LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Wally
 
Posts: n/a
Default Radio question

Bobsprit claims to have made a VHF transmission of over 40nm. Given that his
antenna height is about 50 feet, that would require, for a line of sight
transmission, that the other antenna be about 800 - eight hundred - feet
above the water.

I believe that 40 miles is too close for skip, so could his transmission
have a 'terrain following' effect in the sense that the sea might act as a
ground plane?

Would anyone care to comment on the veracity of Bobsprit's claim?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.



  #2   Report Post  
Simple Simon
 
Posts: n/a
Default Radio question

As usual . . .

Bobsprit lied. His antenna simply isn't high enough to get out forty miles.

I can receive Coast Guard transmissions from Group Key West - 90 miles,
Group Miami - 80 miles. This huge range is because their antennas are about
five hundred feet high. It wouldn't surprise me either if their transmission power
is higher than 25 watts.

S.Simon

"Wally" wrote in message ...
Bobsprit claims to have made a VHF transmission of over 40nm. Given that his
antenna height is about 50 feet, that would require, for a line of sight
transmission, that the other antenna be about 800 - eight hundred - feet
above the water.

I believe that 40 miles is too close for skip, so could his transmission
have a 'terrain following' effect in the sense that the sea might act as a
ground plane?

Would anyone care to comment on the veracity of Bobsprit's claim?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.





  #3   Report Post  
Jeff Morris
 
Posts: n/a
Default Radio question

As I mentioned in another post, its called "ducting" and works between layers of the
atmosphere. Its not the same as "skipping" which is bouncing off the troposphere. In
open water 20 to 40 miles is common - I encountered this a few days ago with some good,
but not very special equipment. Radar will also "duct" allowing you to sometimes see
features behind an island.

BTW, I often hear Woods Hole or Portland Maine CG - 80 and 100 miles from Boston. I
doubt they have a mile high antenna.

-jeff

Wally wrote:
Bobsprit claims to have made a VHF transmission of over 40nm. Given
that his antenna height is about 50 feet, that would require, for a
line of sight transmission, that the other antenna be about 800 -
eight hundred - feet above the water.

I believe that 40 miles is too close for skip, so could his
transmission have a 'terrain following' effect in the sense that the
sea might act as a ground plane?

Would anyone care to comment on the veracity of Bobsprit's claim?



  #4   Report Post  
Jeff Morris
 
Posts: n/a
Default Radio question

That 500 foot antenna only give LOS of 27 miles. You need ducting to get that to 90
miles. I assume that the CG is broadcasting at very high power, so that it will carry in
conditions too marginal for only 25 Watts.

Simple Simon wrote:
As usual . . .

Bobsprit lied. His antenna simply isn't high enough to get out forty
miles.

I can receive Coast Guard transmissions from Group Key West - 90
miles,
Group Miami - 80 miles. This huge range is because their antennas are
about
five hundred feet high. It wouldn't surprise me either if their
transmission power
is higher than 25 watts.

S.Simon

"Wally" wrote in message
...
Bobsprit claims to have made a VHF transmission of over 40nm. Given
that his antenna height is about 50 feet, that would require, for a
line of sight transmission, that the other antenna be about 800 -
eight hundred - feet above the water.

I believe that 40 miles is too close for skip, so could his
transmission have a 'terrain following' effect in the sense that the
sea might act as a ground plane?

Would anyone care to comment on the veracity of Bobsprit's claim?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.



  #5   Report Post  
Shen44
 
Posts: n/a
Default Radio question

Would anyone care to comment on the veracity of Bobsprit's claim?

Don't doubt it at all ..... ducting

Shen


  #6   Report Post  
Flounder
 
Posts: n/a
Default Radio question

Evanescent surface wave at the Brewster angle.



"Wally" wrote in message
...
Bobsprit claims to have made a VHF transmission of over 40nm. Given that

his
antenna height is about 50 feet, that would require, for a line of sight
transmission, that the other antenna be about 800 - eight hundred - feet
above the water.

I believe that 40 miles is too close for skip, so could his transmission
have a 'terrain following' effect in the sense that the sea might act as a
ground plane?

Would anyone care to comment on the veracity of Bobsprit's claim?


--
Wally
www.makearatherlonglinkthattakesyounowhere.com
Things are always clearer in the cold, post-upload light.





  #7   Report Post  
Horvath
 
Posts: n/a
Default Radio question

On Wed, 03 Sep 2003 16:33:14 GMT, "Wally" wrote this
crap:

Bobsprit claims to have made a VHF transmission of over 40nm. Given that his
antenna height is about 50 feet, that would require, for a line of sight
transmission, that the other antenna be about 800 - eight hundred - feet
above the water.

I believe that 40 miles is too close for skip, so could his transmission
have a 'terrain following' effect in the sense that the sea might act as a
ground plane?

Would anyone care to comment on the veracity of Bobsprit's claim?


You must be joking. The sea always acts as a ground plane. But a
skip is always on AM.

(Wally's answer: "Yes you are correct. I was just testing.")




Ave Imperator Bush!
Bush Was Right! Four More Years!
  #8   Report Post  
Flounder
 
Posts: n/a
Default Radio question

AM (600-1600 KHz) is a ground wave. It doesn't skip.

It travels further at night because the ionic concentrations in the Appleton
layer decrease from lack of sunlight and the solar wind.


"Horvath" wrote in message
...
On Wed, 03 Sep 2003 16:33:14 GMT, "Wally" wrote this
crap:

Bobsprit claims to have made a VHF transmission of over 40nm. Given that

his
antenna height is about 50 feet, that would require, for a line of sight
transmission, that the other antenna be about 800 - eight hundred - feet
above the water.

I believe that 40 miles is too close for skip, so could his transmission
have a 'terrain following' effect in the sense that the sea might act as

a
ground plane?

Would anyone care to comment on the veracity of Bobsprit's claim?


You must be joking. The sea always acts as a ground plane. But a
skip is always on AM.

(Wally's answer: "Yes you are correct. I was just testing.")




Ave Imperator Bush!
Bush Was Right! Four More Years!



  #9   Report Post  
Horvath
 
Posts: n/a
Default Radio question

On Thu, 04 Sep 2003 02:26:05 GMT, "Flounder" wrote
this crap:

AM (600-1600 KHz) is a ground wave. It doesn't skip.

It travels further at night because the ionic concentrations in the Appleton
layer decrease from lack of sunlight and the solar wind.


Well gee, that's a skip, isn't it?




Ave Imperator Bush!
Bush Was Right! Four More Years!
  #10   Report Post  
Flounder
 
Posts: n/a
Default Radio question


www.physics.gatech.edu/gcuo/UltrafastOptics/ PhysicalOptics/Class08.ppt


"The Captains Master" wrote in message
...
On Wed, 03 Sep 2003 19:43:38 GMT, "Flounder"
wrote:

Evanescent surface wave at the Brewster angle.

WTF, you wanna try that in English!......if you can.....


Oz1...of the 3 twins.
I welcome you to crackerbox palace,We've been expecting you.




 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
HELP, Boat CB Radio Question! Dman Electronics 16 July 25th 04 12:00 AM
Handheld VHS Radio Question Dave Van Touring 5 July 20th 04 02:17 AM
Modifying Icom IC-M800 Steve Electronics 38 July 10th 04 03:49 PM
VANISHED (stolen?)- a new (and unique) 57' Beneteau [email protected] Cruising 18 January 13th 04 12:26 AM
BASIC Radio Question Bobsprit Cruising 60 December 18th 03 03:56 PM


All times are GMT +1. The time now is 08:00 AM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 BoatBanter.com.
The comments are property of their posters.
 

About Us

"It's about Boats"

 

Copyright © 2017