[Elecraft] whips

[G3VVT at aol.com]

In a message dated 29/06/05 23:50:28 GMT Daylight Time, n6wg at comcast.net  
writes:

Check  the base impedance at hf.  Some antennas have a vhf matching  circuit
in the base
that will look like nearly a short at hf.  If  it doesn't show an open
circuit at hf,



Reply:---------------------------------------------
 
What Bob, N6WG mentions are the VHF antennas that are 1/2 wavelength  or 
multiples of this and where the antenna feed end is at a high impedance. To  match 
this a coil is inserted into the antenna base with the incoming 50 ohm  
feeder tapped in at an early point on the coil. Normally this type can  be located 
even with a sealed marine type antenna by checking the  resistance across the 
unplugged antenna lead should read S/C looking  towards the antenna. This type 
of VHF antenna should not be capable if  working on HF. However if there is 
no measurable S/C there is a good chance the  antenna is one that is a multiple 
of a 1/4 wavelength and as such could be used  as a short whip antenna for 
HF, though with rather limited efficiency.
 
Bob, G3VVT