How much voltage on a vertical?
 

"Bob Glenn" wrote in message
ews.com...
On a typical 25 watt 2 meter setup, how much voltage would there be on
the end of a 1/4 antenna?

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

25 watts into a 1/4-wave vertical antenna on 2 meters -

Base current about 0.82 amps into 37 ohms,

Volts about 160, measured (if you can) at top of antenna across about 1000
ohms.

Things vary slowly with length-to-diameter ratio of the antenna conductor.

As conductor diameter increases, volts at the end tend to decrease.
----
Reg, G4FGQ

"Bob Glenn" wrote in message
ews.com...
On Tue, 15 Jun 2004 19:03:24 +0000 (UTC), "Reg Edwards"
wrote:


"Bob Glenn" wrote in message
news.com...
On a typical 25 watt 2 meter setup, how much voltage would there be on
the end of a 1/4 antenna?

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

25 watts into a 1/4-wave vertical antenna on 2 meters -

Base current about 0.82 amps into 37 ohms,

Volts about 160, measured (if you can) at top of antenna across about
1000
ohms.

Things vary slowly with length-to-diameter ratio of the antenna
conductor.

As conductor diameter increases, volts at the end tend to decrease.
----
Reg, G4FGQ


Thank you, 1,000 is the accepted value then?

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

You can please yourself what the accepted value is.

But on the 2 meter band about 1000 ohms is what it actually is.

On the lower frequency bands it runs into several thousand ohms.

As I said, it's a slowly moving function of antenna length-to-diameter
ratio.

But it doesn't matter very much anyway. No need to make a fuss about it.
===
Reg.

"Reg Edwards" wrote in message
...

"Bob Glenn" wrote in message
ews.com...
On Tue, 15 Jun 2004 19:03:24 +0000 (UTC), "Reg Edwards"
wrote:


"Bob Glenn" wrote in message
news.com...
On a typical 25 watt 2 meter setup, how much voltage would there be
on
the end of a 1/4 antenna?

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

25 watts into a 1/4-wave vertical antenna on 2 meters -

Base current about 0.82 amps into 37 ohms,

Volts about 160, measured (if you can) at top of antenna across about
1000
ohms.

Things vary slowly with length-to-diameter ratio of the antenna
conductor.

As conductor diameter increases, volts at the end tend to decrease.
----
Reg, G4FGQ


Thank you, 1,000 is the accepted value then?

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

You can please yourself what the accepted value is.

But on the 2 meter band about 1000 ohms is what it actually is.

On the lower frequency bands it runs into several thousand ohms.

As I said, it's a slowly moving function of antenna length-to-diameter
ratio.

But it doesn't matter very much anyway. No need to make a fuss about it.
===
Reg.


That's our Reg, spot on.
Remember, V=Q/C, where V is voltage, Q charge and C capacitance.
73
H.
NQ5H

On Tue, 15 Jun 2004 19:44:07 GMT, Bob Glenn
wrote:
Thank you, 1,000 is the accepted value then?

Hi Bob,

It was derived from a contrivance of math that ignores the loss of
radiation resistance. After all, the antenna doesn't exist in a
vacuum, and if it did, it would still be surrounded by a medium
shorting it out to the tune of 377Ohms.

It's enough to allow that it will bite (the voltage) if you contact it
in equally contrived circumstances. Put an NE-2 neon bulb at the end
of the antenna to confirm ionizing voltage (60-90V at least). CBers
used to do that with their whips with just 5W.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Tue, 15 Jun 2004 19:44:07 GMT, Bob Glenn
wrote:
Thank you, 1,000 is the accepted value then?

Hi Bob,

It was derived from a contrivance of math that ignores the loss of
radiation resistance. After all, the antenna doesn't exist in a
vacuum, and if it did, it would still be surrounded by a medium
shorting it out to the tune of 377Ohms.

It's enough to allow that it will bite (the voltage) if you contact it
in equally contrived circumstances. Put an NE-2 neon bulb at the end
of the antenna to confirm ionizing voltage (60-90V at least). CBers
used to do that with their whips with just 5W.

73's
Richard Clark, KB7QHC

And some of us remember before CB.
sigh