[R-390] Sigmapert Balun Review

[John Gedde]

Out of curiosity, I bought a Sigmapert twinax to BNC balun from eBay.
Sigmapert sells them on there from time to time and also offers them in
twinax to UHF.  I had been using a Twinax to UHF connector adapter from Fair
Radio to interface my 50 ohm coax to my R390 and R390A.  All that adapter
does is tie one balanced terminal to the shield and feeds the signal into
the other one.  

 

I wouldn't have expected much improvement with the Sigmapert, but I was very
surprised at the huge reduction of noise I get using it!  I slight bit of
signal strength reduction but the betterment of signal to noise is profound.
I'm quite sure it has nothing to do with 50 ohms versus 125 ohms but rather
the ability for the R390/A to reject common mode noise with a bona fide
balanced input.

 

I haven't yet played around with adjusting the RF input stage balance
adjustments, but it seems the whole common mode noise rejection thing is
very real.

 

John