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Ice on dipole under snow under ice

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David Haines

Ice on dipole under snow under ice

Before I try something crazy, like climbing up on the roof ... .

We had an ice storm. The ice pulled my wire dipole down to the roof,
but didn't break it because one mask was Schedule 30, which leaned over
nicely. It then snowed on top of the ice.

I've been able to free the feedline (ladderline) and most of the dipole,
but part of the dipole is till under the snow under a layer of ice way
up on the roof.

I'm thinking of running 100W from my KXPA100 to melt it out of there,
but before I try:

1. Is there any chance of this working?
2. Should I just transmit a TUNE through it?
3. Can I damage the KXPA100 or tuner?

Right now the coax is not connected to the KX3 and I haven't tried to
receive.

david
KC1DNY
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Elecraft mailing list

Re: Ice on dipole under snow under ice

I haven't given this a lot of thought but:
1. Virtually none. 100W most radiated, leaving very little heating the ice/snow along your long cold wire. The wire itself won't heat up as it has very low resistance.
2. IDK about the KXPA100, but Tune is often done at low power, so if 100W work, Tune certainly won't.
3. Need to check the SWR, but even if good initially, may vary a lot as ice/snow situation changes. This might test the SWR capability of the tuner and protection of the amp, which is best left untested.

If you do try it, keep it legal: Check the freq before transmitting, and be sure to identify. Let us know how it goes. This might be the excuse you've needed to get that legal limit amp you've been wanting.

Lou W7HV

On Sunday, December 13, 2020, 11:40:18 AM MST, David Haines <[hidden email]> wrote:

Before I try something crazy, like climbing up on the roof ... .

We had an ice storm. The ice pulled my wire dipole down to the roof,
but didn't break it because one mask was Schedule 30, which leaned over
nicely. It then snowed on top of the ice.

I've been able to free the feedline (ladderline) and most of the dipole,
but part of the dipole is till under the snow under a layer of ice way
up on the roof.

I'm thinking of running 100W from my KXPA100 to melt it out of there,
but before I try:

1. Is there any chance of this working?
2. Should I just transmit a TUNE through it?
3. Can I damage the KXPA100 or tuner?

Right now the coax is not connected to the KX3 and I haven't tried to
receive.

david
KC1DNY
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Lyn WØLEN

Re: Ice on dipole under snow under ice

In reply to this post by David Haines

David -

Living in Chicagoland, I face similar issues now and then. In fact, just a couple weeks ago we had a very heavy frost. My 360 foot EDZ (dipole) which is normally nearly invisible, suddenly looked like a 2" white PVC pipe. It sagged, but not much. A couple hours' worth of sunlight and a few pops of wind, and it was all good.

Your situation is a bit different, but I've never found that transmitting did much to ice. Or to the little birdies who like to sit on the wire (mostly hummingbirds). That being said, unless you have a steel roof, I don't think it would hurt to try. Ease up on the power just in case. But first try receiving. I doubt there will be much degradation from the ice.

73
Lyn, W0LEN

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of David Haines
Sent: Sunday, December 13, 2020 12:39 PM
To: [hidden email]
Subject: [Elecraft] Ice on dipole under snow under ice

Before I try something crazy, like climbing up on the roof ... .

We had an ice storm. The ice pulled my wire dipole down to the roof,
but didn't break it because one mask was Schedule 30, which leaned over
nicely. It then snowed on top of the ice.

I've been able to free the feedline (ladderline) and most of the dipole,
but part of the dipole is till under the snow under a layer of ice way
up on the roof.

I'm thinking of running 100W from my KXPA100 to melt it out of there,
but before I try:

1. Is there any chance of this working?
2. Should I just transmit a TUNE through it?
3. Can I damage the KXPA100 or tuner?

Right now the coax is not connected to the KX3 and I haven't tried to
receive.

david
KC1DNY
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David Haines

Re: Ice on dipole under snow under ice

In reply to this post by Elecraft mailing list

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

On 12/13/2020 4:36 PM, Louandzip wrote:

> I haven't given this a lot of thought but:
>
> 1. Virtually none. 100W most radiated, leaving very little heating
> the ice/snow along your long cold wire. The wire itself won't heat up
> as it has very low resistance.
>
> 2. IDK about the KXPA100, but Tune is often done at low power, so if
> 100W work, Tune certainly won't.
>
> 3. Need to check the SWR, but even if good initially, may vary a lot
> as ice/snow situation changes. This might test the SWR capability of
> the tuner and protection of the amp, which is best left untested.
>
> If you do try it, keep it legal: Check the freq before transmitting,
> and be sure to identify. Let us know how it goes. This might be the
> excuse you've needed to get that legal limit amp you've been wanting.
>
> Lou W7HV
>
>
> On Sunday, December 13, 2020, 11:40:18 AM MST, David Haines
> <[hidden email]> wrote:
>
>
> Before I try something crazy, like climbing up on the roof ... .
>
> We had an ice storm. The ice pulled my wire dipole down to the roof,
> but didn't break it because one mask was Schedule 30, which leaned over
> nicely. It then snowed on top of the ice.
>
> I've been able to free the feedline (ladderline) and most of the dipole,
> but part of the dipole is till under the snow under a layer of ice way
> up on the roof.
>
> I'm thinking of running 100W from my KXPA100 to melt it out of there,
> but before I try:
>
> 1. Is there any chance of this working?
> 2. Should I just transmit a TUNE through it?
> 3. Can I damage the KXPA100 or tuner?
>
> Right now the coax is not connected to the KX3 and I haven't tried to
> receive.
>
> david
> KC1DNY
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> <http://mailman.qth.net/mailman/listinfo/elecraft>
> Help: http://mailman.qth.net/mmfaq.htm <http://mailman.qth.net/mmfaq.htm>
> Post: mailto:[hidden email] <mailto:[hidden email]>
>
> This list hosted by: http://www.qsl.net <http://www.qsl.net>
> Please help support this email list: http://www.qsl.net/donate.html
> <http://www.qsl.net/donate.html>
> Message delivered to [hidden email] <mailto:[hidden email]>

wa6vab

Re: Ice on dipole under snow under ice

Your Trying to figure out Propagation ?

GoodLuck WA6VAB

From: David Haines
Sent: Tuesday, December 15, 2020 9:47 AM
To: Louandzip; [hidden email]
Subject: Re: [Elecraft] Ice on dipole under snow under ice

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

On 12/13/2020 4:36 PM, Louandzip wrote:

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k6dgw

Re: Ice on dipole under snow under ice

In reply to this post by David Haines

Snow and/or natural ice that fell from the sky is barely conductive if
at all and likely has zero effect. All or part of your antenna laying
on the ground will sure lower it's radiating efficiency [although maybe
not as much as you might think], but HF radio is sometimes magic. Like
quantum mechanics, it's all probabilities. Instead of "shouldn't work,"
ask "what's the probability that it will work?" 😁

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 12/15/2020 9:45 AM, 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
>

Elecraft mailing list

Re: Ice on dipole under snow under ice

In reply to this post by David Haines

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

W3LPL

Re: Ice on dipole under snow under ice

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" <[hidden email]>
To: [hidden email]
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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k6dgw

Re: Ice on dipole under snow under ice

In reply to this post by Elecraft mailing list

Around 1958, I was part of the crew that built KPFK on Mt. Wilson in So
Calif. Our 10 dB antenna was a stacked ring design, and included a
two-stage heater than circulated 60 Hz AC to de-ice it. Icing didn't
affect the SWR or pattern but it did put mechanical strain on the
elements. Mt Wilson is also famous for a large telescope. I don't know
how they deiced that. 😁

Incidentally, the KPFK homebrew 10 KW PA comprised 4 4-1000A's in
parallel. I don't recommend 4-1000A's at 90.7 MHz, it was pretty squirrely

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 12/15/2020 12:21 PM, Mike Harris via Elecraft wrote:
>
> 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
>

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David Haines

Re: Ice on dipole under snow under ice

In reply to this post by k6dgw

Fortunately the wire is caught under snow and ice on a timber frame
building with asphalt shingles. It seems to be working just fine. Even
better than before, the dipole no longer can swing in the wind!
Maybe the next antenna should just lie on the roof!

I really appreciate "Instead of "shouldn't work," ask "what's the
probability that it will work?" Spoken like a true engineer who knows
how to solve problems!

david
KC1DNY in Maine, awaiting another snow storm to put 7 more inches of
protection on my dipole.

On 12/15/2020 2:23 PM, Fred Jensen wrote:

> Snow and/or natural ice that fell from the sky is barely conductive if
> at all and likely has zero effect. All or part of your antenna laying
> on the ground will sure lower it's radiating efficiency [although
> maybe not as much as you might think], but HF radio is sometimes
> magic. Like quantum mechanics, it's all probabilities. Instead of
> "shouldn't work," ask "what's the probability that it will work?" 😁
>
> 73,
>
> Fred ["Skip"] K6DGW
> Sparks NV DM09dn
> Washoe County
>
> On 12/15/2020 9:45 AM, 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
>>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Elecraft mailing list

Re: Ice on dipole under snow under ice

I imagine lying on the roof would usually be fine, except for being a little lower. At a couple of different QTHs I had my antennas in the attic; 40-10m dipoles, 6m and 2m loops. These were wood roofs with cedar shakes or asphalt shingles. They all worked well when the roof was dry. Wet definitely affected the SWR. A wet roof has a lot more contaminants in the water making it more conductive than snow or pristine rainwater ice.

At one point I had the shingles replaced. The dipole SWR was way off from what it had been. It turned out the new building code required metal edging under the shingles at the perimeter of the roof.

On Wednesday, December 16, 2020, 7:18:56 AM MST, David Haines <[hidden email]> wrote:

Fortunately the wire is caught under snow and ice on a timber frame
building with asphalt shingles. It seems to be working just fine. Even
better than before, the dipole no longer can swing in the wind!
Maybe the next antenna should just lie on the roof!

I really appreciate "Instead of "shouldn't work," ask "what's the
probability that it will work?" Spoken like a true engineer who knows
how to solve problems!

david
KC1DNY in Maine, awaiting another snow storm to put 7 more inches of
protection on my dipole.

On 12/15/2020 2:23 PM, Fred Jensen wrote:

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