Hello all,
This base coil provides the correct amount of inductance to tune the
antenna for a low SWR on 75/80. There is no 'magic bullet' to how much
this would be. It all depends on each installation.
I have one installed at a vacation property with about 100 radials. The
antenna was given to me and did not have this coil with it. I wound
10-12 close wound wraps of some #14 solid, insulated house wire. I
hooked it up and measured the SWR in the part of the band I would be
operating. I stretched the coil to lessen the inductance and the SWR
decreased. I kept stretching and measuring till I got a good match. My
nice, tight coil is now about 14 inches long and in a 270 degree arc.
Obviously, I had much more inductance to start with, than I needed. I
probably could replace it with 3-4 close wound turns and re-tune, but
it's not worth the effort. Ugly, but works fine.
Point is this shouldn't be 'rocket science'. Make a coil with plenty of
inductance and then tune it by stretching the coil. Any decent wire is
fine.
BTW, if you have a good RF ground (radials) you will find the 2:1
bandwidth quite narrow. Mine is something like 16 KHz. Beware those
who say 'I only use ONE ground rod and I have a bandwidth of 200 KHz!'
Those antennas generally make good dummy loads, but YMMV.
73 de Steve, NR4M
On 9/14/2016 7:31:PM, Stephen Lee wrote:
Greetings to all,
For the Butternut HF coil, check DX Engineering's Butternut parts web
page. There's a good picture of the coil. On that picture I count 17
coil turns along the top. I'm holding an older Butternut coil in my
hand here in the identical position and count 18 turns across the top
of this coil. On mine, there are no crimped on wire terminals. The
coil wire is simply stripped and looped at each end with both loops
being solder coated.
Holding the coil just like in the web picture and slipping a tape
measure vertically in amongst the coils I measure exactly 1-1/2 inches
across the outside to outside diameter of the coils. The coil wire
itself has a transparent red coating just as the picture indicates.
The overall diameter of the thinly insulated copper wire is 85
thousandths of an inch and that includes the insulation.
Coil length is variable. According to the manual, one simply spreads
it apart to effect a very narrow window of bandwidth within the 75 to
80 meter band. That coil should only effect the 75/80 meter band so it
is possible to dial-in the antenna for use with the other bands. I've
operated my Butternut without the coil; simply avoid transmitting on
75/80 meters.
The Butternut HF series of verticals shipped with a piece of 75 ohm
coax to be used in series with the feedline. Was that included with
your Butternut vertical, and if so, could you send the end-to-end
measurement of that piece of coax please?
Enjoy! Stephen Lee N7RV
On 9/13/2016 7:09 AM, Frank Davis wrote:
I have an HF6V that is missing the coil at the base…the one that
bypasses the base to ground. Can some one send me the dimensions (
length and diameter) and number of turns in that coil so I can make
one. Thanks Frank VO1HP
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|