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Topic Options
#90550 - 08/27/12 08:55 PM Advice for original radios
tim c172 Offline
Safety Pilot

Registered: 06/10/12
Posts: 46
Loc: Ca Van Nuys
I bought a 172M with orignal radios. Some times the tower can not hear me over the static. What should I do first, before spending money replacing radios?

Edited by California Flyer (08/28/12 12:18 AM)
Edit Reason: edited for clarity since this was split off from another thread

#90559 - 08/27/12 09:47 PM Re: East Coast Avionics Repair Shop ? [Re: tim c172]
Don Tedrow Offline
Platinum Pilot

Registered: 07/16/10
Posts: 3659
Loc: Bastrop, TX
Originally Posted By: tim c172
different question. I bought a 172M with orignal radios. Some times the tower can not hear me over the static. What should I do first, before spending money replacing radios?

As a retired Air Traffic Controller who dealt with lousy radios weekend after weekend, my suggestion for your first action would be to remove the original radios and bury them in a landfill. Second action would be to buy a quality headset. Then third, go buy some good reconditioned King radios or new Garmin.

But that's just me. grin

btw, I spent over $2k tweaking and tuning my King radios and on a DC H10-60, just so I wouldn't be one of those guys.
1972 F33A Bonanza

#90595 - 08/28/12 07:23 AM Re: East Coast Avionics Repair Shop ? [Re: Don Tedrow]
IDontFly Offline
Gold Pilot

Registered: 06/22/10
Posts: 1304
Loc: Massachusetts, USA
Before you take Don's advice, check the local ordinances about disposing of electronic equipment in a landfill. You may be required to recycle the radios.

Do you have two radios? Does this happen with both? Does it happen with more than one headset? Does it happen if you plug the headset into the copilot's connections?

The original Cessna ARC radios that are probably in your airplane have a bad reputation for quality and reliability. But if you are lucky the problem is a bad cable or connection.

#90599 - 08/28/12 07:55 AM Re: East Coast Avionics Repair Shop ? [Re: IDontFly]
TheSRQPilot Offline
Pilot in Command

Registered: 04/20/12
Posts: 405
Loc: Florida
When I mentioned that I was getting static in my headset to the owner of the 172 I used to fly he cleaned out the metal in the ports where I would plug in my headset and it worked fine after that.

And if you do decide to a radio shop there's a great place called Sarasota Avionics here at the Sarasota/Bradenton Int'l airport smile

#90600 - 08/28/12 08:01 AM Re: East Coast Avionics Repair Shop ? [Re: IDontFly]
Don Tedrow Offline
Platinum Pilot

Registered: 07/16/10
Posts: 3659
Loc: Bastrop, TX
You may very well have a bad cable/connection in one of the radios, and if you can get one of them to receive acceptably, then you might keep it just for listening to ATIS or such.

However, if they are original 1970s Cessna/ARC, then it's highly unlikely they are 720/760 channel capable. You need at least one radio that is newer and meets the FCC specs to transmit/receive 25 kHz freqs.

As of January 1, 1997, each VHF aircraft radio used on board a U.S. aircraft must be type accepted by the FCC as meeting a 30 parts-per-million (ppm) frequency tolerance (47 C.F.R. 87.133). The vast majority of aircraft radios that have been type accepted under the 30 ppm frequency tolerance utilize 25 kHz spacing and have 720 or 760 channels. Each aircraft radio has a label with an FCC ID number on the unit.
This rule applies to all U.S. aircraft radio stations, including those no longer required to be licensed individually. The effect of this rule is to require a 30 ppm type accepted radio to be placed on board if the pilot intends to use a VHF aircraft radio for communications. There is no requirement, however, for an older radio to be removed from an aircraft in cases where the pilot does not intend to use it to transmit radio signals (e.g., receive-only operation, an integral part of a navigation/communications unit, or decoration in a vintage aircraft).
A radio which has not been type accepted as 30 ppm may not be returned to service by simply changing the crystals, or adjusting the unit to meet the 30 ppm frequency tolerance. The only way to bring a unit into compliance is through the installation of an FCC type accepted "upgrade kit," which may be available from the unit's manufacturer. Like the radio itself the upgrade kit will have an FCC ID number that may be verified against the FCC Aircraft Radio List. Presently, however, few manufacturers offer FCC type accepted upgrade kits. If a kit is not available for a particular model of radio, the radio may not be adjusted and used for communications purposes on board an aircraft. If no kit is available, the radio may be reinstalled in the aircraft so long it is not intended to be used to transmit radio signals.
The Commission adopted the 30 ppm frequency tolerance in 1984 in order to conform its rules with those adopted internationally in the Final Acts of the World Administrative Radio Conference, Geneva, 1979. At that time, this action was endorsed by the Federal Aviation Administration (FAA) and was strongly supported by Aeronautical Radio, Inc., the Air Line Pilots Association, the Air Transport Association, and the National Business Aircraft Association, Inc. This action was found to be consistent with the FAA's three-phase plan to implement 25 kHz channel spacing in the 118-137 MHz band, which creates more radio channels for use by pilots. These organizations also noted that users of older radios would have limited access to FAA air traffic control channels, would experience flight delays in FAA controlled air space, and would be unable to utilize newly available aviation frequencies in the 136-137 MHz band. Based on comments by the FAA and the other groups listed above, the Commission determined that permitting the continued operation of older radios type accepted prior to 1974 would pose a threat to safety in air navigation.
1972 F33A Bonanza

#90773 - 08/29/12 01:01 PM Re: East Coast Avionics Repair Shop ? [Re: Don Tedrow]
Mslisaj Offline
New Member

Registered: 04/27/11
Posts: 17
Loc: Klamath Falls, Oregon
I still have the pair of RT 328-T radio's in my XP. They work great in warm weather or when they get above 45 degrees (I work better then too). Money is the big deal why some of us just don't go out and do the glass panel thing so we have to fly behind these radios. I will attest that when these radio's are working they can't be beat and that is 90% of the time; thus two radios.

On the pin's and connection issues yes this can be a problem. I have sprayed contact cleaner into the sockets and this solves a lot of problems for quite a while. A radio shop that I was lucky to have at my home airport gave me this trick.

The bottom line is they are not bad radios, contrary to popular belief. You just need a good avionics tech once in awhile and for little money can keep them going and going well.


#90796 - 08/29/12 03:29 PM Re: East Coast Avionics Repair Shop ? [Re: Mslisaj]
Don Tedrow Offline
Platinum Pilot

Registered: 07/16/10
Posts: 3659
Loc: Bastrop, TX
The Old Mk-12As worked great when you could take them to the avionics shop to be tuned up every six months. I used to watch the techs change the crystals in the tuner that looked like half an ear of corn. (They always needed a couple crystals)

I don't have, nor really want glass, but I have a KY-197 and a KX-125, along with a KNS-80 Rnav, all of which function very well. You can buy all three together, reconditioned, and have them installed for less than half what a Garmin 430 costs. And they are 760 ch radios.
1972 F33A Bonanza

#90819 - 08/29/12 06:54 PM Re: East Coast Avionics Repair Shop ? [Re: Don Tedrow]
IDontFly Offline
Gold Pilot

Registered: 06/22/10
Posts: 1304
Loc: Massachusetts, USA
The original radios are Cessna ARC, right?

Here's what I would do.

First, I would see if it is one radio or both.

If it is one radio I would remove it from the panel clean the contacts, and re-install it. If it still happened I would swap the two radios and see if the problem moved. If the problem moved it is likely to be the radio and I would consider having it repaired or I'd look for another - lots of people probably have them in their basements because they have removed them to install newer stuff.

If the problem is in both radios I would try to remove the audio panel, clean the contacts, and re-install it. If this doesn't fix it, I would consider it time to spend money at an avionics shop.

I think the owner/pilot is allowed to remove and re-install the radios. It probably needs to be logged.

Replacing the avionics stack is a great idea but if the owner bought the plane recently he probably wants to let his bank account recover a bit first.

#90869 - 08/29/12 11:35 PM Re: East Coast Avionics Repair Shop ? [Re: IDontFly]
Ed M Offline
Second in Command

Registered: 08/31/10
Posts: 134
Loc: Oregon, USA
Check out CFR 43 Appendix A (c)(31)to see what you can do as a pilot regarding avionics,then see 43.3(g), 43.5, 43.7, 43.9, and 43.13 to see how to perform and record your prevenative maintenance.

#91859 - 09/06/12 08:57 PM Re: East Coast Avionics Repair Shop ? [Re: Ed M]
Glenn Darr Offline
Club Sponsor
Gold Pilot

Registered: 03/01/10
Posts: 1708
Loc: Arizona
I use KX-175B radios in my plane. You can buy rebuilt ones for as low as 6-700 dollars. They are cheap and they are good. You don't need to spend money for a glass panel just to have good radios. I take my radios out once in a while and use a pencil eraser on the connectors to clean them up a bit. Also work the knobs back and forth the help keep those contacts clean.
1969 172K

#94670 - 09/27/12 11:49 PM Re: East Coast Avionics Repair Shop ? [Re: Glenn Darr]
LV-CWK Offline
Safety Pilot

Registered: 09/27/12
Posts: 29
Loc: Buenos Aires, Argentina
If TWR is not hearing you while in close range (visual) first try making sure all RF contacts are clean (output connector in radio and back panel, inputs to antenna/s, etc.), then check coax cable condition if possible.
If contacts, cables and antenna/s are in good shape it may be the final RF transistors in the radio... before sending the radio to the shop, if possible, you may measure inline SWR (using a SWR meter between the radio and the coax connector of the cable running to the antenna, that will ensure theres no mismatch in the RF line, correct antenna resonance, and additionally the meter will allow you to make sure the radio is actually delivering abt 10 watts that is the average expected RF power). If none of this gives you a clue its time to send the radio to repair, but most radios are quite abuse-resistant so its probably a problem with poor contacts, try fixing it asap as it may lead to final transistors burn (costly repair). By the way what abt reception? if theres a contact problem you should also experience degraded reception/range...

Good luck!

#94672 - 09/28/12 12:05 AM Re: East Coast Avionics Repair Shop ? [Re: LV-CWK]
LV-CWK Offline
Safety Pilot

Registered: 09/27/12
Posts: 29
Loc: Buenos Aires, Argentina
CONTINUED: I forgot to mention, if you are using an audio box make sure all audio/PTT and mic conections are also clean and secured, remove and reinstall the audio box in place and re-check radio performance, may be the problem is not in the radio but in the line instead...

If theres a RF poor contact in the radio to antenna line you should also experience poor reception, but if reception is still good even in mid-long range then it may be the final stage transistors (no TX or low power) or an issue with the microphone or audio connectors...

#98923 - 11/01/12 04:04 AM Re: East Coast Avionics Repair Shop ? [Re: LV-CWK]
brfly Offline
New Member

Registered: 10/31/12
Posts: 15
Loc: Ukraine, Borispil
Someone, gentlemens.
Can you halp me with (link or other documentation)schematic manuals or repair manuals of radio RT-385A.


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