Today's Message Index:
----------------------
1. 05:55 AM - KX-125 NAV Always FLAGGED (jacklockamy)
2. 07:05 AM - Re: coax (John Schroeder)
3. 07:31 AM - Re: coax (Mike Ferrer)
4. 10:47 AM - Re: coax (Brian Lloyd)
5. 10:51 AM - Re: coax (Brian Lloyd)
6. 10:55 AM - Re: KX-125 NAV Always FLAGGED (Brian Lloyd)
7. 01:49 PM - Re: coax (Doug McNutt)
8. 03:12 PM - Re: coax (Brian Lloyd)
9. 03:44 PM - Re: coax (Mark/Micki Phillips)
Message 1
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| Subject: | KX-125 NAV Always FLAGGED |
--> Avionics-List message posted by: "jacklockamy" <jacklockamy@verizon.net>
Trying to sort out a problem with KX-125 NAV/COM.
I'm the (lucky?) test pilot of my buddy's RV-7A (he's a student pilot
who recently soled). 17.5 hours on the hobbs and counting...
He has installed a KX-125. As I understand the operator/owner's
manual, I dial in the NAV/VOR freq. and I should get a bearing
TO/FROM the station when in the TO or FROM mode. Doesn't happen...
it always shows FLAGGED with three (3) dashes. I should also be able
to be in the OBS mode with radial entered and see the offset...
doesn't happen... it always shows FLAGGED with solid bars off both
sides of center to the edge of the display.
I get good audio verification that the NAV side is picking up the
VORs. Still all I get is "FLAGGED". That is what has me stumped...
I get good tones/IDENT from the VOR so I believe the the antenna is
doing it's thing. Why is the display/unit constantly showing FLAGGED?
BTW... the comm side of the radio works flawlessly.
Any ideas what we should check? Is it possible "Operator Error"?
I've re-read the manual three times now.... It just doens't seem to
be that difficult to operator. I'm sure it is something simple that
we are overlooking. The aircraft builder/owner also wired his own
harness, so that is of course suspect.
Thanks,
Jack Lockamy
Camrillo, CA
Message 2
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--> Avionics-List message posted by: "John Schroeder" <jschroeder@perigee.net>
Another datapoint for this debate/exchange of references: The installation
manual for the Garmin GNS480 (CNX-80) recommends RG-142B or "similar
quality" for all antenna feeds. The 480 has GPS, COMM and NAV antenna
inputs. IMHO, RG-58 is not of similar quality. RG-400 is. Bob Nuckolls has
made this case for quite some time.
For a good source of RG 400 (and all 22759 wire) call Wiremasters in
Franklin, TN. Their number is 800 635-5342. Ask for Deb Sullivan. For
example, we bought our RG-400 for $.086 per foot. Most of the smaller
gages of hookup wire goes for around a nickel per foot. Min. order for a
mix of wire gages & types is $100 and there may be a min. length for the
RG. There is a min. length of 100 ft. for 22759 AWG 12 and up.
Cheers,
John Schroeder
On Tue, 28 Dec 2004 23:10:01 -0700, Ron Davis <l39parts@hotmail.com> wrote:
> --> Avionics-List message posted by: "Ron Davis" <l39parts@hotmail.com>
>
> This is a response to the posting that said to use RG 400 for the GPS
> antenna. Garmin's manual says to use RG 58A/U.
>
Message 3
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--> Avionics-List message posted by: "Mike Ferrer" <mike@ferrer-aviation.com>
Fwiw, the Garmin 300XL installation manual specifies RG-58A/U for COM and
GPS with a maximum length of 40 feet. The Garmin 400 and 500 series
installation manuals recommend 50 ohm coax meeting current aviation
regulations (40' max) and do not specify a particular RG number.
Mike
Message 4
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--> Avionics-List message posted by: Brian Lloyd <brianl@lloyd.com>
On Dec 28, 2004, at 1:04 AM, Garth Shearing wrote:
> --> Avionics-List message posted by: "Garth Shearing"
> <garth@islandnet.com>
>
> I'm going to go against the flow on this one.
>
> The data I have shows the RF loss in RG-58 and RG-400 is about the
> same.
Not quite. The loss in RG-400 is about the same as low-loss RG-58 with
foam dielectric.
Loss per 100M at 1000 MHz
78.6dB for RG-58 with solid dielectric
51.8dB for RG-58 with foam dielectric
52 dB for RG-400
This is a *big* difference.
If you would consider using plain-old RG-58 then you should consider
using LMR-195 microwave cable. It is functionally the same as RG-58 but
lower loss than either RG-58 or RG-400. If you are contemplating using
RG-8 (transponder or DME) then consider using LMR-400.
> RG-58 uses a solid polyethylene dielectric and the RG-400 uses a solid
> teflon which provides operating temperatures up to 200 degrees C.
The teflon construction makes it pretty impervious to just about
everything, heat included.
> RG-58 can
> only go to 80 degrees C. So RG-58 is just fine for comm, nav, GPS, and
> transponder. RG-58 is quite limited in terms of its ability to handle
> continuous high power at high frequencies because the dielectric can
> heat up
> to 80 degrees C easily. This is not a problem with up to 200 watt
> transponders because they are only transmitting a small part of the
> time.
Dielectric heating in aircraft applications just aren't a problem.
> RG-58 can be used up to around 3 GHz, much higher than the 1.2 and 1.5
> GHz
> frequencies of GPS. Same goes for the connectors. Unless the cable
> is in
> the engine compartment, go with the RG-58. Way cheaper, easier to
> work with
> and weighs half as much as RG-400. I have used some teflon wire in my
> engine compartment, so I do think it has its uses.
You can use just about any coax at any frequency if you can accept the
loss. (Actually, there is an upper limit for coax of larger diameter
because at some higher frequency it stops acting as coax and starts
acting as waveguide.)
> I don't understand the moisture problem. There are millions of
> installations out there working just fine. The only moisture problems
> we
> had occurred in outdoor cables where the cable ends were installed
> without
> drip loops and no shrink boots or tape wraps on the installed
> connectors.
Foam-dielectric coax tends to be hygroscopic, i.e. it absorbs moisture
from the atmosphere on its own. It is interesting to measure loss in
the coax with time. I used to use low-loss foam cables in my ham
station until I discovered just how badly they degraded in just a year
or two. I thought that a good coax seal to waterproof the exposed ends
would solve the problem and it just doesn't. Mil-spec double-shielded
RG-58 using silver-plated braid and center conductor does not degrade
appreciably with time so that is what I use for comm and nav runs in
aircraft. Still, RG-400 has lower loss and is even more resistant to
the environment and an airplane is a very hostile environment.
> We used to drill a small hole in the bottom of the drip loop to let any
> moisture drain out, but this would not be needed in a typical aircraft
> installation.
You drill a hole in the coax? That is more likely to let water in than
help it get out.
> If you want lower losses or higher power, you have to go to larger
> diameter,
> which means heavier cable and connectors. You can also choose a cable
> with
> a foam or air dielectric. I think these choices are overkill given the
> short lengths of cable normally required.
In general I agree with you, at least for aircraft. You never have long
runs. In the case of DME and transponder, your runs are usually not
more than about 2M so almost anything will work. Still, an airplane is
a harsh environment and coax does degrade with time. Good stuff
degrades less (mil-spec RG-58) or almost not at all (RG-400).
Consider that this radio installation will be serving someone about 20
years from now. I repaneled my Comanche in 1985. The only change I have
made since then was to replace the IFR LORAN with an IFR GPS last year.
I am still using the same old comm and nav coax, something I should
probably remedy and certainly will if I redo the avionics again.
Brian Lloyd 6501 Red Hook Plaza
brianl@lloyd.com Suite 201
+1.340.998.9447 St. Thomas, VI 00802
I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry
Message 5
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--> Avionics-List message posted by: Brian Lloyd <brianl@lloyd.com>
On Dec 29, 2004, at 12:10 AM, Ron Davis wrote:
> --> Avionics-List message posted by: "Ron Davis" <l39parts@hotmail.com>
>
> This is a response to the posting that said to use RG 400 for the GPS
> antenna. Garmin's manual says to use RG 58A/U.
What Garmin puts in their manual is not my problem. I know the
difference between various types of coax and I would never consider
using run-of-the-mill RG-58 for GPS no matter what the manufacturer
says.
Let me put it another way. I am going to spend $100,000 on the airplane
of my dreams with $20,000 in avionics and I am going to let a $20
difference in the cost of coax determine what I put in? Heck, if you
care that much I urge you to wire your OBAM airplane with PVC wire
instead of Tefzel because it is much cheaper and it will carry
electrons just as well.
Wire is cheap, especially if you go looking for where you can get it at
a reasonable price. Get the good stuff and then don't worry about it.
If a $20 difference in price is going to break you, you should not be
playing with an airplane because you are not going to have the money to
maintain it properly.
Brian Lloyd 6501 Red Hook Plaza
brianl@lloyd.com Suite 201
+1.340.998.9447 St. Thomas, VI 00802
I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry
Message 6
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| Subject: | Re: KX-125 NAV Always FLAGGED |
--> Avionics-List message posted by: Brian Lloyd <brianl@lloyd.com>
On Dec 29, 2004, at 7:55 AM, jacklockamy wrote:
> I get good audio verification that the NAV side is picking up the
> VORs. Still all I get is "FLAGGED". That is what has me stumped...
> I get good tones/IDENT from the VOR so I believe the the antenna is
> doing it's thing. Why is the display/unit constantly showing FLAGGED?
It sounds like there is a problem in the VOR converter.
> Any ideas what we should check? Is it possible "Operator Error"?
> I've re-read the manual three times now.... It just doens't seem to
> be that difficult to operator. I'm sure it is something simple that
> we are overlooking. The aircraft builder/owner also wired his own
> harness, so that is of course suspect.
Does the KX-125 have a jumper on the connector to connect the composite
output from the receiver to the input of the VOR/LOC converter? If that
jumper is not present or the composite output is grounded, you wouldn't
have any composite input to the converter and you would have the
problems you describe, i.e. no VOR/LOC function with good audio/ID when
a VOR is tuned in.
Brian Lloyd 6501 Red Hook Plaza
brianl@lloyd.com Suite 201
+1.340.998.9447 St. Thomas, VI 00802
I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry
Message 7
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--> Avionics-List message posted by: Doug McNutt <douglist@macnauchtan.com>
I can't keep quiet anymore.
RG223 has been around a long time. It's the same size and shape as RG58 and has
a characteristic impedance of 50 ohms. It has silver plated wire and a double
braided shield. At one time it was too expensive for light airplanes but I have
used some surplus stock for DME and transponder service. It's rated well above
2 GHz.
I see that people are selling it on eBay. Search for RG223.
One example:
<http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=73170&item=3863201371&rd=1&ssPageName=WDVW>
The "RG 400" stuff I think is really "400 RG" originally introduced by Thermax
but didn't qualify (or pay for) an approved military RG designation. I have used
it for antennas in small rockets (244 MHz telemetry) where skin heating is
a problem. It's teflon insulation is not as good, RF wise, as the polyethylene
in RG58 or RG223 but it is a whole lot easier to use in the vicinity of a soldering
iron. It's great for making baluns for use with horizontally polarized
VOR antennas. If you're still soldering pins in BNC connectors you'll love it.
--
--> Halloween == Oct 31 == Dec 25 == Christmas <--
Message 8
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--> Avionics-List message posted by: Brian Lloyd <brianl@lloyd.com>
On Dec 29, 2004, at 3:48 PM, Doug McNutt wrote:
> RG223 has been around a long time. It's the same size and shape as
> RG58 and has a characteristic impedance of 50 ohms. It has silver
> plated wire and a double braided shield. At one time it was too
> expensive for light airplanes but I have used some surplus stock for
> DME and transponder service. It's rated well above 2 GHz.
I believe this is the stuff I have been referring to as
"double-shielded mil-spec RG-58." I love it. I find it pretty readily
available at ham radio swap meets. I bought about two hundred feet of
the stuff for about $20. Needless to say I haven't run out yet.
Brian Lloyd 6501 Red Hook Plaza
brianl@lloyd.com Suite 201
+1.340.998.9447 St. Thomas, VI 00802
I fly because it releases my mind from the tyranny of petty things . . .
Antoine de Saint-Exupry
Message 9
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--> Avionics-List message posted by: "Mark/Micki Phillips" <mphill@gcctv.com>
OK OK!!!! My apologies! Before you all dump on me. Your emails were before
Evelyns! A BIG kick in the ass to me :)) Hum...I might like that! love yas
----- Original Message -----
From: "Brian Lloyd" <brianl@lloyd.com>
Subject: Re: Avionics-List: coax
> --> Avionics-List message posted by: Brian Lloyd <brianl@lloyd.com>
>
> On Dec 29, 2004, at 3:48 PM, Doug McNutt wrote:
>
>> RG223 has been around a long time. It's the same size and shape as
>> RG58 and has a characteristic impedance of 50 ohms. It has silver
>> plated wire and a double braided shield. At one time it was too
>> expensive for light airplanes but I have used some surplus stock for
>> DME and transponder service. It's rated well above 2 GHz.
>
> I believe this is the stuff I have been referring to as
> "double-shielded mil-spec RG-58." I love it. I find it pretty readily
> available at ham radio swap meets. I bought about two hundred feet of
> the stuff for about $20. Needless to say I haven't run out yet.
>
> Brian Lloyd 6501 Red Hook Plaza
> brianl@lloyd.com Suite 201
> +1.340.998.9447 St. Thomas, VI 00802
>
> I fly because it releases my mind from the tyranny of petty things . . .
> Antoine de Saint-Exupry
>
>
>
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