New Car Purchase with Upgraded HD Radio

semoochie said:

My reception is completely reliable too but you have to remember that the system was set up to receive only within the protected contour and not get all bent out of shape because bonus coverage isn't what you might expect. It doesn't belong there anyway, even in analog.

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I am in the protected contour for both KHPT and KGLK. Both stations are jammed when a car near me is tuned to KHMX on 96.5. I have tried it in my driveway with my own cars. And two cars equipped with HD radio are jammed the same way. Jamming is up to 100 feet. When I get time, I will post a video of the effect.

http://radio-locator.com/cgi-bin/patg?id=KHPT-FM
http://radio-locator.com/cgi-bin/patg?id=KGLK-FM

These are only two stations on which I have experienced local oscillator jamming. When KRBE 104.1 had an HD-2, it was jammed whenever somebody tuned to 93.7 near me. The number of 10.4 MHz and 11.0 MHz combinations abound in my area. KRBE is full class C 100 kW on a 2000 foot tower over flat terrain that is 20 miles from me. I can see the tower lights at night. It doesn't matter. Somebody tunes to 93.7 in a car near mine, HD is GONE on KRBE. That is the same KRBE that used to have a handful of listeners in South Dallas, so there is NOTHING wrong with their signal. Somebody - really didn't think this system through very well. BAD engineering!!!!

rbrucecarter5 said:

I am in the protected contour for both KHPT and KGLK. Both stations are jammed when a car near me is tuned to KHMX on 96.5. I have tried it in my driveway with my own cars. And two cars equipped with HD radio are jammed the same way. Jamming is up to 100 feet.

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I've always wondered about that. I thought it was the analog radio spewing interference on the IF of the HD radio.

Somebody - really didn't think this system through very well. BAD engineering!!!!

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It might be the analog carrier creating the interference on the IF instead or just low power levels on the digital side vs the analog carrier. But we won't really know until radio has gone digital-only. OTA ATSC was problematic until analog broadcasting was shut down. Now not so much, unless you're in a fringe area.

KTN Corp said:

I've always wondered about that. I thought it was the analog radio spewing interference on the IF of the HD radio.


It might be the analog carrier creating the interference on the IF instead or just low power levels on the digital side vs the analog carrier. But we won't really know until radio has gone digital-only. OTA ATSC was problematic until analog broadcasting was shut down. Now not so much, unless you're in a fringe area.

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I should never have called it "IF jamming" - it is the local oscillator of the radio in adjacent cars leaking out. I am sure the FCC has some sort of standard for this in receivers. They have certainly known about it for decades, because there are 10.6 and 10.8 MHz spacing restrictions on FM stations. They should have added 10.4 and 11.0 MHz to those spacing restrictions when they approved HD, because the HD sidebands are on adjacent frequencies. Unfortunately, that would have shut down or power restricted a huge number of stations that are 10.4 and 11.0 MHz apart.

The station spacing is for another reason.
If you have two very strong signals 10.6 or 10.8 MHz apart getting into your radio, their mixture product will get into your IF amplifiers and you will hear them completely across the dial.
This happened to me when I misaligned a receiver and changed the IF to a frequency equal to the spacing of two local stations.

rbrucecarter5 said:

I should never have called it "IF jamming" - it is the local oscillator of the radio in adjacent cars leaking out. I am sure the FCC has some sort of standard for this in receivers. They have certainly known about it for decades, because there are 10.6 and 10.8 MHz spacing restrictions on FM stations. They should have added 10.4 and 11.0 MHz to those spacing restrictions when they approved HD, because the HD sidebands are on adjacent frequencies. Unfortunately, that would have shut down or power restricted a huge number of stations that are 10.4 and 11.0 MHz apart.

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This is, yet again, complete hogwash. As stated in prior threads where Bruce has made this cockamamie claim, I attempted to replicate the situation, even right in my garage, where field strength for the stations used are attenuated. The cars used was my wife's 2014 Jaguar and my BMW 5series. Then I pulled in my other car next to the Jag with an aftermarket Kenwood HD-capable radio. In all cases, where we duplicated listening to the same stations between the two cars sitting right next to each other, the analog and HD reception was equally fine. There was no "jamming" or interference.

I tried to do it with multiple portable analog and HD radios as well as my car radio and also came up empty-handed. The best result I can recall getting was blanking of the analog signal while the HD remained unaffected. It's just not possible for the IF to overpower both sidebands at the same time, which is what I think it'd take to lose the HD lock.

Perhaps if someone has a station running HD where their reception is possible because only one sideband is in the clear, and that gets blocked, but the chances of it happening seem to be extra slim. I could not detect that IF "signal" more than about two feet from any radio.

Guess the engineering wasn't so BAD after all! The only bad things around here are Bruce's claims.

rbrucecarter5 said:

They should have added 10.4 and 11.0 MHz to those spacing restrictions when they approved HD, because the HD sidebands are on adjacent frequencies.

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B. All the existing stations could not have been shuffled around, although full power stations have not needed to be four channels apart for a verrrry long time.
C. The hybrid mode is not supposed to go on forever.
The eventual digital-only mode will be much narrower, perhaps as narrow as analogue FM, but with more consistent sidebands.

Oops, I had A, B & C, deleted A, and forgot to reletter B & C.

DavidEduardo said:

With the average US car about 11 years old, it will be about 15 years before 75% of cars could have HD, assuming that every new car has it installed this year.

I do not see digital only taking place before the whole concept of OTA radio fades away.

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Now that the AM digital-only testing have been completed and results being released, it will be interesting to see whether some group owners will be interested in taking some of their 'surplus' AM stations that direction. I know of one owner who participated in the digital-only tests who definitely is.

At least the test results will probably re-spark the conversation about options for AM.

Kelly A said:

Guess the engineering wasn't so BAD after all! The only bad things around here are Bruce's claims.

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These are all good data points. We currently have two people living with us, so I have two more cars to add to the experiment. I am replicating YOUR results, not mine. The science is leading me to the conclusion that - as statistically suspicious as it sounds, I have TWO cars - mine and my daughter's boyfriend - that are the exception to the rule. Unlikely, but if that is where the science is pointing, so be it. I am not able to jam the HD with the local oscillator of either of the two new cars added to the mix. The Toyota the DID jam them is laid up with an electrical problem. I am thinking IT has the problem, not HD. It has a good stock Toyota radio in it, but it has been replaced once. I am thinking the grounding on it may not be good.

Which leads me to question- what I am experiencing in traffic? Is it a series of dead zones at traffic lights that would happen regardless of the car next to me? Possibly.

Anyway, I appreciate everybody trying the experiment - and I am the first to say that my previous observations are incorrect, based on too small of a sample size.

rbrucecarter5 said:

Which leads me to question- what I am experiencing in traffic? Is it a series of dead zones at traffic lights that would happen regardless of the car next to me? Possibly.

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Are you using an aftermarket or OEM radio? If aftermarket, what is the brand and about when was it purchased?

They have really made strides to refine the way the analog and digital portions interact, including reception quality. My wife's factory radio in her Jag is heads and shoulders above one the original Kenwood aftermarket HD radio from back in the early 2000's. Your issue still sounds like the product of an older aftermarket radio, or a problem with the installation.

landtuna said:

My cousin and I both own 2012 Hyundai Genesis which come with a Lexicon HD radio. We also tried this experiment with our two cars parked side by side and could not replicate the "interference" claimed by rbrucecarter5.

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Now here are two people who need to get a life.

TheFonz said:

Now here are two people who need to get a life.

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I agree because if anyone actually wastes their time broadcasting all digital AM it will be about as popular as IBOC was and will quickly become a not so interesting footnote to broadcasting like AM IBOC is about to become.

KB1OKL said:

I agree because if anyone actually wastes their time broadcasting all digital AM it will be about as popular as IBOC was and will quickly become a not so interesting footnote to broadcasting like AM IBOC is about to become.

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All digital is still IBOC.

I think some AMs would be good candidates for all-digital operation. Those that play music and feed a translator, for example. Few if any will listen on AM when the FM presents a viable alternative. The AM signal is already just a formality in those situations, so why not embrace something that may work well and have better fidelity?

tomservo said:

Those that play music and feed a translator, for example.
Few if any will listen on AM when the FM presents a viable alternative.
The AM signal is already just a formality in those situations,
so why not embrace something that may work well...?

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There are many that are doing just this, and if they do as you suggest, they use the all-digital AM as a simple STL...why not?