"John Smith I" wrote in message
...
Thomas & Karen Mitchell wrote:

...
So: I'll stay at 25 when in the car.

-- KG7U
--------------------------------------------------------------------------
Tom Mitchell, Port Angeles, Washington, USA
http://www.olympus.net/personal/kg7u
--------------------------------------------------------------------------

Every engineer, worth his pay, which I know, allow at least a 20% excess
on ratings.

50 X 20% = 10 watts

50 + 10 = 60 watts

I'd run the 65 and examine the glass mount now and then. You'll see if
damage begins and switch lower power.

Warm regards,
JS

That sounds like a girl waiting until she is just a litte bit pregnant to
stat us birth control.
Either the glass cracks, it starts to delaminate, or you fry your finals,
all could be too far by the time you see it.

Jimmie D wrote:
"John Smith I" wrote in message
...
Thomas & Karen Mitchell wrote:

...
So: I'll stay at 25 when in the car.

-- KG7U
--------------------------------------------------------------------------
Tom Mitchell, Port Angeles, Washington, USA
http://www.olympus.net/personal/kg7u
--------------------------------------------------------------------------
Every engineer, worth his pay, which I know, allow at least a 20% excess
on ratings.

50 X 20% = 10 watts

50 + 10 = 60 watts

I'd run the 65 and examine the glass mount now and then. You'll see if
damage begins and switch lower power.

Warm regards,
JS

That sounds like a girl waiting until she is just a litte bit pregnant to
stat us birth control.
Either the glass cracks, it starts to delaminate, or you fry your finals,
all could be too far by the time you see it.



If the glass breaks, replace glass (highly unlikely! Bordering on
impossible!)

Glass cracking? Very unlikely!

Delamination? Perhaps, over much time ...

Fry the finals? What idiot would ever start using a rig and antenna
with no SWR indication?

JS

That sounds like a girl waiting until she is just a litte bit pregnant to
stat us birth control.
Either the glass cracks, it starts to delaminate, or you fry your finals,
all could be too far by the time you see it.


It is the ratings of the components in the matching unit that limit the
power rating not the glass, you will get smoke well before any damage to the
glass.

Jeff

"Thomas & Karen Mitchell" kg7uATolympus.net wrote in message
...
(I realize that a through-the-glass antenna is less than ideal.
Nevertheless, that's what I have to use in my situation.) The one I
have is for 2 meters (NOT dual band), and the label says up to 50
watts. I have an Icom IC-2200H, which has a maximum of 65 watts
output.

What bad things may/could/will happen if I put 65 watts through the
antenna?

Thanks!

Tom Mitchell -- KG7U
Port Angeles, Washington. USA
--------------------------------------------------------------------------
Tom Mitchell, Port Angeles, Washington, USA
http://www.olympus.net/personal/kg7u
--------------------------------------------------------------------------
Further to my earlier posting and slightly off topic but I have been
browsing through my car manual and note that the manufacturers specifically
forbid the installation of transmitters operating at more than 10 watts
power. Checking up on this reveals that in the event of some of the
electrical earth bonding connections in the car becoming faulty or breaking
two possible disaster scenarios exist. The first is that the computerised
engine management unit might misfunction causing the engine to suddenly stop
or the antilock braking and stability systems to malfunction. The second is
that the pyrotechnic charges in the airbags might be triggered.

Admittedly these two situations are dependent on a chain of faults/failures
occuring and the manufacturers are just trying to cover themselves against
law suits. Vehicles are tested for electromagnetic immunity at far higher
levels than this, but you might want to double check your manual or with the
manufacturer about the maximum permissible transmitter power if the vehicle
is fairly new, fitted with electronic engine management, safety equipment
and airbags.

Take a deep breath before transmitting with all the controls set to 11...

Mike G0ULI

On Mon, 4 Jun 2007 02:43:18 +0100, "Mike Kaliski"
wrote:

Take a deep breath before transmitting with all the controls set to 11...

Hi Mike,

Is the warrantee void within 100 yards of a 50KW AM antenna? Or
howabout those half megawatt LF stations that litter the continent?

73's
Richard Clark, KB7QHC

In my search for knowledge I recently went through a big thrash with
antenna tuners... Because of cost I built my own variable caps... To
keep the size down I experimented with various insulators between the
plates, from air up to glass...

Being that the tuners on 40 and 20 were end matching a half wave
antenna element the circulating tank current was considerable... On
20 meters where the capacitor plates are 1.5" square for resonance the
glass would simply shatter at about 800W for 5 seconds... Plexiglass
would boil internally in roughly 20 seconds leaving this interesting
rippled piece with 'steam' bubbles in the center of the plexi...
Ceramic tiles seemed to work OK, but I didn't find any thin ones
locally and the thick pieces resulted in plates being awkwardly
large...

On 80 meters the glass plates are 4" X 6" and the glass runs barely
above ambient at 2KW...

denny / k8do

"Denny" wrote in message
ps.com...
In my search for knowledge I recently went through a big thrash with
antenna tuners... Because of cost I built my own variable caps... To
keep the size down I experimented with various insulators between the
plates, from air up to glass...

Being that the tuners on 40 and 20 were end matching a half wave
antenna element the circulating tank current was considerable... On
20 meters where the capacitor plates are 1.5" square for resonance the
glass would simply shatter at about 800W for 5 seconds... Plexiglass
would boil internally in roughly 20 seconds leaving this interesting
rippled piece with 'steam' bubbles in the center of the plexi...
Ceramic tiles seemed to work OK, but I didn't find any thin ones
locally and the thick pieces resulted in plates being awkwardly
large...

On 80 meters the glass plates are 4" X 6" and the glass runs barely
above ambient at 2KW...

denny / k8do


An very odd result considering that glass dielectric capacitors are sold
specifically for high rf current use by people such as AVX and the like. I
guess it depends on what type of glass you used. You shouldn't have used
your old lead crystal glasses (;-))

73
Jeff

Jeff wrote:
"Denny" wrote in message
ps.com...

In my search for knowledge I recently went through a big thrash with
antenna tuners... Because of cost I built my own variable caps... To
keep the size down I experimented with various insulators between the
plates, from air up to glass...

Being that the tuners on 40 and 20 were end matching a half wave
antenna element the circulating tank current was considerable... On
20 meters where the capacitor plates are 1.5" square for resonance the
glass would simply shatter at about 800W for 5 seconds... Plexiglass
would boil internally in roughly 20 seconds leaving this interesting
rippled piece with 'steam' bubbles in the center of the plexi...
Ceramic tiles seemed to work OK, but I didn't find any thin ones
locally and the thick pieces resulted in plates being awkwardly
large...

On 80 meters the glass plates are 4" X 6" and the glass runs barely
above ambient at 2KW...

denny / k8do



An very odd result considering that glass dielectric capacitors are sold
specifically for high rf current use by people such as AVX and the like. I
guess it depends on what type of glass you used. You shouldn't have used
your old lead crystal glasses (;-))



Lots of kinds of "glass" out there.

fused silica is pretty low loss
borosilicate glass (e.g. Pyrex, Kimax, etc.) is medium
windowglass (soda lime) is all over the place.

"Richard Clark" wrote in message
...
On Mon, 4 Jun 2007 02:43:18 +0100, "Mike Kaliski"
wrote:

Take a deep breath before transmitting with all the controls set to 11...

Hi Mike,

Is the warrantee void within 100 yards of a 50KW AM antenna? Or
howabout those half megawatt LF stations that litter the continent?

73's
Richard Clark, KB7QHC

Richard

It's all about RF actually within the vehicle. The bodywork acts like a
Faraday cage against external influences. But I suspect you know that
already :-)

A couple of years back a lightning bolt hit a field I was driving past
during a storm. The dash completely blanked for 2 seconds and then came back
to life - no other ill effects noted - just as well because the road was
nearly completely under water at that point.

The radio key remote locking can fail if you park too close to a mobile
phone mast, or someone is transmitting on 70 cms nearby, but that's about
it.

As I only operate QRP I hadn't given the matter much thought until I checked
in the vehicle manual and saw a footnote.

Mike G0ULI

"Mike Kaliski" wrote in message
...

"Richard Clark" wrote in message
...
On Mon, 4 Jun 2007 02:43:18 +0100, "Mike Kaliski"
wrote:

Take a deep breath before transmitting with all the controls set to
11...

Hi Mike,

Is the warrantee void within 100 yards of a 50KW AM antenna? Or
howabout those half megawatt LF stations that litter the continent?

73's
Richard Clark, KB7QHC

Richard

It's all about RF actually within the vehicle. The bodywork acts like a
Faraday cage against external influences. But I suspect you know that
already :-)

A couple of years back a lightning bolt hit a field I was driving past
during a storm. The dash completely blanked for 2 seconds and then came
back
to life - no other ill effects noted - just as well because the road was
nearly completely under water at that point.

The radio key remote locking can fail if you park too close to a mobile
phone mast, or someone is transmitting on 70 cms nearby, but that's about
it.

As I only operate QRP I hadn't given the matter much thought until I
checked
in the vehicle manual and saw a footnote.

Mike G0ULI




I had a similar experience with lightning. The lightning hit a tall comm
tower on the side of the road, jumped out the side of the tower, hit the
roof of the truck I was in, and then struck a pine tree on the other side of
the road. The engine diesd and I coasted to the side of the road. After a
few minutes of getting my composurer back together and surveying the damage
I was able to start the truck like nothing had happened. I was expecting all
the electronics to be fried.


Jimmie