KX 155 Issue

Soldier64

Soldier64

Pre-takeoff checklist
Joined
Oct 20, 2013
Messages
257
Location
Fort Rucker, AL
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Display name:
Bill H.
Well, I got in the airplane yesterday and the KX 155 is nothing but squelch. I tried a bunch of different freqs, made sure the squelch knob was in, and finally I pulled it to clean the contacts. I reinstalled the radio and still the same issue.

Any ideas? Thanks.
 
Soldier64 said:
Well, I got in the airplane yesterday and the KX 155 is nothing but squelch. I tried a bunch of different freqs, made sure the squelch knob was in, and finally I pulled it to clean the contacts. I reinstalled the radio and still the same issue.

Any ideas? Thanks.
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I don't understand what you mean, "nothing but squelch"???

Jim
 
Since he was making sure the squelch knob was in I am thinking he was hearing all static.

Could be wrong though.
 
Squelch circuit or filter is probably blown. As said you're going to have to take it to the shop, you ain't gonna get it fixed here.
 
Yeah, sorry it's all static. I assumed t was going to need to go to a shop, but I wanted to see if anyone knew of an issue common to the radio that I didn't. Thanks.
 
I was all static and then I realized that it was because of the USB charger I had. When I unplugged all of the 12v chargers and stuff and all other electronics it works fine.
 
ahkahn said:
I was all static and then I realized that it was because of the USB charger I had. When I unplugged all of the 12v chargers and stuff and all other electronics it works fine.
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Mmmmm. Cheap Chinese dogfood. Tasty.
 
I may have to see if my charger is messing with anything. My King KX 170B Nav/Com is acting funny. Isnt picking up anything, I flipped it to "test" in flight yesterday and heard static and what sounded like a social conversation on a radio somewhere, but I was on the local ATIS frequency about 10 miles from the airport.

One time last week it didnt pick up anything either, until we were on the ground.
 
Soldier64 said:
Well, I got in the airplane yesterday and the KX 155 is nothing but squelch. I tried a bunch of different freqs, made sure the squelch knob was in, and finally I pulled it to clean the contacts. I reinstalled the radio and still the same issue.

Any ideas? Thanks.
Click to expand...

Did you try local AWOS/ASOS? Did you try radio check with somebody with a known good radio? Do you get sidetone?
 
gitmo234 said:
I may have to see if my charger is messing with anything. My King KX 170B Nav/Com is acting funny. Isnt picking up anything, I flipped it to "test" in flight yesterday and heard static and what sounded like a social conversation on a radio somewhere, but I was on the local ATIS frequency about 10 miles from the airport.

One time last week it didnt pick up anything either, until we were on the ground.
Click to expand...
If I have a charger plugged in to my power outlet (12VDC in dash, just below the radio stack), both of my radios go haywire.
 
I brought the radio to the local avionics shop. Apparently the receive level was so low that it was picking up local radio stations and everything over the waves causing the static.
 
Soldier64 said:
I brought the radio to the local avionics shop. Apparently the receive level was so low that it was picking up local radio stations and everything over the waves causing the static.
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Wow. The stories avionics shops will tell pilots. LOL.

Receive level is called "sensitivity" and ability to not receive unwanted things is called "selectivity" and the two are polar opposites in RF engineering.

Generally if you raise one you lower the other.

Probably just aligned the thing per the book. Which really just entails injecting a weak signal with a signal generator and tuning pre-selector cavities so they're both properly selective at the desired frequency (pass) and band reject filtering of the relatively nearby FM broadcast band (reject).

I doubt they did anything to make the receiver itself more sensitive. Just adjusted the filters so they allowed the correct portion of the band through.

On the test gear, with the tuning misaligned, the result will be a weakly received signal, but not because the radio isn't sensitive enough. It's because the front-end filter is wiping out all the signal before it ever makes it to the rest of the receiver. A little twist of the non-conductive diddle stick, and boink... Big signal. And magically the other stuff isn't heard anymore either.

The more interesting question is why did it go out of alignment: Broken ferrite slug? Corrosion? Vibration? Capacitor drying out? Tin dendrites? Etc.

Kids. Sometimes they even forget what frequency excites water molecules and operates the microwave oven in the kitchen, and wonder if they've just found space aliens...

But really they're just watching Bob heat up a Hot Pocket for lunch...

http://www.abc.net.au/news/2015-05-...rcSite=news&WT.z_link=Change+to+standard+view
 
denverpilot said:
Wow. The stories avionics shops will tell pilots. LOL.

Receive level is called "sensitivity" and ability to not receive unwanted things is called "selectivity" and the two are polar opposites in RF engineering.

Generally if you raise one you lower the other.

Probably just aligned the thing per the book. Which really just entails injecting a weak signal with a signal generator and tuning pre-selector cavities so they're both properly selective at the desired frequency (pass) and band reject filtering of the relatively nearby FM broadcast band (reject).

I doubt they did anything to make the receiver itself more sensitive. Just adjusted the filters so they allowed the correct portion of the band through.

On the test gear, with the tuning misaligned, the result will be a weakly received signal, but not because the radio isn't sensitive enough. It's because the front-end filter is wiping out all the signal before it ever makes it to the rest of the receiver. A little twist of the non-conductive diddle stick, and boink... Big signal. And magically the other stuff isn't heard anymore either.

The more interesting question is why did it go out of alignment: Broken ferrite slug? Corrosion? Vibration? Capacitor drying out? Tin dendrites? Etc.

Kids. Sometimes they even forget what frequency excites water molecules and operates the microwave oven in the kitchen, and wonder if they've just found space aliens...

But really they're just watching Bob heat up a Hot Pocket for lunch...

http://www.abc.net.au/news/2015-05-...rcSite=news&WT.z_link=Change+to+standard+view
Click to expand...

Well, I'm not an avionics guy. I came here to ask for common problems and the first response was "take it to an avionics shop." I have no idea what was the root cause or if it will happen again in 200 hours. I guess we shall see.

I appreciate your explanation. I am decent with mechanical things but electrons are f'n magic...
 
Soldier64 said:
Well, I'm not an avionics guy. I came here to ask for common problems and the first response was "take it to an avionics shop." I have no idea what was the root cause or if it will happen again in 200 hours. I guess we shall see.

I appreciate your explanation. I am decent with mechanical things but electrons are f'n magic...
Click to expand...


No worries.

Technically the coils are a mechanical thing. ;)

I bet anyone reading here, could be shown how to align that thing with the right test gear and tools and a proper service manual, and they'd "get it" pretty easily.

It only gets difficult if a stage has failed or a power supply section isn't doing its thing. Finding dead or intermittent components is as much science as art.

It'd be fun to dabble in avionics work, but the requirement to get a full A&P to do so, kinda kills the interest for me. That and the price tags if you let the magic smoke out.

A good friend worked for a couple of big name avionics places in Kansas in the 60s-70s and ferried a bunch of new Cessnas rolling off the assembly line to their new homes out West. He has fun stories.

He bailed and founded a fire alarm company he ran as his own thing for over two decades. Paid tons better. He recently retired to a chunk of property not too far from where we live, and he spends his time tinkering on his new tractor and playing banjo. Once in a while we get him to climb trees and hang antennas to play with, while we laugh and call him a "wire guided squirrel".

For me, IT pays the bills better. Slapping 80 GB of RAM and a couple of Terabytes worth of 15K RPM server hard disks into a couple of Dell servers was my evening's fun.

Here's hoping that King hangs in there for a long time. I prefer their audio quality over Garmin's tinny sounding radios any day of the week.
 
denverpilot said:
Here's hoping that King hangs in there for a long time. I prefer their audio quality over Garmin's tinny sounding radios any day of the week.
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Heh.

When I absolutely, positively have to pick a weak transmission out of the ether, nothing works like my good ol' Narco - beats the Garmin 430W by a mile (actually, a bunch of 'em). Especially important when I am flying right over the Cedar Hill antenna farm (every TV and radio station in north Texas broadcasts from there), where the Garmin gives nothin' but noise while the Narco has a very clear signal.
 
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