Name that Antenna!
Nancy Hattaway Miller
recently-purchased Archer and cleaned the belly. I realized that I don't
know what all my antennas are connected to. There is a small whip on top
the airplane which is a COM antenna, an ELT antenna and a stab-type
which is for the Loran. There is another angled metal rod up top which I
have assumed is for the second COM. I can't remember VOR antennas on the
vertical stabilizer... either they aren't there or I've forgotten them.
On the belly, I can identify the transponder as a small rod with a ball
on the end, and the ADF antenna which is the type with a rod bent in a
rounded fashion and attached to a post aft. There are no sharks-fin
antennas.
Other than the missing VOR antennas and the angled metal rod on top,
that leaves me with three items I can't identify, all on the belly. One
is a small oval pan attached to the underside of the airplane. It's
marked "King" so I know it's something related to avionics. There is
also a wire about the same gauge as an ELT antenna but just dangling out
of the bottom of the airplane. It has a cylinder about 3/8" in diameter
attached around the wire a few inches from the end. The best I can say
about this wire is that it looks broken, whatever it is.
Finally there is a small thick metal rod about 3" long and 1/2" in
diameter protruding from the airplane about a foot in front of the
broken-looking wire. When I cleaned all the crud off this rod, I could
see it had a small hole near to the airplane end. That hole was clogged
with grease and I didn't have the proper equipment to clean it out.
The airplane has dual KX-170B's, an ADF, a non-working DME, a Loran,
marker beacon indicators, a transponder and a separate encoder. It also
has a piece of cabling with a BNC connector coming out of the under-dash
which works very nicely with my scanner and probably would work nicely
with a handheld GPS.
I'm going to take the plane to an avionics guy sometime soon and 1)
talk about getting the DME fixed vs replacing it and 2) a flakey
KX-170B and 3) trying to find out where all the antennas go. But in the
meantime, do any of the more experienced pilots here want to hazard a
guess or flat out clue me in?
Thanks,
Nancy
James Grapes
1. The oval is one of the the ADF ant as is probably the dangling wire you
are speaking of (This will probably be the case if the AC does not have a
wire from the top of the vertical stab to the fuselage).
2. The GS and the Transponder ant will both be very short and most likely on
the bottom of the AC.
3. The tube you are refering to may be the battery drain tube, which can be
confirmed by seeing if it is under the battery.
4. The Comm's and the VOR's likely share the same antenna as they use
similar frequencies and are usally located on top of the AC.
5. ELT antenna's are not generally on the outside of the AC but attached to
the ELT itself. At least in all of the AC I have had the ELT is basically a
stand alone self contained unit like a hand held.
6. It is doubtful that your GPS will work properly with an antenna that is
not designed for it. UHF freq and above are very sensitive to where they are
placed on the AC which is why GS antenna are locaated on the bottom of the
AC since this is where the ground facilities are located in relation to the
AC oreintation (Unless you fly inverted), GPS antennas aree located near the
top of the AC since they communicate with satellites above the AC.
7. One of the first clues for antenna ID is to remember, the higher the
frequency the shorter the antenna (with some not so apparant fractional
wavelength antennas ie. ADF). Antenna length is especially important with
equipment that transmits such as Comm, Xponser and DME.
Hope I am not too inaccurate.
James Grapes
N7555J
Nancy Hattaway Miller wrote in message <377331...@value.net>...
Nancy Hattaway Miller
> 1. The oval is one of the the ADF ant as is probably the dangling wire
> you are speaking of (This will probably be the case if the AC does not
> have a wire from the top of the vertical stab to the fuselage).
The ADF antenna, as I mentioned, is underneath the airplane and is of
the type that looks like an elongated "D" cut in half horizontally. I
think that type combines the sense and loop antennas, but I could be
wrong.
===================== belly of the airplane
| |
___|__________/ ADF antenna
> 2. The GS and the Transponder ant will both be very short and most
> likely on the bottom of the AC.
As I mentioned, I'm pretty sure the transponder is the short thin rod
with the ball on the end. I haven't identified GS or marker beacon
antennas (see next response).
> 3. The tube you are refering to may be the battery drain tube, which
> can be confirmed by seeing if it is under the battery.
Tube? I didn't mention any tubes. The short rod midplane is a solid
piece of metal about 3" x 1/2".
> 4. The Comm's and the VOR's likely share the same antenna as they use
> similar frequencies and are usally located on top of the AC.
Most VORs I've seen do not share the same antenna as the COMs. Most I've
seen are the two thin bent rods set at right angles to each other on
either side of the vertical stabilizer. I might have those and just
can't remember!
> 5. ELT antenna's are not generally on the outside of the AC but
> attached to the ELT itself. At least in all of the AC I have had the
> ELT is basically a stand alone self contained unit like a hand held.
Maybe you fly different airplanes that I do... most Cessnas and Pipers
I've seen have an external ELT antenna. Looks like it would snap off in
a strong wind. :)
> 6. It is doubtful that your GPS will work properly with an antenna
> that is not designed for it.
Possibly true, but I strongly suspect that the reason this antenna was
put in was to attach to a handheld GPS or a handheld NAV/COM. Looks like
this is the excuse I need to get in touch with the previous owner, as
the broker didn't even realize the cable was there!
> 7. One of the first clues for antenna ID is to remember, the higher
> the frequency the shorter the antenna (with some not so apparant
> fractional wavelength antennas ie. ADF). Antenna length is especially
> important with equipment that transmits such as Comm, Xponser and DME.
Thanks for this clue!
Nancy
Nonspam
>I've seen have an external ELT antenna. Looks like it would snap off in
>a strong wind. :)
Or a crash?
== Do not reply to "from" address. (Sorry, this is an anti-spam measure.) ==
Ron Natalie
>
> >Maybe you fly different airplanes that I do... most Cessnas and Pipers
> >I've seen have an external ELT antenna. Looks like it would snap off in
> >a strong wind. :)
>
> Or a crash?
My ELT antenna is pretty flimsy (I've seen others on 152's which
are just the one attached to the ELT sticking out through a hole
in the fuselage). However, you can yank the ELT out of it's holder
and it has a second antenna (looks like a piece of tape measure)
if you want to use it out of the plane.
George R. Patterson III
>
> The ADF antenna, as I mentioned, is underneath the airplane and is of
> the type that looks like an elongated "D" cut in half horizontally. I
> think that type combines the sense and loop antennas, but I could be
> wrong.
>
> ===================== belly of the airplane
> | |
> ___|__________/ ADF antenna
>
That looks much more like a marker beacon receiver antenna. ADF antennae
are typically long wires that run from the vertical stabilizer to an
insulator pole on top of the cabin.
> As I mentioned, I'm pretty sure the transponder is the short thin rod
> with the ball on the end. I haven't identified GS or marker beacon
> antennas (see next response).
The GS receiver usually shares the VOR antenna. There's usually a signal
splitter on the antenna cable to allow this. Your short thin rod is the
transponder antenna.
> Most VORs I've seen do not share the same antenna as the COMs. Most I've
> seen are the two thin bent rods set at right angles to each other on
> either side of the vertical stabilizer. I might have those and just
> can't remember!
You're correct. The COM antenna is usually a tapered white ceramic pole
about 12" long, and is usually mounted near the cabin. LORAN antennae
are frequently identical in appearance. The antennae on high speed
aircraft may be bent to minimize resistance, or it may take the form of
a blade. VOR antennae are generally mounted on the vertical stabilizer
and usually consist of two naked steel rods about 12" long extending out
at 45 degrees to the centerline of the aircraft. Again, there are other
forms for fast aircraft.
> > 5. ELT antenna's are not generally on the outside of the AC but
> > attached to the ELT itself. At least in all of the AC I have had the
> > ELT is basically a stand alone self contained unit like a hand held.
>
> Maybe you fly different airplanes that I do... most Cessnas and Pipers
> I've seen have an external ELT antenna. Looks like it would snap off in
> a strong wind. :)
Actually, they are quite thin and flexible to ensure that they will not
break off in the event of a crash. Most aircraft do, indeed, have
external ones, but internal ones are not unknown (my EBC ELT has one,
for example). I suspect that's what James has seen.
> > 6. It is doubtful that your GPS will work properly with an antenna
> > that is not designed for it.
>
> Possibly true, but I strongly suspect that the reason this antenna was
> put in was to attach to a handheld GPS or a handheld NAV/COM. Looks like
> this is the excuse I need to get in touch with the previous owner, as
> the broker didn't even realize the cable was there!
A GPS antenna looks very much like a computer mouse. There's nothing
else that looks quite like it. They are always mounted on top of the
aircraft. A GPS will work poorly, if at all, with anything else.
If you can get a catalog from Chief Aircraft, they have illustrations of
all of the antennae they sell. This can be very helpful in figuring out
what some of them are, but obsolete designs (such as your MBR antenna)
won't be in there.
George Patterson, N3162Q.
Chuck Forsberg
Nancy Hattaway Miller <n...@value.net> wrote:
>James Grapes wrote:
>> 1. The oval is one of the the ADF ant as is probably the dangling wire
>> you are speaking of (This will probably be the case if the AC does not
>> have a wire from the top of the vertical stab to the fuselage).
>
>the type that looks like an elongated "D" cut in half horizontally. I
>think that type combines the sense and loop antennas, but I could be
>wrong.
>
>===================== belly of the airplane
> | |
> ___|__________/ ADF antenna
>
That drawing looks like a Loran-C E-field antenna or possibly
a marker beacon antenna.
Comm antennas are usually rods on top of the wing in the case
of high wing a/c. Usually one for each comm radio.
Nav antennas are usually the cat's whiskers near the top
of the vertical stabilizer. "Towel bars" may be used
instead. Blade style are uncommon in bugsmashers. Glide
Slope is usually diplaxed off the NAV antenna. VOR, LOC,
and (I think) GS are horizontally poliarized.
Marker beacon can be a bent whip or a blade or something
that looks like a boat. The signals are short range so
one doesn't need a skyhook to receive them.
An aerial strung between the cockpit and the vertical stab
would be an ADF sense antenna or possibly HF comms.
Other variations exist.
--
Chuck Forsberg WA7KGX PP-ASEL/HP Skylane N2469R c...@omen.COM
Omen Technology Inc The High Reliability Software www.omen.com
Author of YMODEM, ZMODEM, RZ, SZ, Pro-YAM, ZCOMM, GSZ, and DSZ
TeleGodzilla BBS: 503-617-1698 FTP: ftp.cs.pdx.edu pub/zmodem
POB 4681 Portland OR 97208 503-614-0430 FAX:503-629-0665
Nancy Hattaway Miller
>
> > ===================== belly of the airplane
> > | |
> > ___|__________/ ADF antenna
> >
>
> antennae are typically long wires that run from the vertical
> stabilizer to an insulator pole on top of the cabin.
Well, score another point for misinformation I received from some of my
primary CFIs. I was told that the above was an ADF antenna. But you and
others (via e-mail) confirm it's a marker beacon antenna. If the "oval
pan" is the ADF, then that answers a bunch of questions. I don't have a
wire from the cabin to the vertical stabilizer.
> You're correct. The COM antenna is usually a tapered white ceramic
> pole about 12" long, and is usually mounted near the cabin. LORAN
> antennae are frequently identical in appearance.
Check and check. There is a second, bare metal, slightly bent rod on the
top about mid-fuselage. Could be 2nd com, could be to that BNC adapter,
could be VOR? But it's in the wrong orientation for that.
> A GPS antenna looks very much like a computer mouse. There's nothing
> else that looks quite like it. They are always mounted on top of the
> aircraft. A GPS will work poorly, if at all, with anything else.
Nothing like this. The cable must have been for a handheld NAV/COM.
> If you can get a catalog from Chief Aircraft, they have illustrations
> of all of the antennae they sell. This can be very helpful in figuring
> out what some of them are, but obsolete designs (such as your MBR
> antenna) won't be in there.
Speaking of obsolete, my DME is an older King that fits into a round
cutout on the instrument panel, a KN-61 according to the notes I have.
I'm thinking that it must be attached to that 3" x 1/2" rod (or pole) on
the belly.
I really appreciate the amount of information you can gather quickly on
this newsgroup (this goes for all respondents, not just George).
Especially as I can look like a total idiot about ADF antennas in front
of you guys rather than in front of my avionics guy.
Nancy
Richard Hyde
http://www.rami.com/ga00.htm (VHF, Nav, DME/Transponder)
--
Include "wombat" in Subject: line of mail sent to me [to override spamgard(tm)]
------------------------------------------------------------------------------
| Richard Hyde | R...@netcom.com | This space intentionally left blank |
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Richard Hyde
each type you want to view:
http://www.americanavionics.com/antennas.html
: Pretty antenna pictures
John J. Miller
>Pretty antenna pictures:
>
>http://www.rami.com/ga00.htm (VHF, Nav, DME/Transponder)
>
:-)
John J. Miller
jo...@mcdata.com
James Bieker
things that are on the Archer I usually rent.
The Transponder antenna is the one you identified, 2 inch long with the 1/4"
ball on the tip, located on the belly between the wings.
Both VOR's (VOR + Glide Slope) use the V shaped horizontal antenna at the
top if the vertical stabilizer. Not sure if the Glideslope shares this one.
The external ELT antenna is the very slender looking one forward of the tail
on top of the fuselage, and has a small loop on the tip to avoid impaling
something.
Both COM's have their own separate antennas, both forward of the ELT antenna
on top of the fuselage. Since yours are different in color and texture, I am
guessing one was added later or replaced.
The ADF antenna is the larger mostly circular antenna on the belly
That is all the Archer I fly has, but I can add that:
A GPS antenna would be small, round, on top and most say GPS on them.
The other small horizontal antenna on the belly is a marker antenna.
The Loran antennae are small fins on the belly.
The other one dangling loose on the belly is a bit of a mystery, but my
guess is maybe part of a previous ADF ?
I think it shows that you are a good pilot that you take interest in those
parts of your aircraft. Like a good pilot, you are always learning, as am
I - especially since I expect to be corrected if my nickel's worth was off
target!
John Prickett
>
> James Grapes wrote:
> > 1. The oval is one of the the ADF ant as is probably the dangling wire
> > you are speaking of (This will probably be the case if the AC does not
> > have a wire from the top of the vertical stab to the fuselage).
>
> The ADF antenna, as I mentioned, is underneath the airplane and is of
> the type that looks like an elongated "D" cut in half horizontally. I
> think that type combines the sense and loop antennas, but I could be
> wrong.
>
> | |
> ___|__________/ ADF antenna
>
no, this is the marker beacon antenna (most likely). marker beacon
antennas come in (at least) two flavors: boat and sled. this is
the sled type (named because it looks like the runner on a sled). sort
of incongrous that the least complex receiver (non-tunable, 75 MHz
only) uses the largest antenna, but there you have it.
the oval pan is most likely the loop (or combined loop/sense) adf
antenna. the loop typically has 3 legs at 120 degree angles to
each other in order to 'triangulate' the signal (the received signal
will be stronger in the leg that more nearly broadsides the station,
which is how the goniometer is able to resolve the direction.)
> > 2. The GS and the Transponder ant will both be very short and most
> > likely on the bottom of the AC.
>
> As I mentioned, I'm pretty sure the transponder is the short thin rod
> with the ball on the end. I haven't identified GS or marker beacon
> antennas (see next response).
>
agreed, this is probably the xpndr.
> > 3. The tube you are refering to may be the battery drain tube, which
> > can be confirmed by seeing if it is under the battery.
>
> Tube? I didn't mention any tubes. The short rod midplane is a solid
> piece of metal about 3" x 1/2".
>
this _might_ be the dme, length is about right, but i've never seen
a dme antenna that wasn't enclosed in a 'blade' like thing.
> > 4. The Comm's and the VOR's likely share the same antenna as they use
> > similar frequencies and are usally located on top of the AC.
>
> Most VORs I've seen do not share the same antenna as the COMs. Most I've
> seen are the two thin bent rods set at right angles to each other on
> either side of the vertical stabilizer. I might have those and just
> can't remember!
>
unlikely they will share, as com signals are vertically polarized and
nav signals are horizontally polarized. usually nav antenna's are
as you describe, although i have seen 'towel bar' nav antennas, and
another one that looks like a 'flying wing' on a pedestal. (glideslope
antennas are also made in this form, although in many installations,
the glideslope just couples off the nav antenna.)
> > 5. ELT antenna's are not generally on the outside of the AC but
> > attached to the ELT itself. At least in all of the AC I have had the
> > ELT is basically a stand alone self contained unit like a hand held.
>
> Maybe you fly different airplanes that I do... most Cessnas and Pipers
> I've seen have an external ELT antenna. Looks like it would snap off in
> a strong wind. :)
>
> > 6. It is doubtful that your GPS will work properly with an antenna
> > that is not designed for it.
>
> Possibly true, but I strongly suspect that the reason this antenna was
> put in was to attach to a handheld GPS or a handheld NAV/COM. Looks like
> this is the excuse I need to get in touch with the previous owner, as
> the broker didn't even realize the cable was there!
>
> > 7. One of the first clues for antenna ID is to remember, the higher
> > the frequency the shorter the antenna (with some not so apparant
> > fractional wavelength antennas ie. ADF). Antenna length is especially
> > important with equipment that transmits such as Comm, Xponser and DME.
>
> Thanks for this clue!
>
> Nancy
hope this helps some, anyway.
john
--
'something clever.'
john.p...@amd.com
Nancy Hattaway Miller
>
> The Loran antennae are small fins on the belly.
>
> The other one dangling loose on the belly is a bit of a mystery, but
> my guess is maybe part of a previous ADF ?
>
> I think it shows that you are a good pilot that you take interest in
> those parts of your aircraft. Like a good pilot, you are always
> learning, as am I - especially since I expect to be corrected if my
> nickel's worth was off target!
Thanks, I think your summary was pretty much ON target. However, I'd
like more credit for crawling around degreasing the belly than for
having interest in my antennas! :-)
For the record, I went and looked and, lo and behold, there is a VOR
antenna on the empennage, right where it should be. It must be afraid of
water though because for the life of me I don't remember it being there
the last (and only) time I washed the airplane at the washrack.
I'm reasonably certain the small thick rod (3" x 1/2") is the DME
antenna, as there was one that looked a lot like it on one of the Web
sites someone recommended. So that was helpful too.
I'm sure of my Loran antenna, as it is labeled "Northstar", and it is up
on top. In fact, I have no "shark's fins" at all, which seems unusual.
It would be interesting if both COMs used the same antenna and the
second, different one on top was installed separately for the coax/BNC
accessory. (Do you think the installation of that is anywhere in the
logs? Noooooooo... nor is the installation of a short doubler on the
trailing edge of the rudder. NDH? We don't need no steenkin' logs!)
I think I should have a contest for guessing the mystery wire on the
belly of the plane. We've accounted for all the other antennas and all
the avionics. So my guess is... it goes nowhere!
Nancy
Richard Hyde
: I think I should have a contest for guessing the mystery wire on the
: belly of the plane. We've accounted for all the other antennas and all
: the avionics. So my guess is... it goes nowhere!
I haven't flown an Archer in a long time, but the Cessnas have a
plastic cover aft of the baggage section. The cover pops right
off to allow inspection of the tailcone. If the Archer has
anything similar, perhaps you could just look.
Cheers,
Rick
Roy Smith
> I haven't flown an Archer in a long time, but the Cessnas have a
> plastic cover aft of the baggage section. The cover pops right
> off to allow inspection of the tailcone. If the Archer has
> anything similar, perhaps you could just look.
All the cherokees I've seen have an inspection/access panel at the aft end
of the baggage compartment. Usually, it's just held in with velcro or
something similar and is a cinch to remove and re-install. Pull it off,
and you get a good view of the whole inside of the tail section (a
flashlight helps).
James Bieker
It has Collins avionics, hence the name was on the larger ADF antenna on the
belly. There was also another 18" long 1.5" thick antenna on the bottom not
far behind the one I just mentioned. Since this Archer has only dual NAV/COM
plus the ADF and no Loran/DME, it must be for glideslope. (or it supplements
the ADF?)
I believe there is no way for both COM's to share the same antenna, as each
must transmit independently without interference to the other, hence the
spacing. Also provides redundancy in the event that you lose one antenna or
radio.
BTW, some VOR antennae angle forward instead of rearward. The Cessna 172C on
the ramp was that way.
Even if you were motivated to learn more as a result of cleaning your Archer
top to bottom, it still tells me you have a healthy interest in it.
Amazing what one finds when you just take a look.
James Bieker
final, although I imagine it would break off fairly easily. That must be
where your co-ax cable with the BNC connector goes. Now why didn't I think
of that? Probably because I've never seen HF radios in anything flying short
of some military aircraft.
Jim Weir
shared these priceless pearls of wisdom:
->I think I should have a contest for guessing the mystery wire on the
->belly of the plane. We've accounted for all the other antennas and all
->the avionics. So my guess is... it goes nowhere!
Well, I shadduppa my mouth and watched with interest the good and gawdawful
posts to this question, so my best guess is the mystery wire...
You said it went to a cup or a drogue of some sort. My best guess on the wire
is that it was a trailing wire antenna rolled off of a reel of some sort for HF
communications for long overwater flights. You tune the antenna as a function
of how much wire you reel out. The drogue is there to keep it loosely in trail.
Jim
Jim Weir (A&P, CFI, and other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com j...@rst-engr.com
Jim Weir
shared these priceless pearls of wisdom:
->Wow, a reel it out longwire antenna! You wouldn't want that dangling on
->final, although I imagine it would break off fairly easily. That must be
->where your co-ax cable with the BNC connector goes. Now why didn't I think
->of that? Probably because I've never seen HF radios in anything flying short
->of some military aircraft.
You use bare (uncoated) copper wire on a fishing reel and simply reel out wire
until the SWR meter dips to minimum. If you get fancy-schmancy and use enameled
wire, you have one hell of a base loading coil on that reel!!
Jim Weir
shared these priceless pearls of wisdom:
->BTW, some VOR antennae angle forward instead of rearward. The Cessna 172C on
->the ramp was that way.
There is a slight but measurable increase in the signal strength in the
direction of the V in the antenna arms. Most of us use the VOR more as an
aiming point TO than FROM, so from a performance point of view, the antenna
works best with the V pointing forward.
Cessna's marketing department thought they looked sexier swept back. Guess who
won?
brian whatcott
>
> longwire antenna!...
>You use bare (uncoated) copper wire on a fishing reel and
> simply reel out wire until the SWR meter dips to minimum.
> If you get fancy-schmancy and use enameled
>wire, you have one hell of a base loading coil on that reel!!
>
>Jim
>Jim Weir
What's the preferred reel, Jim?
Baitcasting, fly-fishing or spinning(fixed spool)?
Brian Whatcott
andrew m. boardman
>> | |
>> ___|__________/ ADF antenna
>>
>
>a marker beacon antenna.
So I'm not the only one! The Tiger I fly has two antennas of that style
on the belly, one short one for the marker beacons (very roughly 1.5'
long with no supporting standoffs) and an odd one that's well over 6'
that runs most of the length of the plane with multiple standoffs. Given
that the transponder (stub), ADF (belly box), com (standard verticals),
and nav ("V" on vertical stabilizer) antennas are all readily
identifiable, it's pretty clear that the long horizontal is for the
Loran, though I've never seen another of this style. It must be
hellaciously draggy, though Loran reception is *excellent*.
andrew
Jim Weir
shared these priceless pearls of wisdom:
->So I'm not the only one! The Tiger I fly has two antennas of that style
->on the belly, one short one for the marker beacons (very roughly 1.5'
->long with no supporting standoffs) and an odd one that's well over 6'
->that runs most of the length of the plane with multiple standoffs. Given
->that the transponder (stub), ADF (belly box), com (standard verticals),
->and nav ("V" on vertical stabilizer) antennas are all readily
->identifiable, it's pretty clear that the long horizontal is for the
->Loran, though I've never seen another of this style. It must be
->hellaciously draggy, though Loran reception is *excellent*.
I wouldn't bet so, as only the vertical component of the antenna does you any
good on Loran.
Chuck Forsberg
unit the qould work on my Skylane... WA7KGX
George R. Patterson III
>
> Wow, a reel it out longwire antenna! You wouldn't want that dangling on
In _Fate is the Hunter_, Ernest Gann describes breaking one off. He was
descending through cloud, trying to get into Greenland on a cargo run.
It had been hours since he had been able to reset his altimeter, and he
couldn't contact anybody. He had his radio operator stream the antenna
and yell out when the weight at the end hit the sea. He knew that the
plane would be at about 250' ASL when that happened. As it turned out,
they broke out of the clouds just as the radio operator yelled. His
radio operator was very upset because it was hard to find the weights.
George Patterson, N3162Q.