On Oct 6, 9:41*am, wrote:

A continuous stream of airliners passes over my house. *What I normally see is that PF PCAS function does not detect them until the range is about 2 statute miles. *However, after they have first been detected, they remain displayed until the range reaches 6 statute miles or more.

Gerhard,

Thank you for your interest in this.

To answer you questions:

Is that with the device indoors?

Yes the antenna is indoors, but it is hanging close to a window where
it has a clear view of the airliner's approach path.

ADS-B targets (trianges) or Mode C/S (circles)?

My comments related to the C/S circles. It appears that the range for
first detection is much lower than the range for display after first
detection. However, I see initial detection of ADS-B targets at much
greater range (5 to 6 statute miles).

FYI, Mode S XPDRs also reply to Mode C interrogations.

Since you indicated that there were different threshold settings for
Mode C and Mode S, I wanted to make it clear that the targets were
airliners (with mandatory TCAS) and must have been mode S equipped.

PCAS is limited to 5 NM (the configurator has this wrong unfortunately,
we'll fix that ASAP), trying to set a higher PCASRANGE is ignored.

I didn't use the configurator. Instead I read the data port
specification and the addendum. First I set a high value of PCASRange
but found it was not accepted. I then experimented with different
values to determine the highest value that was accepted and reported
in the dump file. My observations are summarized in my config file
comments -

#
# Sets the PCAS oblique (PCASRANGE) in meters
# Slant (oblique) range is estimated from signal strength
# and is approximate
# Max value appears to be 9250 not 65535 as specified in dataport
addendum
# Values of 9300 and greater will give Amber LED after loading.
#
$PFLAC,S,PCASRANGE,9250
#

The maximum value that I found by experiment is equivalent to 5NM.
Perhaps the dataport addendum has been updated since I downloaded my
copy.

I recommend to leave it above 250 (both Mode S and C). Please let me know how it goes.

I'll do that, but don't know when. The test requires that the traffic
is landing to the East and that I am at home. I also want to set up
the equipment outside so there is no possible antenna issue.

Andy Durbin