# Cheapest solution for Mode C Transponder and ADS-B?

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#### Built2Fly

##### Well-Known Member
I am starting a build, and as life goes I am living under the Mode C veil of SAN.

So basically I have two choices. One, making it non-engine-driven-electrical and being exempted. Two, biting the bullet and getting a Mode-C transponder and an ADS-B. I guess in a busy airspace where we are, being seen offers some safety advantage, so I am looking at transponder/ADS-B solutions.

Now the question, what is the cheapest solution to satisfy the Mode-C and ADS-B requirement? Any ideas? How about a used Garmin 327 with an Uavionix echoUAT? All suggestions are appreciated.

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#### Daleandee

##### Well-Known Member
KT76A‘s go for about $200. Garmin GTX 375s for$250-400. Add a echoUAT with skyfx bundle for $1399. Thats a few hundred less than the tail beacon and you get ADSB IN as well (Saves another couple of hundred putting together a Stratux). It’s UAT so you get “anonymous mode”. Although uavionics anonymous mode is enabled/ disabled using a phone app, which is suboptimal. I haven't gotten the bundle yet but I have a Garmin 320A that was gifted from a friend. As mentioned already the Echo bundle with a GPS position source is$1400.00. I have my transponder check due in November and will likely do the ADSB upgrade then.

Another point on the ECHO is that it will transmit ADSB "In" to you EFB i.e. I use an iFly 740b.

#### Jay Kempf

##### Curmudgeon in Training (CIT)
Lifetime Supporter
I have a KT76A. Trying to figure this same thing out. Stratux and Skybeacon seemed the way to go.

#### Daleandee

##### Well-Known Member
I have a KT76A. Trying to figure this same thing out. Stratux and Skybeacon seemed the way to go.
I have a Raspberry Pi "assemble it yourself" version that works well with my iFly 740b for traffic & weather. I understand (if I'm reading it correctly) that the Echo unit shown above will broadcast the ADSB in so that I can remove the Stratux unit so the weight change should be minimal.

The Skybeacon does make life easier as the Echo Bundle unit requires mounting two additional antennas, one above and one below. .

#### Built2Fly

##### Well-Known Member
Thanks, guys. A lot of good ideas.

I have a question on echoUAT. It has an interesting power transcoder feature. There is no connection needed between transponder and the ADS-B unit. The echoUAT ADS-B unit will figure out what you are squawking on the transponder by picking up the fluctuation on the power bus.

That sounds like a neat feature. But how reliable is that? Does it work in real life, or is a RS232 direct line needed? Any experience?

#### TFF

##### Well-Known Member
It gets the signal through the power wire. They have to be on the same buss. On another forum someone had them powered separately and he could not get it to work that way. Finally it got figured out.

#### Built2Fly

##### Well-Known Member
It gets the signal through the power wire. They have to be on the same buss. On another forum someone had them powered separately and he could not get it to work that way. Finally it got figured out.
Does it work reliably once they are on the same bus? I am wondering how well it works, because no additional wire really saves a lot of hassle.

#### rv7charlie

##### Well-Known Member
A heads-up on older XPs. My neighbor does XP certs, and also does ADSB installs. He will no longer do an ADSB install with an older cavity tube type transponder, because they so frequently won't pass ADSB flight tests, and even if they do, they often start triggering FAA letters soon after the initial install. He says that there are no issues with the later all-solid state models like the Garmin 327, etc.

FWIW...

#### TFF

##### Well-Known Member
The flight school here has most of the fleet with them. They had one take on water and give issues, but it was drowning.

#### Toobuilder

##### Well-Known Member
HBA Supporter
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Does it work reliably once they are on the same bus? I am wondering how well it works, because no additional wire really saves a lot of hassle.
I tried mine with 232 from the 650 (GPS position) and the 327 (squawk/altitude). I could not get all the output protocols to talk to everything so I kept the 232 from the GPS and let the Echo "sniff" the transponder. Could NOT get it to work despite having the 232 hooked to the 650 per the instructions. Turns out that particular output on the 650 did not have the correct protocol as an option. So I switched to another serial output that DID allow the required protocol and it started working perfectly. I did my PAPR flight for "score" and the report came back with zero discrepancies. Its been flawless for me so far.

The product is great, the documentation SUCKS.

#### Built2Fly

##### Well-Known Member
@TFF, @Toobuilder, @rv7charlie

#### edwisch

##### Well-Known Member
There's a reason that some avionics have to be approved and tested at whatever level, even in an experimental. Things like transponders and comm radios have to work within the system cooperatively, so that, say, the transponder meets the requirements of the whole systems, and so that the comm radio doesn't screw things up for somebody else. In contrast, if you do your own ignition system and it fails, that doesn't affect anybody else. If your altitude encoder is off, that could cause ATC to not provide good traffic separation services to *other* aircraft because your plane isn't at its reported altitude.

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Finn