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Turnstile question
On Jun 17, 2:02 pm, "Jerry Martes" wrote:
wrote in message oups.com... On Jun 17, 12:47 pm, "Jerry Martes" wrote: I figured 1.8 inches for 1066 MHz. I wanted to build it into a pvc pipe cap so there isn't much room to work. Also, am I correct to assume the 1.8 is the total length, including what is stripped back to make the connection? Ralph Hi Ralph I dont know what your needs are for this Turnstile antenna, so my input may be of no value. But, a Turnstile can be made to work by feeding both dipoles with one feed point. No phasing harness is needed. Make one dipole a little short so it is capacitive and the other dipole a little long so it is inducvtive. Jerry The only problem with that is the antenna will still have basically a dipole pattern. I assume he is wanting the usual omni pattern with circular polarization at the higher angles.. But maybe not... You need the phase line if you want a true omni "turnstile" pattern. But saying that , I have used turnstiles with no line.. But usually on 80m.. And it does change the pattern a bit from the original single dipole, but not quite the same as using a phase line. MK Hi MK I may have screwed up, but I think that a pair of dipoles on the same plane, configured like a pair of non-symetrical Vs could be fed with one feed point to produce a free space cardiod pattern. That would be one short dipole and one one longer dipole fed in parallel. Jerry Jerry I'm not sure exactly what you mean.. Normally, a turnstile has both the elements the same length. If you feed two dipoles cut for the same band, but at different freq's, and feed with a single feedline, all it will do is effect the SWR plot.. Will look as a "W".. If you feed a normal turnstile with one line, but no phasing line, it will act as a normal dipole in one of the 2 plots you could have from the antenna. In that case, you could feed with two lines, and switch directions. "dipole pattern each way". You could then add 90 degrees to one line, and get an omni pattern.. That would give you three choices in plots.. But if you feed with a single line, you must use the phasing line if you want the omni "turnstile" pattern. This can be easily modeled using any modeling program.. You set the phasing in the "source" menu.. MK |
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