Today's Message Index:
----------------------
1. 09:35 AM - 2018 List of Contributors (Matt Dralle)
2. 12:24 PM - myths about gps antennas (kjlpdx)
3. 12:41 PM - Re: myths about gps antennas (GTH)
4. 12:49 PM - FYI - passing the ADS-B validation flight (kjlpdx)
5. 02:02 PM - Re: myths about gps antennas (Charlie England)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | 2018 List of Contributors |
Dear Listers,
The 2018 Matronics Email List and Forum Fund Raiser officially ended a couple of
weeks ago and it's time that I published this year's List of Contributors.
It is the people on this list that directly make these Email Lists and Forums
possible! Their generous Contributions keep the servers and Internet connection
up and running!
You can still show your support this year and pick up a great gift at the same
time. The Contribution Web Site is fast, easy, and secure:
http://www.matronics.com/contribution
Or, by dropping a personal check in the mail to:
Matt Dralle / Matronics
581 Jeannie Way
Livermore CA 94550
And finally, I'm proud to present The 2018 Fund Raiser List of Contributors:
http://www.matronics.com/loc
Thank you again to everyone that made a Contribution this year!!
Matt Dralle
Matronics Email List & Forum Administrator
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | myths about gps antennas |
I'm interested in hearing from an engineer who might know about what really goes
on with my stratus esg gps antenna. they say to use RG400 cable, 10' minimum,
and never paint the antenna. they also told me the strength ratings should
run in the 30's. I have 3' of RG400 with a mechanical 90 elbow, I spray painted
the antenna flat black and mounted it on the glareshield of my RV. my readings
are all in the 40's. they told me this shows an overdriven condition.
so why use low impedance cable then need 10'? my iFly740 and Lowrance 1000 gps's
have antennas with much smaller cables. the iFly shows WAAS grade accuracy,
using an antenna 1/4 the size of the stratus RAMI antenna.
when does being overdriven prove a problem? is this a situation where I could
add more mechanical connectors to increase impedance rather than more cable length?
I get the feeling things get written and then forever repeated, such as never paint
an antenna, without asking any questions. could I use a different antenna
than the RAMI brand? should I not worry about any of this and just go fly?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=486445#486445
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: myths about gps antennas |
Le 19/12/2018 21:24, kjlpdx a crit:
> I get the feeling things get written and then forever repeated, such as never
paint an antenna, without asking any questions.
Paint could be a problem with *some* conductive paints.
> could I use a different antenna than the RAMI brand?
Yes.
> should I not worry about any of this and just go fly?
I suggest you submit your questions to the Aeroelectric List at Matronics.
You'll get really knowledgeable info.
BTW, as you mentioned the 10' minimum coax length looks like some hangar
tale...
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | FYI - passing the ADS-B validation flight |
for what few of us are left using older encoders I have learned thus - they take
perhaps more than 5 minutes to warm up [the wire for the warmer circuit is actually
a very fine gauge]. with the stratus ESG it will transmit as if you are
flying while you are actually still on the ground. this will fail your flight.
SO, start out in STANDBY mode. press the function key and cycle thru to
see pressure altitude displayed. it will show dashes until the encoder is warmed
up and working. you can also cycle the functions to see if the gps has locked
into your location yet. if you then press ALT the ESG will display GRND
showing you are on the ground, unless you taxi over 15 mph. so, taxi slower
[at least for the validation flight] than 15. setting the altimeter to 29.92,
59F, 15C, you can see what the current pressure altitude is. this is what shows,
to the nearest 100', on the ESG.
I find the stratus user manual needing more info. very little is shown as to what
the display should look like during normal flight for instance. it appears
you can play with the function button while in flight and not affect the output
of the transponder. info displays to the right of the 1200. however, if you
want to see gps signal strength it needs to be restarted pressing the function
and power buttons in order to bring up diagnostic screens. it starts all
over acquiring satellites. I believe the transponder is not transmitting in this
mode. correct me if I'm wrong.
anyway, thought I might save someone else some stress.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=486447#486447
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: myths about gps antennas |
On 12/19/2018 2:24 PM, kjlpdx wrote:
>
> I'm interested in hearing from an engineer who might know about what really goes
on with my stratus esg gps antenna. they say to use RG400 cable, 10' minimum,
and never paint the antenna. they also told me the strength ratings should
run in the 30's. I have 3' of RG400 with a mechanical 90 elbow, I spray painted
the antenna flat black and mounted it on the glareshield of my RV. my readings
are all in the 40's. they told me this shows an overdriven condition.
> so why use low impedance cable then need 10'? my iFly740 and Lowrance 1000 gps's
have antennas with much smaller cables. the iFly shows WAAS grade accuracy,
using an antenna 1/4 the size of the stratus RAMI antenna.
> when does being overdriven prove a problem? is this a situation where I could
add more mechanical connectors to increase impedance rather than more cable
length?
> I get the feeling things get written and then forever repeated, such as never
paint an antenna, without asking any questions. could I use a different antenna
than the RAMI brand? should I not worry about any of this and just go fly?
>
disclaimer: I'm not an engineer (but I do play with airplanes with a
couple of them)
Like Gilles said, paint *can* cause problems in some situations. Not
just with reception, but also by getting on the connector(s). Trust me;
somebody will find a way to paint the entire thing. I'm pretty sure you
won't find any antenna mfgr that says it's ok to paint their antenna,
because the paint (and the painter) is outside their control. Some
antennas are black from the mfgr, so that's obviously ok for them. But
if it wasn't black to start with, do you know for a fact that converting
it to a 'black body' heat absorber won't affect its performance in the
sun? (Another potential reason to restrict painting.)
FWIW, the cable isn't 'low impedance'; it's low loss (that usually means
that it has lower capacitance per foot). Most aviation stuff is '50 ohm'
(impedance) cable, but poorer cables can have higher capacitance per
foot, meaning that their actual impedance at different frequencies will
vary more over longer lengths than the higher quality, lower capacitance
cable. The mfgr knows their device, the frequencies over which it will
operate, the capacitance of their chosen cable, and whether everything
will stay within their needed limits at a given cable length for all
frequencies and signal levels (which can vary quite a bit). You might
get away with what you're doing with no issues whatsoever. But you might
not. And the mfgr isn't likely to tell you it's ok, because they likely
haven't tested the *system* configured the way you configured it. Think
about buying a new fuel injector for your Chevy. Would Porsche tell you
that it'll work fine in your 911?
Charlie
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|