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Whats a decent used transponder that can be upgraded to ADSB Out?

lndwarrior

Well Known Member
I don't have a glass panel, basic steam gages only. I want to buy a used transponder that I can later connect to in ADSB out system.

Can someone recommend a decent used transponder that would have this capability?

TIA
Gary
 
transponder

Gary, you don't upgrade transponders for ADS-B.
You just get a UAT (universal access transceiver) for ADS-B from any of a variety of manufacturers. They either listen for the transponder code, or hook directly to it via serial link. There is a ton of reading material on line that will explain it for you. But, shopping for an antique transponder would be a waste of money. You can also buy a brand new modern xponder that has ADS-B capability built in. A few thousand $ for those.
 
Let me re-phrase.

I want to buy a used transponder that i can later use with an ADSB out solution. I dont want to spend the money on a new Tx if i dont have to.

I have seen a number of posts that suggest that this is possible.

I am trying to learn which common Txs that come up for sale may be appropriate.

Ive seen refernce to some of the Garmin ones that may work for me. I am trying to figure out which model numbers would work.

It is my Understanding that there are a number of transponders that are being replaced due to panel upgrades that would still work for my situation.

I am trying to do this as inexpensively as possible.
 
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I have a Garmin GTX 327 in my 9. I just ordered the GDL82 from Stein Air. The GDL82 will connect to my GTX327. That will give me ADS-B Out at a very reasonable cost. Installation is very straight forward.
 
Oh boy... here we go!

Just about ANY functioning transponder capable of doing Mode C altitude reporting will work as the basis for an ADSB-Out solution IF you want to use a 978 UAT device. The 978 UAT device "sniffs" the squawk code and altitude of your Mode C transponder and uses that information in the 978 ADSB-Out data stream.

That's one method of gaining "out" compliance and many folks see it as the most economically-effective method because they can keep on using their ancient Mode C transponder.

Another method uses a fancier transponder, what we call a Mode S Extended Squitter (Mode S-ES). This type of transponder doesn't require that you add a 978 UAT device. Instead, the Mode S-ES transponder, when coupled to an altitude encoder source and an appropriate GPS position source, IS your ADSB-Out solution.

You need to educate yourself a bit before deciding which route you wish to take, 978 UAT or Mode S-ES. Once you've decided which route you want to take, then start looking at the specifics of which equipment to buy.

The SEARCH function here is a great way to get some good data points drawn from the experiences of others. Spend some time reading and learning, then come back with questions once you've got yourself up to speed.
 
Oh boy... here we go!

Just about ANY functioning transponder capable of doing Mode C altitude reporting will work as the basis for an ADSB-Out solution IF you want to use a 978 UAT device. The 978 UAT device "sniffs" the squawk code and altitude of your Mode C transponder and uses that information in the 978 ADSB-Out data stream.

That's one method of gaining "out" compliance and many folks see it as the most economically-effective method because they can keep on using their ancient Mode C transponder.

Another method uses a fancier transponder, what we call a Mode S Extended Squitter (Mode S-ES). This type of transponder doesn't require that you add a 978 UAT device. Instead, the Mode S-ES transponder, when coupled to an altitude encoder source and an appropriate GPS position source, IS your ADSB-Out solution.

You need to educate yourself a bit before deciding which route you wish to take, 978 UAT or Mode S-ES. Once you've decided which route you want to take, then start looking at the specifics of which equipment to buy.

The SEARCH function here is a great way to get some good data points drawn from the experiences of others. Spend some time reading and learning, then come back with questions once you've got yourself up to speed.

Thanks for taking the time to explain. I appreciate it!
 
GTX-330

Can someone recommend a decent used transponder that would have this capability?

TIA
Gary

You can get a Garmin GTX-330 and upgrade it to Extended Squitter for $1400 ( I think it used to be $1200).

Lately it seems like the going price of a used GTX-330 is in the $800 range.
 
Would a used King KT76 or KT76a with an altitude encoder work. Looks like a lot of these will be available for a couple of hundred dollars as aircraft are upgraded to Mode S installations. It would give you a mode C (978 MHz) transponder. At a later point you could add one of the 978UAT ADS-B out solutions like the uAvionix or Garmin GDL82.

Put the FAA rebate on this and you are 2020 compliant for around 1
$1500. At some point pick up a spare KT76 and you are good to go for several years.

-larosta
 
FAA rebate

I believe the FAA rebate this time is only for certified systems. So, just the expensive all in one new transponders.
 
Thanks for taking the time to explain. I appreciate it!

One additional note...the FAA doesn't allow UAT for ADS-B Out in Class A airspace (usually 18,000' MSL and above). You'd have to equip with a Mode S Extended Squitter transponder if you plan to fly that high - may not apply to you, but some RVers do occasionally punch up into Class A. If you go with a used GTX-330 solution and have a compliant GPS you're covered everywhere if Garmin will still upgrade the -330 for ADS-B Out.

Apologies if I'm telling you something you already know! :)

Dave
 
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GTX-327

You can buy a used GTX-327 Xponder with tray for around $500, will work with the GDL-82 or microavionix ADSB out solutions. Garmin will normally update the 327 software for free at Oshkosh (you need the latest version to use with the GDL-82). Good Xponder, easy to use.
Figs
 
I believe the FAA rebate this time is only for certified systems. So, just the expensive all in one new transponders.

Not so Oaklandaviator, I got the rebate with the GDL-82 that is connected to my GTX-327 transponder. They work amazing together. The GDL-82 works with ANY mode c transponder.

As uk_figs pointed out, you could cover the cost of a used 327 with the rebate. You could be 2020 compliant for about $1800 with ALL GARMIN equipment.
 
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Garmin 330

That's right "MODE C" , not "MODE S". The Model GDL82 will not
work with a Garmin 330 (also 33). John
 
For about the same money as an old transponder and GDL-82, you can buy a Trig TT22 and GPS thats brand-new.

I've installed a GDL-82 and wouldn't do it again.
 
Glad I was wrong

Very good to hear that the rebate applies to more combinations than I thought. I've got to get our RV-3 compliant soon.
 
...If you go with a used GTX-330 solution and have a compliant GPS you're covered everywhere if Garmin will still upgrade the -330 for ADS-B Out.

Apologies if I'm telling you something you already know! :)...

...I need to do more homework!

I have 2 airplanes that need ADS-B

RV-8 has a GNS430 (non WAAS) and a GTX330 (Non ES);
Rocket has GTN650 and a GTX327

Sounds like I can upgrade the 330 to an ES and toss it in the Rocket and that ones good. The 327 goes in the -8 and I use an add on UAT device to satisfy THAT bird.

I guess the current rebate will defray some of the 330 rework cost?
 
Need Waas

Micheal. I think you’ll need waas as well... I have the 430w and 330. Had the 330 upgraded to 330ES and then had to have the 430w software upgraded to latest release. ES upgrade had to go back to Garmin. Stark aviation was able to upgrade 430w in their shop...

All’s fine on the ADS-b out.... now if I could get the stratux to display ADS-B In on the AFS4500.

Nothing easy...
 
Would a used King KT76 or KT76a with an altitude encoder work. Looks like a lot of these will be available for a couple of hundred dollars as aircraft are upgraded to Mode S installations. It would give you a mode C (978 MHz) transponder. At a later point you could add one of the 978UAT ADS-B out solutions like the uAvionix or Garmin GDL82.

Put the FAA rebate on this and you are 2020 compliant for around 1
$1500. At some point pick up a spare KT76 and you are good to go for several years.

-larosta

This is one solution and could be an upgrade path for me, as I have one of the King KT76A's in my airplane. The downside is that an add-on 978UAT would be a halfway step (basing the system on an obsolete transponder) and wouldn't provide ADSB in.

The good side of a 978UAT solution is that most of them (all of them?) have an anonymous mode if you don't want people to track your N-number. For whatever reason, the idea of my personal exact whereabouts being broadcast to the world isn't something I like.
 
...I need to do more homework!

I have 2 airplanes that need ADS-B

RV-8 has a GNS430 (non WAAS) and a GTX330 (Non ES);
Rocket has GTN650 and a GTX327

Sounds like I can upgrade the 330 to an ES and toss it in the Rocket and that ones good. The 327 goes in the -8 and I use an add on UAT device to satisfy THAT bird.

I guess the current rebate will defray some of the 330 rework cost?

Michael, a couple of points, if I may?

1) the RV8 will need an approved position source. Upgrading the 430 to 430W is an expensive path. Consider, rather, selling the 430 and installing an Avidyne IFD440 in the same tray. A bit more money to get a brand new GPS with a better user interface

2) the 330 is a different form factor than the 327. Check available depth behind the 327 tray as the 330 is longer which might make this swap a bit of a challenge from a mechanical standpoing.

While the upgrade of the 330 is a relatively inexpensive thing to do since you already own the 330, the other costs of the 330 are significant to others who may be considering installing a 330. It's heavy, power-hungry and takes up a fair bit of panel space. For some who don't already have a 330 in their panel, consider other options such as the Trig TT22.

For those with a KT76 that might be of dubious longevity, it's worthwhile to look at the Trig slide-in replacement transponder, the TT31. With an appropriate position source you could easily be 2020 compliant and have a solid solution based on Mode S-ES.

As for position sources, even those folks with a straight GNS430 might want to consider a less-expensive solution like GRT's SafeFly GPS module. At $500 it's a lot cheaper than a WAAS upgrade on a 430.
 
Question for Canadian Joy

When you write that the 330 is power hungry, can you please tell me how many amps? Thanks
 
Easy ADS-B out

If you own a GTX327 then the purchase of a GDL82 for $1800 is all you need.
The GDL82 contains the required WASS GPS and is simply installed between the GTX327 RF cable and the antenna. Then there's a power, a ground, and a serial to you altitude encoder source and you're done. Four wires!

I installed one in a friends RV-8. It was easy and strait forward. The GDL82 will work with other mode C transponders as well.
 
For those with a KT76 that might be of dubious longevity, it's worthwhile to look at the Trig slide-in replacement transponder, the TT31. With an appropriate position source you could easily be 2020 compliant and have a solid solution based on Mode S-ES.

Does this solution retain an anonymous mode?

Would one of the $500 GPS pucks from GRT or others serve as a GPS source?
 
Does this solution retain an anonymous mode?

Would one of the $500 GPS pucks from GRT or others serve as a GPS source?

Yes, the $500 GRT GPS source is compatible with these transponders.
As these are mode S-ES transponders, not UAT, they do not have an anonymous mode. But you can go over 18,000? with them!
Honestly, I think the anonymous mode is over-sold. It?s only a matter of time before some web site like liveATC.com links your n number transmission at takeoff with your ADSB out fake number.
 
OP - Whats a decent used transponder that can be upgraded to ADSB Out?

This has become an interesting and informative thread. I am not sure that we have provided the information that Gary was looking for in his original post. I was under the impression that he was looking for an inexpensive transponder that he could install in the near term that still had the capability to be upgraded to ADS-B in the future. There are probably several budget minded builders out there that are looking for something along these lines. By the same token there are probably several persons here that have/are upgrading a KT76(a) installation that would be willing to sell Gary a working / used transponder for a very low price. I may be there myself in a few months.

We may have drifted a few degrees away from that.

- larosta


I don't have a glass panel, basic steam gages only. I want to buy a used transponder that I can later connect to in ADSB out system.

Can someone recommend a decent used transponder that would have this capability?

TIA
Gary
 
Or a brand new Stratus ESG transponder that includes the WAAS GPS and the ability to fly in any airspace.

This is probably the lowest cost solution. RST engineering has a very good deal on these if you're an EAA member. Closer to $2k than $3k. I'm pretty sure it includes ADSB out too.

The only downside is there is no anonymous mode...
 
This has become an interesting and informative thread. I am not sure that we have provided the information that Gary was looking for in his original post.

- larosta

The answer to the OP's question probably lies in a KT-76 plus something from uavionix. The downside is that for a few hundred dollars more (in total), you can get something more modern and more integrated from Stratus or other vendors.
 
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Michael, a couple of points, if I may?

1) the RV8 will need an approved position source. Upgrading the 430 to 430W is an expensive path. Consider, rather, selling the 430 and installing an Avidyne IFD440 in the same tray. A bit more money to get a brand new GPS with a better user interface

2) the 330 is a different form factor than the 327. Check available depth behind the 327 tray as the 330 is longer which might make this swap a bit of a challenge from a mechanical standpoing.

While the upgrade of the 330 is a relatively inexpensive thing to do since you already own the 330, the other costs of the 330 are significant to others who may be considering installing a 330. It's heavy, power-hungry and takes up a fair bit of panel space. For some who don't already have a 330 in their panel, consider other options such as the Trig TT22.

For those with a KT76 that might be of dubious longevity, it's worthwhile to look at the Trig slide-in replacement transponder, the TT31. With an appropriate position source you could easily be 2020 compliant and have a solid solution based on Mode S-ES.

As for position sources, even those folks with a straight GNS430 might want to consider a less-expensive solution like GRT's SafeFly GPS module. At $500 it's a lot cheaper than a WAAS upgrade on a 430.


Appreciate the comments. The Rocket has plenty of room to accept the 330 from the -8. Looks like $1500 for the ES upgrade and I'll get ADS-B out compliance AND the slight benefit of TIS-A through the 650.

The -8 can use the Rocket's 327 and a new GDL-82 providing the position source and other magic to make that compliant. Not planning on the eye watering price for the WAAS upgrade for the 430 for this round.

Now I have to figure out the ADS-B solution for my latest project which cruises well into the flight levels. It has a KT-76A and an ancient SL-60...

Good thing the Taylorcraft doesn't have a generator!
 
If you own a GTX327 then the purchase of a GDL82 for $1800 is all you need.
The GDL82 contains the required WASS GPS and is simply installed between the GTX327 RF cable and the antenna. Then there's a power, a ground, and a serial to you altitude encoder source and you're done. Four wires!

I installed one in a friends RV-8. It was easy and strait forward. The GDL82 will work with other mode C transponders as well.

Danny, I will soon be mounting a GDL-82 in an RV-8. Where did you mount the box itself and where did you mount the GPS antenna?

Thanks
 
When you write that the 330 is power hungry, can you please tell me how many amps? Thanks

From the GTX330 installation manual:
GTX 330 Power Consumption: 11-33VDC, 22 watts typical, 45 watts maximum
And...
GTX 330 Weight, installed with rack and connectors: 4.2lbs

By contrast (and I offer this only as one point of comparison, there are lots of other good choices available on the market these days)
Trig TT22 power consumption: 11-33VDC, typical 6 watts @ 14V
Trig TT22 weight: 0.77lbs including mounting tray
 
327 software update

You can buy a used GTX-327 Xponder with tray for around $500, will work with the GDL-82 or microavionix ADSB out solutions. Garmin will normally update the 327 software for free at Oshkosh (you need the latest version to use with the GDL-82). Good Xponder, easy to use.
Figs

I?m getting close to ordering a GDL82 to complement my GTX 327 which is currently about 6 years old. I?m assuming (?) that it?ll require a software upgrade. I haven?t yet tracked down what software version is required. Any help would be appreciated.

Jim Diehl 7A
Based at KLHV (Lock Haven, Pa)
 
You might want to check with an avionics shop or Garmin. I just installed a GTX-327 that is at least that old, maybe older. I asked the local avionics shop if it needed a software update, he asked for the serial number and got back to me that it didn't need an update. I was happy since I was told the only way to get it updated was to send it to Garmin, through one of their dealers, and pay the flat rate for service.
 
I?m getting close to ordering a GDL82 to complement my GTX 327 which is currently about 6 years old. I?m assuming (?) that it?ll require a software upgrade. I haven?t yet tracked down what software version is required. Any help would be appreciated.

Jim Diehl 7A
Based at KLHV (Lock Haven, Pa)

Hello Jim,

This posting for transponder updates at Oshkosh 2018 explains the latest software versions for the GTX 327.
http://www.vansairforce.com/community/showthread.php?t=162400

Garmin dealers can quickly update the software, when needed. The transponder does not have to come back to Garmin.

Let us know if you have additional questions.

Thanks,
Steve
 
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