What are the ramifications of shortening the cable by cutting and spliceing?
I've heard conflicting advice.

Thanks.

Butch

Butch Davis wrote:

What are the ramifications of shortening the cable by cutting and spliceing?
I've heard conflicting advice.


The GPS antenna cables are not "tuned" to length. A shorter cable
should give you less attenuation loss.

Meticulous work, attention to detail on cutting and trimming lengths,
careful soldering and crimping, all add up to good low loss cabling. In
recent years I started using a length of the adhesive lined shrink tube
about twice the length of the crimp sleeve over the sleeve and coax and
that really makes a nice sealed joint.

If you have to do a mid cable joint to accomplish a cable run, use
dielectic compound on it and seal it with heat shrink (use the non
adhesive if you think you want to get at it from time to time). You'll
lose about 1dB for each fitting, maybe 3dB for something like two BNC's
joined with a barrel.

Powered antennas will have a positive voltage on the center conductor
that is returned to ground via the shield. If you want to make sure
that is not inadvertently shunted to ground somewhere along the run, use
tape or shrink tube on any exposed connectors. You can usually use a VOM
on a coax connector to tell if an antenna is powered or not.

Not all powered antennas use the same voltage, it might be 3.3V or 5V in
my experience, I don't think I've never seen 12V on a GPS antenna though.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)

I cut 2 meter off mine and gave it a new bnc plug. No problem.

It's a Garmin.

Bjarke

"Butch Davis" wrote in message
ink.net...
What are the ramifications of shortening the cable by cutting and
spliceing? I've heard conflicting advice.

Thanks.

Butch

Thank you, gentlemen.

The GPS I most want is unavailable, to date, with an internal antenna. The
external antenna will be mounted less than two feet from the receiver but
has about a thirty foot cable. I prefer not to have this cable wadded up
beneath my center console. Thanks to you, I believe I can safely shorten
the cable.

I'll double check with Lowrance but plan to do it unless it will void the
warranty.

Butch
"Bjarke Christensen" (nej, det skal selvfølgelig
være med K da jeg er dansker) wrote in message
. dk...
I cut 2 meter off mine and gave it a new bnc plug. No problem.

It's a Garmin.

Bjarke

"Butch Davis" wrote in message
ink.net...
What are the ramifications of shortening the cable by cutting and
spliceing? I've heard conflicting advice.

Thanks.

Butch

At 1575Mhz, the loss per connector is around .12db

"Jack Erbes" wrote in message
...

You'll lose about 1dB for each fitting, maybe 3dB for something like two
BNC's joined with a barrel.

Eric Fairbank wrote:
At 1575Mhz, the loss per connector is around .12db


Really? I don't remember where I got that 1 dB figure, I think I got it
when I was installing 2.4GHz wireless systems. Or was the old Thicknet
network wiring? Boy was Thicknet a plumber's nightmare to work with.

I never measured it, just took what I heard at face value.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)

These myths of such high losses in connectors are plastered all over the
internet. It's one of the most common myths in amateur radio for example.
People are always claiming there's a 1 db loss per connector even at hf
frequencies when in fact it ranges from .005 at 3Mhz to .007 at 30Mhz.

Eric

"Jack Erbes" wrote in message
...

Really? I don't remember where I got that 1 dB figure, I think I got it
when I was installing 2.4GHz wireless systems. Or was the old Thicknet
network wiring? Boy was Thicknet a plumber's nightmare to work with.

My GPS 128 works well with its cable in a real state - was pulled out
of the BNC plug and I've just shoved it back in temporarily. I'll fix
it when I too shorten the cable.

Thanks, Colin. That certainly simplfies the procedure.

Butch
wrote in message
ups.com...
My GPS 128 works well with its cable in a real state - was pulled out
of the BNC plug and I've just shoved it back in temporarily. I'll fix
it when I too shorten the cable.

Eric Fairbank wrote:
These myths of such high losses in connectors are plastered all over the
internet. It's one of the most common myths in amateur radio for example.
People are always claiming there's a 1 db loss per connector even at hf
frequencies when in fact it ranges from .005 at 3Mhz to .007 at 30Mhz.

Eric

Okay, thanks for the update, I'll never say that again.

Maybe the 1dB figure is the best case basis for the thoroughly inept
home hacker who heavily nicked the center conductor, then melted all the
insulation with a 100W soldering iron while also managing to get a cold
soldered joint on the contact, and has the whole mess covered with acid
core flux residue. :)

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)