ASW27 Trasponder Antenna Installation Inside Fuselage.

On Sunday, December 31, 2017 at 6:13:39 PM UTC-6, Steve Koerner wrote:
On Sunday, December 31, 2017 at 3:13:42 PM UTC-7, Dan Marotta wrote:
If it's not too much trouble, try a coax cable length of 21 11/16 inches
which would be 2 wavelengths at 1090 MHz (assuming my arithmetic is
correct).Â* You may have reflected power in your coax which will reduce
performance.

Dan: I'm not jumping into the real technical matters here but its pretty obvious that you're neglecting the fact that waves travel slower in coax.

Hey Dan,
I think you may be correct about Too short,
I googled this and there is a couple of opinions that seem to originate
with Garmin, I doubt very many transponders are installed with coax runs
less than 15 inches, maybe this particular problem is rare?
I'm using rg400, and may try a longer coax run.
Thanks,
Scott.

On Sunday, December 31, 2017 at 7:12:51 PM UTC-6, Scott Williams wrote:
On Sunday, December 31, 2017 at 6:13:39 PM UTC-6, Steve Koerner wrote:
On Sunday, December 31, 2017 at 3:13:42 PM UTC-7, Dan Marotta wrote:
If it's not too much trouble, try a coax cable length of 21 11/16 inches
which would be 2 wavelengths at 1090 MHz (assuming my arithmetic is
correct).Â* You may have reflected power in your coax which will reduce
performance.

Dan: I'm not jumping into the real technical matters here but its pretty obvious that you're neglecting the fact that waves travel slower in coax.

Hey Dan,
I think you may be correct about Too short,
I googled this and there is a couple of opinions that seem to originate
with Garmin, I doubt very many transponders are installed with coax runs
less than 15 inches, maybe this particular problem is rare?
I'm using rg400, and may try a longer coax run.
Thanks,
Scott.

In addition,
So does anyone willing to suggest a coax length if not 21 11/16 inches?
maybe tree foot? is there a non critical length range?
Scott.

Scott Williams wrote on 12/31/2017 5:22 PM:
On Sunday, December 31, 2017 at 7:12:51 PM UTC-6, Scott Williams wrote:
On Sunday, December 31, 2017 at 6:13:39 PM UTC-6, Steve Koerner wrote:
On Sunday, December 31, 2017 at 3:13:42 PM UTC-7, Dan Marotta wrote:
If it's not too much trouble, try a coax cable length of 21 11/16 inches
which would be 2 wavelengths at 1090 MHz (assuming my arithmetic is
correct). You may have reflected power in your coax which will reduce
performance.

Dan: I'm not jumping into the real technical matters here but its pretty obvious that you're neglecting the fact that waves travel slower in coax.

Hey Dan,
I think you may be correct about Too short,
I googled this and there is a couple of opinions that seem to originate
with Garmin, I doubt very many transponders are installed with coax runs
less than 15 inches, maybe this particular problem is rare?
I'm using rg400, and may try a longer coax run.
Thanks,
Scott.

In addition,
So does anyone willing to suggest a coax length if not 21 11/16 inches?
maybe tree foot? is there a non critical length range?
Scott.

The coax is a transmission line, and good quality, undamaged coax does not produce
reflections. If the antenna is not properly constructed, it will produce
reflections, and the coax will carry them back to the transmitter (transponder in
this case).

So, with a good antenna and good coax, variations in length will make no
difference. Go fly, as Darryl says.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf

EE school was a very long time ago.Â* Yes, a coax is a transmission line
and, properly terminated, will not produce reflections.Â* If you're
cutting your own line to length, make sure you make a good connection
with the connector on the end.Â* I always preferred the screw together
BNC connectors.Â* The crimp on connectors take a bit of practice to get
right.

On 1/6/2018 8:32 PM, Eric Greenwell wrote:
Scott Williams wrote on 12/31/2017 5:22 PM:
On Sunday, December 31, 2017 at 7:12:51 PM UTC-6, Scott Williams wrote:
On Sunday, December 31, 2017 at 6:13:39 PM UTC-6, Steve Koerner wrote:
On Sunday, December 31, 2017 at 3:13:42 PM UTC-7, Dan Marotta wrote:
If it's not too much trouble, try a coax cable length of 21 11/16
inches
which would be 2 wavelengths at 1090 MHz (assuming my arithmetic is
correct).Â* You may have reflected power in your coax which will
reduce
performance.

Dan: I'm not jumping into the real technical matters here but its
pretty obvious that you're neglecting the fact that waves travel
slower in coax.

Hey Dan,
I think you may be correct about Too short,
I googled this and there is a couple of opinions that seem to originate
with Garmin, I doubt very many transponders are installed with coax
runs
less than 15 inches, maybe this particular problem is rare?
I'm using rg400, and may try a longer coax run.
Thanks,
Scott.

In addition,
So does anyone willing to suggest a coax length if not 21 11/16 inches?
maybe tree foot? is there a non critical length range?
Scott.

The coax is a transmission line, and good quality, undamaged coax does
not produce reflections. If the antenna is not properly constructed,
it will produce reflections, and the coax will carry them back to the
transmitter (transponder in this case).

So, with a good antenna and good coax, variations in length will make
no difference. Go fly, as Darryl says.


--
Dan, 5J

On Sunday, January 7, 2018 at 10:31:02 AM UTC-6, Dan Marotta wrote:
EE school was a very long time ago.Â* Yes, a coax is a transmission line
and, properly terminated, will not produce reflections.Â* If you're
cutting your own line to length, make sure you make a good connection
with the connector on the end.Â* I always preferred the screw together
BNC connectors.Â* The crimp on connectors take a bit of practice to get
right.

On 1/6/2018 8:32 PM, Eric Greenwell wrote:
Scott Williams wrote on 12/31/2017 5:22 PM:
On Sunday, December 31, 2017 at 7:12:51 PM UTC-6, Scott Williams wrote:
On Sunday, December 31, 2017 at 6:13:39 PM UTC-6, Steve Koerner wrote:
On Sunday, December 31, 2017 at 3:13:42 PM UTC-7, Dan Marotta wrote:
If it's not too much trouble, try a coax cable length of 21 11/16
inches
which would be 2 wavelengths at 1090 MHz (assuming my arithmetic is
correct).Â* You may have reflected power in your coax which will
reduce
performance.

Dan: I'm not jumping into the real technical matters here but its
pretty obvious that you're neglecting the fact that waves travel
slower in coax.

Hey Dan,
I think you may be correct about Too short,
I googled this and there is a couple of opinions that seem to originate
with Garmin, I doubt very many transponders are installed with coax
runs
less than 15 inches, maybe this particular problem is rare?
I'm using rg400, and may try a longer coax run.
Thanks,
Scott.

In addition,
So does anyone willing to suggest a coax length if not 21 11/16 inches?
maybe tree foot? is there a non critical length range?
Scott.

The coax is a transmission line, and good quality, undamaged coax does
not produce reflections. If the antenna is not properly constructed,
it will produce reflections, and the coax will carry them back to the
transmitter (transponder in this case).

So, with a good antenna and good coax, variations in length will make
no difference. Go fly, as Darryl says.


--
Dan, 5J

Well,
It's easy enough to have a longer coax on hand for a recheck of the trig TT22,
also a 'direct hookup' request if the sensitivity is still low, also, the antenna is a comant CL105 with a copper ground plane per schempp-hirth drawing.
Continuity and resistive tests of the coax and harness were conducted at the time of installation, Rg400 by the way.
I must admit to being much more confident in the system because of all your input!
I could not have spent these cold winter moments any better, Thanks everyone,
And please feel free to add anything,

Much appreciated,
Scott, N8915