Shortening PowerFLARM Brick Antenna and GPS cables

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

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)

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

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.

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

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

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)

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

Darryl

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

Darryl

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