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Author Topic: Making a HT antenna hat  (Read 2283 times)
NV1P
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Posts: 73




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« on: April 17, 2013, 09:42:46 AM »

Hi all,

I've been using my Wouxun with a speaker mic lately, which has allowed me to leave it on my belt clip. The problem is that doing this greatly impacts the range of my radio. In order to get the antenna in the clear I'm going to attempt to make a hat with an antenna mount. I'm sure I'm not the first to think of this (I know I'm not, I saw a guy in Dayton with one), but I want to make it so that it works as best as it can.

The question is what things will I need to worry about? I've been thinking about the fact that it may be a bit difficult to make a mechanically stable 1/2 wave, so I'd have to go with something that wants a ground plane. Normally the ground plane ends up being the HT itself, so would putting a length of coax in between the rubber duck and the HT cause any kind of problems? I would imagine the coax starts to become part of the radiating element, so that could cause some issues. Would the length of the coax have a huge impact?

73,
Sam
NV1P
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WB6BYU
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Posts: 13337




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« Reply #1 on: April 17, 2013, 11:29:55 AM »

Use an aluminum hard hat for the ground plane.  Otherwise, choose a hat
with a wide brim that will allow for quarter wave radials (even if they have
to be spiraled around the brim.)  You may need to add some sort of stiffener
under the crown of the hat to provide mechanical rigidity.

Without some sort of radial system the shield of the coax will have common
mode currents, which can affect the radiation pattern.  One possible approach
is to slip 1/4 wavelength of coax braid over the outside of the feedline and
connect it to the ground side of the antenna connector to serve as a single
radial.  While there will still be some coupling to the coax, this will work better
than not providing an intentional ground system.

A half wave antenna is probably practical on 440 and higher frequencies, but
would be inconvenient on 2m.

My old TR-2600 had a shoulder strap that included a mount for a rubber
duckie on the shoulder, with two radials built into the strap.  Not as high
as hat mounted, but better than putting the antenna on your belt.
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W0FM
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Posts: 2056




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« Reply #2 on: April 18, 2013, 09:14:11 AM »

If you use a non-metallic hat (standard hard hat) you can line the inside with copper foil tape or aluminum tape.  Be sure to get "bridges" between the tape edges so it is all connected together.  Then install your antenna connector into the top of the had making certain the metal (ground side) of the connector makes good contact with the foil tape.

While the foil *may* provide some RF protection to your head, I'd keep the power low just to be safe.

73,

Terry, WØFM
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G7MRV
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Posts: 480


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« Reply #3 on: April 18, 2013, 09:36:36 AM »

Hi all,


The question is what things will I need to worry about?
73,
Sam
NV1P

I think the biggest thing you need to worry about is your image!  Grin

Ive seen these before, and while they might look a novelty around the rallys and hamfests, I really wouldnt want anyone seeing me wearing one anywhere else!  Cheesy

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G7MRV
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« Reply #4 on: April 18, 2013, 09:40:43 AM »


My old TR-2600 had a shoulder strap that included a mount for a rubber
duckie on the shoulder, with two radials built into the strap.  Not as high
as hat mounted, but better than putting the antenna on your belt.

This was/is a common method used in Public Safety radio - A combined speaker/mic and antenna, 'lapel' mounted. I think this would be far preferable to a hat mounted antenna. For a start, people are used to seeing police etc using these types of antennas, and you wont look like your in need of counselling wearing one!

Also, the cable to a hat mounted antenna will inevitably get in the way of you moving your head/peripheral vision etc and/or get snagged on things!
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WB6BYU
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Posts: 13337




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« Reply #5 on: April 18, 2013, 10:06:08 AM »

If your hat has more of a crown (rather than a baseball cap) then you could
build a DDRR inside it.

Actually, a good solid set of headphones might be a better basis for the antenna
support than a soft hat.  I made a direction-finding unit once with two 18" whips
mounted on opposite ends of a pair of earphones, which allowed me to take a
bearing on a signal by simply turning my head and listening to the sound in the
headphones.  But I really got some odd looks when I walked down a crowded
street wearing that!
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VE5EIS
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« Reply #6 on: April 18, 2013, 01:58:35 PM »

Are you using a short rubber ducky antenna?  Getting a 15"/38 cm one to replace it might just help you out enough to avoid the need for the hat.

As a bonus, when you are using the radio handheld, you will get better signal than you are now also.

They make a big difference.
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KG4RUL
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« Reply #7 on: April 18, 2013, 02:01:51 PM »

Get yourself a vest or harness that allows the radio to be higher up on your body.  That, along with a longer antenna, may salve your problem.
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K1CJS
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Posts: 6045




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« Reply #8 on: April 19, 2013, 04:02:42 AM »

I'm going to speak bluntly, please don't take offense.  You are NOT going to get much of an advantage with a hat mounted antenna.  The only thing you're going to do is to make yourself look silly.  The amount of RF energy that a HT on your belt gets compared to what a hat antenna with coax (and the losses through the connectors and the coax) gets are essentially the same.

I agree with the person who advised you to get a vest and wear the HT there.  THAT is the more practical solution, both from the signal strength and the 'looks' viewpoint.  There is also the question of the HT itself.  You only get what you pay for, so if you want better reception, get a better HT.
« Last Edit: April 19, 2013, 04:09:22 AM by K1CJS » Logged
K4RKY
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Posts: 59




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« Reply #9 on: April 19, 2013, 10:58:57 AM »

Are you using a short rubber ducky antenna?  Getting a 15"/38 cm one to replace it might just help you out enough to avoid the need for the hat.

As a bonus, when you are using the radio handheld, you will get better signal than you are now also.

They make a big difference.
[/quote ]

I agree...  just purchase a 16 inch antenna to replace the OEM? (assuming you haven't already?) My HT works noticeably better since I updated mine. It rarely leaves my belt when I'm out and about.
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Rick ^i^
VE3FMC
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« Reply #10 on: April 19, 2013, 01:54:11 PM »

Seriously, all of this discussion for the 2 meter band?  Grin
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KG4RUL
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« Reply #11 on: April 19, 2013, 02:00:10 PM »

Seriously, all of this discussion for the <insert your least liked band here> meter band?  Grin
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