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