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Stainless Steel Tube for Yagi Directors
Hello All,
I am building a DL6WU Yagi for 2 metres and am wondering if 1/4 inch stainless steel tube would be okay for the directors and reflector. I have been given some so it would save me from having to buy aluminium. I will still use aluminium for the folded dipole and for the boom. Any thoughts would be welcome. Cheers Max |
Stainless Steel Tube for Yagi Directors
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Stainless Steel Tube for Yagi Directors
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Stainless Steel Tube for Yagi Directors
In message , Alan Peake
writes wrote: Hello All, I am building a DL6WU Yagi for 2 metres and am wondering if 1/4 inch stainless steel tube would be okay for the directors and reflector. I have been given some so it would save me from having to buy aluminium. I will still use aluminium for the folded dipole and for the boom. Any thoughts would be welcome. Cheers Max It will probably be a bit lossier than using Al but my first Yagi on 288 MHz(in the early 60s)was made out of 8g fencing wire and it seemed to work reasonably well. Try the evaluation version of Eznec - I think you can specify the material. Alan MMANA gives 3dB degradation for Fe over Al (11ele DK7ZB on 2m), which surprises me. What does Eznec give ? Brian GM4DIJ -- Brian Howie |
Stainless Steel Tube for Yagi Directors
Brian Howie wrote: MMANA gives 3dB degradation for Fe over Al (11ele DK7ZB on 2m), which surprises me. What does Eznec give ? Brian GM4DIJ Using an 11 el DL6WU at 144.2MHz and 10mm elements, EZNEC gives gains of 14.31 dBi for Al and 14.22 for SS. With 5mm elements, it's 14.54 for Al and 14.37 for SS. I used a figure of 7e-7 ohm-m for the resistivity. Most stainless steels range from 5e-7 to 7.4e-7 ohm-m. 3dB does seem excessive. Alan VK2ADB |
Stainless Steel Tube for Yagi Directors
Max,
While there may be some degradation in gain from using stainless steel, would it really make that much difference? I think the 'biggy' is that you already have the stainless steel and would have to find the aluminum. Maybe the next 'biggest' thing would be making electrical contact between sections of that steel? A tenth of a dB loss just ain't no step for a stepper... - 'Doc (all puns intended) |
Stainless Steel Tube for Yagi Directors
Alan Peake wrote:
Brian Howie wrote: MMANA gives 3dB degradation for Fe over Al (11ele DK7ZB on 2m), which surprises me. What does Eznec give ? Brian GM4DIJ Using an 11 el DL6WU at 144.2MHz and 10mm elements, EZNEC gives gains of 14.31 dBi for Al and 14.22 for SS. With 5mm elements, it's 14.54 for Al and 14.37 for SS. I used a figure of 7e-7 ohm-m for the resistivity. Most stainless steels range from 5e-7 to 7.4e-7 ohm-m. 3dB does seem excessive. Alan VK2ADB Apparently Brian used iron as the model material, which of course is magnetic. Skin depth is reduced, and therefore RF resistance increased, by the square root of the permeability. So if the iron model's permeability is, say, 100, it would increase the effective resistance by a factor of 10. Some stainless steels are magnetic, some are not. The magnetic ones have much higher RF resistance than the non-magnetic ones for the above reason. Roy Lewallen, W7EL |
Stainless Steel Tube for Yagi Directors
In message ,
Roy Lewallen writes Alan Peake wrote: Brian Howie wrote: MMANA gives 3dB degradation for Fe over Al (11ele DK7ZB on 2m), which surprises me. What does Eznec give ? Brian GM4DIJ Using an 11 el DL6WU at 144.2MHz and 10mm elements, EZNEC gives gains of 14.31 dBi for Al and 14.22 for SS. With 5mm elements, it's 14.54 for Al and 14.37 for SS. I used a figure of 7e-7 ohm-m for the resistivity. Most stainless steels range from 5e-7 to 7.4e-7 ohm-m. 3dB does seem excessive. Alan VK2ADB Apparently Brian used iron as the model material, which of course is magnetic. Skin depth is reduced, and therefore RF resistance increased, by the square root of the permeability. So if the iron model's permeability is, say, 100, it would increase the effective resistance by a factor of 10. Some stainless steels are magnetic, some are not. The magnetic ones have much higher RF resistance than the non-magnetic ones for the above reason. Yes I rechecked it with 7e-7 ohm-m and 0 permeability and got a lot better results. Moral here is don't use iron wire for antennas . 73 Brian GM4DIJ -- Brian Howie |
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