Transponder installation article- Soaring Magazine

On Monday, December 21, 2020 at 6:23:20 PM UTC-7, wrote:
Get the TT22. Don't consider the TT21. It could save you about $150 on a $2500 USD purchase but does not provide full ADS-B compliance. In the USA this means a TT21 does not allow you to fly in transponder-required airspace.. The TT22 provides a full ADS-B out solution and more transmit power, yet its power consumption is identical to the TT21, according to Trig's spec sheets.

For an experimental glider you can use the same GPS receiver and antenna that you would find in a TT21 ADS-B out package (Trig TN72 and Trig TA50), so the only added cost is the $150 to upgrade to the TT22.

...david
On Monday, December 21, 2020 at 7:19:22 PM UTC-5, John Johnson wrote:
Should I assume it is not legal in the US to use a TT21 with a TN72 for ADS-B out in an experimental glider? That combination is ok in Europe (I think) with the difference being the US wants 2x the xmit power for ADS-B (TT22 at 250W) vs the 125W output of the TT21. I would like to think that having otherwise compliant, lower power ADS-B out is better (and not illegal) than no ADS-B out in an aircraft that is legal without ADS-B.
Probably not a realistic hope - but it would save me the not trivial expense of upgrading my TT21 to a TT22.

JJ
Fully agree a new purchase should be a TT22. Unfortunately, my glider has been setup with mode-S TT21 for some time now. I understand it costs ~$1000 or so to have an existing TT21 upgraded to TT22 specs. Since I can't see any practical need for my glider to have the 2x xmit power compliance, I'd like to save the $1000 and, perhaps, spend it in the future when the next wave of new transponder compliance requirements come about. I could always perform the upgrade later if that made sense for me.

thx, JJ

John Johnson wrote on 12/22/2020 10:38 AM:
On Monday, December 21, 2020 at 6:23:20 PM UTC-7, wrote:
Get the TT22. Don't consider the TT21. It could save you about $150 on a $2500 USD purchase but does not provide full ADS-B compliance. In the USA this means a TT21 does not allow you to fly in transponder-required airspace.. The TT22 provides a full ADS-B out solution and more transmit power, yet its power consumption is identical to the TT21, according to Trig's spec sheets.

For an experimental glider you can use the same GPS receiver and antenna that you would find in a TT21 ADS-B out package (Trig TN72 and Trig TA50), so the only added cost is the $150 to upgrade to the TT22.

...david
On Monday, December 21, 2020 at 7:19:22 PM UTC-5, John Johnson wrote:
Should I assume it is not legal in the US to use a TT21 with a TN72 for ADS-B out in an experimental glider? That combination is ok in Europe (I think) with the difference being the US wants 2x the xmit power for ADS-B (TT22 at 250W) vs the 125W output of the TT21. I would like to think that having otherwise compliant, lower power ADS-B out is better (and not illegal) than no ADS-B out in an aircraft that is legal without ADS-B.
Probably not a realistic hope - but it would save me the not trivial expense of upgrading my TT21 to a TT22.

JJ
Fully agree a new purchase should be a TT22. Unfortunately, my glider has been setup with mode-S TT21 for some time now. I understand it costs ~$1000 or so to have an existing TT21 upgraded to TT22 specs. Since I can't see any practical need for my glider to have the 2x xmit power compliance, I'd like to save the $1000 and, perhaps, spend it in the future when the next wave of new transponder compliance requirements come about. I could always perform the upgrade later if that made sense for me.


I suggest you keep your TT21, but install a TN72 with a TA50 antenna (total equipment cost of
about $460). You can't use it to enter A, B, and C airspace, though there are probably some
exceptions for glider operating areas (and maybe others), but you otherwise have all the
features the TT22 would give you. Here's the Trig document for gliders:

https://www.trig-avionics.com/librar...ust%202018.pdf

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

On Tuesday, December 22, 2020 at 11:56:51 AM UTC-7, Eric Greenwell wrote:
I suggest you keep your TT21, but install a TN72 with a TA50 antenna (total equipment cost of
about $460). You can't use it to enter A, B, and C airspace, though there are probably some
exceptions for glider operating areas (and maybe others), but you otherwise have all the
features the TT22 would give you. Here's the Trig document for gliders:

https://www.trig-avionics.com/librar...ust%202018.pdf


Thanks Eric. I think I will take this route. I received a few PM's from pilots using TT21's in this fashion. It makes a lot of sense for the case where you already have a TT21 and don't see a need to fly in full compliance airspace. I installed a PowerMouse with ADS-B in this year and it's helped me see just how busy the (unseen) traffic is in the Arizona airspace I mostly fly in. I'll start working on the firmware update my older unit almost certainly needs to get it working properly with a TN72.

JJ