coax for 900mhz?
 

what coax is good to 900mhz? i am looking for something as thin and
supple as i can find. i tried a hunk of coax off of an old cb antenna
(wishful thinking) with no luck. should this work? or is hf coax no
good at 900 mhz? i built a ten element yagi off a plan i found on the
net. it should be a rocket ship but its not as good as a wide band
rubber ducky that i have. i am trying to receive a 900mhz wireless
microphone from a distance of about 200 yards. any ideas?

coax for 900mhz?
 

1/2" Superflex (FS4J-50B) is pretty low loss at 900 MHz, but it ain't
exactly supple. How long is the coax run? RG-142 might be OK for
semi-short runs and is fairly flexible (about the same size as RG-58)...

Scott


Jim wrote:

what coax is good to 900mhz? i am looking for something as thin and
supple as i can find. i tried a hunk of coax off of an old cb antenna
(wishful thinking) with no luck. should this work? or is hf coax no
good at 900 mhz? i built a ten element yagi off a plan i found on the
net. it should be a rocket ship but its not as good as a wide band
rubber ducky that i have. i am trying to receive a 900mhz wireless
microphone from a distance of about 200 yards. any ideas?

coax for 900mhz?
 

Scott wrote in
:

1/2" Superflex (FS4J-50B) is pretty low loss at 900 MHz, but it ain't
exactly supple. How long is the coax run? RG-142 might be OK for
semi-short runs and is fairly flexible (about the same size as RG-58)...

Or if the system can play at 75 ohms, satellite TV grade RG6 is pretty fair
and cheap to buy.



--
Dave Oldridge+
ICQ 1800667

coax for 900mhz?
 

On Sat, 12 Nov 2005 19:41:36 -0500, (Jim)
wrote:

what coax is good to 900mhz? i am looking for something as thin and
supple as i can find. i tried a hunk of coax off of an old cb antenna
(wishful thinking) with no luck. should this work? or is hf coax no
good at 900 mhz? i built a ten element yagi off a plan i found on the
net. it should be a rocket ship but its not as good as a wide band
rubber ducky that i have. i am trying to receive a 900mhz wireless
microphone from a distance of about 200 yards. any ideas?

Unless you go for exotica thin low loss coax at 900mhz is a
contradiction in terms.

RG58 at 900mhz is a dummy load after about 15ft. (20db/100ft)
Belden 9914 is around 8db/100ft (.400inch size)

RG8X is a low loss .242" cable thats only 12db/100 at 900mhz
so if you use that and stay under 20ft the loss should be be under
3db still lossy but manageable. Generally if you want low loss cable
at 900mhz you are talking about fat or very expensive cables.

Allison
KB1GMX

coax for 900mhz?
 

On Sat, 12 Nov 2005 19:41:36 -0500, (Jim)
wrote:

what coax is good to 900mhz? i am looking for something as thin and
supple as i can find. i tried a hunk of coax off of an old cb antenna
(wishful thinking) with no luck. should this work? or is hf coax no
good at 900 mhz? i built a ten element yagi off a plan i found on the
net. it should be a rocket ship but its not as good as a wide band
rubber ducky that i have. i am trying to receive a 900mhz wireless
microphone from a distance of about 200 yards. any ideas?

LMR195 uses the same connectors as RG58, and has about 11dB loss /
100' at 900 MHz. You should find it stocked in the WLAN outlets, with
or without connectors.

Another thought is to salvage some foil/foam RG58 style cable from a
car mobile phone antenna.

Owen
--

coax for 900mhz?
 

thanks guys for your input! ok, forget about thin and supple. i need 50
ohm impedance coax at 900mhz into a uniden scanner(bnc connector) with a
15 foot run. what coax of any size is commonly available that would be
suitable?

coax for 900mhz?
 

"Jim" wrote in message
...
thanks guys for your input! ok, forget about thin and supple. i need 50
ohm impedance coax at 900mhz into a uniden scanner(bnc connector) with a
15 foot run. what coax of any size is commonly available that would be
suitable?

Hi Jim

I wonder why you would not use the RG-6 as suggested by Dave Oldridge.
Even Home Depot has the cable and the BNCs for it.
RG-6 is good transmission line at 900 MHz.

I submit that nothing in the system from the antenna all the way to the
receiver will be 50 ohms, no matter what transmission line you choose.

Jerry

coax for 900mhz?
 

Jim wrote:
thanks guys for your input! ok, forget about thin and supple. i need 50
ohm impedance coax at 900mhz into a uniden scanner(bnc connector) with a
15 foot run. what coax of any size is commonly available that would be
suitable?

LMR-1700 looks pretty good on the loss charts. It's about
$10 per foot, 1.67 inch diameter - not sure about the BNC
connector :-)
--
73, Cecil http://www.qsl.net/w5dxp

coax for 900mhz?
 

I suggest you look at a BNC cable assembly available From AAA RF Products of
San Clemente, CA The AAA1003-180 Cable Assembly uses RG213/U cable with BNC
male connectors, lenght is 15 feet and loss at 900 MHz would be about 1.6
dB. Cost about $30. See www.aaarfproducts.com for email & phone #

Murray, W6KRC




"Cecil Moore" wrote in message
om...
Jim wrote:
thanks guys for your input! ok, forget about thin and supple. i need 50
ohm impedance coax at 900mhz into a uniden scanner(bnc connector) with a
15 foot run. what coax of any size is commonly available that would be
suitable?

LMR-1700 looks pretty good on the loss charts. It's about
$10 per foot, 1.67 inch diameter - not sure about the BNC
connector :-)
--
73, Cecil http://www.qsl.net/w5dxp

coax for 900mhz?
 

If you need a nice low-loss coax for 900 MHz, there's not much better
than a 1" outside diameter cable with a 0.3" diameter inner conductor.
Or something like that.

If you cannot find such a line then the best thing to do is re-design
the whole system such that you don't need it.

=========================================

coax for 900mhz?
 

"Jim" wrote in message
...
thanks guys for your input! ok, forget about thin and supple. i need 50
ohm impedance coax at 900mhz into a uniden scanner(bnc connector) with a
15 foot run. what coax of any size is commonly available that would be
suitable?

If you insist on 50 Ohm skinny cable, get the LMR240. Loss for 15 feet will
be 1.15 db. I believe HRO sells it. About the same diameter as RG59. There
is also an LMR240UF, which is very flexible. The UF has slightly more loss,
but at 15 feet you won't see it. $10 should get you 15 feet. We used this
stuff at 2 GHz. The regular 240 has a solid center conductor, the UF is
stranded. You might have trouble getting a BNC connector on the non-UF.

Tam/WB2TT

coax for 900mhz?
 

"Jim" bravely wrote to "All" (13 Nov 05 13:51:06)
--- on the heady topic of " coax for 900mhz?"

Ji From: (Jim)
Ji Xref: core-easynews rec.radio.amateur.antenna:220026

Ji thanks guys for your input! ok, forget about thin and supple. i need
Ji 50 ohm impedance coax at 900mhz into a uniden scanner(bnc connector)
Ji with a 15 foot run. what coax of any size is commonly available that
Ji would be suitable?

Listen, these nice guys are all BS'ing you. Remember that cable is
rated in dB/1,000ft, so that with only 15 of cable -- ANY -- will be
about the same. You will probably have more loss in the connectors!

A*s*i*m*o*v

.... Everyone hates me because I'm paranoid.

coax for 900mhz?
 

Huh? All my charts list loss per one hundred feet...however, unless he
needs every last bit of signal, 15 feet of RG-58 would be OK...see:
http://bwcecom.belden.com/Catalog/Te...cteristics.pdf

Scott

Asimov wrote:
"Jim" bravely wrote to "All" (13 Nov 05 13:51:06)
--- on the heady topic of " coax for 900mhz?"

Ji From: (Jim)
Ji Xref: core-easynews rec.radio.amateur.antenna:220026

Ji thanks guys for your input! ok, forget about thin and supple. i need
Ji 50 ohm impedance coax at 900mhz into a uniden scanner(bnc connector)
Ji with a 15 foot run. what coax of any size is commonly available that
Ji would be suitable?

Listen, these nice guys are all BS'ing you. Remember that cable is
rated in dB/1,000ft, so that with only 15 of cable -- ANY -- will be
about the same. You will probably have more loss in the connectors!

A*s*i*m*o*v

... Everyone hates me because I'm paranoid.

coax for 900mhz?
 

There ain't such no thing as a low loss thin cable! not for high
frequencies, anyway! what experience teaches is to put up the thickest
line you can within the closest reach of the antenna, and use the
absolute minimum of thin, flexible cable from there to the antenna
itself. in any case you need good connectors at these frequencies so
the additional price is not a real killer.
there's no way to dodge the physics at these frequencies. try to fish
out reel ends of CATV cables from your local comapny. usually they're
glad to give it away, if you rid them from it. I even got e afew
connectors for my pain. in any case you need to match the antenna to
the cable, so why not at 75 ohms instead of 50?
Saandy 4Z5KS

coax for 900mhz?
 

A SOLID POLYETHELINE COAXIAL LINE :-

Length = 5 metres (15 feet).
Outer conductor diameter = 25 mm (1 inch).
Inner conductor diameter = 7 mm (1/3 inch).
Impedance = 50 ohms.
Velocity factor = 0.665

At 900 MHz, it has an overall matched loss of about 0.8 decibels. With
an SWR of 2:1 loss may increase to 1 dB.

The above figures will give you some idea of the sort of stuff you are
looking for. Halve the diameters and roughly double the loss.

For any other dimensions download program COAXPAIR from website below.
If you have any cable of unknown characteristics lying around doing
nothing, then have a sensible guess at dimensions and just insert data
into the program. It is very easy to use.

The program itself, from audio frequencies up to the GHz range, is
generally at least as accurate as cable dimensions can be measured
using ordinary engineering instruments. It is of professional grade,
usable by cable designers and workers in the field of resonant
transmission lines for impedance-matching purposes. One useful program
output is the input impedance and SWR of any coaxial line, of any
length, for any terminating impedance at any frequency. It is
necessary to know the line's velocity factor which for solid
polyethylene is always 0.66

Other types of line are similarly covered by other programs available
from the website.

But for your particular application, download program COAXPAIR.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........