Helical Antennas

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Re: Helical Antennas (RE: Kaltman Creations LLC IWxCPA )

Well, what is up with that? I tried to look at those images and I got a message that says "Invalid Attachment". Darn.
 
Re: Helical Antennas (RE: Kaltman Creations LLC IWxCPA )

Stupid question from an RF newbie - what do the three highlighted bands signify? The center one is presumably the center frequency, but what are the outer two? Harmonics of some kind?
 
Re: Helical Antennas (RE: Kaltman Creations LLC IWxCPA )

TJ Cornish said:
Stupid question from an RF newbie - what do the three highlighted bands signify? The center one is presumably the center frequency, but what are the outer two? Harmonics of some kind?
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Hi TJ,

The grey bands mark the three bands that I set for channel power measurement. Each band is 6MHz wide, to show the total power measured within each of those TV channels. It's a more honest way of comparing modulated signal strengths than picking a single frequency within a channel. If the carriers were unmodulated, a single frequency would show a reasonably honest comparison.

FWIW, the center bar is the main measurement channel, with power value shown at the top. The channels to each side are compared channels, with power value at the top, and difference to the main channel value shown immediately beneath that. The left channel effectively shows the noise floor of my rig. The right channel is helpful because measuring a single channel isn't really fair for a wideband antenna comparison. It helps you to see if the main channel's signal power is anomalous due to impedance variations, etc.
 
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Re: Helical Antennas (RE: Kaltman Creations LLC IWxCPA )

Bennett Prescott said:
Jason,

SFN owes you a beer or two for this outstanding post and the work that led up to it. Thank you so much.
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Andrew Broughton said:
Indeed. Since it was me that started all this, send me a PM and let me know when we're in your town and we'll make good on that.
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It's my pleasure, guys. I live for this stuff. I learn something new every time a good discussion comes up, and learn the most when I get hands-on with subjects that I'm familiar with.

Oh, and Sweetwater IPA is nectar of the gods, as far as I'm concerned.
 
Re: Helical Antennas (RE: Kaltman Creations LLC IWxCPA )

Friends, Romans,

I have removed Jason's highly detailed posts at his request. Apparently he was threatened with legal action by one of the manufacturers whose antenna he measured. I wish we had the clout to back him up, but I know personally some small organizations involved in legal action and we would need more money than we make off ad revenue in a decade to go to bat here. I am closing this thread as I don't want any further discussion to land Jason in hot water.
 
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