Make your own hardline?
Bill Turner
copper water pipe?
Seems doable, but have never heard of anyone doing it.
This is what happens when I have too much time on my hands. :-)
--
Bill, W6WRT
kd5sak
wires off power poles and copper tubing from outside air conditioner units,
I think their beady little eyes would glow happily at the sight of a hundred
and fifty or two hundred feet of DIY copper hardline in someones back yard.
Shoot, they'd probably jump the fence flatfooted and fight your family dog
for 25 feet of it.
Harold
KD5SAK
"Bill Turner" <no...@nohow.com> wrote in message
news:lthdg25jovjk3v3lq...@4ax.com...
Bill Turner
On Tue, 12 Sep 2006 15:17:26 GMT, "kd5sak" <kd5...@sbcglobal.net>
wrote:
>Here in southern Oklahoma enterprising copper thieves are stealing ground
>wires off power poles and copper tubing from outside air conditioner units,
>I think their beady little eyes would glow happily at the sight of a hundred
>and fifty or two hundred feet of DIY copper hardline in someones back yard.
>Shoot, they'd probably jump the fence flatfooted and fight your family dog
>for 25 feet of it.
>
>Harold
>KD5SAK
------------ REPLY FOLLOWS ------------
Paint it white so it looks like PVC?
--
Bill, W6WRT
Jimmie D
Yes you can roll your own hard line, Im not sure its worth it though. I had
about 100ft of Cu pipe that had been setting around for about 30 years. I
would have probably been better off selling the pipe and buying the
hardline. After I realisesd I would have to keep it pressurised ti keep out
the water I pulled it out and replaced it with LMR 900.
Jeff
for coax because that happened to be the number that came out using common
British copper pipe sizes.
73
Jeff
n3ox...@gmail.com
come out to 50 ohms.
I think supporting dielectric disks or whatever are the hard part in
rolling your own. We did actually build a small section of 50 ohm
hardline for a sodium droplet pinch-off experiment here... I think it
was 1/2" pipe inside 1 1/2" pipe.
If you were trying to do a long run of it, though, you'd quickly get
into assembly hell. #10 wire inside 1/4" refrigeration tubing comes
out awfully close to 37 ohms; tried to make a matching section for a
440 MHz yagi this way, but I couldn't figure out how to keep it
centered, so it never worked out.
Dan
Cecil Moore
I vaguely remember something about 50 ohms being good
for transmitting and 73 ohms being good for receiving.
--
73, Cecil http://www.w5dxp.com
K7ITM
it together, why bother? I have made short sections for matching and
the like, but wouldn't consider trying to make a long run of it. I do
still have some scraps of 1" thick Teflon from when I helped make a
quarter-wave length of 22 ohm 6-1/8" flanged line to go from 50 ohms to
10 ohms (five 50-ohm ports in parallel). Wow, that was a long time ago
now.
Cheers,
Tom
Rich
> I vaguely remember something about 50 ohms being good
> for transmitting and 73 ohms being good for receiving.
50 ohm line is about optimum for power handling, given the ID of the
outer conductor, and 75 ohm line has about the least attenuation for a
given ID of the outer conductor. I think a European compromise was to
choose 60 ohms as a standard impedance.
RF
Zack
> Jeff wrote:
> > There is an apocryphal story that 50 ohms started out as a common impedance
> > for coax because that happened to be the number that came out using common
> > British copper pipe sizes.
The research I've done indicates that the old British pipe sizes
(1/2",. 3/4", 1") specified internal dimensions, while the new pipe
sizes use external dimensions and a wall thickness. Did the story take
into account this change in convention?
Zack Lau W1VT
K7ITM
:-) It shouldn't be vague. It should be crystal-clear. If lowest
loss is important and you're going to use coax with smooth conductors
and the same metal for inner and outer conductors, and you have a fixed
outer conductor diameter, you want the ratio of the inside of the outer
conductor to inner conductor diameters to be 3.59:1. That assumes
negligible dielectric loss. It's not difficult to find the ratio for
other cases, if you know the ratio of RF resistivities of the inner and
outer conductors and the dielectric loss. The loss doesn't increase
very quickly as you get away from that ratio some, but that's the ratio
for lowest loss. If you have air dielectric, that 3.59:1 ratio gives
you 76.7 ohms. If you have solid polyethylene dielectric, it gives you
about 50.6 ohms. Foam dielectric would give you roughly 60 ohms.
There are different conductor diameter ratios for maximum voltage
handling (assuming uniform dielectric breakdown rating and a fixed
outer conductor size; you want a conductor diameter ratio that
minimizes the maximum voltage gradient, i.e., the gradient next to the
center conductor) and maximum power handling (assuming the line is
voltage-limited, which generally only is the case for very low duty
cycle, like radar pulses). If the line is thermally limited (almost
always the case for typical ham installations), lowest attenuation will
give you very close to the highest power handling...details depend on
how well the center conductor can get rid of heat.
Cheers,
Tom
John Ferrell
sections out of 1/2 inch copper pipe. PL259s on the ends with hose
clamps on the connectors. By varying the inner conductor it was pretty
simply to construct the impedance needed.
The reason for the need was that when you stuff a military surplus
cavity to raise the frequency you also booger up (technical term) the
impedance of the system. An appropriate quarter wave section would go
a long ways toward matching 50 ohm line to antenna.
It would take a lot of motivation to construct your own hardline.
On Tue, 12 Sep 2006 07:46:18 -0700, Bill Turner <no...@nohow.com>
wrote:
John Ferrell W8CCW
Scott
would say no.
Scott
N0EDV
Scott
Scott
N0EDV
K7ITM wrote:
> At about $25 for ten feet of 3/4" copper pipe, plus lots of time to put
> it together, why bother?
> now.
Bill Turner
On Tue, 12 Sep 2006 12:04:30 -0400, "Jimmie D"
<jimm...@bellsouth.net> wrote:
>After I realisesd I would have to keep it pressurised ti keep out
>the water I pulled it out and replaced it with LMR 900.
------------ REPLY FOLLOWS ------------
I thought about that. Perhaps a small aquarium air pump would do the
job. Just a guess.
Bill, W6WRT
Jim - NN7K
Andrew), run an aquarium pump , thru a canister,
that is filled with dissecant (moisture
absorbing), and then to the coax . Also, can
use compressed nitrogen, or another thing,
would be canister of air conditioner rechargeing
material (used to be cheap, but now,??),
as info, Jim NN7K
Harbin Osteen
Might want to check out this site, and download "feedline.exe". The
icon has "single 4 hardlines" on it. Small program calculates dimensions
for building hardline using wire, beads, and conduit.
VE3SQB ANTENNA DESIGN PROGRAMS:
http://www.ve3sqb.com/
--
SeeYaa:) Harbin Osteen KG6URO
When American Citizens with dual citizenship pledges allegiance
to the flag, to which flag do they pledge allegiance too?
-
"John Ferrell" <johnf...@sprintmail.com> wrote in message news:9j4eg2pfc8icqoc32...@4ax.com...