Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Dipole and Snow

Dipole and Snow

Dipole and Snow

I am looking for some input? Using a half wave dipole at 72 megahertz FM with the antenna mounted on a flat roof and with the base of the antenna sitting in 4-6 inches of snow. Will the impedance or SWR change due to the snow?
Thanks in advance

RE: Dipole and Snow

Snow is mostly air, and is not a problem.  Ice is pure water which will load down the end of an antenna--mistuning it.  

RE: Dipole and Snow

If the antenna gets within 30 inches or so of the flat roof, the metal in the roof (if any) will start to degrade the antenna VSWR. 41" is 1/4 wavelength and below that length you can really see VSWR change.

biff44 is right, snow is air, ice is 3.2 dielectric and not too lossy, water is 81 dielectric and very lossy.


RE: Dipole and Snow

I did not realize that ice was only a 3.2!  That is not so bad!

RE: Dipole and Snow

Yup, 3.2.
Not sure of the loss tangent.
When it starts to melt is a problem.
I wonder how Direct TV does in the cold climates.

There is a high dielectric constant for ice at high frequencies (the constant is about 3.2).  Ice has a very high dielectric relaxation time compared to water, and at higher frequencies the molecules are not able to
realign themselves to the changing electric field. This is why ice does not melt in a microwave as quickly as water comes to a boil.


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close