i'd like to see the antenna restrictions lifted off of the 1750m band. there is no real reason for them in this day and age as there is no practical way to make an efficient antenna for 1750m (even if you own lots of farm land) but it would allow for different antenna system designs and experimentation. i also don't know what surrounds that band but some frequency expansion would be nice too. i believe 1 watt is sufficient if the antenna restrictions were lifted. there is nothing that i really know of down there in the basement that loosening of restrictions could cause increased interference to and this idea might have more of a chance than loosening of the am or fm bands. anyone know how well 1750m does with carrier current? seems using neutral loading would make an excellent distribution platform for part 15 am nodes. you could use AM mode and make 1750m to medium wave translators and not need a NRSC limiter at each node as the 1750m would be am and pass the asymmetry along to the am medium wave tx's
I join kc8gpd in re-examining the part 15 long range spectrum and loosening the rules, especially since that is more or less vacant territory, save for the few beacons.
I don't think greater height would matter for most people, because most of us can't manage a 50-foot vertical as it is. So, allowing say, 100-feet, would be a mostly unused benefit, so let's have it.
Trouble is the 1-Watt rule only applies to an intentional radiator and not carrier current, but I also am curious about the long range band as applied to carrier current. The intercoms work very well, but I think they are limited to the milliwatt range, somebody look it up.
I am sold on the neutral injection method as being safer, more stable, and probably more efficient in terms of distance.
The intercoms that use carrier current (CC) at long wave (LW)frequencies may not be under part 15, it is confusing at this point.
Carrier current would not technically be classed as "intentional radiators" yet that is exactly the section where AM on CC is addressed, 15.221, but the main concern is the radiated power at a distance from the power line.
The section on 160 to 180kHz, 15.217, does not mention CC, but it wouldn't apply to new Radio Shack intercoms in any case which operate between 200 and 290kHz.
The online specs on Radio Shack intercoms do not specify what FCC rules apply nor do they give RF power.
From years ago I have two pages for a Radio Shack SELECTaCOM 2-channel system, 140 and 190kHz, with RF Output Power: 40mW across 10 ohm load.
My Radio Shack CC intercom manual specifies RF output at 70 mW across 10 ohms. The frequency range is 160 to 230 kHz.
They claim a 300 foot range.
Consider the formula used to measure a CC signal off the wire, and 300 feet at 160Khz will be like cutting yourself short of a full deck.
157,000/160Khz=981 feet.
Which would be very close to the field strength range for a 1 watt signal off a 15 meter pole and elaborate ground system.
But at 70mW in that frequency range in CC mode, 300 feet is pretty much what one can expect, and well within the 217 limits.
RFB
Part 15.217 applies to radiation in the band 160-190kHz, HOWEVER....
The Radio Shack intercoms operate from 200 to 290kHz.
Doesn't jive.
"Doesn't jive."
Perhaps a different model from a different time.
RFB
The Radio Shack intercoms operating from 200 to 290kHz are current models in the catalog now.
It is not evident what part of the rules apply to these.
Well MRAM could be talking about a different set. MRAM did not specify the model number or vintage.
In any case, RS marketed quite a few different intercom systems over the decades, as did other manufacturers.
If these devices meet the limits called for in 217, then there is no reason why they cannot couple to the power outlet instead of a 15 meter radiator.
There are already too many rules...and why would we want to dig deep into a quicksand pit trying to pry one out of the FCC to add to the long list of over-regulation anyway?!!
RFB
I would like to know what section of the rules applies to intercoms because someone earlier suggested modifying an intercom to use as a CC broadcast transmitter in the LW spectrum. In that case it would be necessary to know the boundaries set by the regulation.
We have discussed CC as a means of sending remote control (RC) commands, and LW would be a place to do it.
One of the strengths here at part15.us is the development of applications for low power which expand our tool chest.
"I would like to know what section of the rules applies to intercoms because someone earlier suggested modifying an intercom to use as a CC broadcast transmitter in the LW spectrum."
I believe wireless license free intercom systems fall under Part 15, and as to which particular sub-part intercoms would fall in, would depend on the band and frequency it operates on. Thus what is written now in the rules for each particular spread of frequencies and bands would apply.
So for LW, don't exceed 1 watt final as called for in 217 and don't allow out of band emissions to exceed 209.
RFB
After spending the whole morning studying the FCC rules, I am now sitting way up here on the over-sized furniture in the transcendental court, ready to render an opinion.
AGREE with RFB that Part 15 applies to wireless intercom systems.
DISAGREE that 15.217 covers ANY carrier current device, it does not list the same frequency range used by the available intercom devices and the 1-Watt specified in 15.217 applies specifically to the use of a 50-foot antenna.
BELIEVE that the ONLY section that could be found to pertain to Long Wave (LW) intercom devices is 15.209, as follows:
Frequency: 0.009 to 0.490mHz ; Field Strength: 2400-microvolts/F(kHz) ; Measured at 300-meters.
This session of Micro-Claims Court is adjourned.
"BELIEVE that the ONLY section that could be found to pertain to Long Wave (LW) intercom devices is 15.209, as follows:
Frequency: 0.009 to 0.490mHz ; Field Strength: 2400-microvolts/F(kHz) ; Measured at 300-meters."
Problem with that is that 209 references to out of band emissions such as spurious and harmonics. It does not refer to the main carrier.
No one said 217 covers any CC device. What was said is that 217 is the current regulation for the 1750 meter band. Yes it does talk about the power limit and antenna length limit. But it does not say anything about no CC down here below.
RFB
Sorry, but 15.209 applies to "Radiation Emission Limits; General Requirements" and is not limited to harmonics or spurious emissions. It pertains exactly to main carriers in the frequency ranges listed...
"Except as provided elsewhere in this subpart."
The Transcendental Court has ruled, there will be no appeals or rebuttals.
No Carl. If 209 applies to fundamental, then everyone out there running a station going beyond the distance called for in the 209 table is in violation.
I am sure many a certified TX's out there shooting a signal in MW well beyond 30 meters would want you to validate 209 as being for the fundamental, and why would 209 would take precedence over 219, or 221, or 239.
ECFR.
(c)The level of any unwanted emissions from an intentional radiator operating under these general provisions shall not exceed the level of the fundamental emission. For intentional radiators which operate under the provisions of other sections within this part and which are required to reduce their unwanted emissions to the limits specified in this table, the limits in this table are based on the frequency of the unwanted emission and not the fundamental frequency. However, the level of any unwanted emissions shall not exceed the level of the fundamental frequency.
You cannot have two field strength limits apply to one signal and both be correct when one defines one FS while another defines something different.
So..splain judge lucy!
But its ok. You can cut back all of your signals down to the 209 table if it makes you feel better. Let's see if anyone else will too!
RFB