Shortening PowerFLARM Brick Antenna and GPS cables

[kirk.stant]

As anyone who has one can testify, the cables on the dipole and GPS antennas that come with a PowerFLARM Brick are absurdly long - you could almost mount the GPS puck on your tail!

Has anyone any experience in shortening these cables and reattaching the connectors, or is there anyone out there who can do this for a reasonable fee?

Kirk
66

[Discus 44]

On Sep 13, 1:34*pm, "kirk.stant" > wrote:
> As anyone who has one can testify, the cables on the dipole and GPS antennas that come with a PowerFLARM Brick are absurdly long - you could almost mount the GPS puck on your tail!
>
> Has anyone any experience in shortening these cables and reattaching the connectors, or is there anyone out there who can do this for a reasonable fee?
>
> Kirk
> 66

Kirk:

I have made all of my cables on my PF Brick shorter. It takes having
the right termination tools and crimpers inorder to do this. Contact
me if you are interested in having yours shortened.

Tom

[[email protected]]

It's probably a lot easier to open the little black box and take a peak at how the cable is soldered at the antenna end. You could probably cut off the excess at the antenna end a lot easier than crimping new connectors. It's a very simple layout. The inner conductor is soldered to one dipole and the shield is soldered to the opposite one. At least the Flarm antenna was done that way and I'd be surprised if the PCAS antenna was any different.

I haven't looked at the GPS antenna other than to remove the two magnets which are hidden under the sticker.

[kirk.stant]

On Thursday, September 13, 2012 6:21:47 PM UTC-7, (unknown) wrote:
> It's probably a lot easier to open the little black box and take a peak at how the cable is soldered at the antenna end. You could probably cut off the excess at the antenna end a lot easier than crimping new connectors. It's a very simple layout. The inner conductor is soldered to one dipole and the shield is soldered to the opposite one. At least the Flarm antenna was done that way and I'd be surprised if the PCAS antenna was any different.

[Bob Gibbons[_2_]]

On Thu, 13 Sep 2012 20:08:49 -0700 (PDT), "kirk.stant"
> wrote:

>>>>Except that voids the seal on the box and the future (?) IGC logger.

I assume Mark is talking about the "black box" around the dipole
antenna where the antenna cable terminates, not anything within the
brick box itself.

Bob

>On Thursday, September 13, 2012 6:21:47 PM UTC-7, (unknown) wrote:
>> It's probably a lot easier to open the little black box and take a peak at how the
cable is soldered at the antenna end. You could probably cut off the
excess at the antenna end a lot easier than crimping new connectors.
It's a very simple layout. The inner conductor is soldered to one
dipole and the shield is soldered to the opposite one. At least the
Flarm antenna was done that way and I'd be surprised if the PCAS
antenna was any different.
>>
>Except that voids the seal on the box and the future (?) IGC logger.
>>
>> I haven't looked at the GPS antenna other than to remove the two magnets
which are hidden under the sticker.
>
>I like the idea of removing the magnets, though - thanks!
>
>Kirk
>66

[kirk.stant]

Doh! That makes a lot more sense. Interesting idea.

I need to practice my reading more...

Kirk
66

[Jim[_32_]]

On Thursday, September 13, 2012 11:08:49 PM UTC-4, kirk.stant wrote:
> On Thursday, September 13, 2012 6:21:47 PM UTC-7, (unknown) wrote:
>
> > It's probably a lot easier to open the little black box and take a peak at how the cable is soldered at the antenna end. You could probably cut off the excess at the antenna end a lot easier than crimping new connectors. It's a very simple layout. The inner conductor is soldered to one dipole and the shield is soldered to the opposite one. At least the Flarm antenna was done that way and I'd be surprised if the PCAS antenna was any different.
>
> >
>
> Except that voids the seal on the box and the future (?) IGC logger.
>
> >
>
> > I haven't looked at the GPS antenna other than to remove the two magnets which are hidden under the sticker.
>
>
>
> I like the idea of removing the magnets, though - thanks!
>
>
>
> Kirk
>
> 66

OMG magnets? I need to get them out of there too! Good catch.

-Jim

[Jim[_32_]]

On Thursday, September 13, 2012 4:34:16 PM UTC-4, kirk.stant wrote:
> As anyone who has one can testify, the cables on the dipole and GPS antennas that come with a PowerFLARM Brick are absurdly long - you could almost mount the GPS puck on your tail!
>
>
>
> Has anyone any experience in shortening these cables and reattaching the connectors, or is there anyone out there who can do this for a reasonable fee?
>
>
>
> Kirk
>
> 66

LOL "absurdly long" is a great way to describe all the antenna wires. I just wound them all up in a tight coil and ty-wrapped them out of the way. I wonder if that is reducing my FLARM range? ...something is. Any ham radio guys of real EE's have an opinion on this?

-Jim

[Dan Marotta]

Coiling the cable won't create a problem unless you coil it too tightly.
The cable manufacturer's specifications should list the minimum bending
radius, but I'll bet you're well above that. As long as the characteristic
impedance of the coax matches that of the antenna and there are no shorts or
opens in the line, you should be getting maximum performance. I'd be more
suspicious of antenna placement.

I'm assuming the designers set the antenna length for the frequencies in
question and chose the correct coaxial cable for the application.

BSEE, 1972, but antennas haven't changed much since then...


"Jim" > wrote in message
...
On Thursday, September 13, 2012 4:34:16 PM UTC-4, kirk.stant wrote:
> As anyone who has one can testify, the cables on the dipole and GPS
> antennas that come with a PowerFLARM Brick are absurdly long - you could
> almost mount the GPS puck on your tail!
>
>
>
> Has anyone any experience in shortening these cables and reattaching the
> connectors, or is there anyone out there who can do this for a reasonable
> fee?
>
>
>
> Kirk
>
> 66

LOL "absurdly long" is a great way to describe all the antenna wires. I just
wound them all up in a tight coil and ty-wrapped them out of the way. I
wonder if that is reducing my FLARM range? ...something is. Any ham radio
guys of real EE's have an opinion on this?

-Jim

[Mike the Strike]

Yes, but all feed lines are lossy and at the frequencies we are using here the lengths of coax are dumb-ass. We don't have an awful lot of signal to begin with, so throwing half of it away is plain stupid. I remember in my ham radio days a friend used an unterminated roll of coax as a dummy load when experimenting up in the GHz range. The signal barely made it to the other end, making a terminating resistor unnecessary!

Mike

[Dan Marotta]

A properly terminated transmission line is infinitely long from the
perspective of the transmitter. The reason the unterminated spool of coax
had nothing coming out the end was due to nearly 100% reflections in the
line.


"Mike the Strike" > wrote in message
...
Yes, but all feed lines are lossy and at the frequencies we are using here
the lengths of coax are dumb-ass. We don't have an awful lot of signal to
begin with, so throwing half of it away is plain stupid. I remember in my
ham radio days a friend used an unterminated roll of coax as a dummy load
when experimenting up in the GHz range. The signal barely made it to the
other end, making a terminating resistor unnecessary!

Mike

[Eric Greenwell[_4_]]

On 9/15/2012 6:56 PM, Dan Marotta wrote:
> A properly terminated transmission line is infinitely long from the
> perspective of the transmitter. The reason the unterminated spool of
> coax had nothing coming out the end was due to nearly 100% reflections
> in the line.
>
>
> "Mike the Strike" > wrote in message
> ...
> Yes, but all feed lines are lossy and at the frequencies we are using
> here the lengths of coax are dumb-ass. We don't have an awful lot of
> signal to begin with, so throwing half of it away is plain stupid. I
> remember in my ham radio days a friend used an unterminated roll of coax
> as a dummy load when experimenting up in the GHz range. The signal
> barely made it to the other end, making a terminating resistor unnecessary!

There should not be any reflections _in_ the line, unless it is
improperly made or damaged. More likely, as Mike suggests, most of the
power was absorbed along the way by the coax itself, so there was
precious little power to be reflected. The coax is effectively
"terminated" by the distributed losses that occur in the center and
outer conductors, and the dielectric.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[Dan Marotta]

Nope.

As a lab experiment in my college days, I located a break in a very long
coax by timing a signal's reflection using an oscilloscope. An undamaged
line, terminated in its characteristic impedance will deliver most of its
power to the load. Reflections will be minimal. I'm describing an ideal
situation which, I know, is not possible. You're describing a poory
designed, built, installed, or maintained system which, considering us
glider pilots, is probably the norm.



"Eric Greenwell" > wrote in message
...
> On 9/15/2012 6:56 PM, Dan Marotta wrote:
>> A properly terminated transmission line is infinitely long from the
>> perspective of the transmitter. The reason the unterminated spool of
>> coax had nothing coming out the end was due to nearly 100% reflections
>> in the line.
>>
>>
>> "Mike the Strike" > wrote in message
>> ...
>> Yes, but all feed lines are lossy and at the frequencies we are using
>> here the lengths of coax are dumb-ass. We don't have an awful lot of
>> signal to begin with, so throwing half of it away is plain stupid. I
>> remember in my ham radio days a friend used an unterminated roll of coax
>> as a dummy load when experimenting up in the GHz range. The signal
>> barely made it to the other end, making a terminating resistor
>> unnecessary!
>
> There should not be any reflections _in_ the line, unless it is improperly
> made or damaged. More likely, as Mike suggests, most of the power was
> absorbed along the way by the coax itself, so there was precious little
> power to be reflected. The coax is effectively "terminated" by the
> distributed losses that occur in the center and outer conductors, and the
> dielectric.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email
> me)

[Eric Greenwell[_4_]]

On 9/16/2012 8:17 AM, Dan Marotta wrote:
> Nope.
>
> As a lab experiment in my college days, I located a break in a very long
> coax by timing a signal's reflection using an oscilloscope. An
> undamaged line, terminated in its characteristic impedance will deliver
> most of its power to the load. Reflections will be minimal. I'm
> describing an ideal situation which, I know, is not possible. You're
> describing a poory designed, built, installed, or maintained system
> which, considering us glider pilots, is probably the norm.

> "Mike the Strike" > wrote in message
> ...
> Yes, but all feed lines are lossy and at the frequencies we are using
> here the lengths of coax are dumb-ass. We don't have an awful lot of
> signal to begin with, so throwing half of it away is plain stupid. I
> remember in my ham radio days a friend used an unterminated roll of coax
> as a dummy load when experimenting up in the GHz range. The signal
> barely made it to the other end, making a terminating resistor unnecessary!


Hi Dan - You are indeed describing an ideal situation; Mike was
describing a non-ideal situation. If you make the line long enough, it
will absorb all the power before it reaches the end of the cable; for
high frequencies (transponder and higher), "long enough" might be only
20 or 30 feet with low-cost cable.

Without knowing the specific cable used in the PF antennas, I can't say
they are significantly degrading the signal, but shorter is better.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[Dan Marotta]

Hi, Eric,

It appears we're talking the same story after all. When I installed my
transponder (Trig TT22) I used some RG-58 that was laying around the
airport. It didn't work too well. So I went to an avionics shop and got
the right stuff. It worked much better.


"Eric Greenwell" > wrote in message
...
> On 9/16/2012 8:17 AM, Dan Marotta wrote:
>> Nope.
>>
>> As a lab experiment in my college days, I located a break in a very long
>> coax by timing a signal's reflection using an oscilloscope. An
>> undamaged line, terminated in its characteristic impedance will deliver
>> most of its power to the load. Reflections will be minimal. I'm
>> describing an ideal situation which, I know, is not possible. You're
>> describing a poory designed, built, installed, or maintained system
>> which, considering us glider pilots, is probably the norm.
>
>> "Mike the Strike" > wrote in message
>> ...
>> Yes, but all feed lines are lossy and at the frequencies we are using
>> here the lengths of coax are dumb-ass. We don't have an awful lot of
>> signal to begin with, so throwing half of it away is plain stupid. I
>> remember in my ham radio days a friend used an unterminated roll of coax
>> as a dummy load when experimenting up in the GHz range. The signal
>> barely made it to the other end, making a terminating resistor
>> unnecessary!
>
>
> Hi Dan - You are indeed describing an ideal situation; Mike was describing
> a non-ideal situation. If you make the line long enough, it will absorb
> all the power before it reaches the end of the cable; for high frequencies
> (transponder and higher), "long enough" might be only 20 or 30 feet with
> low-cost cable.
>
> Without knowing the specific cable used in the PF antennas, I can't say
> they are significantly degrading the signal, but shorter is better.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email
> me)

[bumper[_4_]]

I took one of the little dipole antennas apart today. Easy, once you know that there are two screws hidden under the adhesive pad. Remove the pad to get to the screws. Each element of the dipole has a brass base with coax center conductor soldered to one, shield to the other. Easy to change length to remove the "bundled" excess to minimize line loss.

But, that does bring up a question. I remember years ago that at least for lower frequencies the length of the coax wanted to be multiples of 1/4 or 1/2 wave adjusted for velocity or some such. Is that a factor or worth messing with at >900 MHz?

bumper

[[email protected]]

I took apart the GPS antenna which has by far the LONGEST excess of cable in the brick PowerFlarm setup. It's a wee bit trickier soldering than on the PF antennas, but if you're inclined it's not a huge task. I removed probably 6' of cable. I left the butterfly display back at the gliderport so I haven't been able to test it, but I'm confident it will work. The shield is soldered to one spot and the center conductor is soldered to a small pad on the PC board. The only trick is the careful trimming of the shield and conductor insulation to match what they did. It's also fairly easy to remove and re-use the strain relief.


Mark

[Eric Greenwell[_4_]]

On 9/16/2012 7:18 PM, wrote:
> I took apart the GPS antenna which has by far the LONGEST excess of
> cable in the brick PowerFlarm setup. It's a wee bit trickier
> soldering than on the PF antennas, but if you're inclined it's not a
> huge task. I removed probably 6' of cable. I left the butterfly
> display back at the gliderport so I haven't been able to test it, but
> I'm confident it will work. The shield is soldered to one spot and
> the center conductor is soldered to a small pad on the PC board. The
> only trick is the careful trimming of the shield and conductor
> insulation to match what they did. It's also fairly easy to remove
> and re-use the strain relief.

The GPS antenna cable doesn't carry high frequency RF, so tidiness is
the only value in reducing the length.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[Jim[_32_]]

On Sunday, September 16, 2012 10:27:47 PM UTC-4, Eric Greenwell wrote:
> On 9/16/2012 7:18 PM, wrote:
>
> > I took apart the GPS antenna which has by far the LONGEST excess of
>
> > cable in the brick PowerFlarm setup. It's a wee bit trickier
>
> > soldering than on the PF antennas, but if you're inclined it's not a
>
> > huge task. I removed probably 6' of cable. I left the butterfly
>
> > display back at the gliderport so I haven't been able to test it, but
>
> > I'm confident it will work. The shield is soldered to one spot and
>
> > the center conductor is soldered to a small pad on the PC board. The
>
> > only trick is the careful trimming of the shield and conductor
>
> > insulation to match what they did. It's also fairly easy to remove
>
> > and re-use the strain relief.
>
>
>
> The GPS antenna cable doesn't carry high frequency RF, so tidiness is
>
> the only value in reducing the length.
>
>
>
> --
>
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
>
> email me)

Eric, so why do we need a GPS antenna wire if the signal from the satellite magically gets to the receiver without the RF signal first going through the antenna wire :=P

[Jim[_32_]]

On Sunday, September 16, 2012 10:27:47 PM UTC-4, Eric Greenwell wrote:
> On 9/16/2012 7:18 PM, wrote:
>
> > I took apart the GPS antenna which has by far the LONGEST excess of
>
> > cable in the brick PowerFlarm setup. It's a wee bit trickier
>
> > soldering than on the PF antennas, but if you're inclined it's not a
>
> > huge task. I removed probably 6' of cable. I left the butterfly
>
> > display back at the gliderport so I haven't been able to test it, but
>
> > I'm confident it will work. The shield is soldered to one spot and
>
> > the center conductor is soldered to a small pad on the PC board. The
>
> > only trick is the careful trimming of the shield and conductor
>
> > insulation to match what they did. It's also fairly easy to remove
>
> > and re-use the strain relief.
>
>
>
> The GPS antenna cable doesn't carry high frequency RF, so tidiness is
>
> the only value in reducing the length.
>
> --
>
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
>
> email me)
Eric, so why do we need a GPS antenna wire if the signal from the satellite magically gets to the receiver without the RF signal first going through the antenna wire :=P I'm fairly sure that the GPS antennas are "active" antennas getting phantom dc power from the receiver but I thought they only had an amplifier; are you sure they also have a local oscillator & mixer to convert the RF to an IF (I guess like an LNB)? Amazing for such a cheap device.

[[email protected]]

Eric,

Exactly correct. The only benefit to trimming the GPS cable is to reduce (in my case, by almost 12 feet) the excess cable that I didn't want to bundle up and keep secure.

Mark

[Eric Greenwell[_4_]]

On 9/17/2012 5:12 AM, Jim wrote:

>>
>> The GPS antenna cable doesn't carry high frequency RF, so tidiness
>> is
>>
>> the only value in reducing the length.

> Eric, so why do we need a GPS antenna wire if the signal from the
> satellite magically gets to the receiver without the RF signal first
> going through the antenna wire :=P I'm fairly sure that the GPS
> antennas are "active" antennas getting phantom dc power from the
> receiver but I thought they only had an amplifier; are you sure they
> also have a local oscillator & mixer to convert the RF to an IF (I
> guess like an LNB)? Amazing for such a cheap device.

A lot of antenna "pucks" are not just GPS antennas, but GPS receivers.
What comes out of the cable is data, not RF. That's not true of every
GPS "puck", of course, but I think it's true of the PF units. Even if
it's the active antenna type you mention, because the output is
amplified and a lower frequency than the raw GPS signals, the cable loss
would be an issue. So, reduce the cable length for tidiness, not signal
strength.

The dipole antennas are passive, so shortening their cables might
improve their output. Without knowing the cable type, I can't say how
much, but I'd guess the antenna designers chose cable that did not have
significant losses for the length provided.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl

[Dave Nadler]

On Monday, September 17, 2012 5:02:43 PM UTC-4, Eric Greenwell wrote:
> >> The GPS antenna cable doesn't carry high frequency RF

Wrong.

> A lot of antenna "pucks" are not just GPS antennas, but GPS receivers.
> What comes out of the cable is data, not RF. That's not true of every
> GPS "puck", of course, but I think it's true of the PF units.

Wrong. It's an antenna, NOT a receiver.

> Even if it's the active antenna type you mention, because the output is
> amplified and a lower frequency than the raw GPS signals

Wrong.

Please don't speculate where people may take it seriously,
even on R.A.S...

Thanks,
Best Regards, Dave

[Eric Greenwell[_4_]]

On 9/17/2012 3:34 PM, Dave Nadler wrote:
> On Monday, September 17, 2012 5:02:43 PM UTC-4, Eric Greenwell wrote:
>>>> The GPS antenna cable doesn't carry high frequency RF
>
> Wrong.
>
>> A lot of antenna "pucks" are not just GPS antennas, but GPS receivers.
>> What comes out of the cable is data, not RF. That's not true of every
>> GPS "puck", of course, but I think it's true of the PF units.
>
> Wrong. It's an antenna, NOT a receiver.
>
>> Even if it's the active antenna type you mention, because the output is
>> amplified and a lower frequency than the raw GPS signals
>
> Wrong.
>
> Please don't speculate where people may take it seriously,
> even on R.A.S...
>
> Thanks,
> Best Regards, Dave

Well, humph! It wasn't speculation, it was ignorance!

So, are most of the GPS pucks are passive antennas, or are they
amplified but with no frequency conversion? And is it useful to shorten
the cable to increase signal strength?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[Darryl Ramm]

Outboard antennas are amplified RF, no local mixer/downconversion.

Darryl

[Darryl Ramm]

Outboard antennas are amplified RF, no local mixer/downconversion.

Darryl

[Darryl Ramm]

The only ones "outboard receivers" are things like USB connected pucks, where everything lives in the puck.

Darryl

[kirk.stant]

On Thursday, September 13, 2012 3:34:16 PM UTC-5, kirk.stant wrote:
> As anyone who has one can testify, the cables on the dipole and GPS antennas that come with a PowerFLARM Brick are absurdly long - you could almost mount the GPS puck on your tail!
>
>
>
> Has anyone any experience in shortening these cables and reattaching the connectors, or is there anyone out there who can do this for a reasonable fee?
>
>
>
> Kirk
>
> 66

[Richard[_9_]]

On Sunday, January 27, 2013 10:25:41 AM UTC-8, kirk.stant wrote:
> On Thursday, September 13, 2012 3:34:16 PM UTC-5, kirk.stant wrote: > As anyone who has one can testify, the cables on the dipole and GPS antennas that come with a PowerFLARM Brick are absurdly long - you could almost mount the GPS puck on your tail! > > > > Has anyone any experience in shortening these cables and reattaching the connectors, or is there anyone out there who can do this for a reasonable fee? > > > > Kirk > > 66

The antennas have a crimp connector so it would be hard to remove and reattach the connectors but it may be possible. The GPS end is usually molded so that would be a problem.

http://www.craggyaero.com/cables_&_antennas.htm

Craggy Aero has GPS antennas with a variety of cable lenghts.

Richard
www.craggyaero.com

[[email protected]]

See pictures of my PowerFlarm antenna cable shortening project at:
https://sites.google.com/site/threeuniform/powerflarm/powerflarm-antennas
There are picuters of the opened GPS mouse.
I am also doing some custom bottom-fed dipoles to suit my needs.
3U

[[email protected]]

Excellent information and pics. I have also shortened the cables folr my brick install and it is easy to do as long as you reasonable soldering skills.

ASW27 BV