KBAQ Phoenix - is noise due to IBOC from HD Radio?

In Chandler I get a strong signal from both KBAQ and KJZZ but KBAQ is noisier. The noise goes away in mono.

I've experienced this on both tube and solid-state tuners, three of which are freshly aligned. I'm suspecting in-band-own-channel noise due to HD radio, but I don't have the instrumentation to confirm this. If any RF experts out there have data, I'd really like to know. I'm planning on building an FM decoder and the design depends on the answer.

I wasn't listening to FM much when HD radio got turned on; did anyone in the Phoenix area notice a change? Please let me know.

I've volunteered for both stations, they're in the same building; I don't
believe the source quality is different. KBAQ's online stream is quiet but not the high bitrate I would like.

Have others experienced this problem with KBAQ? Another FM user here in the East Valley reports KBAQ is noisier on several tuners he has tried. Another user in Pinnacle Peak says he does not have that problem.

Thanks for your observations!

Regards, HG
Hi HG,

What you are hearing is most likely multipath noise, caused by slightly different signal paths causing time shift errors at your receiving antenna.

When I moved KBAQ back to South Mountain from the White Tank site many listeners were very happy with the increased signal strength, but many buildings in the Southeast valley caused a noticeable increase in multipath noise.

They are already using a circularly polarized antenna for transmission to minimize this bad effect of the land, and unfortunately, there is nothing more the station can do.

Your best action might be to re-orient your antenna for best quieting on KBAQ. If you do not already have a directional antenna for your receiver, I highly recommend an outdoor one.

Dennis Gilliam
Retired Chief Engineer
Thank you Mr. Gilliam! I'm sorry I didn't see your reply sooner. I finally bought an oscilloscope to check for mulipath. I don't see much from my attic antenna but I may do some experiments with some rabbit ears.
Thanks again to Mr. Gilliam. Here's the email I got today (October 25, 20012) from KBAQ:

Dear Sir,

Thank you for your inquiry concerning reception of KBAQ in the Chandler area. KBAQ is located on South Mountain where a new facility was constructed in 2010 and the station went HD at the same time. At your location in Chandler near the 101 and 202 intersection there should be no difficulty in receiving KBAQ in either analog or HD mode. Thank you again for your inquiry and for listening to KBAQ

Best Regards,

Dave Atkins
Chief Engineer
Rio Salado College
2323 W. 14th. St,
Tempe, AZ 85281
I wrote KBAQ in Phoenix and the station engineer called me. He said they are committed to HD Radio and they expect FM to go all-digital like television did. He did not say in as many words that my noise problem is caused by IBOC, but he didn't deny it either. He was quite courteous and tried to be helpful. He suggested listening online, buying an HD radio, or experimenting with attenuation. He said that they felt it was part of their mission as a nonprofit to broadcast as much programming as possible. With HD they can broadcast four programs versus two with old-fashioned FM.

He confirmed that a tuner with narrower IF bandwidth may help.

Too bad for everyone who bought a tuner over the last 50 years expecting high-fidelity broadcasts!

You will be assimilated; resistance is futile.
I had a similar problem here in central Texas. The local PBS station came in perfectly for several yrears, then for no reason the signal became very noisy. This was the case on all my receivers and seperate tuners, Even the table radios in other parts of the house. The station said they had no signal problems. I read a post on an audio site and a person said the answer was the Sony XDR F1HD tuner. For $100, I took a chance, and wow, all noise disappeared instantly. I check every so often to see if it's still on the other tuners. It is. The Sony is a HD tuner, but the station does not broadcast in HD.