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 Post subject: Other uses for the AM band
PostPosted: Mar Mon 23, 2020 2:55 pm 
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A guy who belongs to the Orange County Woodworkers tells me that he believes that AM is going away because others want to frequencies. Who would want them? All of the new stuff is high frequency, not way down at 550 to 1800 kHz. Do you know of any users who would want to be somewhere in that frequency range?

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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Mon 23, 2020 3:31 pm 
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AM broadcast will be around for ever. No way would another service remove the licensed AM stations. And, there is no value in the frequencies except for AM broadcast.


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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Mon 23, 2020 4:06 pm 
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Tell him to try making a cellphone that works on 600 KHz and see how well that works :lol:

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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Mon 23, 2020 5:51 pm 
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I did ask him who he thinks would want those frequencies. He mentioned something about garage door operators or some such things. He is a serious guy. I mentioned that WWV was threatened, but survived.

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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Mon 23, 2020 6:05 pm 
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Maybe they could make a cellphone that operates there. That would give the kids something to load up their backpacks with. Maybe 30 pounds worth with the batteries. They could put up flags on their whip antennae.

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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Mon 23, 2020 6:23 pm 
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Years ago, I had a complimentary subscription to Microwaves and RF, where papers on ultra-wideband antenna designs by teams of graduate students routinely appeared. I wondered, what if these designs could be upscaled, so that a transmitter site could use a large portion of the mediumwave band for datacasting? Unfortunately, the VSWR of these broadbanded antenna designs is often not that good, nor is it very flat. For close-range systems transmitting milliwatt powers, it is acceptable. The same would not be the case for transmitters delivering hundreds or thousands of watts.


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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Mon 23, 2020 6:25 pm 
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In 1921 hams had everything above about the top of the current AM broadcast band. They shiwed that shortwabe wasn't "useless" by spanning tge Atlantic.

After that, there was a slow whittling down of the ham bands.

But n 1979, a couple of new shortwave ham bands were added, and more recently some slicesbelow tge AM broadcast band.

It happens because others have vacated. The loss of ham frequencies in since 1979 have been at VHF and mostly microwave.

Tv got a massive slice after WWII, and then later UHF channels. Which basically.meant any new service had to come from existing allocations until technology improved to allowuse if much higher frequencies. For a lot of use higher is better.

Nobody wants the AM broadcast band. There is nothing here that rangw woukd actually be needed.


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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Mon 23, 2020 6:40 pm 
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The antenna for GDO xmitt in BCB band would be cumbersome. Garage door openers in '60s were on 27Mc(unused space between CB freq), moved in early '70s to 290-400Mc, eventually settled on 390Mc. These days some are in the 315Mc range, similar to automobile remotes, also I've seen 433Mc mentioned. Nabbing a couple fairly narrow UHF freq from GDO gains little usable bandwidth.

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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Mon 23, 2020 7:03 pm 
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Band allocations are, to a large extent, a market-driven phenomenon. For example, over a decade ago, Qualcomm bought a nationwide license for UHF channel 55 so that it could deploy its now-defunct Media-FLO technology. More recently, we have had UHF channel re-packing, with wireless carriers bidding on the re-allocated UHF channels. If a company or companies wanted to buy part of the AM band in a similar fashion, I am sure that they would present a proposal to the FCC. That hasn't yet happened.

We all know that basic physics dictates that any commercial re-purposing of the mediumwave band (should it happen) would involve one-way transmission from a large antenna to modestly-sized or small receiving antennas. I consider it entirely possible that in today's world, where the paradigm of two-way communications is dominant (that is, interactive media, on-demand content, and the ability for content creators to count individual instances of access to their content), nobody would make a financially serious proposal for rights to use the band. Given such circumstances, the AM band would become largely unused and stay that way for a long time, much as it is now in large parts of Europe. Amateur radio operators might eventually be granted experimental use of portions of the band, as was the case with 500 kHz some years ago, but there isn't any financial incentive that would make this a priority for the FCC.


Last edited by Alfredo_T on Mar Mon 23, 2020 11:32 pm, edited 1 time in total.

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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Mon 23, 2020 8:35 pm 
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Early cordless phones used 160 meters and 49 MHZ. As others have said, no radio service would want those low frequencies. I'm glad because I love AM broadcast.


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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Mon 23, 2020 8:46 pm 
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FStephenMasek wrote:
A guy who belongs to the Orange County Woodworkers tells me that he believes that AM is going away because others want to frequencies.

Tell the guy that people in hell want ice water, but they ain't gonna get it anymore than the 4700 AM stations across the country are gonna give up their livelihoods.

And even IF there were a use for the band, why not simply look at long wave (below 500 kilocycles) instead. There's little to no use of it anymore.

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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Mon 23, 2020 9:20 pm 
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The AM broadcast band is about 1MHz wide. Below is at best 540KHz, but less since below it gets impractical at some point.

Note the tuning ranges of the average short wave radio. If each band covers a 2:1 range, you get diminishing returns the lower you go.

So there isn't much space below the am broadcast band. Remember, a hundred years ago everything was jammed into that space.


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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Tue 24, 2020 1:11 am 
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There used to be an ISM band (Industrial, Scientific, Medical) around 450 KHz. There would be some possible use for Induction Heating at a slightly higher frequency. Would make the tank resonating capacitors a little smaller.

https://www.militaryaerospace.com/direc ... y-used-for

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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Tue 24, 2020 2:45 am 
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I have a theory that I cannot prove without a spectrum analysis, that maybe by now the bands 30-50, 150-170 MHz are hardly utilized like they used to be. Seems to me that most civilian gov't services in that range went to 800-900 and abandoned the lower bands. The bands may still be allocated for stuff that is no longer there. Maybe people hold on to it figuring they will never get it back if they let it go? Maybe alot of business services or things that are low usage. Anyone know about that? Between the two, that is alot of channels if you have say, 20 KHz spacing. Maybe you can have less spacing with the narrow band splinter channel radios.

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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Tue 24, 2020 3:06 am 
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fifties wrote:
Tell the guy that people in hell want ice water, but they ain't gonna get it anymore than the 4700 AM stations across the country are gonna give up their livelihoods.

Agreed.

If AM stations were dropping like flies, I could see serious considerations when maybe 5% of present were remaining. Currently ain't happnin' any time soon.

On other hand, over 60 AM outlets went dark in 2019.

https://www.fcc.gov/media/radio/silent-am-list

On other-other hand, 70 FM outlets went dark during 2019. That's counting only full power stations and not repeaters or low power outlets.

https://www.fcc.gov/media/radio/silent-fm-list

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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Tue 24, 2020 3:31 am 
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30-50MHz was allocated early enough that there weren't many options. They likely soon found that skip was a problem. So a move to higher frequencies as soon as feasible.

I had an SP-600 in the seventies, and I tuned the 30-50MHz band and the only lanky cal stuff I heard was some paging. I know there were articles back then about the move to 450MHz.

You don't want skip, but since it's local higher frequencies aren't a problem.

I don't know about the 150MHz band, I haven't listened in decades, but of course weather radio and the marine band are there, and not so convenient to move. MURS was added 20 years ago, at least an indication that some frequencies could be freed up.

In the past, if a slice was needed, the FCC would decide, and take it from an existing service. So users were expected to vacate. Witness the marine band at 2MHz or so, there was a changeover from am to ssb in the seventies, the announcement well in advance. And the 150MHz marine band added, many users moved there with tye change.

The spectrum for sale thing is fairly recent, I have no idea if it's a constant. TV didn't get grandfathered in recent times with the switchover to dtv, and the more recent repack.


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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Tue 24, 2020 5:47 am 
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35Z5 wrote:
fifties wrote:
Tell the guy that people in hell want ice water, but they ain't gonna get it anymore than the 4700 AM stations across the country are gonna give up their livelihoods.

Agreed.

If AM stations were dropping like flies, I could see serious considerations when maybe 5% of present were remaining. Currently ain't happnin' any time soon.

On other hand, over 60 AM outlets went dark in 2019.

https://www.fcc.gov/media/radio/silent-am-list


60 as a percentage of 4700 = 1.27%. I can't imagine any other line of business having that small of an annual failure rate.

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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Tue 24, 2020 6:22 am 
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Indeed, math helps us understand many things. Mapping the failed stations to show location and transmitter power would be even more useful.

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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Tue 24, 2020 3:24 pm 
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well, 1.27% failure rate just happens to be the fatality rate in the US for covid 19..and that rate has caused the country to go upside down. just sayin...


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 Post subject: Re: Other uses for the AM band
PostPosted: Mar Tue 24, 2020 3:50 pm 
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fifties wrote:
35Z5 wrote:
fifties wrote:
Tell the guy that people in hell want ice water, but they ain't gonna get it anymore than the 4700 AM stations across the country are gonna give up their livelihoods.

Agreed.

If AM stations were dropping like flies, I could see serious considerations when maybe 5% of present were remaining. Currently ain't happnin' any time soon.

On other hand, over 60 AM outlets went dark in 2019.

https://www.fcc.gov/media/radio/silent-am-list


60 as a percentage of 4700 = 1.27%. I can't imagine any other line of business having that small of an annual failure rate.


That was the orig intent of post but somehow I dropped ball mid field. Glad you picked up and made it to goal line.

Originally I was checking to see if WRON was on, as it had gone dark in early '18. Apparently listing only gos back a year. And yes WRON is back on air, none of the listings are necessary permanent.

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