No ATC reception of xponder

[jethound]

I have dual SkyViews and the 261 xponder,  indications are that the transponder is working but ATC can not see me.  They could see no aircraft. At an altitude well above what they. Normally can see.I did my first flight of my RV 7yesterday so I will trouble shoot it and see what I can find,  I will try to attach a picture of the screen.

Any suggestions
Jack

 

[dynonsupport]

I see you are in the USA, so was the transponder checked per FAR 91.413 before the first flight?

 

[jethound]

Yes but it seemed to work on the first flight but on the second was the first time I called ATC to get a verification of the altitude and they had me climb up to see if they could see me when they could not see me at a lower altitude where they normally see other aircraft in this area.
I can see traffic on the map display but on the PDF the targets are only shown as a black diamond

 

[Dynon]

So this can indicate a bunch of things, including an antenna that's not well connected, cable that isn't making good continuity, among other things. The transponder's proper function and depiction of traffic are two pretty different things, although you need to take care of the first before you even look at the second. Again, to be legal, you do need to have your transponder performance tested per 91.413. If you haven't yet, doing so could uncover the reason that ATC isn't always seeing you.