Comm and Nav Antennas For a GNS 430W and KX-155

Arrow3_Dawg

Arrow3_Dawg

Filing Flight Plan
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Feb 1, 2019
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John B
Greetings,

In the very near future, I’m going to be swapping out the old MAC 1700 navcomms for a 430W and a KX-155 (w/ gs) on my Arrow III. It is during that time I plan on replacing the old comm and nav antennas with new ones. My question is what specific model should I replace the comm antennas with, and same for the nav’s. I want to get rid of the silly looking “V” glide slope antenna on the forward top of the fuselage. Any suggestion would be greatly appreciated!

John
 

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Do you have another nav antenna for vor's...where is your other com antenna ?
 
That silly looking antenna gets a better signal than you'll get from a shared tail mounted VOR antenna.
 
Doug Reid said:
Do you have another nav antenna for vor's...where is your other com antenna ?
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I have the standard wire type antenna mounted on the top of both sides of the vertical stab.
 
dmspilot said:
That silly looking antenna gets a better signal than you'll get from a shared tail mounted VOR antenna.
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I would think that a glideslope antenna from 1977 wouldn’t work as well as something more modern?
 
dmspilot said:
Aircraft structure blocks the signal.
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When you are working with 10 watts of power at 10 mile range, you couldn't block the signal with a baseball bat. And, the rudder tip sight distance to the glideslope transmitter is a LOT better than the fuselage mounted GS antenna.

Jim
 
weirdjim said:
When you are working with 10 watts of power at 10 mile range, you couldn't block the signal with a baseball bat. And, the rudder tip sight distance to the glideslope transmitter is a LOT better than the fuselage mounted GS antenna.

Jim
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Personal experience suggests otherwise. And the sight distance from the tail is not better. So you think aircraft manufacturers thought it was worth it putting an extra, inferior antenna in the prop wash because... :confused2:
 
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dmspilot said:
Personal experience suggests otherwise.

My personal experience with avionics, especially antennas, started in 1957. Along the way I did a few antenna things you might have heard of. Surveyor? Apollo? Voyager? Bellanca? Almost every "plastic" homebuilt from my invention in 1974 of the invisible internal antenna systems that outperform the external excited porcupine quills?

And the sight distance from the tail is not better. Greek feller by the name of Pythagoras takes issue with you.

So you think aircraft manufacturers thought it was worth it putting an extra, inferior antenna in the prop wash because... :confused2: Same reason Detroit and Hiroshima will put chrome bumpers on your new car as "optional equipment" that they make a LOT of money on. Makes the car go faster and gets better gas mileage, don'cha know?

Never said the antenna was inferior, just not necessary.
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Now you tell me. The difference in wavelength between a VOR/LOC antenna and the glide slope frequencies is almost exactly 3:1. So you tell me, sir, if a half-wave dipole has a gain of 2.15 dBi at the fundamental frequency, what is the gain at the 3rd harmonic?

Jim
 
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weirdjim said:
Now you tell me. The difference in wavelength between a VOR/LOC antenna and the glide slope frequencies is almost exactly 3:1. So you tell me, sir, if a half-wave dipole has a gain of 2.15 dBi at the fundamental frequency, what is the gain at the 3rd harmonic?

Jim
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I am talking about the location of the antenna, not the kind of antenna.
 
Seems like everyone wants to remove all the antennas except gps and com. I guess that makes me a relic...I still use VOR's, DME and occasionally MB and ADF along with GPS. Jim, my math is rusty, but if you have a dipole and use it on the third harmonic it should have gain 2-3db over the fundamental ?
 
Doug Reid said:
Jim, my math is rusty, but if you have a dipole and use it on the third harmonic it should have gain 2-3db over the fundamental ?
Click to expand...

Yup. Halfwave dipole on the fundamental is 2.15 dB over omnidirectional (isotropic) antenna, and on the third harmonic the gain is 3.5 dBi. Your math isn't all THAT rusty :cheerswine:

Jim
 
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