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redngold
Topic Author
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Joined: Wed Mar 22, 2000 12:26 pm

Cessna 414 What's On Top?

Mon Feb 12, 2001 1:05 pm

I've seen several pictures (real and virtual) of Cessna 414's with some sort of wire running from the top of the tail to a guide over the cockpit to a fastener right in front of the propeller. What is this? Is it a radio wire? Is it part of the electrical system? Or is it structural?

redngold
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Ralgha
Posts: 1589
Joined: Tue Nov 09, 1999 6:20 pm

RE: Cessna 414 What's On Top?

Mon Feb 12, 2001 2:12 pm

It's an ADF antenna. Older ADF systems used two antennas, one of which was long and generally ran from the top of the vertical stabilizer to some point on top of the fuselage. A second antenna was placed on the bottom of the airplane and is generally a box, inside there is an antenna that rotates to align perpendicular with the radio wave. This smaller antenna determines which direction the lines of the wave go, but can't determine which side they originate from, which is where the long antenna on top comes into play.
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tom2katie
Posts: 79
Joined: Sat Nov 11, 2000 8:58 pm

RE: Cessna 414 What's On Top?

Mon Feb 12, 2001 7:34 pm

Could also be an HF antenna. Some HF's use a long wire antenna in GA and light twin applications.
 
redngold
Topic Author
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RE: Cessna 414 What's On Top?

Tue Feb 13, 2001 12:17 pm

Thanks for the answer, y'all! Very helpful.

redngold
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airplay
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RE: ADF Antennas

Wed Feb 14, 2001 2:31 am

Could be an ADF sense antenna, could be an HF this is true, but modern ADF antennas don't rotate. They are fixed loop antennas with 2 windings situated at right angles to each other. Many newer ADF loop antennas have integrated sense antennas making the long wire unneccessary.
 
Ralgha
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Joined: Tue Nov 09, 1999 6:20 pm

RE: ADF Antennas

Wed Feb 14, 2001 5:13 am

It is true that modern ADF antenna don't rotate, but then the 414 isn't the most "modern" of airplanes, and it's usually not worth it to upgrade the ADF antennas when the older type works just fine.
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airplay
Posts: 3369
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RE: ADF Antennas

Wed Feb 14, 2001 10:49 am

I used to work on old ADFs like the ARN 2 and the R30. The last one I worked on with a rotating antenna was an ARC R30. These units were popular in Beech 18 era aircraft. They used vacuum tubes to operate and were introduced just before transistors became popular in the mid-50s.

The main reason for removing them from aircraft was the cost of maintaining the antenna. The R-30 production ceased in the late 50s because they just weren't as reliable as the new transistorized models with stationary antennas like the Bendix T12. The last rotating antenna I tried to fix was going to cost over $1000. At that time you could buy a completely new T12 system for about $1500.

The 414 was first produced in 1969. Every 414 I've ever had the pleasure (?) of working on, either had the 400 series ARC ADF installed at the factory or an updated King ADF both of which had fixed antennas.

As far as airliners go, Really old ADFs like the Collins 51Y4 which you can still find on alot of 727/737/F28 era aircraft have fixed antennas as well.

The rotating type antennas can often be identified on old airplanes by the big tear drop fairing that is seen on many DC-3 pictures for instance. Not too many "modern" airplanes flying around with those.

So...when I said "modern" aircraft I meant pretty much anything produced in the last 50 years.
 
Ralgha
Posts: 1589
Joined: Tue Nov 09, 1999 6:20 pm

RE: ADF Antennas

Wed Feb 14, 2001 2:01 pm

Interesting, I didn't know that Big thumbs up
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