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Guys this could be a problem

J

jras20

I took a video last night of this. I am 30 miles from KVET in Austin. During the tripo skip last night, check it out the KVET HD Signal just wouldnt lock. And the SSI signal was great at 17-18. I think we need to work on this. I'm using HD more and more now. I'm working on it out in my place in Lavaca county.

http://www.youtube.com/watch?v=VqOXd1yz3D0
 
jras20 said:
I took a video last night of this. I am 30 miles from KVET in Austin. During the tripo skip last night, check it out the KVET HD Signal just wouldnt lock. And the SSI signal was great at 17-18. I think we need to work on this. I'm using HD more and more now. I'm working on it out in my place in Lavaca county.

http://www.youtube.com/watch?v=VqOXd1yz3D0
Click to expand...

The tropo skip across the Gulf has been incredible the last few days. You are close enough to the coast to get some effect, I'm even seeing some effect here in Dallas.

This does highlight the idiocy of using adjacent channels for IBOC sidebands. Any analog signal there at all destroys HD lock. That is why it doesn't work on AM, even if there isn't a first adjacent there in daytime, it is sure to be there at night or at least there will be noise there.

It also illustrates why it is foolish to try to resolve the problem by increasing the power. The present sideband levels don't tropo skip very well. Once you get a tenfold increase in power, tropo skips are going to mutually jam HD FM stations around the country.

It is an interesting idea, just the technical details that were poorly done.

Here is my proposal to save HD radio:

(1) Move the FM sidebands to within the existing 200 kHz channel allotment, displacing any subcarrier services other than analog stereo. There is plenty of room if you get rid of SCA, RDS, reading for the deaf, and all that other stuff. It is done better with HD: HD-2, etc., data capability, etc. Once the sidebands are off adjacent frequencies, tropo skip helps HD - not hurts it. And all adjacent channel interference complaints are resolved. Narrower channels mean more gain and less noise due to the gain / bandwidth limitation of receivers, so range and building penetration will increase. Win win scenarios all around, except for a very tiny minority of listeners using existing subcarrier services, who could be subsidized to buy new receivers.

(2) Abandon the IBOC system presently in place, replace with AMAX standards, and have the FCC mandate AMAX including stereo on all receivers costing over $50. C-Quam stereo is very robust, has good range, good building penetration, works at night, sounds great. Most consumers have never heard of it so wouldn't be the wiser, most HD receivers sold to date already decode it in some fashion - and future receivers could be made to do the job better. AM sounds great again on regular radios, the self jamming problem is mitigated on cheap AM radios with broad IF bandwidth, there are no adjacent channel problems. Win win for everybody.
 
You can just imagin what I can get out in Lavaca county during very intense Tripo in the summer months. Sometimes I get FM in Lafayette with my outdoor or dipole. Thats a good idea. I think HD should go to a diffrent band, not the same as FM/AM.
 
rbrucecarter5 said:
Here is my proposal to save HD radio:

(1) Move the FM sidebands to within the existing 200 kHz channel allotment, displacing any subcarrier services other than analog stereo. There is plenty of room if you get rid of SCA, RDS, reading for the deaf, and all that other stuff.
Click to expand...

I'm not so sure about that -- unless we are willing to make a bunch of existing analog receivers obsolete. I doubt they would be able to filter out digital sidebands so close.

Remember Carson's Bandwidth Rule-of-thumb bandwidth = 2m + 2f suggests the occupied bandwidth of a mono station with 15 kHz audio and 75 kHz deviation is 180 kHz.

Of course, with stereo, the L-R subcarrier occupies the range up to 53 kHz, although the deviation of this component rarely exceeds 40-50 percent. Still, Carson's Rule would say the required stereo bandwidth exceeds 220 kHz, assuming 30 kHz deviation of the L-R signal. This is one reason why the 73.317 analog FM mask allows full energy out to 120 kHz from the center of the channel.

However, I think your plan is very considerate of the neighbors -- and at this time, FMeXtra is the digital scheme that probably comes closest to meeting your ideal.
 
I have heard FMeXtra is by far the best out there right now, supposedly kills IBOC but then again so does analog.
 
rbrucecarter5 said:
(1) Move the FM sidebands to within the existing 200 kHz channel allotment, displacing any subcarrier services other than analog stereo. There is plenty of room if you get rid of SCA, RDS, reading for the deaf, and all that other stuff. It is done better with HD: HD-2, etc., data capability, etc. Once the sidebands are off adjacent frequencies, tropo skip helps HD - not hurts it. And all adjacent channel interference complaints are resolved. Narrower channels mean more gain and less noise due to the gain / bandwidth limitation of receivers, so range and building penetration will increase. Win win scenarios all around, except for a very tiny minority of listeners using existing subcarrier services, who could be subsidized to buy new receivers.

(
Click to expand...

I like the idea, but if that actually worked, don't you think they would have done that in the first place? My guess (and it is only a guess) is that moving the sidebands in so they actually were "in band on channel" they would cause lots of interference with the analog portion of the signal.

I wish it could be done as you describe, and maybe it can. I'd have no objection to HD on FM if that were the case. I'm concerned that if a power increase is allowed for HD, then we really will have some interference issues.
 
KB1OKL said:
I have heard FMeXtra is by far the best out there right now, supposedly kills IBOC but then again so does analog.
Click to expand...

Bob,

Unless you've heard something definitive that I have not, FMeXtra is marketed to be 100% HD compatible. From a tech aspect it SHOULD be ok. After all, HD was formulated to leave SCA intact. And FMeXtra IS SCA. FMeXtra appears to be a nice system, although it has virtually no stations and only works on a "Sort Of" available radio. IF DRE could get some receivers to market, it very well MIGHT get some popularity. I pitched it to my SCA client a while back and they were less than enthusiastic about the $200 price tag. (That's a euphemism for "Do it under our existing contract and we'll sue you" :)) Especially since they're quantity selling FM SCA portables for $29.99 and making a profit doing it. Some here may recall the FMeXtra Challenge. :)

I'd suspect if there was a $99 radio available, and hope of lower prices someday, they'd have bitten. Frankly, they'd have bitten on HD at it's cost structure. It was just too pricey for my own little operation, since everyone from desert translators to major market full C's pay the same to iBiquity.

Clouseau
 
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