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Author Topic: Vest Wearable Antennas  (Read 395 times)

N4SRN

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Vest Wearable Antennas
« on: February 19, 2022, 06:56:50 AM »

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Bret/N4SRN
Bedford, NH  USA

K0UA

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Re: Vest Wearable Antennas
« Reply #1 on: February 19, 2022, 08:44:10 AM »

To me, they look like an interesting way to waste from $59 to around $70.
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73  James K0UA

K1KIM

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Re: Vest Wearable Antennas
« Reply #2 on: February 19, 2022, 10:13:36 AM »

To me, they look like an interesting way to waste from $59 to around $70.

^^^
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So Many Toys.......So Little Time!

KG4RUL

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Re: Vest Wearable Antennas
« Reply #3 on: February 19, 2022, 10:28:02 AM »

Yessir, let's wrap an antenna around our torso. 

No POSSIBLE harm in that.  :o

BTW, this does not meet the FCC exposure rules.
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N4SRN

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Re: Vest Wearable Antennas
« Reply #4 on: February 19, 2022, 10:36:56 AM »

Just a 4W HT y'all - the ones we hold next to our brains  ;)

I guess 0.24ft (3in) would be the safe standoff on 70cm and 8in on 2m.

Agreed, not a great idea for regular use.
« Last Edit: February 19, 2022, 10:43:37 AM by N4SRN »
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Bret/N4SRN
Bedford, NH  USA

K1VSK

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Re: Vest Wearable Antennas
« Reply #5 on: February 19, 2022, 12:03:59 PM »

Just a 4W HT y'all - the ones we hold next to our brains  ;)


That explains the use of words like "destinated" so often repeated on VHF
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WB6BYU

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Re: Vest Wearable Antennas
« Reply #6 on: February 19, 2022, 03:05:00 PM »

A 1/4 or 3/4 wave wire would be worth trying.  Just stick one bare
end into the coax connector and try it out.

One advantage of hanging it on a vest is that there would be a bit of
spacing from your body, which would improve the SWR.

All depends on how far you need to talk.  In some cases a stubby
duck with a quarter wave hanging radial wire would probably work
as well, without sticking into your face too much (depending where
you hang your radio).

KB1GMX

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Re: Vest Wearable Antennas
« Reply #7 on: February 22, 2022, 04:44:53 AM »

Body worn antennas (on vest) generally need to be tuned for the
band of interest due to the loading effects of the body.  The bigger
issue is pattern, you want omni-directional but, no matter where the
antenna is put on the vest the body will be in the way for some direction.
On the vest also means potentially lower height and decreased range.
The cable will likely be in the way and need to be dealt with as well.

The average supplied rubber-duck at 6-7" will be far better.

Allison
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WB6BYU

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Re: Vest Wearable Antennas
« Reply #8 on: February 22, 2022, 08:09:29 AM »

Quote from: KB1GMX

Body worn antennas (on vest) generally need to be tuned for the
band of interest due to the loading effects of the body.  The bigger
issue is pattern, you want omni-directional but, no matter where the
antenna is put on the vest the body will be in the way for some direction.
On the vest also means potentially lower height and decreased range.




I agree with Allison that they may not be ideal for most
ham uses.


It might be worthwhile looking at how they are intended
to be used, and how that makes a difference.

The intended application appears to be military wideband
communication using spread spectrum over relatively
short ranges, when you may be focused on doing some
other task. 

A ham equivalent might be chatting with your buddies
while digging through a pile of junk at a hamfest, or
communicating with the ground crew while working
on a tower, rather than hitting a distant repeater.
Most likely with the radio on your belt or in a pocket
where you might squeeze the PTT to transmit, but
aren’t picking it to talk on it.

The wideband SWR curve for the antenna (something
like 30 - 170 MHz, plus UHF) suggests some resistive
loading or other intentional losses.  May not be an
issue at 100 yards, but likely significant at a mile.

Mounting it on a military vest probably puts a few
inches of Kevlar between it and your body, so less
detuning and absorption than a yellow safety vest.
The recommended installation is to run it up from
the radio, over the shoulder, and down the back,
which at least reduces the problems with body
blockage.  And if your radio is also strapped to
the vest and not moved when you use it, the
feedline could be laced to the vest as well, so
it doesn’t get in the way.


Whether or not it makes for ham use depends on
individual circumstances, of course.  I wouldn’t
count on it for reliable communications any further
than I can yell (and perhaps less - I’ve been
measured at 1/3 mile).  But if it keeps me from
needing to shout and annoy everyone else
around me, that might be a good thing,

But since I’m not using wideband spread spectrum
modes, I’d probably try a 1/4 or 3/4 wave wire
woven into my yellow vest and pruned somewhat
to resonance when I’m wearing it, and see if that
serves the purpose at a lower cost.

KB1GMX

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Re: Vest Wearable Antennas
« Reply #9 on: February 23, 2022, 08:33:43 AM »

w6byu,

He's on target for that.  Mil was the primary user.  Did a lot of development
work while working for a boutique antenna engineering firm. 

The kevlar (think IOTV) and plates as ways to make the antenna work
better and keep the RF away from the user.  Matching is also by several
means as needed for the required bandwidth.

Has a high batman cool factor but, not all that useful for average use for
EMCOM events like Boston marathon and other supported sports events.

For the close in use we do short (stubby or vendor stock duck) antenna on
the belt with speaker mic.  For short haul local (to less than a mile) that
works well and is out of the way.  Works fine for simplex ops at the local HAM
fleas at state fairgrounds.  For working events at range though repeaters
antennas high as possible and large as possible is often the requirement
when using HTs.

Allison
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WA3SKN

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Re: Vest Wearable Antennas
« Reply #10 on: April 15, 2022, 04:31:24 PM »

Looking at the MPE specs, there does not appear to be a SAFETY issue with these on 2m/440Mhz.
However, from a practical aspect... whats wrong with just using the supplied rubber duck?

-Mike.
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K3XR

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Re: Vest Wearable Antennas
« Reply #11 on: April 15, 2022, 04:35:37 PM »

Gives new meaning to the phrase..."Toast of the town."
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KB1GMX

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Re: Vest Wearable Antennas
« Reply #12 on: April 25, 2022, 12:22:04 PM »

The SAR (MPE) effects are small and permissible.

The general use model is less than 20% activity (transmitting)
and real may be far less than that.  TX duty cycle is a factor in
the real world and in actual tests.

FYI the mil guys are low power too for their flavors of HT or
for the DSS average power is low enough that SAR is generally
not an issue.

Doesn't mean get stupid and run a long TX.  Battery usually
stops that anyway.  Also using full 5W for local comms may
be wasting your battery.  For distance especially VHF and up
height is the the majik sauce that works better than higher
power.

Oh, the best location for antenna, top of the helmet, its higher
and the bucket if metalized makes a good ground plane
with decent pattern.  Has low user SAR too.   Looks
goofy as all get out.   --[ ;-)

Allison
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N4MU

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Re: Vest Wearable Antennas
« Reply #13 on: May 15, 2022, 06:00:52 AM »

To me, they look like an interesting way to waste from $59 to around $70.

Yes, but they're ON SALE!  How do you get vertical polorization...lay down?
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