LinkBack Thread Tools Search this Thread Display Modes
Prev Previous Post   Next Post Next
  #11   Report Post  
Old November 2nd 03, 05:35 AM
Yuri Blanarovich
 
Posts: n/a
Default


I once had an occasion where the bottom of a coil did get warm, while
the top did not. Yet my RF ammeters showed the same current on both
ends. What was going on?


What was he measuring, where was the coil?
W9UCW used 100 mA at the bottom, I doubt that this would "cook" the coil. You
see the pictures, they are good quality coils and he use two meters and
flippped the coil to eliminate possible error as described here.

I ultimately determined that the soldered connection from the coil to
the lower antenna mast (for experimentation, it was copper) was adding
some undesireable resistance. Solder is not a particularly good
conductor of electricity. I copper-plated over the solder joint. Not
only did the bottom section of the coil no longer get warm, but the
two RF ammeters both showed about 20% more current flowing in the
antenna. And my far-field instruments showed a 1.5dB increase in field
strength.


Again, put on the fricken Hustler 80m resonator, feed it 100W and feel it! No
meters, no hokus pokus, just "naked" antenna.


This is one example of being fooled....If you took coil temp at face
value, you would think the current taper was quite steep, judging from
the temp's of the windings. But nope...A resistive connection seemed
to be the culprit. Note that his meters showed the same current on
both ends. :/ You can see why I'm afraid of that "hook" that usually
is lurking ready to bite at a moments notice.
Don't worry, if you are right, it will come out in the end. But that
hook...Ouch.. MK


One insufficiently described measurement is enough to throw rest out of the
window? W9UCW has shown data from various measurements and positions of the
coil (pictures how it was done) and W5DXP backed it up with explanation of
reflected wave and simulation and comparison with loading stub. It came out,
this is the ned. If you choose not to believe, its a free country :-)

Yuri

 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Inverted ground plane antenna: compared with normal GP and low dipole. Serge Stroobandt, ON4BAA Antenna 8 February 24th 11 10:22 PM
Smith Chart Quiz Radio913 Antenna 315 October 21st 03 05:31 AM
QST Article: An Easy to Build, Dual-Band Collinear Antenna Serge Stroobandt, ON4BAA Antenna 12 October 16th 03 07:44 PM
Eznec modeling loading coils? Roy Lewallen Antenna 11 August 18th 03 02:40 AM


All times are GMT +1. The time now is 11:35 AM.

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

About Us

"It's about Radio"

 

Copyright © 2017