'Cantenna' construction

After some web browsing I decided that I'd build some cantennas to play with. For a long distance link, a cantenna is ideal to use as a feed horn for a disused satellite dish!

I found various calculation spreadsheets, but when I compared the results from the online tools and from the maths from the circular waveguide formulas, I was getting different numbers. I'm wondering whether in converting the various forumulae to/from cm and inches some errors have been introduced in the online tools.

Anyhow I decided to build a spreadsheet to do the maths and work out the ideal exciter location in the can based on the cans diameter. I also added code into the spreadsheet to generate NEC2 models so that the theoretical gains of various cans could be modelled.


Using the 4nec2 modeller to analyse the campari can produces a theoretical gain of 12.7dBi for CampariCan and 7.78dBi for ChunkyCan.

4NEC2 generated antenna model.

I've got quite a bit more to add on calculating the antenna sizes, I'll add another page when I have time. I created a spreadsheet to generate the NEC2 model files for the cantennas.

Interestingly I'm getting slightly different Lg/4 (feed position) calculations from my spreadsheet than from using the various online cantenna calcs I've seen so far. If anyone spots a flaw in my maths please let me know.

Generated NEC2 data files:

Chunky.nec
Campari.nec

My spreadsheet for calculating can dimensioning and generating the .nec files:-
circ_cal.xls (latest 22 Apr 2003)

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