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Post by sparepart on Jun 24, 2019 1:40:00 GMT
Need to lead off with this statement: The tech team had this dropped into our lap after an initial conference call on doing a Christmas light show. We were planning to use the Whole House FM Transmitter that is typically bundled with the lighting controller, along with outdoor speakers. Completely legal under part 15. Here's where is devolves into the twilight zone: We were given a large reel of used Andrew RADIAX RCT4-WBC-1X-RNA Coaxial Radiating Cable (AKA leaky feeder) and a Decade FM 850 Stereo transmitter that were pulled of out a church / school campus by a major donor. There likely will be pressure to use the donation, rather then go with the Whole House transmitter
Before going down that rabbit hole, how the heck would I keep the Decade / Radiax combo under the 250 uV/m @ 3 meters limit without hiring an engineer to test?
SP
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Post by thelegacy on Jun 24, 2019 4:24:09 GMT
Use a Tecsun PL 380 Radio. Per the FCC agent I have talked to about the certified Decade MS 100 because of a real estate company right next to the 711 in Deltaville that use that very same transmitter and was getting out 0.9 miles to my Tecsun PL-380 Radio and I'll admit I sort of complained because if he can do it why can't I?
The agent told me he was aware of range up to 1000 ft on a highly sensitive radio such as a car radio and told me I could do FM if I used the decade ms100 as he recommended that transmitter.
So knowing this and your decade is FCC accepted if your range doesn't go over that 2 the Tecsun PL-380 and you must Fade to Black at that range afterwards you should be fine but if that transmitter has a variable output adjust it to something like 900 Ft so you have a buffer. Also make sure your frequency is 100% blank.
This tells me that the FCC knows that that decade will reach up to a thousand feet if it's high enough. Do keep in mind though you're not using the ms100 so it's not really part 15 certified so don't use more range than what you need on your property it's probably my best advice.
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Post by mark on Jun 28, 2019 5:03:31 GMT
The Decade 850 is the top of the line and is power adjustable from 0-1.8 watts. The steps for power adjustment is every 0.05 watts. This seems to mean that the lowest power setting it can go is 50mW or nothing. The certification is for part 73 not part 15. In Canada its certified for BETS-6 which are licenced catagories in both countries.
And depending on the antenna which can be connected to the BNC terminal 50mW can get quite far.
It's impossible to get the power down to levels with this that would be "safe". Even a BNC rubber duck antenna will still be way over.
The church probably had a license to use this.
Again....impossible since the power adjustment goes from 0 to 50mW and can't go lower like 5 or 10 mW you can't, to answer your question, get this to under 250mV/M@3meters......most likely with NO antenna! But if a one time use for a short period you may get away with it. Not that I am encouraging this.
My mistake....the output antenna connector is a UHF, not BNC.
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Post by thelegacy on Jun 29, 2019 5:43:32 GMT
My broadcast engineer friend came to my house Today. We talked about 15:236 and getting away with running a TX down there:
His response is this "The FCC is cracking HARD on FM and there is a ZERO tolerance for Hobby Pirates trying to skirt the rules and part 15:236 is worded towards devices not transmitters and he has yet to see a 15:236 certified mic, Wireless headphone, audio sender!" He advises to forget that deal. As for the Decade MS100 going 1,000 Ft the FCC does allow it even though its over part 15 a bit. Not every Joe will use it because of the price of $500 New for the MS 100. Its a very professional clean FM transmitter and could get me some listeners on FM but there may be some changing rules for us soon on AM keep our fingers crossed.
He advises AM is the best place but may help me get listeners in Deltaville by making signs the size of realtor signs and put them on the side of the road as they have to be 10 Ft from the ditches on the side of the road. He went around for me advertising my station with his van and people took him seriously with his van and antennas and the spectrum analyzer on the dash like the FCC uses.
I want to stay in good with him he has helped me a lot and knows his stuff. What he says I can take as gospel as what is going to pass muster and what won't. He has dealt with the FCC a few times when he went to work on Radio stations where he is from. So again Decade MS 100 for Hobby Broadcasting Yes 850 No! Maybe with leaky coax but you had better have that FIM 71 because the FCC is not going to let you off if your past spec.
Good Luck to you all and stay clean and out of trouble's path on FM!!
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Post by sparepart on Jun 29, 2019 12:09:07 GMT
Met with the tech team last night - decision might be not the most popular, however, IMO the safest:
Since we essentially only need to cover our parking lot (area bounded in red) for the Christmas light show, we will defer using the "new" gear until we can make a determination if licensing is even possible.
SP
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Post by mark on Jun 29, 2019 16:54:48 GMT
Legacy said....."His response is this "The FCC is cracking HARD on FM and there is a ZERO tolerance for Hobby Pirates trying to skirt the rules and part 15:236 is worded towards devices not transmitters and he has yet to see a 15:236 certified mic, Wireless headphone, audio sender!" He advises to forget that deal. As for the Decade MS100 going 1,000 Ft the FCC does allow it even though its over part 15 a bit. Not every Joe will use it because of the price of $500 New for the MS 100. Its a very professional clean FM transmitter and could get me some listeners on FM but there may be some changing rules for us soon on AM keep our fingers crossed".
Even a new one costs less that the 2 best AM transmitters and the Talking House with the range extender.
If the FCC will let you get up to 1000ft. with a Decade that will get a good part of your neighborhood. You can be on both AM and FM. Don't let the slim chance of a change stop you from getting a Decade
To Sparepart....a wise decision to not use the Decade 850. See if the FCC has short term permits for "events" like this and you MAY be able to use it.
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Post by part15engineer on Jul 9, 2019 12:49:01 GMT
sparepart,,
i sent you a PM. i'm not sure if you got it or not. there is no indicator of receipt that i noticed.
just letting you know its there if you haven't seen it.
thanks
part15engineer
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Post by part15engineer on Jul 9, 2019 12:53:34 GMT
actually the radiating cable in combination with the decade at 50mW when the cable is strung inside a building should be at legal f/s outside the walls of the building. radiating cable is not very efficient as far as i'm aware. it is designed to control rf radiation and contain it to certain area's in a building.
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Post by Druid Hills Radio on Jul 22, 2019 13:09:33 GMT
Hello All, I'm not sure how well signals in the FM radio band would work with leaky coax.
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Post by thelegacy on Jul 22, 2019 17:53:48 GMT
If you want to "Broadcast" open to folks within the range of the legal FM transmitter even outside your property the Decade MS 100 is the way to go but leaky coax would be nice for a school campus like Lions World Services For The Blind in Arkansas or back when the Michigan School For the Blind was actually having normal mental capacity students who want to learn Radio. The campus is 1/4 mile long and if they would have strung up leaky coax from the Main Building to say the cottages on the other end of the campus we could have had a really nice campus wide Legal FM station that while you were visiting MSB or living on campus you could have heard us in Stereo.
During my younger years at 14 we were on AM till 1979 when the school started going multi handicapped. Would have loved FM back then however and the signal would have gone 200 Ft off campus. Maybe you could try that.
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Rich
Full Member
RF Systems Engr (retired)
Posts: 112
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Post by Rich on Jul 22, 2019 18:23:23 GMT
Hello All, I'm not sure how well signals in the FM radio band would work with leaky coax. However they would "work," leaky coax free-radiate FM setups are not included in the unlicensed transmit systems authorized by the FCC in Part 15. Neither is "campus broadcasting" using the FM broadcast band, as it is for the AM broadcast band. |
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Post by sparepart on Nov 28, 2019 17:21:23 GMT
Starting early for next year (2020): Looking at how the Green Bay Packers and Live Sports Radio LLC manage the process. Here's the STA: fcc.report/ELS/Live-Sports-Radio-LLC/1685-EX-ST-2018Wondering if we could request an STA as investigational test for 180 days, and agree to adhere to Part 15 contours afterward on a non-interference basis using the donated hardware and radiax? Any Broadcast engineers want to assist in the application? 9 |
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Post by Boomer on Nov 28, 2019 22:42:17 GMT
I've heard of several bands who have run small radio stations while on tour, using them for traffic control, and likely other things like ticket locations. After the shows, members of the at least one of the bands go on the air to unwind, broadcasting to the campus of the event. I don't remember the band names now, this might have been in the 1990s.
The Grateful Dead have been said to have a radio station, though it may have been run by fans.
I'll have to brush up on all this, but it shows that stations are regularly used at events. It's surprising how many small stations abound, churches, care homes, and unexplained signals playing music which seem like SiriusXM transmitters, and more.
The latest stray signals I've been hearing are from car sound systems that use FM transmitters. I was in a Wendy's parking lot this fall, tuning around and heard a strong dead carrier, and an electronic woman said "(Name of device) Good bye." The signal stayed on.
Boomer
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Post by End80 on Nov 29, 2019 5:17:06 GMT
Maybe I'm missing something, but it seems you may be going a little overboard to be considering submitting a request for a STA for your undertaking, when all you aim to cover is the parking lot you've outlined in red.. It appears that is entirely accomplishable with part 15 either AM or FM.. But, since part of your objective is also to use the donated cable you received, you might want to try contacting the eBay seller who sold a Radio Systems TR-20 Transmitter and CP-15 Coupler about a week or two ago for $150 [www.ebay.com/itm/333393831893], that, along with your cable would be a complete and certified part 15 system. The seller stated he had multiple of these units for sale, but so far I've only seen him sell one of them. Apparently these transmitter and couplers are being surpluses from Hastings College old station in Nebraska.
Still think it would be simpler to just use the Whole House Transmitter you have, which I would suspect to cover that parking lot fine.
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Post by Boomer on Nov 29, 2019 7:00:46 GMT
Yeah, and AM would certainly cover a parking lot, and FM should too, like the Christmas display at a church in my area, they put on an animated light show with LED light bars synced to a soundtrack, and the unobstructed whip to car radio antenna distance they cover could be at least a few hundred cars in their parking spaces. They do it just right, and it's an efficient system, all line of sight signals.
The carrier current system would probably cover the parking lot too, especially if there are any lighting poles you're feeding from the main building to the lot. Xmas display lighting would have the AM signal on it too.
I got my LPB 5 watt unit on Ebay too, 2014, and it was working, and $75, and I forgot how much the coupler cost. It was from SEMO university apparently. If you have someone who knows discrete electronics repair, that would be good, to cover anything that might happen. They're old rigs, and Radio Systems the company is still around, but I don't know if they support or service older rigs.
My LPB has been great though, it's been running constantly for 5 years after a tuneup. Right now I'm just using the linear amplifier part of it, since I put my stereo exciter in and it already generates the AM signal, so I don't need to use the modulator on the LPB's board. I want to make my own amplifier and then put the LPB aside as a backup.
Heck, you could even have students design and build a transmitter for credit, some college stations have gone on the air that way. Since LPB and Radio Systems transmit on a single frequency, you guys could design a PLL to change frequency within its range, if you had one of those units.
Boomer
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