Anyone confirming recent digital interference on KNEW-AM 910?

[8hhaggis]

I sometimes listen to KNEW-910 talk programs. When the station first added IBOC, sometime ago, it would no longer come in correctly on my Icom R-75 radio, a communications receiver that has elaborate filters and is optimized for SSB reception and SWL'ing. Odd: despite the sharp, narrowband IF system of this radio, there is so much IBOC hiss that the intelligibility and S/N ratio of KNEW's audio is SEVERELY affected.

But, then sometime after Thursday 31 August 2006, I noticed that on many other radios I own that KNEW was now inundated by a new, horrible, gurgling signal that sounds like it might be an artifact of the complex IBOC carrier system. It completely covers up the KNEW audio on my Sherwood receivers, model RX4103, that I have in three rooms of my house. On various other conventional analogue radios the gurgling is there but not as loud: on my Grundig FR-200 it seems to be located on KNEW's lower sideband, between the digital subcarrier and the LSB of the analogue carrier. One some of my small portable radios this noise is quite objectionable though not nearly as loud as on the Sherwoods, where it TOTALLY drowns out the program audio.

I have checked to see if there is some new interference signal presence in the area around my home, using wideband receivers that I employ to test for TV cable leakage ... nothing perceived. The only spurious signal that has not been previously detected -- aside from "tweedles" in the HF bands caused by my ethernet distribution system and DSL modem -- seems to be this gurgling that obliterates KNEW.

To try to isolate this signal I have shut off my Internet routers as well as my TV distribution system: no change in the interference has occurred. I'm puzzled, and cannot seem to find a LOCAL cause: is this an intermod product created by the IBOC system on KNEW's carrier?

Any other suggestions?

8H Haggis
retired broadcast engineer
San Jose

 

[davideduardo]

To try to isolate this signal I have shut off my Internet routers as well as my TV distribution system: no change in the interference has occurred. I'm puzzled, and cannot seem to find a LOCAL cause: is this an intermod product created by the IBOC system on KNEW's carrier?

Any other suggestions?

What is the IF frequency of many radios? This is why I would never buy a 910 AM, and whey so few of them ever were successful in the past.

 

[ajhenderson]

What is this KNEW you speak of?

 

[ajhenderson]

While I'd agree with you David (I've typically used 870-950 as a part of the AM band to avoid - any clarification?), I'd say the programming on 910 is just as much a part of the problem.

 

[8hhaggis]

Well, as usual, no useful replies from anybody. I guess I will unsubscribe to this forum.

My choice of what to listen to is not any stranger -- to me -- than the choice of other people to fill their waking moments with what to OTHER people is juvenile, pointless noise masquerading as "music".

Second: apparently nobody actually READS and THINKS about posts that are longer than a couple of sentences.

The IF frequency of a radio receiver might be of significance but *obviously* not in this instance. Three identical model radios that worked fine -- a week earlier -- would obviously not have an IF image problem that would occur suddenly after 31 August, now, would they, children?

Useless waste of my time to attempt to enter into any meaningful discussions here.

Ta-ta!

8HHaggis

 

[ajhenderson]

Don't get so upset. I don't listen to music radio either, but take a joke and realize that KNEW isn't exactly setting the Bay Area on fire. That's all.

 

[DyingMedium]

Two things:

1) You probably should've posted on a more Engineer friendly section of the board. I'm sure there is one.

2) The interference you speak of was just the Jerry Doyle show.