Question about my AM/FM tuner.

edisonprime

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I have an NAD C 427 AM/FM tuner connected to my A/V receiver and there is interference from one of the AM stations on a couple others near its number (KROC AM 1340 Rochester, MN). This happened even after exchanging my device. I believe, but not positive that this is a very sensitive tuner, plus I have a very sensitive AM/FM antenna outside. Now this is not a big issue for me, for I can deal with it, but this happens with AM occasionally, right?
 

radio

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Can you please clarify for me? Are you saying that one station is spilling on AM over to two others? If so, is it one on each side, a couple on each side? Across the dial? On CERTAIN frequencies only but not adjacent? And, how close are you to the station that seems to cause the issue? What kind of AM/FM antenna is outside? Perhaps a picture or two of the hookup, the antenna, and the unit?

I know it's much to ask, but the only way to diagnose is to KNOW the setup and situation a bit better.
 
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Iceberg

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Nov 17, 2003
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I am going to take a wild guess and it has to do with the closeness of KROC's transmitter to possibly your location?

You've got 3 AM's licensed to Rochester. Here are there tower locations. I got all this info off of radio-locator.com They show the tower locations
KFAN 1270. Their tower is between Hwy 52 & Broadway and County Rd 1...looks like about a mile behind the Menards
http://maps.google.com/maps?f=q&hl=en&q=43.979722,+-92.447500&om=1

KOLM 1520 shows around 30th Ave SE and Marion Rd SE...basically SE of town and further east of KFAN's tower
http://maps.google.com/maps?f=q&hl=en&q=43.986111,+-92.417500&om=1

KROC is right in Rochester off 14 (Civic Center Dr) & 52 by Cascade Lake
http://maps.google.com/maps?f=q&hl=en&q=44.029722,+-92.491944&om=1

Again I dont know your proximity to KROC but I have a feeling that is probably why you are getting adjacent interference.

But as radio mentioned we need some more info. I guess my question would be what frequencies are you getting the bleedover?
 

radio

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Under our towers, highly selective tuners need to be run either in "local" mode if there is a switch for that, or, with a proper resistor across the AM terminal to ground,
you can reduce the signal on the strong stations. Granted, reduction in the full AM band will result, but you can do this. Another way, believe it or not is to add a "select a tenna" and tune only to what you want, actually detuning all else, or try a terk "advantage" unit. Play with those AND a resistor across the terminals and you may find the proper mix. Works here, but all situations are different. We have only one signal to null at full power, yet maintain a good signal at night for our streaming receiver, a Carver in my office, putting out AM stereo to the 'net listeners.
 
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edisonprime

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Under our towers, highly selective tuners need to be run either in "local" mode if there is a switch for that, or, with a proper resistor across the AM terminal to ground,
you can reduce the signal on the strong stations. Granted, reduction in the full AM band will result, but you can do this. Another way, believe it or not is to add a "select a tenna" and tune only to what you want, actually detuning all else, or try a terk "advantage" unit. Play with those AND a resistor across the terminals and you may find the proper mix. Works here, but all situations are different. We have only one signal to null at full power, yet maintain a good signal at night for our streaming receiver, a Carver in my office, putting out AM stereo to the 'net listeners.
Any ideas on where I could get such a resistor?
 
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Iceberg

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since you mentioned your semi-location in your other thread (couple blocks north of ST Marys hospital) that puts you about 1/2 mile from their tower. Hence the bleedover
 

edisonprime

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Iceberg

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I'm sure its just one of the 1/2 watt resistor (the ones for 1.49)

The difference is how much resistance they apply. Jim (radio) hopefully can chime in and let ya know what he is using (he lives real close to the tower of the radio station he owns) ;)

Too bad there isnt a Radio Shack still in Apache Mall. You could just go buy a couple packs of random resistance and see what works the best with trial and error. I dont know of who else would seel resistors like that locally
 

lfp302

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I would start by trying a resitor equal to the impedance of the antenna lead. Example: if yu are jumpering 300 ohm twin lead, try a 300 ohm resistor. If you are doing this to 75 ohm coax, try 75 ohm. I think that either case would drop the signal by 50 pecent (3db). One alternative wrt coax, get a 1 to 2 splitter, hook rx to one output, put the 75 ohm resistor on the other output. In geeral, smaller resistors would bleed off more signal, larger ones would lessen the effect. Warning I don't know if a really small resistor could act as a short and damage the receiver!!! I see in the antenna instructons that they do offer attenuators in 10 and 20 db.
 

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