Management ignored me when I suggested LPFM....

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spareparts
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Management ignored me when I suggested LPFM....

Post by spareparts » Sat Feb 24, 2018 10:26 am

Management ignored me when I suggested LPFM....
Now they want a transmitter.......
And there are a zillion new translators in every FM slot..........

So, I'm left with Part 15, so what's the legality of reducing the PO of a Harris MS-15 FM Exciter to Part 15 compliance.

Where do I start?

TPT
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Re: Management ignored me when I suggested LPFM....

Post by TPT » Sat Feb 24, 2018 11:19 am

An in-line pad. My BE kilowatt has a flaky exciter--but the 250 mw output is run to an external BNC and looped back in. Got a 25 DB pad & put it on the output of another exciter to drive the transmitter. Pad runs warm, but the transmitter is there when I need it--back-up to my 10 KW.

Don't remember where I got the pad...might have been RF parts. Someone else on the list can probably do the math & give you a source. Remember, too, for Part 15 the antenna is figured in to the equation.

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Deep Thought
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Re: Management ignored me when I suggested LPFM....

Post by Deep Thought » Sat Feb 24, 2018 12:18 pm

You can't. The limit is 100 milliwatts DC input power to the transmitter on AM and 250 uV/m at three meters field intensity on FM. That MS-15 will radiate more than that from the cabinet.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

spareparts
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Re: Management ignored me when I suggested LPFM....

Post by spareparts » Sat Feb 24, 2018 2:10 pm

Deep Thought wrote:
Sat Feb 24, 2018 12:18 pm
You can't. The limit is 100 milliwatts DC input power to the transmitter on AM and 250 uV/m at three meters field intensity on FM. That MS-15 will radiate more than that from the cabinet.
Nuts - How bad is the Harris Micro Max in terms of incidental RF leakage? It can be dialed back to 1W in software.

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NECRAT
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Re: Management ignored me when I suggested LPFM....

Post by NECRAT » Sat Feb 24, 2018 4:10 pm

spareparts wrote:
Sat Feb 24, 2018 2:10 pm
Deep Thought wrote:
Sat Feb 24, 2018 12:18 pm
You can't. The limit is 100 milliwatts DC input power to the transmitter on AM and 250 uV/m at three meters field intensity on FM. That MS-15 will radiate more than that from the cabinet.
Nuts - How bad is the Harris Micro Max in terms of incidental RF leakage? It can be dialed back to 1W in software.
Bad enough that you can't use it for this purpose. You need to go another route with this. (You need to find a Part 15 transmitter, and buy it, or build it, yourself).
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Re: Management ignored me when I suggested LPFM....

Post by Bill DeFelice » Sat Feb 24, 2018 4:28 pm

I've see cases where a commercial FM exciter on a test bench into a dummy load could generate a field close, if not exceeding, Part 15 legal limits. Some time ago I did a quick and dirty test with an exciter I had in the shop and with its output turned down as far as it would allow the Potomac 71 showed it exceeded the Part 15.239 allowed field intensity.

Unless your AM station is going to scatter hundreds of these micro-powered transmitters throughout your service area I would imagine legal and compliant Part 15 FM field strength to be useless to cover the desired service area with any sort of reliability, and that's not even considering beating between transmitters or other interference issues (assuming you can even find a clear frequency). Being unlicensed you won't have protections if an LPFM were to launch and take over the frequency you camped out on, either.

Small town or larger AM? If they have decent coverage maybe you can partner with the local cable company and be background on a TV guide channel or perhaps a streaming web presence with a phone app would be a much better solution.
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Re: Management ignored me when I suggested LPFM....

Post by Deep Thought » Sat Feb 24, 2018 4:51 pm

Bill DeFelice wrote:
Sat Feb 24, 2018 4:28 pm
a streaming web presence with a phone app would be a much better solution.
This.

Legal Part 15 operation on the FM band will get you about a 200 foot radius and that is if you can find a clear frequency. *All* of the transmitters on eBay and Amazon except for the CCrane units are illegal to operate in the US, and that one will barely get you across the house.
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spareparts
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Re: Management ignored me when I suggested LPFM....

Post by spareparts » Sat Feb 24, 2018 6:38 pm

Will tell them they missed the boat on the LPFM, and they are out of luck....

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Re: Management ignored me when I suggested LPFM....

Post by Deep Thought » Sat Feb 24, 2018 8:34 pm

They can still buy a translator to use with the AM (if that's what this is all about...hard to tell since "LPFM" is another thing entirely) but it'll have to comply with the minor change rules if they want to relocate it.
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spareparts
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Re: Management ignored me when I suggested LPFM....

Post by spareparts » Sun Feb 25, 2018 10:01 am

Deep Thought wrote:
Sat Feb 24, 2018 8:34 pm
They can still buy a translator to use with the AM (if that's what this is all about...hard to tell since "LPFM" is another thing entirely) but it'll have to comply with the minor change rules if they want to relocate it.
They don't own any broadcast facilities at all - just a high end podcast studio.

They did not allow the staff to apply for an LPFM license when the FCC window was open, and there were local frequencies open (well prior to the translator landrush we are now seeing)

What it boils down to if they want a transmitter with more than 200 foot range, they need to face the reality they need to buy an existing station

Like I said, they missed the boat....

SP

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Re: Management ignored me when I suggested LPFM....

Post by RodeoJack » Sun Feb 25, 2018 10:57 am

If your area has that many signals, chances are an existing LPFM will eventually become available.

Lots of people built these things without a practical knowledge of their care and feeding. Once they've had their fill of finding reliable volunteer staff, keeping equipment running, possibly paying rent on a water tower somewhere, paying for the electricity and, maybe, letting people tromp through their homes at all hours of the day and night, the novelty wears off. Even a fully automated signal takes time and money to operate, and a bunch of them wind up being run out of Cousin George's garage.

A certain number of them fail, due to political infighting among the "board of directors".

You can't make any money off these things, most of them don't cover all that much distance, and when you decide to unload one, the FCC won't let you sell it for more than the value of the equipment.

Not to say there aren't successful LPs out there, but the practical odds aren't stacked in their favor, especially if the founders see them as some sort of answer to the big, bad commercial outlets in their towns.

So... if you're patient and really want one, it may be only a matter of time.

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Re: Management ignored me when I suggested LPFM....

Post by Deep Thought » Sun Feb 25, 2018 9:17 pm

spareparts wrote:
Sun Feb 25, 2018 10:01 am
They don't own any broadcast facilities at all - just a high end podcast studio.
I doubt they would have qualified for an LPFM anyway. These are not for commercial interests.
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spareparts
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Re: Management ignored me when I suggested LPFM....

Post by spareparts » Mon Feb 26, 2018 5:36 pm

Deep Thought wrote:
Sun Feb 25, 2018 9:17 pm
I doubt they would have qualified for an LPFM anyway. These are not for commercial interests.
Actually they would have. They are a 501(c)(3), a public museum, and a National Historic Landmark. On the education side, they are partnered with a major university, and the local school district.

That being said, a bit short sighted as well.

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Re: Management ignored me when I suggested LPFM....

Post by kc8gpd » Sun Mar 11, 2018 9:16 pm

Here is something you may want to try. your mileage may vary (IE: sometimes it works great and sometimes it works absolutely shitty) depending on how your utility has the wiring setup and whether it is above ground or beneath ground.

you may want to experiment using a neutral loaded configuration carrier current am system employing an isolated ground from the buildings electrical ground.

i know of a couple gents who passed fcc inspection with this method and are covering their entire small towns. these guys are getting approx. 4 mile radius along the neutrals.

it is worth investigating.

you can also get a rangemaster and the new schlockwood SW200 processor jim wood has just put out.

either setup should get you at least a good mile coverage under the right conditions.

you could also get the community involved and maybe encourage community members to be hosts for multiple remote sites.

there are lots of possibilities only limited by the imagination and your budget that can be done legally within the part 15 rules.

i would stay away from FM. the band is so congested that there is just no room and legally FM will only go about 300ft radius and with the FCC crackdown on piracy especially on the FM band. it's just an all around good idea to only use a certified part 15 FM transmitter which as i stated the best ones will get you 200-300ft to a good portable radio on a clear frequency.

the fcc seems to be showing wide latitude to am operators right now. i have seen very few if any AM nOUO's in the last few years. i think there might have been one for a guy running full blown pirate on a cochannel to a NYC 1700 kHz frequency and imho that one was well deserved.

as a side note the applicable rule parts under part 15 you will be most interested in is part 15.221 for carrier current, 15.223 if you wish to operate on 1710 and 15.219 which is the rule part everyone is most familiar with the typical 3m antenna and 100mw input to final.

feel free to PM me and i will give you my cell and you can pick my brain on everything part 15 offline if you like. i will try to be the best help i can.
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Re: Management ignored me when I suggested LPFM....

Post by Deep Thought » Mon Mar 12, 2018 9:50 am

kc8gpd wrote:
Sun Mar 11, 2018 9:16 pm
these guys are getting approx. 4 mile radius along the neutrals.
I'm going to assume that you meant the neutrals run for 4 miles, because radiating a readable signal from a carrier current system more than a couple dozen meters from the power line is wholly in violation of the rules.
§15.221 Operation in the band 525-1705 kHz.
(a) Carrier current systems and transmitters employing a leaky coaxial cable as the radiating antenna may operate in the band 525-1705 kHz provided the field strength levels of the radiated emissions do not exceed 15 uV/m, as measured at a distance of 47,715/(frequency in kHz) meters (equivalent to Lambda/2Pi) from the electric power line or the coaxial cable, respectively. The field strength levels of emissions outside this band shall not exceed the general radiated emission limits in §15.209.
At the least restrictive frequency (540 KHz) that translates to a 15 uV/m level at 88 meters, and will be in the noise. Something more usable like 500 uV/m would be around 3 meters assuming a straight-up inverse-distance calculation.
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