View Single Post
  #2   Report Post  
Old February 23rd 05, 04:11 PM
Dave
 
Posts: n/a
Default


Richard Clark wrote:
On 22 Feb 2005 18:10:53 -0800, "Dave" wrote:
Thanks for the advise. However, I thought 1/4 wave antennas were

more
isotropic than 'most' other antennas... (see link below)

http://www.astrosurf.com/lombry/Radio/dipole-height.gif

What am I missing?


Hi Dave,

Umm, those are lobes for a HORIZONTAL dipole --- wrong polarization,
wrong size. Cross polarized signals come with beaucoup loss.


Are there any online sources that show vertical whip antenna take-off
angles vs. antenna length (as a function of wavelength)?

If the balloon is overhead (or off of overhead by =B115=B0) you are

10dB
down at best, or sitting in a deep null (deaf city). To compare that
30=B0 cone of silence: Hold your hand directly overhead, spread out
your fingers and thumb, the distance between little finger and thumb
tips spans 13 to 15 degrees (half that cone).

Is your balloon in that cone? Worst possible place for a short
vertical antenna to hear; and for a balloon with a short vertical,

you
are in the worst place for it to shout down to you. This is a deadly
combination that puts your normal signal at -20dB (or worse).


I don't know about "deadly"... atleast not in this scenario. :-)

Keeping the transmitter and reciever constant, what would you recommend
for the transmitting and receiving antennas in this case?

Thanks,
Dave