 pm

Don’t let you discouraged! Try and see the performance of your Sky dish. Eventual you could also make a rectangular horn feed and compare.

For larger f/D you could add a small conical horn to your cantenna. Originally calculation and template was present in the HDL_ANT32 software of W1GHZ. The newer Windows version is more easy to use with W10 but it does not include these conical horns anymore. If you run DOSbox or you have PC with old version Windows available it is worth looking at that older software to find your answers.
You can download it here: http://www.w1ghz.org/software/hdl_3b4.zip

Good luck!
Chris PA3CRX

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