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Helical/Corkscrew in Mobile Antennas: What’s the high-level science explanation?


CALO50

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4 minutes ago, OffRoaderX said:

I've always assumed that the corkscrew makes the RF electricities spin-around faster and then squirt out of the antenna at a higher rate, making them go more fars..

..i could be wrong though.

Ahhhh... RF electricities centripetal force.

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2 minutes ago, OffRoaderX said:

My OTHER theory is that the corkscrew just allows you to have a shorter antenna with the same electrical length, and it has nothing to do with performance, other than having a shorter antenna that is just as performant as a longer one.

New theory...  RF electricities centripetal fars.

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Okay, I will try to make this as painless as possible.  No promises though.  Hopefully, if I make a mistake, some of the smarter guys will let us know.

 

High-level Science

OffRoaderX is correct, but there is one other reason that is pretty common that comes to mind, specifically for phasing multi-band antennas.  Though, this obviously doesn't apply to GMRS specific antennas.

Quick example... the Diamond NR770 dual-band mobile antenna is listed as a 1/2 wave VHF antenna and a 2 phase 5/8 wave UHF antenna.  There is a coil in the center of the antenna to electrically make a VHF half wave antenna, which has almost no gain.  The coil also acts like a separator and a phase coupler(?) for each 5/8 wave segment, being the straight parts below and above the coil, leading to having about 3 dB of gain.

 

Is there a compromise?

eh... for GMRS, there is normally a benefit associated with it, such as having a gain antenna in a smaller package.  I am not really sure of any drawbacks if it built right.

 

Is performance advantage material dependent? 

Sort of.  Some materials conduct electricity better than others, but the common materials used for antennas have negligible performance differences.

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Okay, I will try to make this as painless as possible.  No promises though.  Hopefully, if I make a mistake, some of the smarter guys will let us ..


Lol...

Smarter???.. one of the few people that knows his shit. Then there is Mike W, when he talks, I just try to not look like a mouth breather next to him.

Sent from my SM-S901U using Tapatalk

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1 hour ago, back4more70 said:

I see that my Nagoya UT-72G GMRS antenna does not have a coil, but my Tram 1181 VHF/UHF antenna does.  Hmm...

 

On the Nagoya UT-72G, the coil in in the base of the antenna, referred to as a bottom load.  The Tram 1181 has a coil in the middle, referred to as a center load.

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19 hours ago, marcspaz said:

 

 

Okay, I will try to make this as painless as possible.  No promises though.  Hopefully, if I make a mistake, some of the smarter guys will let us know.

 

High-level Science

OffRoaderX is correct, but there is one other reason that is pretty common that comes to mind, specifically for phasing multi-band antennas.  Though, this obviously doesn't apply to GMRS specific antennas.

Quick example... the Diamond NR770 dual-band mobile antenna is listed as a 1/2 wave VHF antenna and a 2 phase 5/8 wave UHF antenna.  There is a coil in the center of the antenna to electrically make a VHF half wave antenna, which has almost no gain.  The coil also acts like a separator and a phase coupler(?) for each 5/8 wave segment, being the straight parts below and above the coil, leading to having about 3 dB of gain.

 

Is there a compromise?

eh... for GMRS, there is normally a benefit associated with it, such as having a gain antenna in a smaller package.  I am not really sure of any drawbacks if it built right.

 

Is performance advantage material dependent? 

Sort of.  Some materials conduct electricity better than others, but the common materials used for antennas have negligible performance differences.

Sounds reasonable. Thank you for not sending us into a differential equation coma. 

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