Transponder antenna installations
Dick
original antenna was located where the cg hook used to be on my
discus. This location often tangled with the trailer ramp when
loading the glider. Next I tried a whip style on top of my instrument
panel cover. All of the self proclaimed experts said that was a
terrible place. Much to much power too close to the rest of my
avionics and electronics. I now intend to place it on the underside
of the fuselage as far aft of the main gear housing as I can reach.
My question is, does it have to be mounted near the centerline, I'd
rather not tangle with the overlap of the two fuselage halves. How
far off the center line can I go before the biannual inspector will
object or I will lose effectiveness? IT
Alpha Eight
Have a look at the glider manufactures website or contact the dealer
as many have very specific directions for transponder antenna
location. On the Ventus 2b there is an engineering drawing showing the
location which puts the antenna is substantially off centerline on the
right side. This works well as it clears the trailer easily and is
generally out of the way.
John Seaborn (A8)
twocool...@juno.com
We've use the Advanced Aircraft Electronics L2 antenna on several
installations, with excellent results. This antenna mounts
internally in the fuselage tail boom. (won't work with carbon fiber
in the fuselage though...)
On gliders with carbon fiber, we used typical stub antenna, mounted
per manufacturer's drawings....we fabricated a "ground plane" plate to
go inside the fuselage......you need some space for this.
The antenna can be quite far off center line...but I would worry about
not going too far off vertical orientation.
Cookie
JJ Sinclair
> We've use the Advanced Aircraft Electronics L2 antenna on several
> installations, with excellent results. This antenna mounts
> internally in the fuselage tail boom. (won't work with carbon fiber
> in the fuselage though...)
I second the L-2, di-pole antenna suggestion, all inside with nothing
sticking out to get ripped off. Carve a1"X 1"X4" balsawood block so
that it matches the inside curve of your non-carbon fuselage, then
glue the antenna vertical to the flat side and the curved side to the
inside aft fuselage. Keep it about 6" away from metal objects like
your elevator push-rod, etc. Secure the RG-58 lead so that it can't
get tangled with controls and you're good to go.
Hope this helps,
JJ
jcarlyle
attenuation per foot. Times Microwave LM240 is a much better choice,
with only 1/3 of the attenuation of RG-58 at 1 GHz. I usually use
Times Microwave LM300, with only 1/4 the attenuation of RG-58, but it
has double the diameter. Both of these cables have a greater than 20
year life outdoors.
-john
jcarlyle
of the dB loss per 100 feet, which is wrong. The correct figures are
that LM240 has 20% of the attenuation of RG-58 at 1 GHZ, while LM300
has 13% of RG-58.
-John
John Scott
are carbon fiber, the nose of my glider is fiberglass. I installed the L-2
vertically on the bulkhead that closes off the nose ahead of my feet. I've
not noticed any effect on my other instruments in the panel or on my GPS
(CA302). I have noticed that my feet still get cold at altitude, so I don't
think the power output is a problem. The vertical orientation means my
glider is at the center of a very fat horizontal donut.
John Scott
JJ Sinclair
>
> - Show quoted text -
The instructions from Advanced Aircraft Electronics call for RG-58A/U
unless wire bundle size is critical where the smaller RG-174/U may be
used if length is held to 20 feet or less.
JJ
jcarlyle
instructions, laughed, and pitched it. Why should you pay for
transponder output just to heat up the antenna cable with outdated
RG-58, when low loss LM240 is only $0.70 more per foot? And if RG-58
is bad, RG-174 is 4 times worse...
-John
JJ Sinclair
>
> - Show quoted text -
You're right John.................I'll disregard the manufactures
instructions and go with something I heard on ras.............
Yeah, right!
JJ
jcarlyle
Would you believe an attenuation calculator from Times Microwave? See
http://www.timesmicrowave.com/cgi-bin/calculate.pl
Another option is to look up attenuation values on Newark and Allied,
since a manufacturer has a vested interest in lying. Oh, wait -
Advanced Airborne Electronics is a manufacturer...
-John
twocool...@juno.com
We did an LS-3 this way with good results.
Cookie
Eric Greenwell
> On Feb 6, 11:12 am, jcarlyle<jmcarl...@gmail.com> wrote:
>> I understand your point - I saw those suggestions on my L2
>> instructions, laughed, and pitched it. Why should you pay for
>> transponder output just to heat up the antenna cable with outdated
>> RG-58, when low loss LM240 is only $0.70 more per foot? And if RG-58
>> is bad, RG-174 is 4 times worse...
>>
>>
>>> The instructions from Advanced Aircraft Electronics call for RG-58A/U
>>> unless wire bundle size is critical where the smaller RG-174/U may be
>>> used if length is held to 20 feet or less.
>>> JJ- Hide quoted text -
>>
>> - Show quoted text -
>
> You're right John.................I'll disregard the manufactures
> instructions and go with something I heard on ras.............
> Yeah, right!
JJ, call AAE and ask about the LM240 cable. It might be their
recommendation was aimed at airplanes carrying 200+ watt transponders
and using shorter cable runs, compared to gliders that might using units
with 150 watts or less and long cable runs. Also, looking at the
transponder manufacturer's recommendation is probably a better
indication of what's needed than the antenna manufacturer. My Becker
instructions made quite a fuss about which cable to use.
Generally, I like to go the "good stuff" for transponders, as
attenuation per foot is much higher at transponder frequencies than our
communication radios frequencies (factor of 8).
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
Paul Remde
The Trig TT21 and TT22 manual is also quite fussy about transponder antenna
cable. But it important to note that many of the "long run" antenna cables
they recommend are extremely expensive.
I recommend mounting the transponder unit (it is separate from the control
head) as close to the antenna as possible. When that is done I have
received customer feedback that RG-58 cable works fine - with all required
tests passed with flying colors.
Paul Remde
"Eric Greenwell" <ow...@thegreenwells.netto> wrote in message
news:iinks9$jvc$1...@speranza.aioe.org...
JJ Sinclair
>
> - Show quoted text -
The Becker 4401-175 manual does say that RG-223/U is preferred over
RGU-58, but it doesn't mention LM-240? As a mechanic I am bound to
follow the appropriate tech data. Does LM-240 use the same BNC
fittings I have in stock? Can I use my crimper? What would my log book
entry say? Installed Becker 4401-175 transponder in accordance with
opinions found on ras?
:>) JJ
Willy VINKEN
'Aircell 5' is a good substitute for plain vanilla RG 58/U coax
cable.
It fits standard BNC connectors.
Attenuation at 1000 MHz is about 32 dB/100m (compared to 54 for RG58)
Willy VINKEN -ON5WV-
Grider Pirate
>
> - Show quoted text -
...and Aircell 5 IS listed in the manual for the Trig transponders.
RG-58 is not.
jcarlyle
transponder power to the antenna, not use it to heat the cable. I
think it's significant that Trig doesn’t specify the use of RG-58 at
all.
Aircell cables are European, they aren’t easily available in the US,
and would be expensive if you could order them. Attenuation for
Aircell 7 (the best cable recommended by Trig) is 6.9 dB per 100 feet
at 1 GHz. US made LMR300 is even better, it has an attenuation of 6.4
dB per 100 feet at 1 GHz. LMR240 comes in with a bit higher
attenuation at 8.0 dB per 100 feet at 1 GHz.
As for cost, 15 feet of bare LMR240 is $13.35. You can get a complete
LMR240 cable made with a TNC at one end and a BNC at the other for
only $30. Doesn’t seem outrageous.
-John
twocool...@juno.com
We use RG 400 for our transponder antenna cables. Trig says it is
good for up to 8'4".....(So does Garmin.)
Since you can mount the trig transmitter box wherever you need,
staying less than 8' is easy.
Cookie
jcarlyle
as an antenna line violates Becker’s instructions. They state in
paragraph 5C that only RG-223 is to be used with the 4401-175. RG-58
can only be used with a 4401-250. Don’t overlook that you also must
comply with paragraph 6E, where you must check the power at the
antenna end of the cable. I’d bet that a 4401-175 using RG-58 will not
meet Becker’s power spec of 18.5 dBW.
As far as the non-mention of LM240 in the Becker manual, I’d bet
you’re allowed as an A&P to attach data showing that LM240 exceeds the
performance of RG-223. This data, combined with the mandatory power
test proving that the 4401-175 installed using LM240 exceeds the
Becker requirement of 18.5 dBW at the antenna end of the cable, would
make you golden.
Unfortunately, you have to buy male BNC and male TNC crimp connectors
when you buy the LM240. They’re a buck more expensive than RG-58
connectors. But your crimper will definitely work.
Your log book entry would simply say that the Becker 4401-175 was
installed in accordance with the manufacturer’s instructions, except
for the use of an antenna cable that exceeds the manufacturer’s cable
specifications which results in greater power being delivered to the
antenna. I guess you could attribute the idea of using a better cable
to RAS, if you liked – humor shouldn’t a violation of the A&P code, is
it?
-John
Alan
>I hate to break it to you, but a Becker 4401-175 installed using RG-58
>as an antenna line violates Becker's instructions. They state in
>paragraph 5C that only RG-223 is to be used with the 4401-175. RG-58
>can only be used with a 4401-250. Don't overlook that you also must
>comply with paragraph 6E, where you must check the power at the
>antenna end of the cable. I'd bet that a 4401-175 using RG-58 will not
>meet Becker's power spec of 18.5 dBW.
Remember to account for the greater loss of the cable after 10 - 20 years.
>As far as the non-mention of LM240 in the Becker manual, I'd bet
>you're allowed as an A&P to attach data showing that LM240 exceeds the
>performance of RG-223. This data, combined with the mandatory power
>test proving that the 4401-175 installed using LM240 exceeds the
>Becker requirement of 18.5 dBW at the antenna end of the cable, would
>make you golden.
>
>Unfortunately, you have to buy male BNC and male TNC crimp connectors
>when you buy the LM240. They're a buck more expensive than RG-58
>connectors. But your crimper will definitely work.
I doubt it. LMR 240 is larger in diameter than RG-58. The crimper for
RG-59 might be a closer fit.
>Your log book entry would simply say that the Becker 4401-175 was
>installed in accordance with the manufacturer's instructions, except
>for the use of an antenna cable that exceeds the manufacturer's cable
>specifications which results in greater power being delivered to the
>antenna. I guess you could attribute the idea of using a better cable
>to RAS, if you liked =96 humor shouldn't a violation of the A&P code, is
>it?
The problem is that "better" isn't just lower loss per foot when the cable
is new. There may be a lot of other factors that the manufacturer took into
account with their cable selection. "Better" needs to be better in all of
these factors.
The transponder may need a minimum amount of loss in the coax to ensure that
the SWR seen by the transmitter is low enough in case something gets near the
antenna. (This would protect both the transmitter, and the receiver, as a mismatch
at the duplexer often reduces the isolation between the transmitter output and the
receiver input.)
>-John
>
>On Feb 7, 9:18 am, JJ Sinclair <johnsinclai...@yahoo.com> wrote:
>> The Becker 4401-175 manual does say that RG-223/U is preferred over
>> RGU-58, but it doesn't mention LM-240? As a mechanic I am bound to
>> follow the appropriate tech data. Does LM-240 use the same BNC
>> fittings I have in stock? Can I use my crimper? What would my log book
>> entry say? Installed Becker 4401-175 transponder in accordance with
>> opinions found on ras?
>> :>) JJ
I suspect it LMR 240 would work better than the other cables, both in loss and
service life, but I don't know it. As JJ notes, he doesn't know it for sure, and
and would need to.
Alan
jcarlyle
The best way to answer is to quote from section 5.11.2 of the Trig
installation manual. They state that excessive cable loss will degrade
both transmitter output power and receiver sensitivity. Then they
define the three qualities of an acceptable cable:
(1) less than 1.5 dB loss for the run length,
(2) a characteristic impedance of 50 ohms, and
(3) double braid screens, or a foil and braid screen.
They then say that their table of maximum usable lengths for common
cable types is a guide only, and tell you to refer to manufacturer’s
data sheets for your specific chosen cable. This is clearly permission
to choose your cable type, as long as it meets Trig’s three acceptance
criteria above as backed up by specific manufacturer’s data.
As for “knowing” about cables, like anything else you need to do
research and get educated. I’ve tried to let this forum know that
there are much better choices for microwave cable than RG-58 and
RG-400. Naturally, people will do as they wish, even to the extent of
tossing away transponder output power and getting less receiver
sensitivity. It may work out OK, or it might possibly be a link in an
accident chain someday. I have the satisfaction of knowing that in my
transponder installations pilots are getting 175 W transponders that
meet or exceed their performance specifications for just $20 extra in
cable.
-John
On Feb 8, 2:04 am, nos...@w6yx.stanford.edu (Alan) wrote:
>
> The problem is that "better" isn't just lower loss per foot when the cable
> is new. There may be a lot of other factors that the manufacturer took into
> account with their cable selection. "Better" needs to be better in all of
> these factors.
>
> The transponder may need a minimum amount of loss in the coax to ensure that
> the SWR seen by the transmitter is low enough in case something gets near the
> antenna. (This would protect both the transmitter, and the receiver, as a mismatch
> at the duplexer often reduces the isolation between the transmitter output and the
> receiver input.)
>
mdfa...@gmail.com
Darryl Ramm
> A bit off topic but when I bought my glider the transponder antenna (flat L2 type) was mounted under the seatpan on the "floor" of the fuselage. After reading some links in this thread I see that, according to the manufacturer, the antenna should be mounted vertically. Where would one typically do this? There aren't many flat vertical surfaces other than the main bulkhead. Glass, not carbon fiber, ship. This is my first glider with a transponder and I admit ignorance on the topic.
As you likely are working out there often is no *great* place to mount an antenna.
Many people would make up a vertical mount out of plywood or fiberglass or just a block of balsa and find a place on one side of the fuselage to mount this down the tail boom to mount this. You want to avoid the antenna being near conductive components and that is often a problem finding space away from control linkage and other hardware, and you have rudder cables and elevator etc. running down the fuselage. Have a look around and see. It may be better to mount an external 1/4 wave antenna with internal ground plane....
If you end up with longer coax runs pay attention to using a correct high-spec cable, especially with Trig transponders. And secure the cable well so there is no movement.
SoaringXCellence
Mike
SoaringXCellence
George Haeh
AND get an adequate coax there. See
https://www.timesmicrowave.com for a coax calculator.
Do make very sure that nothing will come loose and interfere with the elevator pushrod, or anything else.
Darryl and I disagree on mounting an L2 antenna in the forward fuselage.
That said, my installation forward of the rudder pedals in my previous ASW-20 passed the transponder test and ATC had no complaints.
To shape the balsa, stick 80 grit sandpaper on the site with double sided tape and sand away.
tow...@gmail.com
2G
Tom