[Antennas] Fat rugged dipole?

Wed Jul 27 16:35:38 EDT 2016

Frank,
Kirk was talking about:
Generally, for an element of 4" or 6" length, how fat would it need to be to
> be resonant at 312 MHz?
>
That's what I meant about he's not going to change the laws of physics -
he's not going to make a half wave which is 1.5 feet change into 4 inches.
He's asking for a 300% to 450% percent reduction in size.
Ain't going to happen without losses.
But with good coil construction - more difficult at 312 MHz than at 7 MHz
for sure, but just think of a handi-talkie - we have 2meter with a stubby
whip.
Not great efficiency but it works.
Something like that should work for Kirk.
73
David N1EA
On Wed, Jul 27, 2016 at 3:08 PM, frank <frank at k5dkz.com> wrote:
> On 2016年7月27日 12:44:54 -0400
> "D.J.J. Ring, Jr." <n1ea at arrl.net> wrote:
>> > Kurt,
> >
> > You're not going to change the rules of physics, one half wave is always
> > going to be the same size.
>> Well, my physics book says that very fat dipole elements are shorter than
> very thin dipole elements to be resonant at the same frequency. How much
> shorter depends on how fat is fat. I am pretty sure you will not get more
> than a 10% length reduction no matter how fat the element gets.
>> The same holds true for verticals. Maybe you can go up instead of out?
>>>> > On Jul 27, 2016 12:16 AM, "KD7JYK DM09" <kd7jyk at earthlink.net> wrote:
> >
> > > I've been running some number for a dipole at 312 MHz.
> > >
> > > Using 468/f, I get 1.5', too large for my installation and that's for a
> > > "wire" antenna.
> > >
> > > I need something rugged to avoid possible damage grom vandals, and most
> > > likely, large animals. No problem with a couple of elements turned
> out of
> > > solid aluminum looking like a couple of small soup cans...
> > >
> > > I know a radial can be shortened to an extent if it's fattened...
> > >
> > > Generally, for an element of 4" or 6" length, how fat would it need to
> be
> > > to
> > > be resonant at 312 MHz?
> > >
> > > Is there a resaonably easy to use calculation for such things?
> > >
> > > Thanks.
> > >
> > > Kurt
> > >
> > >
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>>> --
> 73, Frank
>>