antenna lengths
 

There are some commonly occurring lengths for multi-band dipoles. I see
105', 135', and 140'. Is 140' preferred over 135'? If so, what is the
benefit of going from 135' to 140'? Just curious.

antenna lengths
 

RB wrote:
There are some commonly occurring lengths for multi-band dipoles. I see
105', 135', and 140'. Is 140' preferred over 135'? If so, what is the
benefit of going from 135' to 140'? Just curious.

That's about a 3.5% difference. You get just about that much difference
between insulated and uninsulated wire. That much difference in length
doesn't much matter for non-resonant length dipoles. However, for
resonant dipoles, length certainly matters and 140 ft. would probably
be resonant outside of the 80m band. For instance, a resonant 1/2WL
dipole for 3.8 MHz would be about 123 foot long.
--
73, Cecil http://www.qsl.net/w5dxp

antenna lengths
 

Hi RB, With multi-band dipoles you will have to use an antenna tuner.
The lengths you see in the charts are chosen such that the
antenna+feedline will have an impedance (hopefully) on multiple bands
that your antenna tuner can handle. Usually if a 135' dipole won't
load on a certain band, the feedline length is changed, because it is
easier than bringing down the dipole and changing to 140'.
Gary N4AST

antenna lengths
 

On Tue, 25 Oct 2005 21:40:09 GMT, Cecil Moore wrote:


That's about a 3.5% difference. You get just about that much difference
between insulated and uninsulated wire. That much difference in length

Cecil, do you have theoretical or experimental support for the
inference that insulated vs uninsulated wire will be different in
length by around 3.5%? What thickness wire / insulation?

Owen
--

antenna lengths
 

do you have theoretical or experimental support for the
inference that insulated vs uninsulated wire will be different in
length by around 3.5%? What thickness wire / insulation?

Owen

=========================================

To calculate change in velocity due to plastic PVC insulation we need
to know :-

Wire diameter = d
Diameter over insulation = D
Height of wire above ground = H
Permittivity of insulating material = K

First calculate capacitance of bare wire to ground.
Then calculate capacitance of insulated wire to ground.
Velocity Factor = SquareRoot of their ratio.
Neither Terman's nor Kraus' Bibles will mention the following
formulae. So you'll just have to take my word for it.


Velocity Factor = SquareRoot( ( A + B ) / C )

Where -

A = K * Ln( 4 * H / D )

B = Ln( D / d )

C = K * Ln( 4 * H / d )

Example :
Bare wire diameter = 1.6 mm = 14 awg.
Diameter over insulation = 2.6 mm.
Height above ground = 10 metres = 33 feet.
Permittivity of insulation = 3.5

Velocity factor = 0.983
Or a decrease in resonant frequency of 1.7 percent which can nearly
always be forgotten about.

The electrical effect of the enamel on magnet wire is entirely
negligible. But it does protect the wire from atmospheric pollution.
----
Reg.

antenna lengths
 

"RB" wrote in message
...
There are some commonly occurring lengths for multi-band dipoles. I see
105', 135', and 140'. Is 140' preferred over 135'? If so, what is the
benefit of going from 135' to 140'? Just curious.

Read the following:
http://members.dslextreme.com/users/w6wqc/antenna.html
The data on antenna efficiency is a misinterpretation of the NEC output
file. It refers only to copper losses, and does not include ground losses.
The discussion that "The length of an antenna wire is irrelevant" is the key
point made.

73,

Frank

antenna lengths
 

There are some commonly occurring lengths for multi-band dipoles. I see
105', 135', and 140'. Is 140' preferred over 135'? If so, what is the
benefit of going from 135' to 140'? Just curious.

Pse look at the web: http://www.qsl.net/aa1ll/cfwire.htm
Depending on your location (length of the feeder and free space for the
dipole) consider Region 1, 3 or G5RV Region.

73 Chris SP7ICE

antenna lengths
 

There are some commonly occurring lengths for multi-band dipoles. I see
105', 135', and 140'. Is 140' preferred over 135'? If so, what is the
benefit of going from 135' to 140'? Just curious.

Pse look at the web: http://www.qsl.net/aa1ll/cfwire.htm
Depending on your location (length of the feeder and free space for the
dipole) consider Region 1, 3 or G5RV Region.

73 Chris SP7ICE

antenna lengths
 

Owen Duffy wrote:
Cecil, do you have theoretical or experimental support for the
inference that insulated vs uninsulated wire will be different in
length by around 3.5%? What thickness wire / insulation?

Owen, that info came from Roy, W7EL, who built it into the latest
version of EZNEC. It has to do with the VF of insulated wire Vs
uninsulated wire which affects wire antennas as well as transmission
lines.

I discovered it for myself when I was building vertical loop
antennas many years ago. The equation 1005/f wasn't even close
using insulated wire.

For instance, my 130 foot bare copper wire dipole is resonant at
3.633 MHz according to EZNEC. Adding 0.05 inch of PE insulation
drops the resonant frequency to 3.526 MHz, about a 3% drop
according to EZNEC.
--
73, Cecil http://www.qsl.net/w5dxp

antenna lengths
 

On Wed, 26 Oct 2005 00:15:11 +0000 (UTC), "Reg Edwards"
wrote:

do you have theoretical or experimental support for the
inference that insulated vs uninsulated wire will be different in
length by around 3.5%? What thickness wire / insulation?

Owen

=========================================

To calculate change in velocity due to plastic PVC insulation we need
to know :-

Wire diameter = d
Diameter over insulation = D
Height of wire above ground = H
Permittivity of insulating material = K

First calculate capacitance of bare wire to ground.
Then calculate capacitance of insulated wire to ground.
Velocity Factor = SquareRoot of their ratio.
Neither Terman's nor Kraus' Bibles will mention the following
formulae. So you'll just have to take my word for it.


Velocity Factor = SquareRoot( ( A + B ) / C )

Where -

A = K * Ln( 4 * H / D )

B = Ln( D / d )

C = K * Ln( 4 * H / d )

Example :
Bare wire diameter = 1.6 mm = 14 awg.
Diameter over insulation = 2.6 mm.
Height above ground = 10 metres = 33 feet.
Permittivity of insulation = 3.5

Velocity factor = 0.983
Or a decrease in resonant frequency of 1.7 percent which can nearly
always be forgotten about.

The electrical effect of the enamel on magnet wire is entirely
negligible. But it does protect the wire from atmospheric pollution.

Thanks Reg. I had not doubt there was an effect, but it was the
arbitrary percentage figure that was implied irrespective of physical
parameters which could have a large range (such as your examples).

Clearly, the effect is a minor one in practical HF wire antenna cases
compared to the influence of nearby structures, ground conditions etc,
and one that is adequately dealt with by normal expectations of
trimming length of an antenna for resonance (where that is the
objective) rather than "designing" for the insulation factor.

Owen
--

antenna lengths
 

"Reg Edwards" wrote

To calculate change in velocity due to plastic PVC insulation we
need
to know :-

Wire diameter = d
Diameter over insulation = D
Height of wire above ground = H
Permittivity of insulating material = K

First calculate capacitance of bare wire to ground.
Then calculate capacitance of insulated wire to ground.
Velocity Factor = SquareRoot of their ratio.
Neither Terman's nor Kraus' Bibles will mention the following
formulae. So you'll just have to take my word for it.


Velocity Factor = SquareRoot( ( A + B ) / C )

Where -

A = K * Ln( 4 * H / D )

B = Ln( D / d )

C = K * Ln( 4 * H / d )

Example :
Bare wire diameter = 1.6 mm = 14 awg.
Diameter over insulation = 2.6 mm.
Height above ground = 10 metres = 33 feet.
Permittivity of insulation = 3.5

Velocity factor = 0.983
Or a decrease in resonant frequency of 1.7 percent which can nearly
always be forgotten about.

The electrical effect of the enamel on magnet wire is entirely
negligible. But it does protect the wire from atmospheric pollution.

========================================

After a couple of days, and the time it took to derive the equations,
does nobody want to argue about it ? What about you, my dear Richard
Clark ?

By the way, I have now reverted to Australian, Banrock Station red
plonk as being the best buy in my local supermarket. To get into my
glass it has to come 12,000 miles. But, like it or not, our small
globe gets smaller day by day.
----
Reg, G4FGQ.

antenna lengths
 

On Sat, 29 Oct 2005 22:31:04 +0000 (UTC), "Reg Edwards"
wrote:
does nobody want to argue about it ? What about you, my dear Richard Clark ?
By the way, I have now reverted to Australian, Banrock Station red

I've been drinking "Tango" labels from Argentina. Wanna step out into
the parking lot to talk about this?

antenna lengths
 

On 2005-10-29, Reg Edwards wrote:
By the way, I have now reverted to Australian, Banrock Station red

Yellow Tail Shiraz

antenna lengths
 

"Richard Clark" wrote -

Wanna step out into
the parking lot to talk about this?

===================================

A typical USA aggresive attitude towards foreigners. ;o)

antenna lengths
 

What da ya mean by that, you want me to kick your limey ass...

"Reg Edwards" wrote in message
...
===================================

A typical USA aggresive attitude towards foreigners. ;o)

antenna lengths
 

Reg Edwards wrote:
"Richard Clark" wrote -
Wanna step out into
the parking lot to talk about this?

A typical USA aggresive attitude towards foreigners. ;o)

That's also a pick up line, Reg. :-)
--
73, Cecil http://www.qsl.net/w5dxp

antenna lengths
 

On Sun, 30 Oct 2005 20:50:17 GMT, Cecil Moore wrote:

Reg Edwards wrote:
"Richard Clark" wrote -
Wanna step out into
the parking lot to talk about this?

A typical USA aggresive attitude towards foreigners. ;o)

That's also a pick up line, Reg. :-)

Cecil, I don't know whether these guys want to step into the parking
lot to trade kicks to the groin, or to smooch... but neither is too
edifying!

Owen
--

antenna lengths
 

Reg Edwards wrote:

A typical USA aggresive attitude towards foreigners. ;o)


I hope none of the readers of this newsgroup are tempted to consider
Reg's attitude or abrasiveness as typical of his countrymen. I recently
returned from three weeks in Great Britain, ranging from southern
England to the Isle of Skye in Scotland, and to southern and central
Wales. Like on my previous three trips there, I was treated very well by
some of the nicest people I know and have met. I, my wife, and son were
taken in as house guests by two very good friends in different parts of
the country.

I'm sure that if I'd displayed the sort of attitude toward the British
that Reg constantly does toward Americans, I would have had an entirely
different experience. But I'd rather concentrate on what good people
have in common. And there are a lot of good people in all countries. As
well as a few grumps, of course.

Roy Lewallen, W7EL

antenna lengths
 

Roy, I have to second your opinion. The last time the wife and I were in
Europe, we were standing in the airport in Frankfurt heading to Italy, we
both at the same time said "Let's go back to England".

We like to stay at the Bull in Gerrard's Cross and find the people are
wonderful. I was readily accepted into the Denham flying club and enjoyed
touring England via private plane. The huge chalk carvings south of London
can only be appreciated from the air.

I picture Reg as an old socialist that time has passed by, and he has since
decided to become a professional curmudgeon. He does provide humor from time
to time. We must always remember - Everyone has a purpose in life, even if
it is only as a bad example -.

I think of him every time I see the brother-in-law on "Keeping Up
Appearances" on the BBC.

"Roy Lewallen" wrote in message
...
Reg Edwards wrote:

A typical USA aggresive attitude towards foreigners. ;o)


I hope none of the readers of this newsgroup are tempted to consider
Reg's attitude or abrasiveness as typical of his countrymen. I recently
returned from three weeks in Great Britain, ranging from southern
England to the Isle of Skye in Scotland, and to southern and central
Wales. Like on my previous three trips there, I was treated very well by
some of the nicest people I know and have met. I, my wife, and son were
taken in as house guests by two very good friends in different parts of
the country.

I'm sure that if I'd displayed the sort of attitude toward the British
that Reg constantly does toward Americans, I would have had an entirely
different experience. But I'd rather concentrate on what good people
have in common. And there are a lot of good people in all countries. As
well as a few grumps, of course.

Roy Lewallen, W7EL

antenna lengths
 

On Sun, 30 Oct 2005 17:53:45 -0500, "Fred W4JLE"
wrote:

I think of him every time I see the brother-in-law on "Keeping Up
Appearances" on the BBC.

Don't you feel that's a bit complimentary whats-his-name and a bit
derogatory to the brother-in-law.

Danny, K6MHE

email: k6mheatarrldotnet
http://www.k6mhe.com/

antenna lengths
 

Dan Richardson wrote:
On Sun, 30 Oct 2005 17:53:45 -0500, "Fred W4JLE"
wrote:


I think of him every time I see the brother-in-law on "Keeping Up
Appearances" on the BBC.


Don't you feel that's a bit complimentary whats-his-name and a bit
derogatory to the brother-in-law.

Danny, K6MHE

Samuel Clemens (Mark Twain) is one of the characters in one of Harry
Turtledove's excellent "alternate history" books. In the story, Clemens
is living in San Francisco and has a dog named after the mayor, whom he
detests. After a particularly frustrating meeting with the mayor,
Clemens returns home and apologizes to the dog -- "When I named you," he
says, "I thought I was insulting the mayor. But it turns out that I was
insulting you."

Roy Lewallen, W7EL