ADS-B for 1984 M20J with original equipment

Beard · July 24

I have a 1984 M20J with what I believe is original equipment. It has a King KT 79 transponder.

I want to install ADS-B, in and out.

Does anyone have any suggestions on what I should purchase that can be installed easily with my current equipment. I am not an expert on this stuff so if I have phrased anything awkwardly please excuse me.

**Fly Boomer** · July 24

16 minutes ago, Beard said:

I have a 1984 M20J with what I believe is original equipment. It has a King KT 79 transponder.

I want to install ADS-B, in and out.

Does anyone have any suggestions on what I should purchase that can be installed easily with my current equipment. I am not an expert on this stuff so if I have phrased anything awkwardly please excuse me.

I don't know anything about the costs, but I see a huge number of GTX-345s -- either going in to solve a problem like yours, or already installed in airplanes on the market.

Jackk · July 24

You sure you want ADSB?

If you really need it, or really really want it, Garmin GDL-82 or echoUAT and make sure it’s set to anonymous mode when squawking 1200.

There have been far to many people targeted by everyone from FAA, vector, crazy enviro/noise NIMBYs, to disgruntled coworkers/lovers/etc for me to take the financial and security risk of full time N number broadcasting ADSB.

ADSB was a good sales pitch for theoretical safety, but it has sadly turned into what it was always inevitably going to turn into

Personally I’d just get a stratus to get the weather and limited traffic advisories plus backup gyros/GPS/Hdg for foreflight, and call it a day.

**Ragsf15e** · July 24

40 minutes ago, Beard said:

I have a 1984 M20J with what I believe is original equipment. It has a King KT 79 transponder.

I want to install ADS-B, in and out.

Does anyone have any suggestions on what I should purchase that can be installed easily with my current equipment. I am not an expert on this stuff so if I have phrased anything awkwardly please excuse me.

Depending on how much work you want to do and how much money you’re going to spend, you’ll need to be careful about this. What are you going to use for your waas gps source? What are you going to display your adsb-in info on? These two questions will guide your process. Potentially the easiest way to go will be something like the wingtip nav light adsb out solution (uavionix skybeacon) coupled with a sentry or similar portable adsb-in that will display on an ipad. The skybeacon has its own internal waas gps and will work with your current transponder.
If you’re interested in a panel display, that will lead to a much different discussion.

ProtoFly · July 24

Understanding that there's mixed feelings about them, my plane 'came with' the uAvionics SkyBeacon TSO. It works with your existing transponder, and has its own WAAS source. Since I've had zero issues with it, I live with it, and added the SkySensor to the other wingtip to give me ADSB dual-band in, along with the LED position and strobes, which were a definite upgrade from the old nav lights.

That being said: It's not 1090, so that limits me to 17,999 altitude, and no flights into Canada. If something ever goes wrong with it, I'll be disabling the ADSB Out, and putting a 'proper' ADSB transponder in place of the Garmin 327. Probably will go with a Lynx NGT9000, as I had one of those in a Piper, and really liked it.

kortopates · July 24

Before you go with the wingtip uavonix solution consider this is dependent on your existing transponder. If you had a modern mode S transponder, like the above poster, it could be a fine solution for a J. But i would fear that your old KT-76a days are numbered. If your located under rule class airspace as I am your grounded when either of them stops working. So I would expect a GTN-345 would be a more reliable and integrated option. It does require a WAAS GPS position source or can be purchased with the added WAAS card for $600 more.
GDL-88’s lost popularity as soon as the GTX-345 came out and there are probably used ones still available on eBay.

Sent from my iPhone using Tapatalk

Jackk · July 24

27 minutes ago, ProtoFly said:

Understanding that there's mixed feelings about them, my plane 'came with' the uAvionics SkyBeacon TSO. It works with your existing transponder, and has its own WAAS source. Since I've had zero issues with it, I live with it, and added the SkySensor to the other wingtip to give me ADSB dual-band in, along with the LED position and strobes, which were a definite upgrade from the old nav lights.

That being said: It's not 1090, so that limits me to 17,999 altitude, and no flights into Canada. If something ever goes wrong with it, I'll be disabling the ADSB Out, and putting a 'proper' ADSB transponder in place of the Garmin 327. Probably will go with a Lynx NGT9000, as I had one of those in a Piper, and really liked it.

1090 does not allow anonymous mode, add to that a Mooney can make it from the lower 48 to AK without having to stop in Canada, and most make for a better cross country trip below FL180, al la not sure the 1090 juice is worth the squeeze

Jackk · July 24

22 minutes ago, kortopates said:

Before you go with the wingtip uavonix solution consider this is dependent on your existing transponder. If you had a modern mode S transponder, like the above poster, it could be a fine solution for a J. But i would fear that your old KT-76a days are numbered. If your located under rule class airspace as I am your grounded when either of them stops working. So I would expect a GTN-345 would be a more reliable and integrated option. It does require a WAAS GPS position source or can be purchased with the added WAAS card for $600 more.
GDL-88’s lost popularity as soon as the GTX-345 came out and there are probably used ones still available on eBay.

Sent from my iPhone using Tapatalk

Those old transponders are so basic they just keep going and going, I wouldn’t be too concerned.

If the sky beacon broke (not likely) you are not grounded if under airspace, just use this tool and get a exemption

https://www.faa.gov/air_traffic/technology/equipadsb/adapt

Funny thing is if you had a new ADSB transponder and it went out, you would be stuck as you wouldn’t meet the requirements for ADAPT

**anthonydesmet** · July 24

1 hour ago, Jackk said:

Personally I’d just get a stratus to get the weather and limited traffic advisories plus backup gyros/GPS/Hdg for foreflight, and call it a day.

That’s the way I went. ESG puts it ADSB-IN on your iPad in Florefight and gets you ADSB-out.

https://stratusbyappareo.com/products/stratus-transponders/?utm_medium=Search&utm_source=Google&utm_campaign=AppareoAviation&utm_content=StratusTransponders&gad_source=1&gad_campaignid=927090911&gbraid=0AAAAADHEuq3oudFNk-LRr1wvG-8ibYTMh&gclid=EAIaIQobChMIzP7Gy5rWjgMVoqJaBR1cey7HEAAYAyAAEgIgt_D_BwE

**MikeOH** · July 24

Another happy uAvionix Tailbeacon TSO owner here It was, by far, the low cost solution (about $2300 with installation). I was already using a Scout for ADSB-in ($200).

As far as the KT-76 croaking...well, mine did. Cost all of $125 to get a used one and my A&P friend had me buy him lunch to sign off the 'install'. That was 3 or 4 years ago. I'll just put another used one in when the 'new' one dies

EDIT: @Beard Sorry! I didn't pay attention to the fact you're in Canada. You will need the more expensive TailBeaconX with 1090 capability.

Elijah · July 24

I just went through this same calculation on my project last year - my conclusion was the Garmin GDL82. It has a built-in WAAS source and goes inline with your existing mode C transponder. I have an old KT-76 transponder. My thoughts were as follows:

There are a bunch of relatively inexpensive ADSB-in solutions out there (stratus, stratux, sentry etc) and I'm happy with that. In the panel ADSB-in adds a lot of cost over these solutions and I am always flying with an ipad or phone anyway.
The uAvionix skybeacon is the cheapest and easiest ADSB out solution, but I have had issues in other planes with their LED strobe making noise on the radio. It's out in the elements, plastic, and surely has limited life from that. The connection to the transponder is wireless and this makes the configuration a bit more fiddly to get it to reliably pickup your squawk code. It does support anonymous mode but you can only switch it from the app, while on the ground - also a bit fiddly.
The garmin GDL-82 is about the same price as the skybeacon and requires more install work. But, it's very robust and I have no doubt it will last for many years. It's hardwired to the transponder and as such is always synced to the squawk code. You can switch in and out of anonymous mode at any time. I mounted the GPS antenna on the tail behind the baggage area and the GDL box is in the belly under the passenger seat. I bought the GDL-82 used for $1200 and am very happy with it.

These are all "UAT" solutions and the only way to avoid your tail number going out on the air all the time. The other path you can take is a new transponder. As others have mentioned, the Garmin GTX-345 or Stratus ESG are popular. I considered both of those as well but given the cost and all the ADSB billing nonsense, the GDL-82 made the most sense to me.

BTW after a few cross country trips, I will say that FlightAware's coverage of the UAT frequencies is not that great.

Edit: just noticed you're in Canada. UATs are of no use for you there. The GTX-345 is the only transponder I'm aware of that has the required antenna diversity (antenna on top and bottom of the airplane). I think the uAvionix tailbeacon X would work as well.

Edited July 24 by Elijah

McMooney · July 25

if it's really all original, i'd go knx-375, adsb-in/out and gps

**rklems** · July 25

There are a lot of good options, new and used, but I think I'd start with, what are your plans with the panel longer term? I wouldn't spend time and money putting something in, that you might then end up yanking out in a couple years time if you are planning larger panel upgrades.

A GDL82 (not sold anymore by Garmin, but available used) can be interfaced easily with your existing transponder, and has it's own WAAS position source, but is a bit more invasive of an install than just tossing a tail beacon or wing tip device on, and I'd only recommend that option if your current transponder is still in good shape, and you didn't want to go with a nav-light based solution.

A GDL88+GTX330 can be had fairly inexpensively on the used market, and would get you ADS-B in/out (UAT out), but you'd need something in the panel to display the ADS-B in, if you don't have anything in the panel and wanted it to only display on a portable device, you'd also need to add a Flightstream 210, and would need to get a GDL88 with the position source, assuming you don't have a WAAS navigator already (if you are all original equipment, I'm guessing you don't!). The install would also be more involved as you would have a panel mount box and a remote mount box and the wiring between.

There are two options that are mostly all in one, and should likely fit in the same-ish space as your existing transponder (they are a bit taller) would be a GTX 345 or a GNX375. A GTX345 w/WAAS will do in and out, stream to your iPad or other portable without any additional equipment and provide its own position source. Other than adding the WAAS antenna, the install wouldn't be terribly involved, it should mount in the same space as the existing transponder. This will also interface well with any future panel modifications, like adding a GPS navigator etc. The GNX375 would give you the same in/out as the GTX345, as well as being a WAAS position source, it is also a WAAS navigator. You'd need somewhere to install an indicator, and it's a little more involved of an installation, but it's probably the most forward looking, and would open up the world of GPS navigation to your panel.

Something like a stratus ESG also works for easy ADS-B out with a modern transponder, but it can only use its own internal WAAS position source. The drawback of that is if you ever were to add a GPS navigator to the panel, you couldn't just use the antenna you installed for the stratus for the navigator, and then send position source over serial from the navigator to the ESG, so instead you have to add a second antenna. Plus it doesn't get you in, other than through essentially a portable device.

The Lynx NGT9000 is another interesting unit, would get you in/out as well as a minimal display for traffic and weather, but their big problem is support these days (L3 has sold them off), and it also doesn't interface completely with all panel mount stuff (some units you might be able to display traffic, but no weather, etc).

**Slick Nick** · July 25

20 hours ago, ProtoFly said:

Understanding that there's mixed feelings about them, my plane 'came with' the uAvionics SkyBeacon TSO. It works with your existing transponder, and has its own WAAS source. Since I've had zero issues with it, I live with it, and added the SkySensor to the other wingtip to give me ADSB dual-band in, along with the LED position and strobes, which were a definite upgrade from the old nav lights.

That being said: It's not 1090, so that limits me to 17,999 altitude, and no flights into Canada. If something ever goes wrong with it, I'll be disabling the ADSB Out, and putting a 'proper' ADSB transponder in place of the Garmin 327. Probably will go with a Lynx NGT9000, as I had one of those in a Piper, and really liked it.

You can fly into Canada without ADS-B at all. Even if you don’t have 978. It’s only “recommended” in class B (ours starts at 12,500) but it’s mandatory above 17,999.

**Aerodon** · July 25

23 hours ago, Beard said:

I have a 1984 M20J with what I believe is original equipment. It has a King KT 79 transponder.

I want to install ADS-B, in and out.

Does anyone have any suggestions on what I should purchase that can be installed easily with my current equipment. I am not an expert on this stuff so if I have phrased anything awkwardly please excuse me.

Beard,

UAT solutions (GDL82 etc.) do not work well in Canada. 1090Mhz systems do - good flight tracking etc. GTX335 / 345 etc.

Post a picture of your panel - my recommendation would be look at what is already installed and space available. You need a WAAS GPS position for an ADSB transponder. Or a Txpdr with a GPS, that leads to another GPS antenna and the costs associated with it. A GTX345 can get altitude form numerous sources, easiest is to install a GAE12, even if it is a second encoder. You might need to keep your encoder for a KFC150 autopilot?

Aerodon

**MikeOH** · July 25

1 hour ago, Slick Nick said:

You can fly into Canada without ADS-B at all. Even if you don’t have 978. It’s only “recommended” in class B (ours starts at 12,500) but it’s mandatory above 17,999.

Interesting! I did not know that.

However, a quick Google suggests that it may be required in Class C, D, and E airspace in 2028....something to consider.

**MikeOH** · July 25

3 minutes ago, Aerodon said:

Beard,

UAT solutions (GDL82 etc.) do not work well in Canada. 1090Mhz systems do - good flight tracking etc. GTX335 / 345 etc.

Post a picture of your panel - my recommendation would be look at what is already installed and space available. You need a WAAS GPS position for an ADSB transponder. Or a Txpdr with a GPS, that leads to another GPS antenna and the costs associated with it. A GTX345 can get altitude form numerous sources, easiest is to install a GAE12, even if it is a second encoder. You might need to keep your encoder for a KFC150 autopilot?

Aerodon

The TailBeaconX is $2500 (plus install, of course) which is going to be considerably cheaper. Just sayin'

**Hank** · July 25

45 minutes ago, MikeOH said:

The TailBeaconX is $2500 (plus install, of course) which is going to be considerably cheaper. Just sayin'

Yep, I just put one in last fall. On sale for $2100, and I forget the install, ~$300? It's two screws, three wires and the configuration. Then you need to do the ADSB flight around a VOR, 4 directions with prescribed climbs and descents so that the FAA can confirm that it works properly (95% or so).

**Slick Nick** · July 25

3 hours ago, MikeOH said:

Interesting! I did not know that.

However, a quick Google suggests that it may be required in Class C, D, and E airspace in 2028....something to consider.

They’ve pushed that deadline back 6 times now, I doubt it will be “mandatory” anytime soon. The adoption rate is abysmal because of the cost. NavCanada (our ATC provider) is a private, not for profit corporation that was given exclusive control of the skies way back when the federal government sold organizations off to balance their budget.

One of Navcanada’s not-so-brilliant ideas to save themselves money, was to decomission the ground based radar stations, in favour of a space based coverage solution. With the enormous geography of Canada, you can see why this is appealing. Without any public consultation, NavCan kept releasing “mandates” for 1090 ADS-B implementation. It’s worth noting there was also some funny business regarding the ownership of the satellites that were put up in orbit, as to who stands to profit from their use, etc. but I digress.

So, all of a sudden, the user (me) who ALREADY PAYS USER FEES is now told that I better hurry up and go spend $20,000 Canuckistan copecks on a fancy ADS-B install or else I’ll be grounded. Imagine being forced to buy something that expensive that you neither want or need?

It didn’t work. The adoption rate was so abysmal that NavCan had no choice but to leave their radar operational, and it’s been going on like that for close to a decade now.

I fly for the airlines and I’ve had the chance to sit down with some center controllers and discuss this. As far as they’re concerned, your ADS-B is invisible, unless they really go looking for your data which they have no time to do. The only time it’s of concern is when outside an area of radar coverage in the mountains, in which case they usually pick you back up on the other side shortly. The same thing they’ve done since radar was invented.

I don’t have ADS-B, even 978. I’m still on my original KT-79 Mode C. I fly across Canada up to 18,000 all the time IFR as well as down into the States frequently. Hasn’t been an issue. In fact, last week flying north from Provo, UT I had filed IFR way around the class B rule airspace. In addition to having the mode C equipment code on my flight plan, I reminded the SLC Center controller I was not ADS-B equipped, twice, and still I was provided clearance straight through the Bravo. They really didn’t seem to mind. Might have gotten lucky and they made an exception that day for the “silly Canadian in his little Mooney” but I can confirm, in Canada, you’ll have no problem getting around without ADS-B.

**Ragsf15e** · July 25

4 minutes ago, Slick Nick said:

They’ve pushed that deadline back 6 times now, I doubt it will be “mandatory” anytime soon. The adoption rate is abysmal because of the cost. NavCanada (our ATC provider) is a private, not for profit corporation that was given exclusive control of the skies way back when the federal government sold organizations off to balance their budget.

One of Navcanada’s not-so-brilliant ideas to save themselves money, was to decomission the ground based radar stations, in favour of a space based coverage solution. With the enormous geography of Canada, you can see why this is appealing. Without any public consultation, NavCan kept releasing “mandates” for 1090 ADS-B implementation. It’s worth noting there was also some funny business regarding the ownership of the satellites that were put up in orbit, as to who stands to profit from their use, etc. but I digress.

So, all of a sudden, the user (me) who ALREADY PAYS USER FEES is now told that I better hurry up and go spend $20,000 Canuckistan copecks on a fancy ADS-B install or else I’ll be grounded. Imagine being forced to buy something that expensive that you neither want or need?

It didn’t work. The adoption rate was so abysmal that NavCan had no choice but to leave their radar operational, and it’s been going on like that for close to a decade now.

I fly for the airlines and I’ve had the chance to sit down with some center controllers and discuss this. As far as they’re concerned, your ADS-B is invisible, unless they really go looking for your data which they have no time to do. The only time it’s of concern is when outside an area of radar coverage in the mountains, in which case they usually pick you back up on the other side shortly. The same thing they’ve done since radar was invented.

I don’t have ADS-B, even 978. I’m still on my original KT-79 Mode C. I fly across Canada up to 18,000 all the time IFR as well as down into the States frequently. Hasn’t been an issue. In fact, last week flying north from Provo, UT I had filed IFR way around the class B rule airspace. In addition to having the mode C equipment code on my flight plan, I reminded the SLC Center controller I was not ADS-B equipped, twice, and still I was provided clearance straight through the Bravo. They really didn’t seem to mind. Might have gotten lucky and they made an exception that day for the “silly Canadian in his little Mooney” but I can confirm, in Canada, you’ll have no problem getting around without ADS-B.

I agree. We had to spend ~30k to have “diversity” installed on our company PA-46T since we occasionally fly to Canada and go above 18k. Kinda overkill in the normal places we go (Calgary), but all to make the satellites work right!

Beard · July 25

Thank you everyone for the sage advice on ADS-B. I will ponder it and decide what to do.

Joshua Blackh4t · July 25

Australia is lucky that the government is giving a subsidy of 50% of the cost up to $5000 AUD per plane to install ADSB out.

It made Sentrys affordable for ultralights and made an AV30/Tailbeaconx about half price.

Yes, its annoying getting stalked but the amount of times it has made my life easier and safer makes it worth it. Especially at busy non controlled places and you get 3 people with bad radios in the same area, now instead of trying to work out what the little rag and tube things are doing you can see them on the screen.

And with the tailbeaconx, you can always forget to turn on the nav lights. Oh dear, small gap on flight aware. Happened to a friend of mine.

**Fly Boomer** · July 26

5 hours ago, Slick Nick said:

Canuckistan copecks

:lol: Best laugh I have had today.

Doug G · July 27

I don't know anything about the costs, but I see a huge number of GTX-345s -- either going in to solve a problem like yours, or already installed in airplanes on the market.

The GTX-345 isn’t cheap but is certainly one of the best, the Skybeacon will get you legal and the wingtip version can provide ADS-B in for very little money. It worked in my Swift just fine. As people have mentioned it depends on if you want to keep a basic panel or if you want to keep improving the avionics as many net becomes available. Spending the money once is better than doing the same thing twice.

Sent from my iPhone using Tapatalk

**Schllc** · July 27

On 7/24/2025 at 12:55 PM, Beard said:

I have a 1984 M20J with what I believe is original equipment. It has a King KT 79 transponder.

I want to install ADS-B, in and out.

Does anyone have any suggestions on what I should purchase that can be installed easily with my current equipment. I am not an expert on this stuff so if I have phrased anything awkwardly please excuse me.

OP said he had a 1984 with original equipment.
that would not include a gps…

that being said since Canada added the new requirement there are a lot of used 345’s on the market. Probably around 7k

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ADS-B for 1984 M20J with original equipment

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