[Antennas] Butternut HF-6V Antenna

Sun Jul 18 14:42:50 EDT 2010

I am doing a survey of the other bands too see if there are any 
additional changes or problems. I did try to connect my Boonton RX 
meter to the transmitter end of the coax and I measure about 28 ohms 
impedance. Given that I really don't know the exact length of my feed 
line, I really don't know what that means or exactly where on the Smith 
chart to start to get impedance at the antenna. I have not don anything 
to the matching transformer.
David
KW4DH
On 7/18/2010 2:18 PM, Ray Brown wrote:
> ----- Original Message -----
> From: "David C. Hallam"<dhallam at knology.net>
>>>>> I am having a problem with my Butternut HF-6V vertical antenna. After a
>> year or so of geed service, the 20M VSWR suddenly increased to 2:1 and
>> nothing I have been able to do has moved it back down. Adjusting the
>> tap position on the coil has no effect. I don't have an antenna
>> analyzer and am out of ideas.
>>> Well, you really need an analyzer. But let's try a few things.
>> First off, did your SWR change on any other band at all?
> Second, did you re-read the theory of operation starting on page 8?
> It discusses in great detail how it works, and how 20M is always a
> little problematic. I'll go ahead and quote the section on 20M:
>> "On 20 meters, the entire radiator operates as a 3/8 [wave] vertical,
> with much higher radiation resistance, and VSWR bandwidth, than
> conventional or trapped antennas having a physical height of 1/4 [wave]
> or less. Because the 20 meter radiation resistance will be several times
> as greater as that of conventional vertical antennas, an electrical 1/4
> [wave] section of 75-ohm coax is used as a geometric mean transformer
> to match the 100-odd [level] of feedpoint impedance on that band to a 50
> [ohm] main transmission line of any convenient length."
>> So... another thing to check - did you alter or replace the matching 75-ohm
> coax that immediately attaches to the coil at the bottom of the antenna?
>>> Ray, KB0STN
> (owns 1 at home and takes care of 1 at work :-)
>>>>> ______________________________________________________________
> Antennas mailing list
> Home: http://mailman.qth.net/mailman/listinfo/antennas
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Antennas at mailman.qth.net
>> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>>>