On 11/16/2016 11:39 AM, Jeff Liebermann wrote:
On 16 Nov 2016 16:58:21 GMT, Rob wrote:

John S wrote:
I've been thinking about a 70cm antenna made by using copper tape on a
window. It seems that I can get a 50 ohm match by drooping the two
radials about 38 degrees below horizontal. Of course, I don't know how
to include the effects of glass on the antenna nor rectangular coppper,
but it is a starting point. The azimuth pattern looks very good
according to EZNEC.

Any thoughts?
N1JLS

Make sure the window is not coated (highly effient dual-pane glass
normally is coated to shield IR radiation). The coating is metallic.

Yep. The Low-E coating makes an excellent RF shield and short. Try
it with an HT or cell phone, comparing the signal strength with and
through the glass.
http://buyat.ppg.com/glasstechlib/128_TD-151-Radio%20and%20Microwave%20Frequency%20Attenuation% 20in%20Glass.pdf
Looks like 30-40dB loss at UHF through Low-E glass.

Window glass also has a dielectric constant of about 6.5, which will
shorten the tuned length of the antenna elements by the square root of
the dielectric constant.


Excellent point, guys. I forgot all about that. Thanks.