- April 11, 2019 at 7:22 am #110860
The Rolls website says that the HR70 has a transmitter output power of 40 milliwatts, antenna impedance of 75 ohms, and 150 milliamps of current.
Can any of that data be used to determine if the field strength of this transmitter is under 250 microvolts per meter?April 11, 2019 at 7:39 am #110861
The transmitter output power, antenna impedance, and the current it uses has nothing to do with the field strength or whether it is legal.April 11, 2019 at 10:52 am #110864
Thanks for the info…just making sure it was too good to be true. I’ll stick with the cigarette adapter transmitters I’ve been using for FM. Those at least have FCCID numbers.April 11, 2019 at 2:07 pm #110866
@RFCCLebanon: The FCC agent I’ve been in contact with after he visited my house has offered me his Email and his contact number when I have a question about these transmitters. Recently I called to ask him about a Wireless Headphone set with transmitter which transmitted on 84.950 Mhz and an output of 50 mW and is there any legal rule that prevents me from giving out the frequency out on the Deltaville, VA Facebook page as a Radio station telling people to throw their Radio in Japanese mode.
His reaction was for me to try and get the model number picture of the device if I could and FCC ID number to verify it was not a fake FCC ID number or a faulty FM transmitter because he himself had to force Walmart to remove some of its part 15 devices from their store shelves after his tests revealed harmful interference issues.
If you publish the FCC ID of this illusive part 15 FM Transmitter I’ll check with him and see just what he tells me about it. He knows about New Radio Revolution and knows about my activities regarding my C-Quam AM Stereo campaign too.
Lets hope this thing is what they claim it is.April 11, 2019 at 2:44 pm #110868
RFCCLebanon, You can still use something better than a car FM transmitter that goes 10 ft.
Looked at that Rolls one and of course not certified for part 15 and connecting any BNC antenna to the jack at 40 mW will put you way over the limit but I noticed it has a variable RF control on the front. Probably with a rubber duck BNC antenna type and adjusting the output control to get no more than 200ft or so to a decent radio you could operate it within the limit. I don’t know how good it is, but I saw the frequency response is only to 12K. For the price, and it doesn’t look like junk, it should be better than that. Maybe thelegacy’s agent friends have some knowledge about this model.
Saw this is available in Canada also from recording gear online shops and is around $300.
For that price you can look at Broadcastvision which is good and certified in the USA for part 15.
To get the actual field strength you need a very expensive FIM meter.April 13, 2019 at 10:06 am #110875
Actually, the Scosche TuneIt and the Prime Audio I have both have a range of about 100 or so feet without fading and they fade out completely around 200 to 250 feet depending on the terrain, with no modifications. I’ve posted about them a while back. The Prime Audio can work off a 12V AC Wall Adapter, and the Scosche can work off any adapter that has a cigarette female to wall male connection. I just used the Scosche the other night for some softball games. The fields and press box are set up to where anyone with a decent radio can listen from the bleachers.April 13, 2019 at 2:20 pm #110877ArtisanRadioParticipant
Total posts : 498
Not all car mp3 players are under powered. In fact, the FCC pulled a number off the shelves years ago for not being Part 15 compliant. It sounds like the ones you’re using are OK.
Just to give you how much the Rolls is NOT compliant…
The amount of power required to meet the Part 15 FM rules is measured in nanowatts (around 20), not milliwatts. That’s into a matched antenna, of course. 40 milliwatts output into a matched antenna is over a MILLION times the power of a compliant transmitter. Given that the field strength is proportional to the square root of the power, you’re looking at around 1,000 times the field strength of a compliant transmitter, or 250,000 uv/m at 3 meters. Not even close to being within the rules.
Even with a mismatched antenna, I doubt you’ll get your field strength low enough.
Unfortunately, you’re either stuck using your current transmitters, or spending big bucks (hundreds of dollars) to get a decent, true Part 15 certified, transmitter, such as the Decade MS-100 or the Broadcastvision BV-3001 or its successor. You can usually find a used Broadcastvision 3001 on e-bay for anywhere between $50-150, but used Decades are expensive. Not sure its worth it, particularly since you seem to be operating close to the limits of the rules already.April 14, 2019 at 4:54 am #110881
I’d be leery of the Broadcastvision models.
While the last one I tested was about 2 1/2 years ago, it was WAY over the legal limit. See my test report at:
TIBApril 14, 2019 at 5:25 am #110883
Yeah, there’s ZERO chance the Rolls HR70 is even legal for sale in the USA. It doesn’t seem to be certified, at least it’s not mentioned in any listings for it and a search of the FCC database has no mention of it. Most legit Part 15 certifications are readily searchable at the FCC.
Not surprising as it has several readily apparent issues that would prevent it from passing certification. For one, certification for Part 15 FM requires either a permanently affixed antenna — being the same one it was certified with, or a removable antenna that connects with a non-standard connector. A BNC connector is quite standard. And apparently no antenna is even supplied.
Also the FCC Part 15 compliance statement and ID number must be affixed to the transmitter.
Further, a certified unit must not be able to broadcast outside of the FM broadcast band in the USA. Operating abilities down to 87.5 would eliminate this from certification in the USA.
As previously mentioned 40mW output even into a crummy antenna would put output well over the legal limit.
I just read the manual. No mention of certification, and a lot of info on finding a good, preferably directional antenna for best results. This would only further put it over the limit.
This thing has been out for at least a couple years now. I’m amused that is states “Made in the USA” but the word “Transmitter” on the front is spelled wrong.
And it has pretty crummy frequency response as well.
I say avoid at all costs.
TIBApril 14, 2019 at 6:00 am #110885
I’m also amused that this is a “digital transmitter”. It does not accept any digital form of audio, it has analog inputs only, and it does not transmit any digital data, as well. No digital audio, not even RDS. It’s “digital” in the fact that the frequency used is read out digitally. LOL.
TIBApril 14, 2019 at 7:40 am #110887
And to add, the IC number(on the Broadcastvision) for Canada is not valid!….as I forgot about that so yes you can’t trust this company.
Sorry, RFCCLebanon, maybe the Broadcastvision wasn’t a good recommendation.
April 16, 2019 at 5:29 pm #110898
- This reply was modified 9 months, 1 week ago by Mark.
Ok guys very good news could be under way. I found the model number and FCC ID for the Wireless headphones that are FCC certified and transmits on 84.922 Mhz at an output of 5mW.
I Emailed as well as a follow up call and I’m waiting for the green light. If I get it the USA well have its Hobby Broadcasting frequency of 84.922 Mhz FM Stereo.
The Legacy will have truly paved the way for us to get real listeners. People in Deltaville, VA will be informed how to receive us on America`s true Hobby Broadcasy frequency. I cannot wait.April 16, 2019 at 7:22 pm #110900
But no radio goes below 87.5, at least for the N America market. And 84.922 isn’t a designated frequency that a digital tuner would go to, especially a selective one. You would be detuned. The only radios that would receive it properly would be an analog tuning radio that goes from 76-108 or an older radio with TV VHF audio and wouldn’t have the sensitivity of .9uV you say you need.
Not trying to put a damper on your enthusiasum but don’t be expecting this to work as good as you think.April 17, 2019 at 9:41 am #110902
More Experimenting needed at $20-30 for each wireless headphone set and for the agent to check on his analyzer.
If I get approval for this Mark has a few concerns but does point out those VHF TV sound Radios that were analog. It also occurs to me maybe we can order Radios or get Mitsubishi car Radios that will tune in Japanese mode. We need to play around and see. My Broadcast engineer is trying to find me such a Radio.April 17, 2019 at 10:27 am #110904
Now we have our National Hobby Broadcast frequency 84.922 Mhz @ 50 me as the agent told me the Wireless headphone made by ONN is 100% legal and if I wanted to experiment and post it on the Deltaville VA Facebook page I could.
He is saying that not everyone will get the same range but being that I’m near water you’re in Deltaville it may cause the signal to carry out pretty far to a very sensitive radio and there’s nothing bend the rules that prevent me fromm telling whoever I want my frequency and the fact that I’m transmitting there you.
These headphones are quite affordable and I think it could be the resolution that will stop FM piracy as I have explained to the agent and told him I am very excited to let everyone know about this. He sort of laughed but he also says to be careful that there is not a Channel 6 to close to you that you might interfere with but that’s easily to find out about. He did say that most Channel 6 has that are operating at low power will be off the air in 2020 and that the frequency should be blank for everybody. This means hobby Broadcasting on that frequency.
Thanks to everyone that brought this to my attention the new radio Revolution has now done everyone a great favor bye making this loophole as the agent says and very legal a way that we can broadcast without getting into trouble. So the Legacy will be promoting radios that will go down there. I suspect the makers of these headphones are going to be getting tons of orders now. I’m also going to spread this all over the internet this is going to be the national hobby broadcast frequency
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