Tuner whine antenna issue - help needed - Newbie alert

[Lendorien]

I recently picked up a dedicated Tuner at a thrift store. I don't need a tuner, as I have an AVR I use for that, but given that this was a dedicated tuner and likely better than my AVR for radio usage, I thought I'd give it a try. it was also dirt cheap. You guys have corrupted me. >_<

Anyway, it's a Denon TU-550. My research has shown that it's an older digital tuner from 1988 that retailed for about 300 dollars US. That's a hefty price for back then if you ask me, so It's probably not a bad piece of equipment.

As far as I can tell, it works fairly well. It seems to be forgiving with FM radio signals, locking on to even weak signals that a my other digital equipment has a hard time finding. I've been impressed with that part of it. It also has an MPX filter (for hooking to tape decks maybe?), wide and narrow bad selection and a signal strength indicator.

That said, I'm running into an issue that I am hoping that wiser minds can help me with.

It concerns using an antenna with the AM band. If you get an antenna close to the tuner, it picks up AM signals but when you actually attach the antenna into the AM pickup, the signal is distorted by a low whine. This only happens with AM.

I know it's not the antenna as I was able to test it elsewhere (It's one that came with my main AVR). I also built a simple loop antenna to see if that had the same effect. Same results, regardless of if a ground is in or not. Any touch to the antenna pickup, wire, hand, whatever and it whines.

I'm stymied at what the problem might be. I've been unable to find a service manual (on a site that doesn't require me to pay for it.) Is it a hardware issue? None of my other equipment with tuners act this way. I did try to turn off lights and tvs and the like to make sure that wasn't the issue. This isn't exactly my realm of knowledge, so any advice is welcome!

 

[Punker X]

You are experiencing interference from these days just about anything in your house. Wifi, smart meters, computers, dimmer switches are all know problem. Start tuning things off and see how it affects your reception.

 

[empirelvr]

I recently picked up a dedicated Tuner at a thrift store. I don't need a tuner, as I have an AVR I use for that, but given that this was a dedicated tuner and likely better than my AVR for radio usage, I thought I'd give it a try. it was also dirt cheap. You guys have corrupted me. >_<

Anyway, it's a Denon TU-550. My research has shown that it's an older digital tuner from 1988 that retailed for about 300 dollars US. That's a hefty price for back then if you ask me, so It's probably not a bad piece of equipment.

As far as I can tell, it works fairly well. It seems to be forgiving with FM radio signals, locking on to even weak signals that a my other digital equipment has a hard time finding. I've been impressed with that part of it. It also has an MPX filter (for hooking to tape decks maybe?), wide and narrow bad selection and a signal strength indicator.

That said, I'm running into an issue that I am hoping that wiser minds can help me with.

It concerns using an antenna with the AM band. If you get an antenna close to the tuner, it picks up AM signals but when you actually attach the antenna into the AM pickup, the signal is distorted by a low whine. This only happens with AM.

I know it's not the antenna as I was able to test it elsewhere (It's one that came with my main AVR). I also built a simple loop antenna to see if that had the same effect. Same results, regardless of if a ground is in or not. Any touch to the antenna pickup, wire, hand, whatever and it whines.

I'm stymied at what the problem might be. I've been unable to find a service manual (on a site that doesn't require me to pay for it.) Is it a hardware issue? None of my other equipment with tuners act this way. I did try to turn off lights and tvs and the like to make sure that wasn't the issue. This isn't exactly my realm of knowledge, so any advice is welcome!

Let me make a couple of quick guesses....

The tuner output is being fed into the AVR, so you have to have the AVR on in order to listen to it.
And the tuner is sitting on top/below/aside the AVR.

If I'm right, dollars to doughnuts the whine is the Denon picking up interference from the digital circuit side of the AVR. If you were to separate the two far enough I bet the whine would go away.

This would also be valid if the tuner is above/below/aside a CD/DVD/Blu-Ray player or cable box that's either on or on standby.

Even a nearby computer or laptop can do this to AM reception. (not sure about tablets or smartphones though I suspect they might also be a source of AM radio issues.)

And if your answer is, "no, the tuner isn't located near the AVR, computer, etc." my next question is, are you using florescent lights of any kind? Either the old-fashioned tubular kind of the new CFL bulbs? Florescent bulbs cause hideous AM interference.

 

[Lendorien]

Let me make a couple of quick guesses....

The tuner output is being fed into the AVR, so you have to have the AVR on in order to listen to it.
And the tuner is sitting on top/below/aside the AVR.

If I'm right, dollars to doughnuts the whine is the Denon picking up interference from the digital circuit side of the AVR. If you were to separate the two far enough I bet the whine would go away.

This would also be valid if the tuner is above/below/aside a CD/DVD/Blu-Ray player or cable box that's either on or on standby.

Even a nearby computer or laptop can do this to AM reception. (not sure about tablets or smartphones though I suspect they might also be a source of AM radio issues.)

And if your answer is, "no, the tuner isn't located near the AVR, computer, etc." my next question is, are you using florescent lights of any kind? Either the old-fashioned tubular kind of the new CFL bulbs? Florescent bulbs cause hideous AM interference.

But wouldn't the whine be consistent then even when the antenna is not plugged in? It only happens when something is touching the antenna jack. I have a fair number of radios in my home, from an old 50s tube radio to transistor and solid state radios. Not to mention three separate AVRs. None have this issue.

The whine is a consistent one. Moving the antenna around, and even the tuner itself doesn't seem to affect anything. Granted, I didn't try moving it more than a foot or two from the AVR. But I did kill the lights, so unless it's picking up something farther away, that isn't it. The whine is strong enough that it drowns out any reception at all. As I said, it only happens when antenna is in. If you have it close to the jack, reception is normal.

I'll do some experiments when I get home tonight, but I'm inclined to think it's something with this radio tuner in specific.

 

[empirelvr]

But wouldn't the whine be consistent then even when the antenna is not plugged in? ...

Nope, not necessarily. Again, that's from my own personal experience. AM radio is kind of like grounding issues; a tricky beast which doesn't always work even when it's done "right."

 

[Lendorien]

We

Nope, not necessarily. Again, that's from my own personal experience. AM radio is kind of like grounding issues; a tricky beast which doesn't always work even when it's done "right."

Well, I'll try plugging it into my other avrs and try to do a shutting stuff off process of elimination and get back to you.

Odd to me that this is the only radio I have with this sort of problem.

 

[Lesterbest]

You are experiencing interference from these days just about anything in your house. Wifi, smart meters, computers, dimmer switches are all know problem. Start tuning things off and see how it affects your reception.

It also might be a shielding issue caused by the items listed above.