power supply interference with radio broadcast

Richard Crowley · July 23rd, 2011, 06:31 PM

The primary info for LPFM is at: Low Power FM (LPFM) Radio Service * * *(FCC) USA (imagine that)
The power limit is 100W.
There are currently 955 licenses (they may not all be on the air.
IIRC, the application window hasn't been open for several years.
Not that would do any good, as the FM spectrum is pretty much saturated in most larger cities.

There is also "Part 15" where power is limited to 100mW (1/10 W) and range is effectively a few hundred feet. You must not interfere with licensed services, but no license is required.

Greg Miller · July 23rd, 2011, 07:45 PM

Yes, I'm aware of both of those options. But it sounds as if the NZ plan might be better.

Our LPFM licenses are largely being scarfed up by "religious" stations (e.g. the Joe's Garage Church of the Holy Smoke, etc.), conning the faithful believers out of enough money to run the broadcasts (and probably slip a little into the broadcasters' pockets as well), crowding the airwaves with content that is frequently syndicated and redundant, not to mention any of the political issues. IMHO a lot of these religious broadcasters have been a huge legal scam going back 50 years or more.

The Part 15 rules don't allow enough power to really cover any significant geographical area. Meanwhile, they do allow lots of $10 "modulators" that people use to feed their satellite radios, etc., into their FM receivers, thereby muddying up random FM channels (since Part 15 has no frequency limits) and ruining any chance for FM broadcast DX.

Renton Maclachlan · July 23rd, 2011, 08:55 PM

My stations are funded by myself and I receive no money from them whatsoever, in fact it costs me. What little advertising I carry is of no financial gain to myself - I don't charge for putting it on - and is there simply because I choose to put it on for the producers to benefit from. My stations are run to promote a message not make money...

Greg Miller · July 24th, 2011, 07:15 AM

Renton, I think that's wonderful, and I wish it were like that in this country.

Unfortunately, a 100-watt license has enough coverage to make it tempting and competitive as a money-making entity. And the Part 15 unlicensed transmitters are becoming a blight all over the FM band. The FCC made it bad enough several years ago, when they authorized first-adjacent channel spacing, without narrowing the transmitted bandwidth. Splatter, coupled with wideband receivers, has created a real mess. Now as the RF people retire, the FCC is being taken over by IT people and lawyers, so any reasonable broadcasting measures will probably never be implemented.

Renton Maclachlan · July 24th, 2011, 01:51 PM

Quote:

Originally Posted by Greg Miller

Unfortunately, a 100-watt license...

Our free to air licence has a max output of 1 watt not 100 watt...so it is very localised...max about 5>10km range depending on location of aerial. At the mo my original station is coming off virtually the top of a high hill at the centre of the population area so get about 75% of my small city - hills block the signal.

There can be an issue of interference with other stations and so there has to be a .1 separation in the frequencies 87.5, 87.7,87.9, 88.1

Only four stations can satisfactorily fit at any one place on each of the band sections made available, and it is all voluntarily controlled. If there is space on the band, anyone can go on it, and so long as you're broadcasting, you have the frequency. Major centres generally are filled up but small towns have plenty of options available apparently...

The hardware side of things is a piece of cake compared to producing a program. To produce my present 82 hour program would have taken me hundreds and hundreds of hours...6-7-800?...all in my spare time. I have about another 10-15 hours of material that could be added but I'm onto a major video production so it won't get added for months. That's no issue however as 82 hours is a hang of a long time for the program to loop. It's been running 18 months or so now - perhaps 2 years. I hear stuff on it I had forgotten I had put on!!! I think I have something unique in the world...

Greg Miller · July 24th, 2011, 02:13 PM

Yep, Renton, I think a 1-watt license is a great solution! It allows you to cover at least a "small community" so it's worthwhile to run such a station. It encourages public use and "free speech" on the airwaves, which is good, since the airwaves allegedly belong to the people (at least that was the original concept here, up through our Communications Act of 1934, although recent FCC actions have largely diluted or removed the concept of perpetual public ownership).

And by setting aside a certain part of the spectrum for these 1W allocations, you avoid the problems we have here with the "Part 15" very-low-power stations which can still produce enough RF to interfere with FM broadcast DX reception. (A local health center, which broadcasts their exercise music on 104.5MHz, prevents my listening for any distant legitimate stations on 104.3, 104.5, 104.7 MHz.)

There are a lot of other problems with the LPFM allocations here, and the channel spacing, but I won't go into that here.

So yes, I think NZ has come up with a much better solution.

And kudos to you and anyone else who is willing to invest enough time and energy to run such a station at your own expense. I do believe in free speech. 8-)

Brian P. Reynolds · July 24th, 2011, 08:16 PM

I bought a 1w FM transmitter off eBay and it works well on the occasions I have used it... I don't have a license and never even tried to get one. The times I have used it for wouldn't have mattered anyway.
It worked well as a 2 channel radio mic transmitter for about 2km in a forestry area at a car rally and I use it regularly as an FX mic transmitter on the starting gates for horse races, most of those tracks I work at are well out of town.
I work on the attitude if some one does come across the frequency, then works out what the sound is, then finds it.... I would have finished the job and out of there.
I have also used it as an IFB feed for some rowing championships.
In Australia they are used for things like Drive in movie theatres (and listen on the car radio), Real Estate sales info in new housing estates, Localised radio for outdoor sporting events like car and bike racing. One of the small towns nearby do a wonderful Christmas lights display with all the houses up in lights, run a Low Power FM TX for music of the season.

Renton Maclachlan · August 23rd, 2011, 02:46 AM

Just thought folks may like an UPDATE on this radio interference issue...

The problem definitely was the switching power supply for the Ipod...

After chasing a rabbit around for awhile, distilling all the advice I was getting from kind people all over the show, I finally got a 5v linear power supply out of Hong Kong (They seem as rare as hens teeth in NZ).

On Monday this was connect to a USB lead and I installed it tonight and the problem is solved.

There was a potential issue discovered on the web that fourth gen ipods will not charge if only the power wires are connected - a 'something er rather' reputedly needed to be installed across the data wires, but as it turned out, this was not necessary.

We could have got another power supply, one that could be switched between various voltages and put a different sort of 'something er rather' in the cable to limit a higher voltage output down to 5v, but as I got a 5v, one that wasn't needed. Ipod power input is limited to 4.75v > 5.25v.

So...thanks everyone for all the help given in tracking down and solving this issue...

July 23rd, 2011, 06:31 PM	#61
Richard Crowley Trustee Join Date: Aug 2007 Location: Portland, Oregon Posts: 1,238	Re: power supply interference with radio broadcast The primary info for LPFM is at: Low Power FM (LPFM) Radio Service * * *(FCC) USA (imagine that) The power limit is 100W. There are currently 955 licenses (they may not all be on the air. IIRC, the application window hasn't been open for several years. Not that would do any good, as the FM spectrum is pretty much saturated in most larger cities. There is also "Part 15" where power is limited to 100mW (1/10 W) and range is effectively a few hundred feet. You must not interfere with licensed services, but no license is required.

July 23rd, 2011, 07:45 PM	#62
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,791	Re: power supply interference with radio broadcast Yes, I'm aware of both of those options. But it sounds as if the NZ plan might be better. Our LPFM licenses are largely being scarfed up by "religious" stations (e.g. the Joe's Garage Church of the Holy Smoke, etc.), conning the faithful believers out of enough money to run the broadcasts (and probably slip a little into the broadcasters' pockets as well), crowding the airwaves with content that is frequently syndicated and redundant, not to mention any of the political issues. IMHO a lot of these religious broadcasters have been a huge legal scam going back 50 years or more. The Part 15 rules don't allow enough power to really cover any significant geographical area. Meanwhile, they do allow lots of $10 "modulators" that people use to feed their satellite radios, etc., into their FM receivers, thereby muddying up random FM channels (since Part 15 has no frequency limits) and ruining any chance for FM broadcast DX.

July 23rd, 2011, 08:55 PM	#63
Renton Maclachlan Trustee Join Date: Jul 2007 Location: New Zealand Posts: 1,180	Re: power supply interference with radio broadcast My stations are funded by myself and I receive no money from them whatsoever, in fact it costs me. What little advertising I carry is of no financial gain to myself - I don't charge for putting it on - and is there simply because I choose to put it on for the producers to benefit from. My stations are run to promote a message not make money...

July 24th, 2011, 07:15 AM	#64
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,791	Re: power supply interference with radio broadcast Renton, I think that's wonderful, and I wish it were like that in this country. Unfortunately, a 100-watt license has enough coverage to make it tempting and competitive as a money-making entity. And the Part 15 unlicensed transmitters are becoming a blight all over the FM band. The FCC made it bad enough several years ago, when they authorized first-adjacent channel spacing, without narrowing the transmitted bandwidth. Splatter, coupled with wideband receivers, has created a real mess. Now as the RF people retire, the FCC is being taken over by IT people and lawyers, so any reasonable broadcasting measures will probably never be implemented.

July 24th, 2011, 02:13 PM	#66
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,791	Re: power supply interference with radio broadcast Yep, Renton, I think a 1-watt license is a great solution! It allows you to cover at least a "small community" so it's worthwhile to run such a station. It encourages public use and "free speech" on the airwaves, which is good, since the airwaves allegedly belong to the people (at least that was the original concept here, up through our Communications Act of 1934, although recent FCC actions have largely diluted or removed the concept of perpetual public ownership). And by setting aside a certain part of the spectrum for these 1W allocations, you avoid the problems we have here with the "Part 15" very-low-power stations which can still produce enough RF to interfere with FM broadcast DX reception. (A local health center, which broadcasts their exercise music on 104.5MHz, prevents my listening for any distant legitimate stations on 104.3, 104.5, 104.7 MHz.) There are a lot of other problems with the LPFM allocations here, and the channel spacing, but I won't go into that here. So yes, I think NZ has come up with a much better solution. And kudos to you and anyone else who is willing to invest enough time and energy to run such a station at your own expense. I do believe in free speech. 8-)

July 24th, 2011, 08:16 PM	#67
Brian P. Reynolds Major Player Join Date: Jan 2010 Location: Adelaide, South Australia Posts: 466	Re: power supply interference with radio broadcast I bought a 1w FM transmitter off eBay and it works well on the occasions I have used it... I don't have a license and never even tried to get one. The times I have used it for wouldn't have mattered anyway. It worked well as a 2 channel radio mic transmitter for about 2km in a forestry area at a car rally and I use it regularly as an FX mic transmitter on the starting gates for horse races, most of those tracks I work at are well out of town. I work on the attitude if some one does come across the frequency, then works out what the sound is, then finds it.... I would have finished the job and out of there. I have also used it as an IFB feed for some rowing championships. In Australia they are used for things like Drive in movie theatres (and listen on the car radio), Real Estate sales info in new housing estates, Localised radio for outdoor sporting events like car and bike racing. One of the small towns nearby do a wonderful Christmas lights display with all the houses up in lights, run a Low Power FM TX for music of the season.

August 23rd, 2011, 02:46 AM	#68
Renton Maclachlan Trustee Join Date: Jul 2007 Location: New Zealand Posts: 1,180	Re: power supply interference with radio broadcast Just thought folks may like an UPDATE on this radio interference issue... The problem definitely was the switching power supply for the Ipod... After chasing a rabbit around for awhile, distilling all the advice I was getting from kind people all over the show, I finally got a 5v linear power supply out of Hong Kong (They seem as rare as hens teeth in NZ). On Monday this was connect to a USB lead and I installed it tonight and the problem is solved. There was a potential issue discovered on the web that fourth gen ipods will not charge if only the power wires are connected - a 'something er rather' reputedly needed to be installed across the data wires, but as it turned out, this was not necessary. We could have got another power supply, one that could be switched between various voltages and put a different sort of 'something er rather' in the cable to limit a higher voltage output down to 5v, but as I got a 5v, one that wasn't needed. Ipod power input is limited to 4.75v > 5.25v. So...thanks everyone for all the help given in tracking down and solving this issue...