Through-glass antenna power limits
 

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

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

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

Through-glass antenna power limits
 

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

Through-glass antenna power limits
 

Thomas & Karen Mitchell kg7uATolympus.net wrote in
:

(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?

If your transceiver really does make 65W into a 50 ohm load, and you
connected say 4m of RG58C/U to a 50 ohm load, line losses are such that
only 54W reaches the load. So you might not be quite feeding the antenna
with 65W, the likely amount depends on your feedline type and length.

Your antenna is probably not exactly 50 ohms, and there could be higher
current or higher voltage at the coupler than for a true 50 ohm load...
but the designers should have included a safety margin to cover this
factor. (The on-glass coupler is the achilles heel of these things, you
will feel them warm up with a bit of use.)

If the antenna is rated for 50W, and can't reliably stand 60W, it is a
bit marginally rated, but on-glass mounts are a bit that way.

Owen

Through-glass antenna power limits
 

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

Through-glass antenna power limits
 

On Jun 3, 9:57 am, Thomas & Karen Mitchell kg7uATolympus.net wrote:
(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, USAhttp://www.olympus.net/personal/kg7u
--------------------------------------------------------------------------

On a personal note, I have a dual bander through the glass mount. I
use a 857 yeasu and managed to fry the matching unit on the inside of
the car. From what I saw when I repaired the unit was the main
resonating cap is a brass screw in a brass tube with a 'plastic'
insulator in between. With the wattage I get from the 857 the plastic
dia-lectic melted. I replaced the cap with a professional glass 0.5 to
5 pF trimmer cap and it has worked fine ever since.

Regards bob zs6bxi

Through-glass antenna power limits
 

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.- Hide quoted text -

Exactly... If I were serious about using my capacitor design for the
higher bands I would either redesign the circuit to increase the plate
area or go to borosilicate glass...
My 80 - 160 remote tuners are working like gangbusters, take all the
power I can make, and cost roughly a hundred bucks a pop to build... I
don't operate the other bands much and can make do with simple
dipoles.... Being that I have ADD (antenna deficit disorder) I am
busily working on other ideas now...

denny / k8do

Through-glass antenna power limits
 

"Jeff" wrote in message
. com...

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

So far the only damageI have seen from this is to the lamination inside the
glass. I wouldnt want to wait until this occurs before I decided to quit.

Through-glass antenna power limits
 

Jimmie D wrote:

...
So far the only damageI have seen from this is to the lamination inside the
glass. I wouldnt want to wait until this occurs before I decided to quit.


De-lamination on the vettes' rear window? Absolutely WON'T take the chance!

The Park Avenue Buick? Who cares? Doubt it would even affect
resale/trade-in value ...

JS