Nikko nt-850 am/fm stereo tuner

[Josh00023]

I recently purchased a NIKKO NT-850 AM/FM STEREO TUNER and anyone got any idea witch is better to hook the outdoor FM antenna to? The 75 OHM or use the 300 OHM connection?

 

[chazix]

What is the cable that brings the antenna signal into the house? If it's round coaxial cable, use the 75 ohm input on the tuner. If it's flat twinlead cable, use the 300 ohm input.

Cheers,

chazix

 

[WaynerN]

:worthless

 

[Josh00023]

it's a 75 OHM cable that comes in, but the connection on the back of tuner for the 75 ohm means you would have to cut the head off the cable and screw it down to the leads. Someone suggested a 300 OHM to 75 OHM Balun or Matching transformer to connect it to the tuner.

 

[chazix]

The matching transformer scheme will work and has a convenience advantage - but it will cost you some sensitivity. I don't know how much - some loss is fundamental, some depends on the construction of the transformer

It may be that ultimate sensitivity is not your main concern - in which case, sure, go for what's convenient.

FWIW, I mildly disagree with the idea that pictures are essential to answering this. What information is lacking that pictures will supply?

Your ever-so-contentious correspondent,

chazix

 

[JBL GUY]

There is no harm in trying a balun transformer all though the signal loss through a balun transformer may range from 0.5 dB to over 2 dB.

These are values that I have measured for various balun transformers at FM broadcast band frequencies.

Again there is no harm in trying to use a balun transformer. Unfortunately there is no way to know the amount of loss unless it is specified by the manufacture or you have the equipment to measure the loss.

Again, there is no harm in trying and if you have enough RF signal strength at the end of your coaxial cable for adequate reception of your stations of interest you are good to go as they say.

BTW, due to the internal construction of some balun transformers, there may be more signal if you reverse the connections to the tuner. That is try connecting the balun one way and then reverse the leads as they connect to the tuner.

It may or may not make a difference, but it is easy to try.

 

[Josh00023]

I Connected to the 75 ohm connection and it was ok. 300 ohm had way to much loss at 4-6db. I lost half my signal using that Transformer. My connection on the back of the tuner uses screws for the 75 ohm connection, so I had to cut the head off of a cable and screw it down.

 

[rcs16]

That makes sense!!
Using lower loss RG-6/U over RG-58/U can help, as well, if the coax run is long. I distribute my FM signals through the house using RG-6/U.

 

[JBL GUY]

The characteristic impedance of RG-58/U is 50 Ohms not 75 Ohms, so even for short jumpers is not recommended.

The characteristic impedance of RG-59/U is 75 Ohms.

 

[Sam Cogley]

You can get coax/screw-terminal 1:1 adapters for 75ohm.