-
Get involved.
We want your input!
Apply for Membership and join the conversations about everything related to broadcasting.
After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
If you use a disposable or false email address, your registration will be rejected.
After your membership is approved, please take a minute to tell us a little bit about yourself.
https://www.radiodiscussions.com/forums/introduce-yourself.1088/
Thanks in advance and have fun!
RadioDiscussions Administrators
IBUZ; therefore, I am
- Thread starter 4CX1000A
- Start date
Apparently my "lurking" has gotten a little lackluster, so I'm late to this party. (I was up late at the Barney Frank departure party so I'm a little hung over.) This morning's "most unfortunate Chyron" winner from the NBC Today Show starring Savannah Guthrie and the soon to be ex-Congressman: BARNEY FRANK ONE-ON-ONE (fire "Rimshot" on rattling grey Fidelipac....)
Anyway, my Number One Son "hair" has pretty much covered the waterfront in response to Dan Strassberg's question - all I can add is that all of which Hair says about suppression of the first-adjacent digital carriers is true. BUT: the -25dBc limit applies to the carriers individually. Of course they are additive as perceived by the detector at your receiver. And, being digital carriers, they are ON 100% of the time. I think that's why the amplitude of the hiss is so high. Take fifty full-on fulltime digital carriers and superimpose them on desired audio, and small wonder they're such a problem - even at relatively low power.
Anyway, my Number One Son "hair" has pretty much covered the waterfront in response to Dan Strassberg's question - all I can add is that all of which Hair says about suppression of the first-adjacent digital carriers is true. BUT: the -25dBc limit applies to the carriers individually. Of course they are additive as perceived by the detector at your receiver. And, being digital carriers, they are ON 100% of the time. I think that's why the amplitude of the hiss is so high. Take fifty full-on fulltime digital carriers and superimpose them on desired audio, and small wonder they're such a problem - even at relatively low power.
Until the advent of DSP-based HD Radios, "modern" radios were generally of poorer reception quality than their counterparts of the 1960's and even 70's. But the new HD Radio tuners?? WOW those suckers are sensitive. If nothing else comes out of HD Radio, one really good thing is that it's ushered in a new era of high-quality receivers. Perhaps too late to make any difference, but still!
To answer your question, though, there are three main reasons why the AM band is of questionable viability today, and they're intertwined:
- Too many stations, especially on the Class C graveyard channels, leading to significant co- and adjacent-channel perceived interface for the bulk of listeners. The FCC has made this problem worse in its attempts to solve it by allowing stations to increase ERP, especially at night, to provide theoretically better NIF at the COL but at the cost of the entire band being total hash after sunset.
- Increasing sources of interference from non-radio sources, especially wallwart power supplies/chargers for cellphones, laptops, iPods, etc etc etc. There's a lot more stuff plugged into wall outlets than there was before 1980 and a lot of relies on very "noisy" power sources. This is ESPECIALLY noticeable with 12VDC "cigarette lighter" style chargers in the car, which put out a HUGE amount of noise on your average car radio.
- Broadcasters generally electing to narrow their transmitted bandwidth (often to only 5 kHz) to decrease fidelity but increase resilience to perceived interference. Thus making AM sound sonically inferior to FM...and also to CD's and (most) MP3's.
aaronread said:
a sad piece to this is that manufacturers are skimping on about 5 cents of parts, literally leaving off lowpass filter capacitors where there are screened places on the board for, as the device "works" without them (and a FCC sticker gets slapped on anyways!)
even if you have terrible powersupplies, a common-mode choke before antenna feedpoint can kill most everything from getting into the antenna, at surprisingly close distances to the noise source. im saying i really dont consider modern electronics that much of a problem
voix divine is about 32khz and concorde about 24khz wide. stick a 10khz notch filter to nuke carrier of next station and you have pretty damn good AM signal, at least within a couple miles of stab'n'kill..
carmen said:
And what, pray tell, are voix divine, concorde, and stab'n'kill??? I have two degrees in electrical engineering but, until I read your post, I had never heard any of these terms used in the context of EMI (electromagnetic interference). When you post (here or anywhere), remember your audience. The buzz words may impress the nontechnical readers, but when you leave members of your own profession in the dust, you aren't helping the discussion or your own image!
DanStrassberg said:
Agree 100% bro! The real problem is mine and your misunderstanding of radio. We believe knowledge and understanding trumps a guy judging $1,000,000 worth of broadcast equipment with a $50.00 radio. The myriad anti IBOC posts prove us wrong. Well, we live and learn... It is extremely difficult for the wisdom of two EE degrees to compete with a guy that has TWO HD radios -- An Insignia AND an Accurian!
-
see my response to your 720 question...DanStrassberg said:
judging $1,000,000 worth of broadcast equipment with a $50.00 radio
i've no idea how much WBZ or WMKI spent but i have full confidence in qualifying the final result - crap. older radios bleed in the IBOC hash over the analog audio due to -6db/octave selectivity or whatever it is (havent measured) and the artificially narrowed AM audio to make room has been discussed nuermous times
can we establish theres an inverse correlation with money spent and audio quality, after the $1000 mark? chances are thats what these pirates paid for their transmitters off ebay ,or what youd spend in parts to build a Class E rig..beyond that you start complying with FCC regulations on bandwidth in broadcast bands due to being a legal station or operating out of the ham bands, or even splurging for IBOC...further guaranteeing the craptitude of your signal
anyways, boston has some of the best AM audio around, that is what i was oriignally getting at, and at $50 for a SDR it is more accessible than ver. not that this will prevent AM radio from dying soon
carmen said:
That's also the context in which I thought you were using those terms, even though I had read your response in the 720 thread. I just didn't memorize it. But I'm not sure that using as examples some pirates who use much more bandwidth than is allowed (even before NRSC-2) is a good argument, even though I agree AM is being written off prematurely and better (analog) radios would help.
- Status