TNC coax line

[mccdeuce]

Upgrading my GPS antenna to WAAS.  Tech and I disagree. But I could be wrong.

Current setup has BNC connections with a straight terminal to a 90 adapter into the antenna. 

Upgrading to the TNC connections can we do an adapter that is 90 bnc to tnc? Or is it better to crimp on a 90deg TNC connector?

[jetdriven]

The 90 degree TNC has less insertion loss than a 90 adapter. Basically half as much loss, because it's only one connection, not two. You can get those TNC crimp connectors from Mouser.  The RG-58 crino connectors  will work on RG-400 which is the standard for low loss WAAS cable. You just have to carefully put the ferrule over the braided outer jacket.  most of my airplane is now crimped RG-400. 

http://www.mouser.com/Search/m_ProductDetail.aspx?Amphenol-RF%2f122140%2f&qs=sGAEpiMZZMuLQf%2bEuFsOrh35k6jkGdFnxgy96MWLNrY%3d

Edited December 6, 2016 by jetdriven

[mccdeuce]

That's what I thought. He seemed to think that the loss would be negligible. 

I have RG-142 for my GPS line so won't be replacing it. Not sure if the above listed connector will work but he should have some or something similar. 

Thanks.

[N601RX]

Read the install manual and it will most likely give and min and max loss for the cable assembly. The mooney cable is going to be on the short end of what is allowed so the small extra loss would still be well within the acceptable range. Also the antenna is an active antenna, not passive. 

It would be interesting to know how BNC connectors became the standard for aircraft, other than they are cheap.  N style screw on connectors are much more robust.

 

[mccdeuce]

Well I guess that was his point.

"The GPS antenna cable loss should not be greater than 6.5dB or less than 1.5 dB. Each connector on the GPS coaxial cable will add an additional 0.2 dB loss to the cable. "

So the extra connector will still be inside acceptable losses.  My point I guess was shouldn't you strive for minimum losses? Or does it not really matter as long as you are in the acceptable region?

[N601RX]

You are going to be at the lower end of the acceptable range either way.  AGC will take of the rest. With the active antenna it is a little different situation than a com or nav antenna where you want to pull every last bit of the possible signal out.