New HD radio owner

[briankay]

Both run HD, and neither one locks throughout a major portion of the Bay Area. The analog signal of each is full of static in Fremont and Mountain View, with severe picket-fencing. Figure 2.5.2 of that document presents a great theory, but in practice it doesn't work with a Sony, Visteon, or JVC receiver. I'll let you know when I get my little Mighty Red unit.

But do you agree that the digital signals don't overlap? Of course the analog of each station is going to obliterate one of the digital sidebands of the other station in the Bay area example of 98.9 & 99.1, after all the analog has 200 times the power. (each sideband is a 1/2 % of the power with both sidebands totalling 1 % power) So if you're unable to lock, it appears the opposite sidebands are also being trashed by other 1st adjacent analogs on the other side also. This overlap of the primary contours scenario happens in the Chicago market also (where I live) on 96.9 and 97.1 with WWDV & WDRV, It falls out of HD lock over a small area of the overlap, however because the analog signal of both these stations (they simulcast) is so strong in this overlap area, it blends to good quality analog, which I think is an acceptable compromise for a digital system that the FCC stated had to be shoehorned in on existing specturm. I know for some here this is not acceptable, but I'm prepared to live with it.

In these extreme short spaced cases (which are the exception) a non-symmetrical power increase is the proposed solution.

 

[rbrucecarter5]

But do you agree that the digital signals don't overlap?

In these extreme short spaced cases (which are the exception) a non-symmetrical power increase is the proposed solution.

Nope - your not going to make your point by trying to trap me. Remember - I drove that road. The signals don't blend - they fall off a cliff! One bend of the road, you get only 99.1, the next bend, only 98.9. It is quite dramatic. About the only thing that could benefit that situation would be the alternate frequency lists - and HD radio doesn't have that capability. Certainly - no power increase in the world will stop the attenuation in that mountainous area. It is several decades, and in the few feet where the stations might overlap as first adjacents, you are still going 15 to 25 miles an hour - far too fast to give HD time to lock. Once you get a clear shot at one or the other, you still have a lock, and the best scenario on that road would be 30 seconds of HD lock, followed by manual re-tuning when the station drops, then seconds before HD lock again, etc. NOT a very good advertisement for the improved reception due to HD radio. The maximum power increase proposed is 10 dB. Take a spectrum analyzer up there if you don't believe me. I guarantee you are seeing 50 to 60 dB of signal fluctuations. The power increase won't help there, any more than 6 additional feet in office buildings will help. The only thing you will succeed in doing with the power increase is jamming stations across the country when the next solar max occurs - about 2012 or 2013.
There is a huge difference between the 500 to 1000W power level skipping across country, as opposed to 5kW to 10 kW. The lower power levels skipping hundreds of miles is comparatively rare, but the higher power levels - skip is commonplace. But let's go ahead and re-make the FM band in the image of AM - just in time for the radio streaming revolution to hit in cars - and see whether streaming or HD comes out on top ---

 

[DaveBayArea]

rbrucecarter5 is right. Using the spectrum analyzer that counts (a pair of ears) I can tell you that the nulls must be greater than 20 db because there's digital noise on the analog audio of both of those stations. Probably the difference between the plains of Illinois and the mountains of the Bay Area. We get the same thing on 107.5/107.7, 91.5/91.7, and 95.9/95.7. But in those cases the suburban stations aren't running HD.

You bring up an interesting point, however. If an HD receiver is supposed to lock on either the upper or lower set of carriers independently, then there's something seriously wrong. That doesn't happen at all from what I've seen.

Dave B.

 

[briankay]

It definitely can pull from either sideband and continuously compares the integrity of the data from each band and I believe it seamlessly switches sometimes time thousands of times a second, for the audio data stream to stay above a given error threshold.

As an experiment, if you have one (or better yet two) of those mini FM transmitters you can confirm this. Tune in to a local HD station that doesn't have easily receivable first adjacents. Tune the mini TX to 0.2 MHz higher for a few moments and then to 0.2 MHz lower than the local HD station frequency, the HD reception should continue. Now if you have 2 TXs tuned 0.2 above and 0.2 below, then the HD lock will fail after a few seconds. Also another thing you can try is if the TX is not too close, tune the TX to the actual frequency of the local HD station, the HD signal will likely remain receivable if the mini FM TX is of good technical quality.

As I said before in a perfect FCC world, digital radio would have its own spectrum, now that HD radio is here, I feel it's wasted energy putting my focus and time into discovering what's wrong with HD radio and instead focus on what will make it work long term even if that is at the expense of analog FM not being receivable in 100% of areas (which was never the case anyway in an analog only world, pre-HD)

 

[DaveBayArea]

Also another thing you can try is if the TX is not too close, tune the TX to the actual frequency of the local HD station, the HD signal will likely remain receivable if the mini FM TX is of good technical quality.

I don't have the ability to do these tests real soon, as I'm not at my home QTH. But I can tell you for sure that this test would work. We have an interesting situation here in the Bay Area with the 92.7 frequency. The one in Alameda doesn't run HD, and the one in the Monterey Bay does. The Alameda signal is stronger, and is captured on analog FM. So you get a few seconds of KREV. Then HD locks and you get country from KTOM. I don't listen to either one of the stations on a regular basis, but if you're driving around the transition is somewhat amusing.

Dave B.