Towertalk
[Top] [All Lists]

[TowerTalk] Steve Best on Mismatch loss, transmitters and tuners

To: <towertalk@contesting.com>
Subject: [TowerTalk] Steve Best on Mismatch loss, transmitters and tuners
From: davidc@bit-net.com (DavidC)
Date: Wed, 22 Jul 1998 17:29:52 -0400
> Steve,  I have a Bird 43 watt meter that says I am sending more power
> out my transmission line than is coming out of the transmitter!!  From
> where do you suppose that power came.  

Wait a minute, now you are really confusing me.
Are you saying that a mismatched feed system creates gain?

> This is ridiculous!!  Transmitters get hot,  but not because they
> are dissipating reflected antenna power!! If true,  the output
> inductor of the transmitter would soon melt,  as the reflected
> power keeps on a'coming!

Again, are you saying that the output from the transmitter is amplified
within the feed system (not the antenna, because what it amplifies it
radiates towards the intended object ... not the transmitter, I hope!)

>> " You do not radiate more power
> [KH7M comment: Of course not.
> Steve,  what happens to those couple hundred extra watts read
> on my Bird, that did not come out of the transmitter,  were they
> generated in my tuner?? ]

Sounds as though there is something fooling the Bird into reading what is
not there ... unless as above you intend to suggest that mismatches
multiply power.

>>      "If you feed an antenna with a 20:1 VSWR you will
>>      give up 7.41 dB of radiated power.  VSWR results in a mismatch loss
>>      regardless of cable attenuation. "
> Steve,  then why,  when using the Smith chart to design such a system
> as you go on to describe,  it is  true that the greater the reflection
loss,
> the better the system match is to the antenna system???

Is this because once the energy is lost (gone as heat or radiated by the
pre-antenna components) there is no longer anything stimulating a mismatch
at the antenna?

73, DavidC  AA1FA

--
FAQ on WWW:               http://www.contesting.com/towertalkfaq.html
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm


<Prev in Thread] Current Thread [Next in Thread>