Moxon Rectangles for Satellite Use

[VK2MUS]

Have been playing around learning the digital modes on HF (love jt65A) and now want to have a play with Satelitte on 2m and 70cm bands (very little voice activity on these bands where I am). Thinking of buiding a turnstyle type antenna based on two sets of Moxon Rectangles to cover the two band freqs. The Moxgen programs does the calucaltions based on solid ie wire or rod however I have a load of steel brake line laying about not doing anything so would like to use it for the elements but unsure what effect the use of the tube would be over say solid rod, the measurement appear to change as the diameter (or circumfence) of the material used changes . Any experts out there that can make a suggestion on this.

I am in the process of building a quadrifilar helix for 2m for weather Sat work but this is a more complex project and the Moxon looks like it could be built in a hour or so.
John

[VK3ALB]

My head is telling me that steel may not be the best material to use but for the sake of a one hour experiment I think I'd be inclined to give it a go.

[VK7DB]

Steel is no good.. Use aluminium.. Have a play with MMANA software, model some antennas and run the calculation with al or cu wire vs fe and you'll see the difference.. You could even model the turnstile Moxon and see how it will perform, something makes me think I've already modelled one, I'll see if I can find it..

[VK2MUS]

thanks for the replies - have MMana and have used that to see the differences as diameter changes etc but for the life of me can't find where to change the source material. I assumed that steel would be low down on the list when construction antennas however as this is soft steel and it can be built fairly fast just might knock one up and see what happens - called experiementing I suppose. I am still getting over the dual band catus J pole I built (just for the fun of building it)- booms in better then the commercial vertical I bought. The Jpole cost me $45 the commercial one cost me about $250
John
correction: found the setting for material type - will go off and model the moxon and see what happens

[VK7DB]

I just modelled a Turnstile Moxon, I have attached it for you to look at.. Rename to MOXON.maa

[VK2GOM]

If you want a super-simple satellite antenna that will work well for the FM satellites, have a look at an IOio antenna.

http://personales.ya.com/ea4cax/paginae ... ingles.pdf

I have published my own crossed Yagi antenna design on the AMSAT site, but it's probably pushing the limits of what can be portable and hand-held.

73 - Rob VK2GOM / G0MOH

[VK7DB]

I re-read your original post.. The use of tube rather than solid has little to no effect as RF flows on the skin.. Skin Effect The version of Moxgen that I have allows me to input the tube diameter in mm rather than AWG. I guess it assumes the builder uses material with better conductivity than steel, something like copper or aluminium.. You could generate a model to start with using Moxgen then optimise or scale it to suit steel with MMANA before you build it..

The moxon is a good compact antenna, I use one gamma matched vertical polarised for the local 6 metre repeaters..

[VK2XSO]

Brasing wire, thin copper tubing or I might still have some aluminium tube I can drop off next time I pass by.

[VK2MUS]

Brasing wire, thin copper tubing or I might still have some aluminium tube I can drop off next time I pass by.

Your better then the local JayCar outlet. The solf steel tube comes out on the bottom scale but it would still be workable but then if you have some brasing wire laying around (about 2m). I was just thinking about all that copper pipe etc I sold when I sold up the the farm .Why didn't you talk me back in to radio before I left the farm! )
We finally have an antenna raising day tomorrow with all the boys on hand


Thanks to VK7DB for the moxon.maa file

[VK2MUS]

I re-read your original post.. The use of tube rather than solid has little to no effect as RF flows on the skin.. Skin Effect The version of Moxgen that I have allows me to input the tube diameter in mm rather than AWG. I guess it assumes the builder uses material with better conductivity than steel, something like copper or aluminium.. You could generate a model to start with using Moxgen then optimise or scale it to suit steel with MMANA before you build it..

The moxon is a good compact antenna, I use one gamma matched vertical polarised for the local 6 metre repeaters..

I was thinking of the skin effect - the conductivity of the soft steel should also be better then the conductivity of hard steel maybe due to the fact that the solt steel tubing would be more a steel alloy mix. I came across another antenna design program where one can enter the detail specs of the metal used however this was a professional commercial program with a professional commercial price to match. With some thing as simple as the moxon a build it and run it up the flag pole approach is probably the best way to go. It just interests me on how these 'unusual' designs work - generally they are so simple to build and take up so little space.