[TowerTalk] HF6V choke coil

[Steve Bookout]

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
>
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