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Author Topic: Butternut HF-6V 'Q' coil?????  (Read 1171 times)
N5ZDD
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Posts: 18




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« on: May 15, 2002, 01:30:20 PM »

I have recently aquired a Butternut HF-6V that was missing some parts.  I contacted Butternut for the coil, and they want $37 for a piece of wire.  I realize that research and developement count for something, but I still think that's a little high.  I have tons of wire just laying around with nothing to do.  I need to know the inside diameter of the coil, size, and length of wire.  I would even settle for the microhenry value of it and figure it from there.  Any help is greatly appreciated.  Thanks and 73...........
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WB2WIK
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Posts: 20540




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« Reply #1 on: May 15, 2002, 03:01:23 PM »

Hopefully someone with a ground-mounted HF6V will go measure his and come to the rescue on this one!  However, in lieu of that, I have used HF6V's many times without the "base matching coil Q," including at many Field Day setups, etc, and never really noticed the difference.  This coil obviously is there to cancel some of the capacitive reactance of the antenna, and since it directly shorts the radiator to the grounded base (for DC) it likely provides a nice static drain-off mechanism, which could easily be provided by an RF choke.  

A 10uH RFC has 220 Ohms XL at 3.5 MHz and obviously more at higher frequencies, might be a good place to start!  The issue is that it might be somewhat dissipative, especially at the lowest frequencies (like 80m) and thus is made of large gauge wire, air core.  The original Butternut "Q" coil is definitely air-wound of about #16 gauge or so, I've used them enough times to remember that!

73 de Steve, WB2WIK/6
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WB6BYU
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Posts: 12980




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« Reply #2 on: May 15, 2002, 04:30:26 PM »

From the description, this sounds like a shunt coil for impedance
matching, and it probably has the most impact on the lowest bands.
Try the coil as Steve suggested, and tweak it for minimum SWR on
80m and 40m. (Presuming the coil changes the SWR at all on those
bands.)

One thing you can do is to start with a piece of coil stock and
a clip lead to select the desired number of turns.  Adjust the tap
point for best SWR using low power.  Once you find the right
amount of inductance, you can wind a larger coil that will handle
full power.
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N5ZDD
Member

Posts: 18




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« Reply #3 on: May 17, 2002, 01:51:06 AM »

Thanks guys,
   I plan to roof mount it when I get it together.  The 'Q' coil at the bottom is the only piece left to figure out.  I have come across a few pictures of the antenna on different web pages, but the coil is really hard to make out.  It looks to be about 6-8 inches long and about 2 inches in diameter.  If there were no replies I was going to use a long fixed coil, and tap with a jumper clip to find the right length.  I thank you both for all the help and hope I can return the favor....73......
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WB2WIK
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Posts: 20540




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« Reply #4 on: May 17, 2002, 02:43:17 PM »

N5ZDD: I'm going by memory only, since I have no HF-6V to look at right now, but I don't think the Q coil is 2" diameter, or 8" long.

I recall it's about 1" diameter, and 4" long, air-wound of stiff wire about #16 gauge (and of course enameled or formvar -- so the turns don't short against each other!).

I also recall not using it at all, in many installations, and it didn't appear to make a lot of difference!

73 de Steve, WB2WIK/6
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K5LXP
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Posts: 4439


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« Reply #5 on: May 18, 2002, 03:28:33 PM »

I just went and measured the coil on my butternut HF6V.

It's a 1.25 ID, 17-turn coil wound with solid 12ga enameled copper wire. Length will be dependent on the installation, stretch or shrink it according to the tuning directions.

I've had my butternut HF-6V since 1988, about 5 years ago installed the 12/17M kit.  It's a great antenna for all-band coverage, very convienent to just change bands on the rig and the antenna is right there, no tuning.

There are some excellent articles on grounding, counterpoises and radials on the butternut website that are well worth reading, along with the owner's manual for the HF6/9V antennas.

Happy rebuilding, 73...

Mark K5LXP
Albuquerque, NM
http://www.qsl.net/k5lxp
k5lxp@arrl.net
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N5ZDD
Member

Posts: 18




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« Reply #6 on: May 24, 2002, 01:24:01 AM »

Thank you all for the help.  I have just gotten it back together and should have it up over the weekend.  I'll let you'll know how it turns out.  73........
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