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Old 01-16-2021, 05:55 PM
funflying funflying is offline
Join Date: Oct 2006
Location: arvada, co
Posts: 464
Default Problems with SL40

My last two flights my comm radio, Garmin Apollo SL40, started a “feedback” noise when transmitting or a sound like a double transmission. The tower couldn’t hear me well at all but enough to continue. I knew at the first of the year I was going to start annual inspection so I decided to start checking the connections to and from the radio.
Pulled it out of the tray, looked okay, disconnected the coax at the antenna and it looked okay. Didn’t remove the antenna but what I could see looked good.
Talked to support at Garmin and they talked about a SWR test with equipment connected between the coax and the antenna. This would determine it the coax and antenna are good.
I contacted an avionics shop at my home airport and left the radio with them for a bench check. This revealed an “over modulation” condition. The tech said it was putting out 30 watts when it should be only 10 maybe 16 watts. The radio needed to go back to Garmin for service and this will cost $875 and I believe when it is returned it will have a 6 month warranty.
The avionics shop still recommend the SWR check to be sure the antenna is okay as a bad antenna or coax could cause the damage creating the over modulation.

Has this malfunction happened to others?
Hoping this radio is worth fixing. 7 years and 490hrs of operation but a pretty pricey repair cost.
Is there another radio that would use the same tray? Basically a direct swap?
What comm radio option comes with the current RV12s?
Patrick Claar
Arvada, CO BJC
RV12, #401, Flying 2013, N612PC
RV6, 1996-2010 sold
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Old 01-16-2021, 06:16 PM
Piper J3's Avatar
Piper J3 Piper J3 is online now
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,227

I had a problem with my SL40 last spring at 600TT. Turned out to be coax connector on back of tray was loose. Easy fix once problem was identified.

You might check VAF classifieds or eBay. Lots of panel upgrades being done, and every so often, a SL40 comes up for sale. Pretty sure you can do better than Garmin’s $875 plus shipping costs.
Jim Stricker
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 633

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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Old 01-16-2021, 07:57 PM
NinerBikes NinerBikes is offline
Join Date: Dec 2018
Location: Granada Hills
Posts: 1,040

My SL-40 might be up for sale if I ever get around to installing the GTR-200 that came with my plane, when I bought it. Previous owner never got around to installing it, either.
RV-12, #212 N72DJ, bought flying. A Blessing in disguise. Thank you Double D!

Last edited by NinerBikes : 01-16-2021 at 08:18 PM.
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Old 01-17-2021, 08:32 AM
funflying funflying is offline
Join Date: Oct 2006
Location: arvada, co
Posts: 464

If you do replace you SL40 I would be interested. Send me a PM or better yet an email or phone call (303-435-4098) if the swap occurs. Thanks
Patrick Claar
Arvada, CO BJC
RV12, #401, Flying 2013, N612PC
RV6, 1996-2010 sold

Last edited by funflying : 01-17-2021 at 08:35 AM.
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Old 01-17-2021, 09:41 AM
dothetime dothetime is offline
Join Date: Jul 2015
Location: Boynton Beach, Florida
Posts: 129
Default Garmin

Find a local ham radio operator
He can check your swr and antenna for you
I’m a ham and would be glad to assist a fellow pilot
As far as their claims of the radio putting out 30 wattsI highly doubt it.
Id buy a used radio before spending that much for a repair
It sound like it could be a antenna, or antenna cable problem, or a bad or missing ground.
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Old 01-17-2021, 04:55 PM
BobTurner BobTurner is online now
Join Date: Dec 2011
Location: Livermore, CA
Posts: 7,151

I wouldn’t recommend paying Garmin’s ‘one price’ repair option. This is a great radio, but it’s been out of production for some time, and some components are getting hard to find. Get a ham or the shop to check out all the connectors/coax/antenna, and if they’re okay, try to find a used SL-40.
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Old 01-18-2021, 01:19 PM
funflying funflying is offline
Join Date: Oct 2006
Location: arvada, co
Posts: 464

Thanks Bob and Dave!
I do feel a bit stuck with not a lot of options. I did see one used radio that sold for $600, but the couple others were a part of package with other avionics.
Then two avionics shops how had SL40s wanted $1,500+ for them. Might look into a more current radio or since I have a Dynon Skyview might look at their comm radio.
Patrick Claar
Arvada, CO BJC
RV12, #401, Flying 2013, N612PC
RV6, 1996-2010 sold
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Old 01-18-2021, 01:33 PM
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Walt Walt is offline
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,839

The Trig TY96A is the same rack size as the SL40, you still need to change the rack and rewire though. If I couldn't fit a GTR200 in the stack this would be your next best option I think. At some point repairing old equipment is just not worth it.
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
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RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
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