Simongkhon From Sweden, joined Oct 2003, 49 posts, RR: 0 Posted (9 years 4 months 1 week 5 hours ago) and read 3467 times:
In older pix of 737-100:s and 200:s, u sometime can see some kind of wire mounted between the center top of the fuselage and the tail fin. What is that?
Leskova From Germany, joined Oct 2003, 6075 posts, RR: 72 Reply 1, posted (9 years 4 months 1 week 5 hours ago) and read 3405 times:
You can actually still find a lot of 737s around that have that wire - there was at least one thread about that about 1-2 months ago, but since I cannot find that at the moment: if I recall correctly, that wire's an antenna...
Jwenting From Netherlands, joined Apr 2001, 10213 posts, RR: 21 Reply 2, posted (9 years 4 months 1 week 5 hours ago) and read 3382 times:
It's a radio antenna for long range radio transmitters.
In these days of satelite radio it's no longer required so most aircraft had the equipment removed.
MD11Engineer From Germany, joined Oct 2003, 13336 posts, RR: 64 Reply 3, posted (9 years 4 months 1 week 5 hours ago) and read 3374 times:
Looks like a HF antenna for short wave transmissions. You only need it if you are out of range of VHF stations, most 737s flying in Europe or North America don´t have HF installed becauseof the good VHF coverage of the countries. You´ll need it if you fly over oceans or lowly poulated areas. Additionaly today they are much smaller and usualy incorporated in the vertical stabilizer or wing tip.
5T6 From United States of America, joined Dec 2003, 283 posts, RR: 0 Reply 4, posted (9 years 4 months 1 week 5 hours ago) and read 3352 times:
My guess is that it's an HF antenna for comms outside the range of normal VHF radios.
I think that most aircraft now use satellite tranceivers for long-haul communication thus the lack of HF antennas on most planes now. I believe that there's still some HF used for transoceanic flights, though.
Mike
I see my Cats as Companions. My Cats see Me as Furniture!
Mr Spaceman From Canada, joined Mar 2001, 2780 posts, RR: 15 Reply 6, posted (9 years 4 months 1 week 2 hours ago) and read 3200 times:
Hi guys.
Didn't some older aircraft, such as the DC-3s in the photos below use "long wire" antennas for the radio compass (ADF), or am I confused?
In this photo, you can see 3 wires that are attached to the bottom of the DC-3's pitot tubes. Is it possible that the 2 thin wires (that are obviously in a set together) are for the 2 ADF's in the cockpit? Perhaps the thicker wire (also attached to the pitot tubes), is for a HF antenna.
If the 2 thin wires are not used for the 2 ADF's, could the 2 black "pod shaped" antennas on the DC-3's belly (aft of the pitot tubes), be used for them?
Here's a photo showing both the black pods and the set of thin wires.
This DC-3 has a lot of antennas on it. The only one that I'm pretty sure about is the silver metal one that's curved & protruding out of the middle of the nose. It's an ILS receiver antenna ....... I believe.
Mr Spaceman From Canada, joined Mar 2001, 2780 posts, RR: 15 Reply 7, posted (9 years 4 months 1 week 2 hours ago) and read 3188 times:
Hi guys.
I wanted to add these photos too, of DC-3's with the same type of antenna as the 737-1. Other smaller GA aircraft and Bush Planes have them as well (but I didn't want to go to crazy with the pix )
Danman From United Kingdom, joined Jul 2002, 39 posts, RR: 0 Reply 8, posted (9 years 4 months 1 week 2 hours ago) and read 3163 times:
This opens a whole can of worms however;
The wire on the 737 is the HF antenna. Wire antenna were used on the slower flying a/c types before the more modern suppressed types of antenna came into use. Mention has been made of Satcom, this is available but the bulk of the world's fleet does not yet have it fitted. I am not aware of it's use anywhere for ATC purposes.
To the DC3.
As you may or may not be aware ADF requires two antenna, even in a very modern installation, where they are combined. They are the loop and sense antenna. The loop is housed in the 'pod shaped' housings, the sense antenna is probably the wire, although it could also be something that looks like a towel rail on this generation of aircraft.
On to the antenna on the nose, the pic is not too good but it looks like a glide slope antenna (part of the ILS system) The other part of the ILS system (Localizer) will use the 'cow's horn' antenna on the flight deck roof (probably also used for VOR)
Hope this helps
Mr Spaceman From Canada, joined Mar 2001, 2780 posts, RR: 15 Reply 9, posted (9 years 4 months 1 week 1 hour ago) and read 3137 times:
Hello Danman.
Thank You for your info about the ADF and it's 2 different antennas and for explaining that the "Cow's Horn" antenna on top of the cockpit's roof is for receiving the localizer part of an ILS signal.
Well, I don't know if this will open a whole can of worms, but, it will inform people that if you see an aircraft with a wire running from the tail down to the top of the fuselage, or along the belly (usually on larger, older aircraft), the wire could be part of an ADF's antenna system.
I'm just showing another possibility.
Here's some better shots of the 2 ILS antennas on the DC-3.
>> I found this link about ADF's. It has good, easy to read info in it.
This is stated in the link ..........
"All ADF systems have two antennas. With the older ADF systems you have two separate antennas. The loop antenna is usually located on the bottom of the aircraft and is a flat antenna. The sense antenna is the long wire that runs normally from the top of the tail to the top of the cabin. This antenna is sometimes located on the bottom of the aircraft, especially on larger aircraft."
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