- March 20, 2019 at 4:33 pm #110514
Many wireless microphone models are part 15 devices, and along with the general category of wireless mics have been undergoing a still unsettled shuffling as frequencies are being re-assigned during the ongoing large-scale repack in which almost every broadcaster has to move elsewhere involving frequencies and towers.
Imagine trying to do all this on a global scale!March 25, 2019 at 9:45 am #110591
There still is talk about using wireless mic’s for Part 15 broadcasting in the whitespace frequencies 76-88 Mhz.
Has anyone ever found out if this is considered legal in the U.S.? Are there any certified for that use? I’ve heard of the Comtek BST-25, but most wireless microphones now use UHF frequencies, or high band VHF (170 Mhz & above).
It is NOT legal to broadcast on those frequencies in Canada with wireless microphones (at least, how Canada defines broadcasting in its regulations). You have to use RSS210 (as opposed to BETS), and that doesn’t allow broadcasting (i.e., transmitting to the general public – it would be legal to transmit to an audience using these devices in a defined area to specific audiences, such as a church).March 25, 2019 at 12:26 pm #110593March 25, 2019 at 1:09 pm #110594
I suspect that wireless microphone users in the U.S. in the 76-88 Mhz whitespace frequencies are meant to be similar to those in Canada. These devices are not intended for Part 15 broadcasting as we know it (continuous transmission to general audiences in the 88-108 Mhz band), but rather targeted audiences in specific locations (such as stadiums, churches, etc.).
If you are not a licensed user, at least in the U.S., you would have to check the whitespace database on a regular basis to ensure that you’re not interfering with any other user and event (licensed users can update this database without even approaching the FCC, unlicensed users can apply to get their event put into the database).
If anyone knows differently, and/or has other information, please elucidate us.March 25, 2019 at 5:18 pm #110607
The FCC Part 15 Rules Themselves
A section of the rules starting with 15.701 deals with these white-space frequencies for a variety of devices including wireless mics and some fixed transmitter/receive equipment, but because so many frequencies are involved it takes patience to pick through this section.
Here is part of 15.707:
(b) Only fixed white space devices that communicate only with other
fixed white space devices may operate on available channels in the
bands 54-72 MHz (TV channels 2-4), 76-88 MHz (TV channels 5 and 6), and
174-216 MHz (TV channels 7-13), subject to the interference protection
requirements in § § 15.711 and 15.712.March 26, 2019 at 6:23 am #110608March 26, 2019 at 1:42 pm #110613
The basic problem with using wireless microphones for broadcasting is that it appears the FCC did not intend them for that purpose.
The FCC maintains a Whitespace Database, which contains events at which these microphones are going to be used, the geographic location, the date/times and the power levels.
ALL wireless microphone users are supposed to check this database before transmitting, to ensure that they will not cause interference.
Non licensed users are allowed 50mw output, but if they want to put an entry into this database, they have to approach the FCC (who will do it).
Licensed users (those with I believe over 50 transmitters, such as a production studio) are allowed 250mw output and can put entries into this database themselves.
I suspect that the FCC will not allow someone who wants to broadcast continuously to put an entry into this database. Particularly an unlicensed user. I don’t even think it is set up to handle this condition.
Licensed users have priority over unlicensed ones (by the fact that they can make their own entries into this database).
This isn’t like the situation with licensed broadcasters on the 88-108 Mhz band, where you know well in advance that there will be a station locating on a frequency that you, as an unlicensed Part 15 broadcaster, may be using, or may want to use.
I think you’re setting yourself up for a heap of FCC trouble if you attempt to broadcast on wireless microphones, given these rules.March 27, 2019 at 6:21 am #110625
Looking Into 2 Aspects
So far it seems to me that these wireless-mic rules would legitimize one particular use for part 15 radio stations, namely to stage a “broadcast” as an “event” and send it to a fixed receiver at the “main transmitter” location: in other words a Studio Transmitter Link STL).
Technically the STL channel would not be intended to reach the audience directly but would do so indirectly by retransmission on a part 15 frequency intended for broadcast.
Of course radios capable of tuning the STL wireless-mic channel could do so on an incidental but unofficial basis, assuming the modulation type matched.
Which leads to the question: are the wireless mic applications on TV 5 & 6 using modulation compatible with FM radios? We haven’t talked about this.March 27, 2019 at 8:41 am #110630
Other Reflections On 15.236
Overcoming our own confirmation bias in studying this wireless mic section, two factors jump out that may further lock out those of us with radio applications in mind.
Almost nothing is said about modulation regarding devices in the low TV band, saying only “converting into electrical signals that can be demodulated at the receiving device”; that could mean any modulation is possible, even digital.
Next, I see a few indications that these wireless mics are intended for use in TV broadcast production, which would certainly exclude any radio use.
The writing of 15.236 is very scrambled and may be destined for careful revisions in the future to better clarify what is actually being said.
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