44 ft. doublet magic lead length and "bats in my belfry"

[Doug Netherton-2]

I'm preparing to put a 44 foot doublet into my attic and I'm wondering
if there is a magic lead length that allows me to work 10 to 40 meters
with minimal Z on all/ most of the bands.  I plan on using either 300
ohm twin lead or 450 ohm lead to a tuner with a built in balan.  Shack
is close to the middle of the house immediately below attic, so lead
could be less than 20 feet.  How about 22 feet times velocity factor of
lead???  Any comments?

BTW:  I disturbed a furry flying insect eater in my foray into the
attic, so I'm looking for potential entry points.  Any pointers for
encouraging its/their departure with something like moth balls?

73, Doug, VE3MCF
k2 #1322
 

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[Stuart Rohre]

Doug,
I guarantee that a whole box of moth balls will evict your furry attic
resident.  However, it will permeate to the house, unless you can seal the
attic entry from the house with masking tape for a few days.

Be sure to find the entry point and be ready to screen it off as soon as the
furry friend is gone.  Normally, they are nocturnal feeders, and leave at
dusk to hunt insects and return at dawn to rest.

I live about a quarter mile from one of the largest SW bat colonies; under
an Interstate bridge is where they live, in spite of traffic noise and
vibration.  Millions come out at dark and range over wide areas for insect
meals.  You want to get a bat out before he invites friends over.   The
stench of many bats is pretty bad, and there are health concerns from them.
-Stuart
K5KVH


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[N2EY]

(insert standard "no connection" disclaimer HERE)

1) Google up G4FGQ (Reg Edwards) website

2) Download DIPOLE#.EXE freeware

3) Have fun tring different dipole/feedline combos.

(note that it's all metric!)

73 de Jim, N2EY
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[Joe-aa4nn]

Hi Doug & all,
I used a doublet (center fed zepp) with 22 feet on each horizontal side then
a 44 foot piece of 300 ohm TV lead back to the tuner.  In my case the tuner
was the KAT100 which tuned this doublet 1.1 to 1, 40m to 10m.  Good luck &
73.
de Joe, aa4nn
------------------------------------
I'm preparing to put a 44 foot doublet into my attic and I'm wondering
if there is a magic lead length that allows me to work 10 to 40 meters
with minimal Z on all/ most of the bands.  I plan on using either 300
ohm twin lead or 450 ohm lead to a tuner with a built in balan.  Shack
is close to the middle of the house immediately below attic, so lead
could be less than 20 feet.  How about 22 feet times velocity factor of
lead???  Any comments?


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[Don Wilhelm-2]

Doug,

I would not say that there is any 'magic' length for the feedline.  Try what
you can do and see what works.  If it ends up that the tuner has difficulty
matching the shack end on one or two bands, add some extra feedline and try
again.

Depending on the matching range of your tuner, you may encounter difficulty
tuning the combination if the feedline length plus half the flattop length
come close to a half wavelength or multiple (those lengths result as a high
impedance feedpoint).

There are several programs that will tell you what the shack feedpoint
impedance will be, and I recall that LB Cebik has the antenna feedpoint
impedance for the 44 ft. doublet listed on his website www.cebik.com - look
for an article titled something like - If I Could Only Have One Antenna.

73,
Don W3FPR

----- Original Message -----

> I'm preparing to put a 44 foot doublet into my attic and I'm wondering
> if there is a magic lead length that allows me to work 10 to 40 meters
> with minimal Z on all/ most of the bands.  I plan on using either 300
> ohm twin lead or 450 ohm lead to a tuner with a built in balan.  Shack
> is close to the middle of the house immediately below attic, so lead
> could be less than 20 feet.  How about 22 feet times velocity factor of
> lead???  Any comments?
>


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