[Hallicrafters] Snow / Antenna question.

[jeremy-ca]

An ice induced high VSWR will cause heating in some traps and loading coils. 
Heat melts ice, melted ice becomes water, water becomes steam. Ive seen it 
all right in my own yard.

Your   "Snow or ice is virtually invisible to RF unless it has minerals or
> salt
> in it.  Other than that, it's not there"  can be very misleading if read 
> the wrong way.

It would be better to say that HF RF waves will pass thru ice but will 
detune an antenna when in contact.

Carl
KM1H



----- Original Message ----- 
From: "Bill Gerhold" <k2wh at optonline.net>
To: "'jeremy-ca'" <km1h at jeremy.mv.com>; <hallicrafters at mailman.qth.net>
Sent: Saturday, February 02, 2008 7:54 PM
Subject: RE: [Hallicrafters] Snow / Antenna question.


> The question was as follows: "Will transmitting on 40 m at about
> 100 watts do any warming of the antenna and remove the snow?"
>
> To which my answer and the others was "No".  The VSWR going "Way Up" does
> not contribute to heat build up.  As another reply stated, heating of the
> antenna is something that should be avoided since it is wasted power. 
> VSWR
> going "Way UP', just means the antenna "System" needs to be retuned or
> adjusted.
>
> This has nothing to do with melting snow on "ANY" antenna using RF.  As to
> your "Ice Belt" statement, I'm at 1200 feet here in NNJ and we just had an
> ice storm that brought down trees and power lines.  All my antennas were
> about twice as thick as normal up to and including 900 MHz without any ill
> effects except the SWR.  The SWR on my 80-meter dipole fed with ladder 
> line
> changed quite a bit but a simple adjustment of the tuner and it was fine.
> Running 1.5kw did not start a rain storm.
>
> The absorption of RF by snow or ice is negligible.
>
> K2WH
>
> ----Original Message-----
> From: jeremy-ca [mailto:km1h at jeremy.mv.com]
> Sent: Saturday, February 02, 2008 7:04 PM
> To: Bill Gerhold; hallicrafters at mailman.qth.net
> Subject: Re: [Hallicrafters] Snow / Antenna question.
>
> Try telling that to anyone who has had HF yagis ice up. The VSWR goes WAY 
> up
>
> until the sun melts the ice. Its no fun when it happens during a contest!
> Since these antennas are quite narrow band the effect is dramatic.
>
> I and anyone else in the ice belt has experienced it. Light snow just
> sitting on the elements has no effect.
>
> VHF/UHF high performance yagis are designed so that the bandwidth is wide
> enough so that they arent detuned in plain old rain. They become rotary
> dummy loads when iced up.
>
> Carl
> KM1H
>
>
>
> ----- Original Message ----- 
> From: "Bill Gerhold" <k2wh at optonline.net>
> To: <hallicrafters at mailman.qth.net>
> Sent: Saturday, February 02, 2008 4:41 PM
> Subject: RE: [Hallicrafters] Snow / Antenna question.
>
>
>> No.  Snow or ice is virtually invisible to RF unless it has minerals or
>> salt
>> in it.  Other than that, it's not there.
>>
>> K2WH
>>
>> -----Original Message-----
>> From: hallicrafters-bounces at mailman.qth.net
>> [mailto:hallicrafters-bounces at mailman.qth.net] On Behalf Of Waldo 
>> Magnuson
>> Sent: Saturday, February 02, 2008 11:51 AM
>> To: hallicrafters at mailman.qth.net
>> Cc: Waldo Magnuson
>> Subject: [Hallicrafters] Snow / Antenna question.
>>
>> Spokane, WA has been getting a lot of snow this winter (about 70 inches
>> so far) and yesterday my horizontal 40 m dipole had about 2 or 3 inches
>> piled up on it (and it did sag a little).  My transmitter is currently
>> undergoing some repair so I couldn't check but I know some of you will
>> know the answer to this question.  Will transmitting on 40 m at about
>> 100 watts do any warming of the antenna and remove the snow?  Thanks.
>> 73,  Skip  W7WGM
>>
>> ______________________________________________________________
>>
>>
>> ______________________________________________________________
>>
>
>
>
>