Effect of snow-cover on wire antenna - Elmers Forum at eHam.net

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eHam.net Forum : Elmers : Effect of snow-cover on wire antenna

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Effect of snow-cover on wire antenna	Reply
by W2RDD on June 20, 2007	Mail this to a friend!
A little early to talk about snow, but... I just put a short end-fed zepp out, laying flat on a shingled roof (restrictions). Works ok now but I am wondering about what will happen when the antenna is covered by snow. I am already using a trans-match. Anyone have a similiar situation and what have you observed in effectiveness and radically changed swr? Thanks 73

RE: Effect of snow-cover on wire antenna	Reply
by KB9CRY on June 20, 2007	Mail this to a friend!
It will detune the antenna and it may not resonate anywhere well. Also the snow is conductive and will affect the signal, if not even effectively short it out.

RE: Effect of snow-cover on wire antenna	Reply
by W3LK on June 20, 2007	Mail this to a friend!
And laying directly on the roof pretty much guarantees RF is going to get into everything electronic in the house. 73, Lon - W3LK Baltimore, Maryland - soon to be Naugatuck, Connecticut

RE: Effect of snow-cover on wire antenna	Reply
by WW5AA on June 20, 2007	Mail this to a friend!
Make your zep out of 50 or 75 ohm coax. It will not be effected as much by rain or snow and a better signal to noise ratio than a wire as a bonus. Also much safer if running some power. Have fun! 73, de Lindy

RE: Effect of snow-cover on wire antenna	Reply
by WR8D on June 20, 2007	Mail this to a friend!
Snow does weird things. Skin effect and all that. One winter my loop and the homemade feedline were frozen solid and completely covered in snow. The number 12 wire was bigger than your thumb. My signal just was'nt going anywhere, "honestly"...i took a broom stick and gave it a whack to make the snow fall away and every thing was fine after that. My feed line is spaced 6inches apart so there's certainly no skin effect between the two leads...the snow though was just soaking up the signal is the best way to describe what happened to me. 73 John WR8D

RE: Effect of snow-cover on wire antenna	Reply
by WA3SKN on June 20, 2007	Mail this to a friend!
OK, snow normally affects the "Hi-voltage" points along the antenna, like putting a resistor accross your insulators... increasing losses and decreasing your radiated signal. Since the Zepp is noted for high voltage points, This will affect you. Just raising the antenna enough to clear snow build-up, will help. Also, protecting the high voltage feedpoint from the weather would be a good idea. But, make any changes before the weather gets bad! -Mike.

RE: Effect of snow-cover on wire antenna	Reply
by KE3WD on June 20, 2007	Mail this to a friend!
Your bigger problem may lie in the shingles on that roof. Not very many shingles are actually nonconductive, asphault shingles in particular can contain metals and that antenna flat on them, well. One quick and dirty trick that works well when wanting to use PVC pipe compounds as antenna radome coverings is to take a small sample and place it in a microwave oven. Start with small increments of time on the microwave and if you detect significant heating in the substance, that is a sure sign of conductive metals in it and it should be kept well away from RF antennas. I'd expect your pattern -- and angle of radiation -- to be significantly affected by the antenna wire laying on the shingles. Likely a significant portion of the signal is going almost straight up, which might be fine for "local" net comms, not so fine for any DX. Here is a fact to consider, too: Snow is frozen water and pure water, contrary to popular belief, is NOT conductive. But we are talking RF here and not DC. If your rain or snow contains any salts at all, and that is a safe bet, it will then start to conduct DC, too. But also take into consideration that radio waves starting at the lower HF bands do not propagate well under water at all. Perhaps you should look into some sort of nonintrusive vertical antenna system. Or the ISOTRON antennas. .

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