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DC short on antenna connector #v3


Kit Peters
 

I just replaced the antenna connector on the uBITX v3 mainboard with a PCB mount female SMA connector. There is a DC short between center pin and shield. Normally I'd think I messed up the soldering, but I removed the connector and there's still a short. Is that normal?

--
Kit Peters, W0KEH
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Jerry Gaffke
 

Yes, it's normal that the antenna center pin appears to be grounded.
If you look at the schematic, relay K3 in the lower right is in its receive position,
it connects the antenna center pin to inductors L1,2,3 and transformer T2.
The signal gets grounded at T2.

Since all those inductors look like just a short piece of magnet wire at DC,
the ohmmeter reports close to zero ohms.
 
Jerry, KE7ER 


On Wed, Oct 7, 2020 at 12:16 PM, Kit Peters wrote:
I just replaced the antenna connector on the uBITX v3 mainboard with a PCB mount female SMA connector. There is a DC short between center pin and shield. Normally I'd think I messed up the soldering, but I removed the connector and there's still a short. Is that normal?
 


Skip Davis
 

Yes you’ll see a DC short because your seeing the input/output winding of T2 the first mixer transformer on the other side of the low pass filter. 

Skip Davis, NC9O

On Oct 7, 2020, at 15:16, Kit Peters <popefelix@...> wrote:


I just replaced the antenna connector on the uBITX v3 mainboard with a PCB mount female SMA connector. There is a DC short between center pin and shield. Normally I'd think I messed up the soldering, but I removed the connector and there's still a short. Is that normal?

--
Kit Peters, W0KEH
GPG public key fingerpint: D4FF AA62 AFEA 83D6 CC98 ACE5 6FAE 7E74 7F56 ED1D
Hello to any and all NSA, DEA, or other government or non-government agents reading this email.  Tell me about your life; I'll tell you about mine.