power on random wire antenna
 

Hi guys,
I would like to use a (not so) random wire antenna to transmit on HF
band.
What is the power (watt) that I can use on my rig to feed the antenna?
Of course after tuning it.
I can use it full power (100W) or no?
For 100W which kind o wire is good?


Thanks.

Andrea
IZ2LSC

power on random wire antenna
 

On Thu, 07 Jun 2007 14:36:23 -0000, Andrea wrote:

Hi guys,
I would like to use a (not so) random wire antenna to transmit on HF
band.
What is the power (watt) that I can use on my rig to feed the antenna?
Of course after tuning it.
I can use it full power (100W) or no?
For 100W which kind o wire is good?

Hi Andrea,

100W will work just fine. Use copper wire with a diameter of 1mm or
more.

73's
Richard Clark, KB7QHC

power on random wire antenna
 

Thanks Richard.
Do you know if there is a formula to calculare the max power that a
wire can supports?

Thanks.

Andrea
IZ2LSC

power on random wire antenna
 

Andrea wrote:
Thanks Richard.
Do you know if there is a formula to calculare the max power that a
wire can supports?

Thanks.

Andrea
IZ2LSC


Max power that the wire can support would be based solely on the
amperage it can carry. You would need to know what the amps are at a
current node ... but, I have run a KW+ on #12.

Currently, I use 1/4 inch copper tubing over steel fencing wire (steel
wire is for strength.) It has supported 5KW+ easily ...

JS

power on random wire antenna
 

On Thu, 07 Jun 2007 13:11:38 -0700, Andrea wrote:

Thanks Richard.
Do you know if there is a formula to calculare the max power that a
wire can supports?

Hi Andrea,

No. Not off-hand. I use "wire tables" to reference what is called
"fuse current." This is the current that will burn a wire open. For
a 1mm wire, that would be around 50 to 80 Amperes. Your antenna would
have to be a very small loop to encounter that kind of current. Very
small means less than 0.1 wavelength in diameter. You would encounter
other problems long before the wire would melt.

73's
Richard Clark, KB7QHC

power on random wire antenna
 

Richard Clark wrote in
:

On Thu, 07 Jun 2007 13:11:38 -0700, Andrea wrote:

Thanks Richard.
Do you know if there is a formula to calculare the max power that a
wire can supports?

Hi Andrea,

No. Not off-hand. I use "wire tables" to reference what is called
"fuse current." This is the current that will burn a wire open. For

Are those tables based on the DC resistance or low frequency AC resistance
of the wire?

If so, are they relevant to rating the wire for current handling capacity
at RF where for example skin effect increases the dissipation for a given
current?

Owen

power on random wire antenna
 

On Fri, 08 Jun 2007 06:27:13 GMT, Owen Duffy wrote:

If so, are they relevant to rating the wire for current handling capacity
at RF where for example skin effect increases the dissipation for a given
current?

Hi Owen,

Really, a 1mm wire is sufficient for a 100W transmitter in a long wire
antenna application. There is no need to elaborate.

73's
Richard Clark, KB7QHC

power on random wire antenna
 

Richard Clark wrote:

...

Richard Clark, KB7QHC

Richard:

I should think I could probably power a 100 watt light bulb though a 1mm
wire. Perhaps a 150 watt one?

At 200 watts, I'd more than expect the wire to be getting rather warm,
even with enamel insulation and in free space ...

At a KW, I'd expect to be breathing some copper ions/particles!

JS

power on random wire antenna
 

John Smith I wrote:

[stuff]

In the previous post, 1 mm wire is #18 gauge AWG. (#12 = ~2 mm)

And, every 6 gauge decrease results in a doubling of the wires diameter,
every 3 gauge decrease results in a doubling of the wires cross
section--just as for db in signal levels ...

JS

power on random wire antenna
 

John Smith I wrote:

Further, I meant to point out that 100% skin depth only occurs to
~17Khz. And, while #18 may be ok for a max of 16 amps when used in
chassis wiring, it is only rated at ~2.3 amps for power transmission ...

Anyone know how many amps commonly flow through a current node on a 1/4
or 1/2 wave ant? Now, that's the real question, isn't it? And, if all
that power is all concentrated in just the skin of the copper, wouldn't
there be a degradation of power handling directly related to frequency?

Regards,
JS

power on random wire antenna
 

On 8 Jun, 11:20, Richard Clark wrote:
On Fri, 08 Jun 2007 06:27:13 GMT, Owen Duffy wrote:
If so, are they relevant to rating the wire for current handling capacity
at RF where for example skin effect increases the dissipation for a given
current?

Hi Owen,

Really, a 1mm wire is sufficient for a 100W transmitter in a long wire
antenna application. There is no need to elaborate.

73's
Richard Clark, KB7QHC

Sorry Owen, you have been censored.

power on random wire antenna
 

John Smith I wrote:
Anyone know how many amps commonly flow through a current node on a 1/4
or 1/2 wave ant? Now, that's the real question, isn't it?

John, you should be talking about the current anti-node,
i.e. the current maximum, not the current node (minimum).
For a 1/2WL center-fed dipole or a 1/4WL monopole, the
current is maximum at the feedpoint which is easy to
calculate, e.g. 1.414 amps for 100 watts into 50 ohms.
--
73, Cecil http://www.w5dxp.com

power on random wire antenna
 

Cecil Moore wrote:

...
calculate, e.g. 1.414 amps for 100 watts into 50 ohms.

Cecil:

Then, since E = I*R, 70.7 volts ... thanks.

Still, I like my 1/4 copper tubing, silver would be better ...

Regards,
JS

power on random wire antenna
 

Then, since E = I*R, 70.7 volts ... thanks.

But on the other ends where there could be 6000 ohms the current is
low (0.13 A) but the voltage is around 775 V.

Andrea
IZ2LSC

power on random wire antenna
 

Andrea wrote:
Then, since E = I*R, 70.7 volts ... thanks.

But on the other ends where there could be 6000 ohms the current is
low (0.13 A) but the voltage is around 775 V.

Andrea
IZ2LSC


Exactly, tape a ne-2 bulb on the antenna, will light when you xmit ...

JS

power on random wire antenna
 

the answer makes prefect sense professor!

On Jun 8, 12:00 pm, art wrote:
On 8 Jun, 11:20, Richard Clark wrote:

On Fri, 08 Jun 2007 06:27:13 GMT, Owen Duffy wrote:
If so, are they relevant to rating the wire for current handling capacity
at RF where for example skin effect increases the dissipation for a given
current?

Hi Owen,

Really, a 1mm wire is sufficient for a 100W transmitter in a long wire
antenna application. There is no need to elaborate.

73's
Richard Clark, KB7QHC

Sorry Owen, you have been censored.

power on random wire antenna
 

Andrea wrote in news:1181394846.390221.30080
@c77g2000hse.googlegroups.com:


Then, since E = I*R, 70.7 volts ... thanks.

But on the other ends where there could be 6000 ohms the current is
low (0.13 A) but the voltage is around 775 V.

Something tells me we're going to end up with tapered wires here
pretty soon... ;^)

power on random wire antenna
 

One more thing is not clear to me:
If I use a 1/4 wave wire, where are the 6000 ohms?
Near the feed point or on the far end?

Thanks

Andrea
IZ2LSC


On Jun 9, 11:44 pm, Mike Coslo wrote:
Andrea wrote in news:1181394846.390221.30080
@c77g2000hse.googlegroups.com:



Then, since E = I*R, 70.7 volts ... thanks.

But on the other ends where there could be 6000 ohms the current is
low (0.13 A) but the voltage is around 775 V.

Something tells me we're going to end up with tapered wires here
pretty soon... ;^)

power on random wire antenna
 

On Mon, 11 Jun 2007 08:34:06 -0000, Andrea wrote:

One more thing is not clear to me:
If I use a 1/4 wave wire, where are the 6000 ohms?
Near the feed point or on the far end?

Hi Andrea,

At the far end. Think of the antenna as a resonant transmission line
(meaning it is not terminated in its characteristic Z) and that hi
impedance at the end is transformed through the length to the lower 30
- 50 Ohms typically encountered (accumulating real resistances of the
wire and radiation resistance along the way).

73's
Richard Clark, KB7QHC

power on random wire antenna
 

Andrea wrote in news:1181550846.846262.75560
@m36g2000hse.googlegroups.com:

One more thing is not clear to me:
If I use a 1/4 wave wire, where are the 6000 ohms?
Near the feed point or on the far end?


It will be at the far end of the antenna, Andrea.

- 73 de Mike KB3EIA -

power on random wire antenna
 

On Jun 13, 6:12 am, Mike Coslo wrote:
Andrea wrote in news:1181550846.846262.75560
@m36g2000hse.googlegroups.com:

One more thing is not clear to me:
If I use a 1/4 wave wire, where are the 6000 ohms?
Near the feed point or on the far end?

It will be at the far end of the antenna, Andrea.

- 73 de Mike KB3EIA -

Thanks everybody.
Andrea.

power on random wire antenna
 

Mike Coslo wrote:
Andrea wrote:

One more thing is not clear to me:
If I use a 1/4 wave wire, where are the 6000 ohms?
Near the feed point or on the far end?

It will be at the far end of the antenna, Andrea.

One way to remember that:
The Z = V/I ratio is sky high at the end of an antenna
because the current is obviously very close to zero.
--
73, Cecil http://www.w5dxp.com