[Helmut Wabnig[_2_]]

Somebody wrote:

If 10 watts is delivered to a short antenna, where does it go if it is not
radiated just as well as 10 watts delivered to a long antenna?


Make it 100 Watts, make it 1000 Watts,

Transmit for 5 minutes, then switch off and measure temperature.

Is the short antenna hotter?


w.

[Fred McKenzie]

In article ,
Helmut Wabnig [email protected] --- -.dotat wrote:

Somebody wrote:

If 10 watts is delivered to a short antenna, where does it go if it is not
radiated just as well as 10 watts delivered to a long antenna?


Make it 100 Watts, make it 1000 Watts,

Transmit for 5 minutes, then switch off and measure temperature.

Is the short antenna hotter?

W.-

Yes. I use a Hustler mobile antenna with resonators for each band.
After transmitting 100 Watts, the resonator coils become hot to the
touch. It seems to be worse on the lower bands with larger resonators.

Fred
K4DII

[[email protected]]

On Wednesday, October 22, 2014 5:09:16 PM UTC-5, Fred McKenzie wrote:
In article ,
Helmut Wabnig [email protected] --- -.dotat wrote:

Somebody wrote:

If 10 watts is delivered to a short antenna, where does it go if it is not
radiated just as well as 10 watts delivered to a long antenna?


Make it 100 Watts, make it 1000 Watts,

Transmit for 5 minutes, then switch off and measure temperature.

Is the short antenna hotter?

W.-

Yes. I use a Hustler mobile antenna with resonators for each band.
After transmitting 100 Watts, the resonator coils become hot to the
touch. It seems to be worse on the lower bands with larger resonators.

Fred
K4DII

I consider that part of the matching network though.
If you were to apply the same power to a non loaded same length
whip alone, and the matching were before the whip, IE: a tuner, the
whip would change temp very little, while the heat would build
in the tuner inductor. With the loaded antenna, the inductor is part
of the antenna, instead of in the tuner, and that part will get
warmer. But the whip above it, and the mast below it if center
loaded, will stay fairly cool.

[Wayne]

"Helmut Wabnig" wrote in message
...



Somebody wrote:

If 10 watts is delivered to a short antenna, where does it go if it is not
radiated just as well as 10 watts delivered to a long antenna?


Make it 100 Watts, make it 1000 Watts,

Transmit for 5 minutes, then switch off and measure temperature.

Is the short antenna hotter?

No.

The matching network might heat up, but the matching network doesn't have to
be at the antenna, and is not part of the original theoretical assertion.

[Wayne]

wrote in message
...

On Wednesday, October 22, 2014 5:09:16 PM UTC-5, Fred McKenzie wrote:
In article ,
Helmut Wabnig [email protected] --- -.dotat wrote:

Somebody wrote:

If 10 watts is delivered to a short antenna, where does it go if it is
not
radiated just as well as 10 watts delivered to a long antenna?


Make it 100 Watts, make it 1000 Watts,

Transmit for 5 minutes, then switch off and measure temperature.

Is the short antenna hotter?

W.-

Yes. I use a Hustler mobile antenna with resonators for each band.
After transmitting 100 Watts, the resonator coils become hot to the
touch. It seems to be worse on the lower bands with larger resonators.

Fred
K4DII

# I consider that part of the matching network though.
# If you were to apply the same power to a non loaded same length
# whip alone, and the matching were before the whip, IE: a tuner, the
# whip would change temp very little, while the heat would build
#in the tuner inductor. With the loaded antenna, the inductor is part
# of the antenna, instead of in the tuner, and that part will get
# warmer. But the whip above it, and the mast below it if center
# loaded, will stay fairly cool.

I use a 14 foot whip over a good ground plane on 10-30 meters. Matching is
in the shack, with coax feed to the antenna. I tune for maximum RF current
at the base of the whip.

The matching network can get hot, but the whip itself has very low
resistance. I consider I^2 R loss to be negligible.

[Channel Jumper]

I think someone is confused.

You said antenna, you said nothing about traps!

Antenna to me would either be a vertical radiator - or a horizontal dipole.

Would either of these antenna's get warm from 10 watts? The answer is no!
Not unless the antenna was grounded to something - which shorted it out.

Would 100 watts make an antenna get warm? The answer is NO! Not unless it was not resonant to begin with, and even then, only if there was something in the atmosphere to cause it to short.

Feel your coax - does RG 8 get hot if the antenna is resonant? NO!

Maybe if you were running full legal power into a non resonant antenna, or 3500 watts into a antenna that was designed for 1500 watts...

Power is more or less vanity.
Some people thinks that they cannot talk unless they have more power.
Some old people thinks that they can't talk unless their signal is 20/9!
Technically this is called BROADCASTING!

The problem is - no one is brave enough to stand up to the LIDS to tell them that what they are doing is in fact ILLEGAL!

[John S]

On 10/22/2014 1:57 PM, Helmut Wabnig wrote:


Somebody wrote:

If 10 watts is delivered to a short antenna, where does it go if it is not
radiated just as well as 10 watts delivered to a long antenna?


Make it 100 Watts, make it 1000 Watts,

Transmit for 5 minutes, then switch off and measure temperature.

Is the short antenna hotter?


w.

Theoretically, yes. For #18ga Cu wi

Lambda Efficiency
0.5 0.9690
0.25 0.9402
0.1 0.8622
0.05 0.7571

Hence, about 24% of the power in the shortest antenna is lost due to
I^2*R. In addition, the shorter antenna has less surface area to rid
itself of the heat.

However, as a practical matter, it would be exceedingly difficult to get
much power into the antenna as its terminal impedance is 0.69-j5323.51 ohms.

John KD5YI

[[email protected]]

On Thursday, October 23, 2014 6:25:12 AM UTC-5, John S wrote:
On 10/22/2014 1:57 PM, Helmut Wabnig wrote:


Somebody wrote:

If 10 watts is delivered to a short antenna, where does it go if it is not
radiated just as well as 10 watts delivered to a long antenna?


Make it 100 Watts, make it 1000 Watts,

Transmit for 5 minutes, then switch off and measure temperature.

Is the short antenna hotter?


w.

I'd have to ask how short is short... ??


Theoretically, yes. For #18ga Cu wi

Lambda Efficiency
0.5 0.9690
0.25 0.9402
0.1 0.8622
0.05 0.7571

Hence, about 24% of the power in the shortest antenna is lost due to
I^2*R. In addition, the shorter antenna has less surface area to rid
itself of the heat.

However, as a practical matter, it would be exceedingly difficult to get
much power into the antenna as its terminal impedance is 0.69-j5323.51 ohms.

John KD5YI

Yep, you want a fat radiator and good connections with a real small
antenna. But most whips and such as themselves will still run fairly
cool unless you were really cranking the power. I've never run more
than 100w mobile.. But I've never had a whip get warm with that power.
I don't think my loading coil gets hot either. Or at least I've never
noticed it when taking it off to change the tap on the coil.
A KW is a lot of juice, so if it got a coil warm, I wouldn't be too
surprised.. The mast and whip might get a little bit warm, but I don't
think it would be too much compared to the coil.

It's the small HF loops and such where the fat tubing, and solid low
loss connections really pay off. May apply some also to the mobiles,
but fat tubing and such is kind of impractical on a car..

[John S]

On 10/24/2014 12:56 AM, wrote:
On Thursday, October 23, 2014 6:25:12 AM UTC-5, John S wrote:
On 10/22/2014 1:57 PM, Helmut Wabnig wrote:


Somebody wrote:

If 10 watts is delivered to a short antenna, where does it go if it is not
radiated just as well as 10 watts delivered to a long antenna?


Make it 100 Watts, make it 1000 Watts,

Transmit for 5 minutes, then switch off and measure temperature.

Is the short antenna hotter?


w.

I'd have to ask how short is short... ??


Theoretically, yes. For #18ga Cu wi

Lambda Efficiency
0.5 0.9690
0.25 0.9402
0.1 0.8622
0.05 0.7571

Hence, about 24% of the power in the shortest antenna is lost due to
I^2*R. In addition, the shorter antenna has less surface area to rid
itself of the heat.

However, as a practical matter, it would be exceedingly difficult to get
much power into the antenna as its terminal impedance is 0.69-j5323.51 ohms.

John KD5YI

Yep, you want a fat radiator and good connections with a real small
antenna. But most whips and such as themselves will still run fairly
cool unless you were really cranking the power. I've never run more
than 100w mobile.. But I've never had a whip get warm with that power.
I don't think my loading coil gets hot either. Or at least I've never
noticed it when taking it off to change the tap on the coil.
A KW is a lot of juice, so if it got a coil warm, I wouldn't be too
surprised.. The mast and whip might get a little bit warm, but I don't
think it would be too much compared to the coil.

It's the small HF loops and such where the fat tubing, and solid low
loss connections really pay off. May apply some also to the mobiles,
but fat tubing and such is kind of impractical on a car..

I knew you knew that, Mark. For a bit of information for others, if I
change the .05 lambda radiator (wire) to #8 Cu (about .125"+ diameter),
I then get an efficiency of 91%. The terminal impedance is now
0.57-j4397. Still not an easy feed, but you know that.

I guess the lesson is that you can heat almost anything if you try hard
enough.

Cheers,
John KD5YI