April 25, 2020 at 1:45 am #46022
“RF Spectrum Ranges include:
Very Low Frequency VLF 3 – 30 kHz
Low Frequency LF 30 – 300 kHz
Medium Frequency MF 300kHz – 3 MHz
High Frequency HF 3 – 30 MHz
Very High Frequency VHF 30 – 300 MHz
Ultra High Frequency UHF 300 MHz – 3 GHz
Super High Frequency SHF 3 GHz – 30 GHz
Extremely High Frequency EHF 30 GHz – 300 GHz”
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April 25, 2020 at 8:01 pm #46029washnotoreParticipant
- This reply was modified 1 month, 1 week ago by semoochie.
RF Spectrum also include this band too.
Extremely low frequency 3 to 30 HzApril 25, 2020 at 11:55 pm #46030
It must have been added after 1971.April 26, 2020 at 12:52 pm #46034
ITU, magnetospheric scientists, and atmospheric scientists have differing definitions for ULF and ELF. For more information, see the beginning of this article:
The ITU definitions are as follows:
ELF is 3-30 Hz.
SLF is 30-300 Hz.
ULF is 300-3000 Hz.April 26, 2020 at 4:05 pm #46037Andy BrownParticipant
Any frequency can be used as a carrier. The question becomes will it propagate through the medium chosen.
Generally, apart from the research scientists the lowest “radio frequency” is 3 kHZ (3,000 Hz.).
Frequencies below that are not considered “practical” radio frequencies. In most discussions, the band between D.C. and 20 Hz. is considered sub-audible. 20 Hz. to 20 kHz. is considered audible frequencies which overlap the lowest radio frequencies. If you recall tape recording techniques, bias frequencies were often in the audible range and used as a carrier to be modulated by full spectrum audio to get it great enough in magnitude to leave their electromagnetic waveform on the tape. Submarines communicate with ELF carriers but it’s not practical for mainstream use due to the size of the antennae needed.
The true bottom line in this discussion is that the U.S. Government has no allocation below 9 kHz. Of course if they figure out a way to make money at those frequencies, they’ll change that but for now . . .April 27, 2020 at 1:19 am #46050
I find it fitting that ELF is extremely low. 🙂April 27, 2020 at 9:16 am #46055
And yet ELF, at present, is so much more popular than ancient a.out or COFF.
(Alfredo_t, please don’t jump in and explain that joke. Let’s let them research and figure it on their own.)
If you recall tape recording techniques, bias frequencies were often in the audible range and used as a carrier to be modulated by full spectrum audio to get it great enough in magnitude to leave their electromagnetic waveform on the tape.
AC bias, the basis of so-called “crossfield” recording. A continuous high-frequency audio signal is written to the tape by the erase head, before being partially overwritten and modulated by the audio signal from the record head. This is done to increase the recording’s frequency response and fidelity. IIRC this method is used on virtually all cassette and reel decks made since the late 60s that are worth spending money on, except for shittiest-of-the-shitty cheapo recorders with DC bias and permanent-magnet erase heads.
Domestic 8-track cart recorders were not capable of this since most (if not all) lacked erase heads, instead using a “brute force” recording method of pushing a high-amplitude record signal out the audio head in the hope that it would mostly erase the existing recording on its own. Just like the 8-track format itself, it was a kludge. This is why most home-recorded 8 track tapes tend to sound very muddy and noisy compared to better-quality commercial tapes like those from Columbia and RCA.April 27, 2020 at 10:58 am #46056
I may have a very dim recollection of recordable 8-tracks. How long were they around and was there any appreciable success?April 27, 2020 at 12:11 pm #46057
I have a very vague memory that Radio Shack had an all-in-one stereo system in the early 1980s that was capable of recording 8-tracks. I did not know about the brute force erase method, though.April 27, 2020 at 12:42 pm #46059
To me, it seems ironic that the scientists who study atmospheric phenomena, such as whistlers and Schumann resonances, would deliberately use nomenclature for frequency bands that differs from the ITU’s decade-based naming scheme. However, they might have their reasons for wanting certain frequency ranges in common “bands.” I guess that it’s not my place to tell them how to do their jobs.April 27, 2020 at 12:57 pm #46060jr_techParticipant
My Pioneer H-R100 8 track recorder uses AC bias and AC erase IIRC, around 60 khz. It also has Dolby noise reduction available. Fairly decent sounding, for an eight track device.April 28, 2020 at 12:40 pm #46071
Okay, I stand corrected! :thumbup!
Unfortunately, though, high-quality decks that did that were certainly not terribly common. The bulk of recorders, especially those built into combination stereos of the day, were very simplistic machines as I described above. Maybe there were more that had AC bias but most certainly didn’t have erase heads.
How are the heads in your machine arranged, narrow erase and record/play heads mounted together on the same movable bracket (where a large audio head would be in most other machines) or a 2-in-1 device of some sort?
As a kid I had a boombox-type machine that had a DC bias 8-track recorder. It was an average-joe, Juilette (Topp) “Brixton briefcase”-type stereo machine that my dad purchased at Fred Meyer’s or Sears about 45 years ago with AM/FM and a line input. Curiously, though recordings made on it were quite lacking in high end response even with treble all the way open on a proper component player runing through a stereo system, it didn’t seem to have that staticky “rumbling” noise in the background like cassettes recorded on 80s/90s DC bias equipment had. Were 8-track and cassette emulsions really THAT different or were low-end electronics just designed and constructed better in the mid-70s?
(Sidenote: I had acquired a Frontier cassette adapter, with the box and documentation, at a yard sale for something like $1. This was about 20 years ago when there was so little demand for 8 tracks and records that you coulan’t even give them away. That unit was so well aligned that it blew my Sony component cassette deck’s ass to the kerb! I think somebody might had twerkosquinkulated the adapter’s head azimuth at some point because it likely wouldn’t have been that dead-on coming from Hong Kong. With it, the Juliette was such a decent-sounding combination that I used it as my workhorse portable cassette machine and PA amp for PDAs and pocket CD players until it finally died about 10 years ago. I never did try recording a cassette through the adapter, though I doubt it would have worked.)
I have a couple Dolby System tapes in my box, and I think it came along fairly late in the format’s lifecycle. The only commercial releases I’ve ever seen that have it were on Columbia, were others using it?April 28, 2020 at 1:21 pm #46072
I may have a very dim recollection of recordable 8-tracks. How long were they around and was there any appreciable success?
I know they were around in the mid to late 70s and possibly early 80s. The few I’ve seen had the notch in the front corner to activate quad machines.May 9, 2020 at 12:58 am #46226
I can’t even get fibre since Centuryshit have stated they have no plans to pull cables into my neighborhood. Unless I were to develop a masochistic side that pushes me to live with the headaches and bleeding ulcers that come with dealling with Commiecast, I’m stuck paying for 15M/5M VDSL2 and getting 9.2M/896K on a good day. Closest thing I can hope for is fiber to the concentrator with a decrepit last-quarter-mile copper pair to the house.
Rereading my earlier post, I am reminded of the late, great Andy Williams:
“No! We will NEVER give you fiber! Not now, not ever, NEVER!”May 11, 2020 at 4:19 pm #46256e_dawgParticipant
I recently notice that KEZI antenna is located on top of Prairie Mountain which is home to KFLY/KDUK radio stations. Can anybody pick up KEZI OTA in Salem or south metro Portland area easily? Also, how easy in Salem and south metro Portland area to pick up Eugene TV stations? I know KVAL-13, KMTR-16 KEPB-28, and KLSR-34 transmit from Blanton Heights.
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