Monday, January 21, 2013

Snow on the roof


This morning we woke up to a covering of a couple of centimetres of snow. It's fairly wet snow: The temperature is just above freezing so it is already beginning to thaw. This is about as much snow as we usually get here, but the less time it hangs around the better. When it's cold the smow doesn't melt and eventually gets compacted into ice which, especially as we are on a hill, is a real nuisance.

I am often asked whether snow on the roof affects the performance of attic antennas. My answer is: Not so as I've noticed. The SWR of my attic antennas remains exactly the same (in fact it changes more on hot days when the attic temperature reaches 40 degrees plus, due to expansion.)

My magnetic loop on 30m did not need any re-tuning this morning and the first APRS packet sent was received by a German digipeater. My 2m APRS gateway is also functioning normally. I've put the K3 and multiband dipole on beacon monitoring duty and the beacons are coming through just as I would expect. In other words, all is normal.

Perhaps if there was a metre or more of snow I might notice a difference. But I think the amount of frozen water the RF has to pass through on the roof is negligible compared to the clouds it must traverse on its way to and from the ionosphere.

5 comments:

VE3WDM said...

Good morning Julian, I have noticed with my attic dipole the SWR does go up just a little in the winter time. I have been told that was due to snow on the roof. Now as for the amount on the roof it's about 1 to 3 inches. At this point we have very little on the roof and all is well with the SWR. Now when the snow does affect the SWR it is by a very little and nothing that the K3's ATU can't handle.
Mike

K9CHP said...

Well, here is a pic of my Cobra Ultra lite,antenna under,heavy snow and ice: https://www.box.com/shared/zbt7l7dkntoczsgn63ro
I hope the link will work. And no, the swr was so bad,my tuner could not get it down to workable range. It was fine again, once the ice was gone and the antenna,went back up, by itself. The antenna had a counterweight and that prevented it from breaking under the stress.

2E0HTS Simon said...

Hi Julian, looks like the snow decided to go easy on you. The attic antennas are invaluable when we get hit. My outdoor stuff is iced up and showing a high SWR 3.0 until I can launch a few snowballs at them to try and loosen off the build up. Keep warm and all the best from Yorkshire. 73 de Simon

Anonymous said...

I have been a ham 25 yrs and the snow or rain on my outside antennas only affects the swr .
They perform great . Nice picture of the snow . I love the snow , it makes everything look beautiful .

Lawrence Banks said...

It's a good thing we moved to Florida where the temperature is just perfect for us. Though my kids kinda missed the snow too, especially since they love ice skating and sledding. -Lawrence