attic dipole question

[Whiplash-265]

hi all..

came across someone's idea of making a dipole for the attic using 2 firestix and wanna give this a try seeing i have two 4'ers sitting here collecting dust..
the only thing i didn't see mentioned was a ground? seeing as it was just being mounted to what appeared to be a 2x4 in the original plan am i to assume that the only ground being utilized it the shielding in the coax and the radio? is this the best option or should i be looking at something else to ground the bracket?

A Stealthy Homebrew Vertical Dipole Antenna Using Mobile CB Antennas

thanx

 

[Beetle]

A properly-made dipole/doublet is a balanced antenna and doesn't require a ground to work properly.

 

[unit_399]

I ran a pair of 5' firesticks in a horizontal dipole configuration as a makeshift antenna for a while and it worked surprisingly well. Most people don't have a lot of success with attic antennas, and I think it's because all of the nails in the rafters, roofing, etc., disrupt the transmitting pattern. Just a thought. Let me know how yours works out.

- 399

 

[522]

you have the stuff to make it. i say do it. youre out nothing if it doesnt work. thats half the fun.

try it out, and let us know how it works.

 

[Whiplash-265]

thanx everyone..

will give it a shot over the next couple of weeks and report.
going to try both vert and horizontal, especially looking forward to testing horizontal

 

[glsmith1544]

My attic dipoloe for CB

Third floor apartment attic w/double bazooka dipole hanging from peak in an inverted V configuration w/ cheap 20' coax from RS. Best I can tell there's no metal up there except nails used in construction. There are no ducts or wiring.

I was pleasantly surprised when SWR ran only 1.4 to about 1.65 across 40 channels.

Performance is nothing to brag about but beats the alternative of no radio. It may compare to my mobile parked in front or SLIGHTLY better, hard to judge. At least I can hear all the DX!

 

[Whiplash-265]

i've got pretty much the same setup but i do have wiring throughout the attic. when i bought the place i had to have all the knob and tube removed and w/o destroying the walls it was my only option to go up/over/down

i'll try and find the cleanest spot

won't cost me any more than $50 to try it out....if it totally sux i'll see what i can get for a small duallie on a rotor
eventually i'd like to throw up a tower but that's prob a couple of years away yet

 

[Needle Bender]

when i tested a 5 foot firestick on my mobile it was 2-3db down from the 102 whip so why handicap yourself even more by buying expensive firesticks when 17 feet of wire is alot cheeper and will perform better?

 

[HomerBB]

I just built and tried a matched set of center wound antennas about three feet long each as a dipole. Seemed to work okay at about 10' up on a test pole, but the bandwidth from 2:1.1 was very narrow.

 

[Wrench]

Looks like a great setup. I would ground to earth at the junction, although you could just ground the radio chassis like a lot of my friends do. I am building a dipole by winding 11 meters of insulated #12 wire around a piece of 3/4" PVC. Then, It will be on top of an old camera tripod, ground wire to tripod. It will be the same height as the window. I have to do it this way until I move out of this apartment. No antennas except for dish type for cable. At the house, I will use my trusty Antron 99, I bought in the 90's.

 

[Whiplash-265]

No antennas except for dish type for cable.

sounds like discrimination ,)


i already have the firestix needlebender so the only out of pocket will be for a length of new coax, which will hopefully be next week

i do tho think i might go with the wire idea..
do i need a balun? need to make a choke? bare wire or insulated? i've been trying to read up on them but there's so many different variations and opinions on them it's actually getting way more confusing to me than it probably is in reality. too many projects at one time? lol

i've have tho finally gotten around to rigging this thing up (the twin stix version), and maybe it's the 2' coax i'm using to test it with on the 259b, but i'll be damned if i can find anything even close to a sweet spot. best swr i've been able to come up with is 3.8, best r being mid 30s (i hears what you're saying HomerBB...that "best" only covers about 100hz before it's off the map again)

Wrench, let me know how your project works out please? i jusy so happen to have what's left of 100' roll of 12ga. here that i bought to make a choke for the truck
my attic is smaller than i thought....height about 7' at it's peak. guess i could use a junction box as a ground? or could sharing the "house" ground make things go screwy??

cheers!!

 

[Whiplash-265]

k, wtf is it with me and dipoles?

i've now tried a wire dipole..have left extra on the ends for adjustment so presently have 9' per side
have a 4x7 piece of 1/2" plexi with 1 bolts at either end that tie in the wire to the split coax...one side core the other braid
so theoretically i should be about perfect at around 27Mhz

so i'm running it thru the 259b and can't find shyt...so i figure, k it's gotta be good for something, right?

why for the love of (enter your favourite religious figure here) am i perfect @ 54Mhz? it's 1/4 wave a side right? = 1/2 wave overall

i need a bigger attic so i can buy a frickin' beam lol

 

[wavrider]

k, wtf is it with me and dipoles?

i've now tried a wire dipole..have left extra on the ends for adjustment so presently have 9' per side
have a 4x7 piece of 1/2" plexi with 1 bolts at either end that tie in the wire to the split coax...one side core the other braid
so theoretically i should be about perfect at around 27Mhz

so i'm running it thru the 259b and can't find shyt...so i figure, k it's gotta be good for something, right?

why for the love of (enter your favourite religious figure here) am i perfect @ 54Mhz? it's 1/4 wave a side right? = 1/2 wave overall

i need a bigger attic so i can buy a frickin' beam lol

Try wrapping an RF choke at the feed point and then sweep it with the analyzer. This may help.

 

[Needle Bender]

k, wtf is it with me and dipoles?

i've now tried a wire dipole..have left extra on the ends for adjustment so presently have 9' per side
have a 4x7 piece of 1/2" plexi with 1 bolts at either end that tie in the wire to the split coax...one side core the other braid
so theoretically i should be about perfect at around 27Mhz

so i'm running it thru the 259b and can't find shyt...so i figure, k it's gotta be good for something, right?

why for the love of (enter your favourite religious figure here) am i perfect @ 54Mhz? it's 1/4 wave a side right? = 1/2 wave overall

i need a bigger attic so i can buy a frickin' beam lol

depends how you folded it back and the velosity facter of the wire if its stranded and insulated it might look more like a resanant 3/4 wave at 54.
you need 8 feet 7 inches on each side including the lenth of the coax split. dont worry about keeping extra on the ends. 8 feet 7 inches has to work and if anything might be a little to long if its insulated and stranded.
you could wrap a coil in the coax just below the dipole make it 5 1/2 turns on a 4 inch circle like a large plastic skippy peanut butter jar. dont use black abs because it has carbon in it

 

[Whiplash-265]

depends how you folded it back and the velosity facter of the wire if its stranded and insulated it might look more like a resanant 3/4 wave at 54.
you need 8 feet 7 inches on each side including the lenth of the coax split. dont worry about keeping extra on the ends. 8 feet 7 inches has to work and if anything might be a little to long if its insulated and stranded.
you could wrap a coil in the coax just below the dipole make it 5 1/2 turns on a 4 inch circle like a large plastic skippy peanut butter jar. dont use black abs because it has carbon in it

thanx for the feedback Needle Bender
i had read that the insulation is redundant so i figured i'd leave it on..it is 12ga. 7 strand
wouldn't longer take me to say the 12m band rather than the 5?

it's running straight across, no v, no bends..
i originally tried an inverted v but after seeing the first results i figured i'd play things safe and run it straight (ya that didn't change anything lol)
will give the choke a try. 5.5" on 4 and no touchy-touchy between first and last wrap

i'll find something other than a peanut butter jar, i think i've already had squirrels looking for a way in

again, much thanx!!