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BL2 Question Follow Up

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David Dietrich

BL2 Question Follow Up

Whoops! I should have added this when I was composing last night. I have the KAT1 tuner
installed. At the present, my four band module is for 40, 30, 20, & 15. I plan on at least
operating on 40 & 20 for sure, and possibly 15 if the SWR isn't too bad. Original message below
for reference:

Howdy Everyone,

I am seriously considering the purchase & construction of a BL2 switched balun so I can construct
a lighter dipole antenna for field use than the dipole I have been using with my K1-4 (#2051). I
am planning on taking the K1 down to TX over Christmas and I don't want to take the heavier dipole
I have with me like I did this past summer. It's rather bulky and takes up valuable suitcase
space.

Here is my plan: Construct a 20 and/or 40 meter 1/2 wave dipole and feed it using standard TV
twin-lead as my feedline (found in any hardware/home improvement store), and some #18 wire (I have
some on hand). Since the antenna would be balanced, I would attach the twin-lead to the balun and
the balun to the back of my K1. I am thinking that this design would make for a good performing,
lightweight antenna that will be easier to pack & set up.

Questions:
1. Will the BL2 work well with TV twin-lead antenna I am going to build? There's no sense in
buying it if it won't work with this antenna.

2. What kind of luck have those of you who have built it had with fitting it into some sort of
plastic or metal enclosure? What works and what won't?

3. Will I need to do any sort of grounding with this?

I'd really like responses from those who either (A) own one OR (B) do a lot of antenna homebrewing
& experimentation.

Many thanks,

David
KC9EHQ
K1-4 #2051

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Don Wilhelm-3

RE: BL2 Question Follow Up

David,

It will work if you can load it - and whether or not you can load it easily
is highly dependent on the length of the feedline. The switchable balun
will help you obtain a match.

I would suggest a flattop antenna cut near resonance at 30 meters and a
feedline length that is near a halfwavelength long at 30 meters (even though
you may not plan operation on 30). The key is to avoid extremely high
impedances at the feedpoint - if the sum of the feedline length and half the
antenna length is near a multiple of a half wave on any band, the feedpoint
impedance is likely to be high, similarly if that sum is near a multiple of
a quarter wave, the feedpoint impedance will be near 50 ohms (but that is
just a 'rule-of-thumb' starting point.

If you can obtain the feedpoint impedance of your proposed dipole for all
bands of interest, a bit of work with TLW (available from the ARRL website)
can help you determine a length of feedline that should work for all bands.
The KAT1 has a good matching range, and the switchable balun extends it. I
would say if you can keep the impedance at the balun end between 20 ohms and
1200 ohms you should be successful, but you need to stay away from points
that are highly reactive as well.

After all the 'figuring' is done on paper, put it up and try it - it is
quite wise to verify whether it works or not before you take off and try to
use it at a portable location.

73,
Don W3FPR

> -----Original Message-----

>
> Whoops! I should have added this when I was composing last
> night. I have the KAT1 tuner
> installed. At the present, my four band module is for 40, 30,
> 20, & 15. I plan on at least
> operating on 40 & 20 for sure, and possibly 15 if the SWR isn't
> too bad. Original message below
> for reference:
>
> Howdy Everyone,
>
> I am seriously considering the purchase & construction of a BL2
> switched balun so I can construct
> a lighter dipole antenna for field use than the dipole I have
> been using with my K1-4 (#2051). I
> am planning on taking the K1 down to TX over Christmas and I
> don't want to take the heavier dipole
> I have with me like I did this past summer. It's rather bulky
> and takes up valuable suitcase
> space.
>
> Here is my plan: Construct a 20 and/or 40 meter 1/2 wave dipole
> and feed it using standard TV
> twin-lead as my feedline (found in any hardware/home improvement
> store), and some #18 wire (I have
> some on hand). Since the antenna would be balanced, I would
> attach the twin-lead to the balun and
> the balun to the back of my K1. I am thinking that this design
> would make for a good performing,
> lightweight antenna that will be easier to pack & set up.
>
> Questions:
> 1. Will the BL2 work well with TV twin-lead antenna I am going
> to build? There's no sense in
> buying it if it won't work with this antenna.
>
> 2. What kind of luck have those of you who have built it had
> with fitting it into some sort of
> plastic or metal enclosure? What works and what won't?
>
> 3. Will I need to do any sort of grounding with this?
>
> I'd really like responses from those who either (A) own one OR
> (B) do a lot of antenna homebrewing
> & experimentation.
>
> Many thanks,
>
> David
> KC9EHQ
> K1-4 #2051
>

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Leigh L. Klotz Jr WA5ZNU

Re: BL2 Question Follow Up

Administrator

In reply to this post by David Dietrich

You might also compare your 44' doublet by itself and with a 25'
extension on one side, if you have room. That makes it into an OCF, and
the impedance swings will be less extreme than a center-fed 40m dipole,
particularly on 20m. I had a 44' doublet up and found improved
performance. The last 5 feet of mine point straight down. It is an easy
change to do and undo.
Leigh/WA5ZNU
On Sun, 22 Oct 2006 6:43 am, David Dietrich wrote:

> Whoops! I should have added this when I was composing last night. I
> have the KAT1 tuner
> installed. At the present, my four band module is for 40, 30, 20, &
> 15. I plan on at least
> operating on 40 & 20 for sure, and possibly 15 if the SWR isn't too
> bad. Original message below
> for reference:
>
> Howdy Everyone,
>
> I am seriously considering the purchase & construction of a BL2
> switched balun so I can construct
> a lighter dipole antenna for field use than the dipole I have been
> using with my K1-4 (#2051). I
> am planning on taking the K1 down to TX over Christmas and I don't want
> to take the heavier dipole
> I have with me like I did this past summer. It's rather bulky and
> takes up valuable suitcase
> space.
>
> Here is my plan: Construct a 20 and/or 40 meter 1/2 wave dipole and
> feed it using standard TV
> twin-lead as my feedline (found in any hardware/home improvement
> store), and some #18 wire (I have
> some on hand). Since the antenna would be balanced, I would attach the
> twin-lead to the balun and
> the balun to the back of my K1. I am thinking that this design would
> make for a good performing,
> lightweight antenna that will be easier to pack & set up.
>
> Questions:
> 1. Will the BL2 work well with TV twin-lead antenna I am going to
> build? There's no sense in
> buying it if it won't work with this antenna.
>
> 2. What kind of luck have those of you who have built it had with
> fitting it into some sort of
> plastic or metal enclosure? What works and what won't?
>
> 3. Will I need to do any sort of grounding with this?
>
> I'd really like responses from those who either (A) own one OR (B) do a
> lot of antenna homebrewing
> & experimentation.
>
> Many thanks,
>
> David
> KC9EHQ
> K1-4 #2051
>
> __________________________________________________
> Do You Yahoo!?
> Tired of spam? Yahoo! Mail has the best spam protection around
> http://mail.yahoo.com
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> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
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> Elecraft web page: http://www.elecraft.com

AA5CK

Re: BL2 Question Follow Up

In reply to this post by David Dietrich

Hi David

Don't get the cart in front of the horse or sell the KAT1 short. You
may not need a balun!

Build your antenna first and see if the KAT1 has any problems on any of
the bands. If so, try varying the length of the antenna or feed-line in
small increments until you find a combination the KAT1 likes.

I ended up with an antenna about 100ft long with about 30ft of twin-lead
that tuned up on 40 thru 15 FB as one of the portable antennas used with
my K1. Other combinations should work as well!

If you are locked in on Antenna or feed line length and having problems
the BL2 is there for your rescue!

I use one to tame a Double Extended Zepp at the home QTH on a couple of
bands the KAT100 needs help with.

I haven't enclosed my BL2 but that doesn't sound like a bad idea.

I normally use a battery with my K1 so everything is isolated from
ground. Connecting a ground would upset feed line balance whether it was
coax or twin-lead.(Lewallen, W7EL Ant Comp.#1 p.159)

Good Luck and let us know what you end up with.......Ted......aa5ck

David Dietrich wrote:
>
> Howdy Everyone,
>
> I am seriously considering the purchase & construction of a BL2 switched balun so I can construct
> a lighter dipole antenna for field use than the dipole I have been using with my K1-4 (#2051).
>
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Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
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