http://www.audioasylum.com/forums/tuner/messages/1/13436.html

(openmind had hit the nail on the head in the original thread...)

As I stated previously, my two favorite Dayton, Ohio area stations are WYSO (50,000 watts, 4 miles SSE) and WDPR (600 watt classical, 22 miles ESE).

Even when either station is perfectly tuned I hear constant low-level noise superimposed on the audio that is similar to the "white" noise heard with a weak station, but a bit more harsh and "swishy".

The tuner is connected to a six-element yagi antenna on a rotator in my attic. Both stations show full strength on the tuner's signal strength meter, and multipath shows zero.

The noise increases symmetrically as either station is de-tuned off center, but it cannot be eliminated, no matter how carefully tuned.

I can markedly decrease (but not quite eliminate) the noise by switching the tuner to its narrow bandwidth.

I have finally been able to experiment with re-orienting my antenna...

There is no change in quality or level of the noise when the antenna is pointed directly at either station, and the noise does not increase at all until the antenna is moved to roughly 70 degrees to either side of centered. In other words, even on the weaker of the two stations I can sweep the antenna through an arc of about 140 degrees without the noise increasing or decreasing.

After additional research I have come to a conclusion...

Both of the stations in question are Public Radio stations, and both broadcast a HD radio signal.

I am pretty sure what I am hearing is "HD radio self-noise". See the excellent outline here:

http://www.ham-radio.com/k6sti/hdrsn.htm

Now I guess I need to see if there is any way I can hear the otherwise excellent, unprocessed and uncompressed audio from these stations (the classical station actually uses tube gear in their broadcast chain!) without the noise intruding.

Temporarily I can tolerate the noise if I listen to the tuner in narrow IF bandwidth.

It sounds like the "real" fix is to use a tuner that includes a "post-detection filter" or equivalent design, but I wonder if the newer, more selective Magnum Dynalab tuners (MD-100 or higher) would be more able to reject the HD radio self-noise? I really love the sound I get with my Etude!

Maybe the Magnum Dynalab MD-205 Signal Sleuth might help?

I can find no information anywhere specifically about the ability of the newer tuners or the Signal Sleuth to reject HD radio self-noise.

Any comments or advice will be welcomed!

Ken

 RE: Noise, even on a strong station: Update - aldoallen 19:58:49 06/13/12 (2)
 A very pervasive problem - FidPup 04:01:34 06/14/12 (1)
 RE: A very pervasive problem - openmind 13:45:24 06/15/12 (0)

...

Show full thread outline!

 RE: Noise, even on a strong station: Update - aldoallen 19:58:49 06/13/12 (2)
 A very pervasive problem - FidPup 04:01:34 06/14/12 (1)
 RE: A very pervasive problem - openmind 13:45:24 06/15/12 (0)
 RE: Noise, even on a strong station: Update - Neff 14:01:24 06/13/12 (0)

It is very frustrating and disappointing that the very stations that are broadcasting the high quality and minimally processed music I enjoy most are all NPR stations deeply committed to HD radio, and so have their audio overlaid by that constant hiss.

The problem has been going on for at least several years now, and is becoming more common.

I am surprised that Magnum Dynalab does not even mention HD self-noise on their website or in any of the information available for their tuners. I have also not found any mention of the problem in any reviews of their gear on the 'net.

I am considering calling the company and ASKING if any of their newer tuners address the issue.

Thanks for answering one of my questions: I was planning to get a Signal Sleuth to see if it would improve the noise. No dice, I guess!

At least I find that HD hiss is decreased to a tolerable level on my Etude if I flip to the narrow IF bandwidth setting.

Ken

• Tuners that do or do not handle IBOC