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considering an M400 starduster. whats the deal?

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  #17  
Old 09-06-2009, 10:30 PM
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dontya just love it when you learn new things and they just create more questions? LOL

after reading numerous threads about this stuff, as well as other articles online;
im not sure if this antenna is a vertical dipole, or a 1/4 wave groundplane antenna, or what!

for example, to make a vertical "bazooka" antenna; you peel back about a 1/4 wavelength of the coax shield.

if the starduster didnt have the drooping radials; i would say thats what the antenna is. a vertical bazooka type antenna.

but then, why the need for the drooping radials?
if its a 1/4 wave groundplane antenna, then why the "sleeve", or "bazooka" formed by the metal mast?

i sure hope we get somewhere with this!
LC
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Old 09-07-2009, 02:23 AM
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From looking at the assembly instructions, this thing is a vertical, center fed, half wave length antenna. Or, just another 1/4 w groundplane type with really droopy radials. That depends on if that 'large hub' provides any insulation between the radiator above it and the radials and mounting pipe. I would assume that it does, or the whole thing would be just one 'electrical' piece and a terrible antenna.
I don't think I'd confuse things by describing any part of this thing as a 'bazooka'. That indicates a completely different antenna and feeding system. The coax may go through that pipe, but since the radials appear to be insulated from that pipe, the pipe is just to support the hub, not really a part of the antenna as such.
Without getting my hands on one that's about as much as I can 'guess' from the assembly instructions. It appears to be ust another 1/4 w groundplane type antenna of a slightly different shape. And all 1/4 w groundplane type antennas are the same as a vertical dipole, just in a slightly different shape.
- 'Doc

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  #19  
Old 09-07-2009, 02:58 AM
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Doc, I thought this antenna was a droopy 1/4 wave vertical too. If it is 1/2 wave dipole by effect - I couldn't say. I don't know much about antennas as I should for a Ham. I'm glad that being a Ham is really a learning process...

I know that I got the IMAX from so many great reports on eHam - as well as other web pages. I almost bought the StarDuster because of the price and its great reputation. The fact that Palco Elec. has them for a really fair price makes it an attractive and effective choice. The IMAX I bought eight months ago from Palco for $85 is now selling for $95. Probably the effect of inflation in that time period - or they are more popular now. Maybe both. But if I had to budget myself and wanted an antenna with a great reputation, I would have gotten the StarDuster. It was close.
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  #20  
Old 09-07-2009, 01:24 PM
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Just for grins, take one 1/4 w groundplane antenna. Fold the radials so that they are parallel to, and the other direction of that vertical part. Looks a whole lot like a 1/2 w dipole if you turn it sideways. Same dimensions most of the time.
- 'Doc

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  #21  
Old 09-07-2009, 06:07 PM
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W5LZ, (Led Zepplin?)

the radials are not insulated from the lower portion of the hub.

the only thing insulated from the "ground" portion of this antenna is the vertical radiator.

both the radials, and the mounting pole are connected to the shield of the coax.


hope that helps clear things up.
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Old 09-07-2009, 10:30 PM
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loosecannon,
Going by the assembly instruction posted, the radials are insulated from that pole, there are insulators on the radials between the support pieces holding the radials away from the pole (both ends). That makes me tend to think that the 'large hub' is also insulated from the pole, otherwise, why bother with the other insulators??
- 'Doc

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  #23  
Old 09-08-2009, 08:29 AM
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"....the 'large hub' is also insulated from the pole"

it isn't. the hub, the radials and the mast are all at the same current potential.

Last edited by freecell; 09-08-2009 at 10:56 AM.

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  #24  
Old 09-08-2009, 01:31 PM
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doc,

the only reason those radials are attached to the mast at all is for wind support.

im not sure how else to say it.
they are radials. they are connected to the shield of the coax, and they extend down from there.

i am not guessing about this. thats the way it is.


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