Good morning, JC
Well, in its present configuration, Carl's antenna is not really a folded
monopole, although it did start our as one when he had his gamma match
connected at full height of 90'. At present he has his gamma attached at
67' - about 2/3 of the way up the tower. But that's sort of a "nit-pick" -
otherwise, I do agree that the gamma match (with its 3-wire cage, is a
shorted transmission line section. Since it's less than 1/4 wavelength it
will have inductive reactance that needs to be canceled with the series
tuning capacitor.
Carl should have a good topband transmit antenna! As he builds out his
radial field, the efficiency will hopefully improve some more. I hope he had
fun with it last night, but 160 conditions of late have been rather poor -
apparently because of the sun's coronal mass ejection a few days ago.
Have a good day!\
73,
Charlie, K4OTV
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of JC N4IS
Sent: Sunday, February 23, 2014 7:20 AM
To: 'Richard (Rick) Karlquist'; 'Carl Braun'; 'Carl'; '160'
Cc: WX9J@att.net; ad6dk@arrl.net
Subject: Re: Topband: Shunt feeding the Skyneedle - new developments
>>
I'm sure it will play well in terms of keeping your transmitter happy but
the relatively large bandwidth you are measuring is indicative of
substantial loss in the system somewhere.
This would be a large bandwidth even if you did not have the bandwidth
narrowing effects of a shunt feed.
<<
Hi guys, the 3 wires is actually a transmission line and the antenna is well
known as Folded Unipole with 200 ohms impedance. My antenna is a Folded
Unipole as well and has the same broadband SWR measurement's. The loss is
the same for any tuning circuit it has nothing to do with the bandwidth. The
ground plane does, and in this case it is the same, right?
73's
JC
N4IS
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|