- April 20, 2019 at 3:23 am #110954timinboveyParticipant
Total posts : 649
Well, I certainly doubt the use of these wireless headphones, as they come from the store is illegal or “pirate”. The only possible discussion would be if “broadcasting” with them is outside of the realm of their legal use. In which case we need a legal definition of broadcasting.
Now, I don’t know where you’re finding the review of the guy who gets one mile to his boat with this ONN transmitter. But I have no trouble finding a slew of reviews that complain it won’t go ten feet, and complain that they barely work, with static and interference, and dropouts, etc. Then again, those reviews are from people who used them as wireless headphones and weren’t trying to receive them on a radio. Perhaps the receivers in the headphones themselves are horrible. This is likely.
Also this whole “it’s not the field strength it’s the power”, as I explained above is not really correct. The FCC specification for certification and use under 15.236 and under Part 74 clearly states 50 mW EIRP, which is NOT a measurement of the output power of the transmitter. It is a measurement of the output of the transmitter, plus the gain of the antenna. The gain of the antenna with this transmitter is probably zero, or more likely less than zero. Certainly connecting any other sort of antenna would cancel the certification. Is it legal to use something under 15.236 that is not certified? If so, are you prepared to determine the output computing actual output power times accurately computed antenna gain, to determine legality? Will anyone care?
As for the Rolls transmitter, as I explained somewhere, it can’t possibly be certified. Just it’s physical characteristics make it an unsuitable candidate for certification. Further, specs indicate audio response only to 12.5k. Typical is to at least 20k. It wouldn’t sound much better than AM radio.
And we need to remember, when we say something is Part 15 certified, that just doesn’t refer to our AM and FM band transmitters. There is a practically uncountable number of devices out there that aren’t on the broadcast bands that are certified under Part 15 and legal for use by consumers. Your cordless phones are Part 15. Your wifi is Part 15. Your baby monitor is Part 15. Your cordless outdoor thermometer is Part 15. Your kids walkie talkies are Part 15. Heck, when I was a kid I used awake talkies to do a “show” and play records and announce them to my sister who listened on the other walkie-talkie. I was probably 10. This was I’m sure “broadcasting” by definition. But I’ve never seen walkie talkies that say you can’t “broadcast” with them. Or course these were on the CB band, and 100 mW, and sold to kids with no manual on what you could legally transmit. Heck, just bought my grandson a pair of these. They were “Spiderman” walkie-talkies. Are they limited only to crime fighting communications? That’s what a kid might think. As a curious adult I read the instructions completely. No mention of what you could transmit. I imagine a guy could rig up a cordless phone to an audio source and pump music into it. Is it legal? Hard to say. But I bet plenty of people have help up a phone to a speaker and said “Listen to this!” Do the instructions for these wireless headphones come with a list of things you can’t do with them?
We’ll know more once mine arrives.
Random food for thought.
TIBApril 20, 2019 at 8:29 am #110955MarkModerator
Total posts : 525
The Rolls would still sound better than AM as AM tops out at 5K with the 10 klz bandwidth. FM tops out at 15K so any quality FM transmitter should be pretty flat from 30Hz-15Klz. That it only gets to 12.5K, and probably with drop out at that, tells me it’s not that good an item.April 20, 2019 at 10:00 am #110956ThelegacyParticipant
Total posts : 273
I’m sure the receiver in those ONN headphones suck. I think those also can be wired.
I’m thinking we can find a better device but these are just to start our efforts. I’m talking about this on Facebook quite a bit and also promoting The New Radio Revolution’s site as a Hobby Broadcast set of frequencies is what we wanted to petition the FCC for. Now we may not have to unless by the agent telling me this and my posting it and starting a swarm of hobby broadcasters ordering the ONN headphones may cause the FCC to finally allow makers of FM transmitters like the Whole House FM Transmitter and C. Crane to start pushing this. The NAB should be jumping for joy now that I’m promoting this and getting the Pirates to think about this. I’ll go to some Pirate sites I know and post it too if we can find some great devices.
I even had some folks who work in Radio congrats me but if it weren’t for some folks daring me to call the FCC agent that visited me maybe it would not. Call me crazy but it was a temptation that did pay off.April 22, 2019 at 2:19 pm #110963timinboveyParticipant
Total posts : 649
Just heard back from one of the sellers of a Rolls HR70. He reports that it has no FCC certification numbers, no required FCC compliance sticker or label, and near as he can tell has no connection with the FCC in any way.
I suspected as much as neither the FCC nor Part 15 was mentioned anywhere in it’s advertising or the manual.
Conclusion: Not legal for sale in the USA. Period.
Not that this stops anyone from selling illegal transmitters. But for those of you wondering. It’s a big no from me.
TIBApril 22, 2019 at 6:11 pm #110966radio8zSenior Moderator
Total posts : 232
Thank you for replacing opinion, hearsay, and speculation with the facts you posted.
NeilApril 22, 2019 at 10:08 pm #110968ThelegacyParticipant
Total posts : 273
Thanks Tim I definitely won’t be getting that thing. Now we know the real deal.July 19, 2019 at 3:00 pm #111936RobertSParticipant
Total posts : 3
I’m new to the forums, but not new to Part 15 FM. I’ve been running Part 15 Low Power FM since 2001. Jolly Roger radio FM in Minnesota. I’ve had EDM, Ramsey 25b, 35b, and 100, a whole house and a CCrane. Loved those Ramsey transmitters, but all good things come to end. One by one my beloved Ramsey xmitters failed. I bought a Rolls HR70 and here is my review. The station is stable, sounds good, and REALLY reminds me of Ramsey 25B both for sound and signal strength. The setup is a little touchy, you really got to tweak it a bit, but not too bad. I understand my 25b was 25 milliwatts the Rolls is supposedly 40 milliwatts. My range with the Rolls is exactly the same. I’m not an electronics guy. I cant give you any real technical differences, only my experience. I always go out in my car and listen to the car radio, along with a boombox on the passenger seat. EXACTLY the same as my 25b for range with both using the telescoping antenna. If I attach a custom made Dipole using a coax cable to the antenna port. I get out a little further, but again, exactly the same range for the two transmitters. I have to say I like my Rolls so far. I know the some may get excited about range. But, I’ve been doing this for 18 years, and never had an issue. There is a professional AM station three blocks from my house. I know the owner well. He knows about Jolly Roger FM and he always asks how it’s going. I even did an interview at his station about it. I was just careful not to give away too much info. Just talked about Part 15. But I digress. The Rolls seems to be the closest thing I’ve found to an EDM or Ramsey transmitter replacement. Well that’s my 200 cents.July 19, 2019 at 3:33 pm #112079MarkModerator
Total posts : 525
Like how you said the Ramsey’s one by one conked out! That is because the output chip they all used was the GAL-5 that was very susceptable to any electrical shocks from your finger if touching it or going near it with static electricity. Whether it was on or off! I had a Ramsey 25B way back when I started doing this(didn’t know it wasn’t legal at the time) in Canada and I had to get from Ebay a large supply of GAL-5s from China and I got tired of having to replace them and they are tiny surface mounts and not too easy!
Later I found out that a 2.2uH coil across the antenna to ground will protect the output on these transmitters.July 19, 2019 at 6:21 pm #112081ArtisanRadioParticipant
Total posts : 498
As it was stated previously in this thread, the Rolls transmitter is not legal for use in the U.S. (or Canada). It is highly unlikely that 40mw output, even to a bad antenna, will produce a legal field strength.
BETS-1 certified transmitters in Canada are allowed much more field strength than the U.S. (100uv/m at 30 meters, as opposed to 250uv/m at 3 meters), and they generally have around 1 microwatt output (about 40,000 times less than the Rolls).
I also note the poster giving the review was careful not to give out details on the range he was getting. It it is significantly more than 200 feet to a portable radio, and it would be with that kind of power, then it’s not legal.
Given that the transmitter isn’t certified, and doesn’t even pretend to be Part 15 compliant, I think that users of said transmitter would be in a whole lot of trouble if the FCC comes a knocking (regardless of who else tolerates it). It would be difficult to convince an inspector that you were attempting to be legal, and just made a mistake, when using a non-certified transmitter.July 29, 2019 at 1:58 am #112123
It been along time since I have been up here with Carl and Neil.
Anyways lets get down to the rules that are for broadcasting on the FM Radio band.
Ok part 15.239 states the opperation of frequencies of 88-108 Mhz.
Now go to subpart C of 15.239
It states The field strength of any emissions radiated on any frequency outside of the specified 200khz band shall not exceed the general radiated emissions limits in 15.209
If you look under 15.209
You will see 30-88mhz is aloud 100 uv@3 meters but there a special notes for the frequencies from 76-88mhz and it refers you to 15.231
Part 15.231 periodic operation in the bands 40.66-40.70 Mhz and above 70 Mhz
(a) The provisions of this section are restricted to the transmissions of a control signal such as those used with alarm systems, door openers, remote switches, etc.. Radio control of toys is not permitted. Continues transmission, such as voice or video, and data transmissions are not permitted.
This kills any transmitter like the decade or any other legal part 15.239 transmitter being aloud to transmit below 88mhz and almost every part 15.239 transmitter will only go down to 88.1 Mhz.
If you look at any transmitter that falls under the 15.236 rule will never transmit up in the 88-108 Mhz range. I am hoping with Most channel 6 tV stations moving into digital transmissions that they will expand the frequency down to 87.9Mhz but realize that they only reserve that frequency for non commercial education broadcast radio station and I only know of 2 stations in the entire country that can operate on 87.9 mhz. They are very low power stations running around 10 to 25 watts of power at that.
Channel 6 TV stations are being moved in to the UHF frequencies for better digital streaming their signals over the air. I have been an electronic engineer for more than 47 years and work in broadcasting as well. Along with working for Raytheon and NASA.
Which all these jobs require me to get a license to work on transmitters. Also been a Ham radio operator for 43 years.
The FCC knows you are going to broadcast with part 15.239 transmitters but the headphones they probably think most will just listen to their favorite programs from a TV or radio . Now even an Ipod or phone. Anyways Not sure if everyone has seen the distance chart that Ramsey use to post if you used the 250uv@3meters.
It showed distances greater than 200ft but you would have to have a very sensitive receiver to achieve these distances.
I hope this will help out with distance under part 15.239 and 250uv@3meters.
These are expected field strengths at these measured distances.
Wow all my really old post must of went away because I have been on this site
for more than 14 or 15 years.July 29, 2019 at 3:46 am #112129RichParticipant
Total posts : 188
RE: Not sure if everyone has seen the distance chart that Ramsey use to post if you used the 250uv@3meters. … I hope this will help out with distance under part 15.239 and 250uv@3meters. These are expected field strengths at these measured distances.
A caveat: that table shows the fields that would exist in free space. However the fields radiated from an antenna near the earth will produce reflections from the earth, as well as from other nearby reflecting objects and surfaces such as wires, metal buildings/roofs, signs etc. Those reflections can either reduce, or increase the field at each given location, and can/may result in a field that exceeds what is produced under free space conditions.
FCC field agents measure the fields radiated from Part 15 systems at locations near the surface of the earth, which will include the effects of all its reflections. Those fields could be larger than expected when using the Ramsey table as a reference.July 29, 2019 at 9:44 am #112130July 29, 2019 at 9:51 am #112132
I am thinking that these measurements were done in a wide open space what most people do not have.
I was just posting them to show that a more sensitive FM receiver with a possible
elevated antenna could maybe receive a part 15 transmission more than 200 ft away.
This was to show you may be able to set up your FM transmitter outside in a weather proof box at a height above your roof top of your home. Then a neighbor down the street maybe able to place an outdoor FM antenna on their roof with a very sensitive receiver and get your signal. Which would be better than the standard portable FM Receiver .This is the only reason why I place the table up there. Not for measuring your transmitter but to show possibilities of your signal being pick up further than 200ft away. I know that I have tried out various receivers and found some to be far more sensitive than others. Most receivers did cut off around 200ft at 250 so week hard to hear.
The strangest thing I have discovered was that the Realistic DX 360 is very sensitive on FM that it was picking up my FM signal past the 200FT mark while almost every other radio I had just stop around that 200 ft mark. I know some very sensitive car radios have been reported to pick up part 15 radio signals 600 ft away. The chart could be used to reference the sensitivity of a receiver you want to purchase. A lot of receivers will give their sensitivity in the specifications part and you could use this to compare to the chart what the signal may be like at that range.
If you wanted the best range of all by a receiver. Then you could check and see if the receiver has the sensitivity of .5uv with a s/n ratio of 20db
This is just an example but it just a way to get a possible range found on the chart but if it does not it still may get you closer to a distance you want. People with indoor stereos with an antenna on their roof will have a better chance of picking your station up on FM.
Anyways it was only to be used as a reference to choosing a very sensitive receiver.
hope this clears things up a little bit. I am going to let everyone get back to talking about part 15.236 and the new transmitters being made under that rule.
- You must be logged in to reply to this topic.