[Elecraft] Ice on dipole under snow under ice

[donovanf at erols.com]

Hi Mike, 


While its true that snow and ice are transparent to HF, its also true that 
they affect antenna performance by dielectric loading of the antenna 
elements. In most cases it affects mainly the feed point impedance, 
but in extreme cases it can also affect the directivity of a directive antenna. 


73 
Frank 
W3LPL 

----- Original Message -----

From: "Mike Harris via Elecraft" <elecraft at mailman.qth.net> 
To: elecraft at mailman.qth.net 
Sent: Tuesday, December 15, 2020 8:21:03 PM 
Subject: Re: [Elecraft] Ice on dipole under snow under ice 

Snow and ice is transparent to HF. When I was in Antarctica we had an 
ice depth radar sounding programme. A DH Twin Otter would fly at 50 feet 
above the snow surface as indicated by the radar altimeter and beneath 
the wings were a couple of 70Mhz dipoles, TX and RX. The 70MHz TX pulses 
penetrated to the underlying rock. Take one height from the other, ice 
depth. 

Fantastic flying that was. 

It is mentioned in the ARRL Antenna Handbook that a closed loop array 
like a Sterba curtain could be could be fed with a low voltage DC or AC 
current to heat the wire to relieve it of accumulated snow and ice. 

Regards, 

Mike VP8NO 

On 15/12/2020 14:45, David Haines wrote: 
> Update: 
> 
> With one-quarter of one leg of the dipole still under ice, I got a 
> reception report from PSKReporter on FT8 with 2 watts to Italy. That 
> shouldn't work, should it? Maybe the ice doesn't matter? 
> 
> KD5VXH recalled a discussion in QST on this very subject, where 400W AM 
> melted the ice on one leg of the dipole (fed by coax), but not the other. 
> ' 
> You can follow the controversy in May and July 1960 letters in QST! 
> 
> david 
> KC1DNY 
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