It sounds like our situations are pretty
similar. What are the odds of that?
Thanks again for the info.
I've got to go.
I would really like to figure out a way so
we can talk. We'll have to do that.
Best Wishes,
Brooce, DOGRADIO
If you tune into my station (See my signature) you can talk to me. I usually have the Google voice forwarded to my cell so that won't be an issue. I'm sure we can catch up on some good stuff dealing with FM Transmitters. I'm sure we can share ideas as well. I'd be more than glad to help those who want to make a change for Radio and part 15 for the good. As long as your not an Anti FM troll I'd be glad to help those. But then again that is why I have apps that block the bad guys lol.
Oh trust me, I love streaming Part 15
stations and finding out about them and
the people who run them.
I will show up to talk to you hopefully soon.
But we have the eye thing in common too,
and I'm wondering how you deal with it.
I try, but I need to do better.
Very Best Wishes,
Brooce, DOGRADIO
P.S. Oh, I'm not an anti-FM troll,
either, but it sounds like a good idea
for a comic strip or something.
(I was a cartoonist in early life.)
Can't remember if I've already blogged about it, but I fancied the idea of starting a "Troll Patrol," but then realized that to carry it out we'd need to become trolls in search of other trolls.
That's probably why U.S. spying is such a mess.
WE should also monitor those who do not wash their hands when departing a restroom. We can issue "Golden Handshake" awards.
Big greasy finger blotches on vinyl discs, crud on headphones, gummy telephones, strange aromas from the waste basket, it's public radio.
Okay, let's talk about Chinese transmitters for a bit.
Like any person who likes broadcasting as a hobby, I like visiting websites that carry AM and FM related equipment. Be it receivers or transmitters, or equipment that helps either end of the hobby.
I have seen some high powered FM transmitters out there, that are sold on line and also the same units are sold on ebay.
Looking at the internal designs of these transmitter, by way of published photos, showing the transmitter with its top cover removed, has shown quite a few have internal 5 poles for filtering to cut the 109MHz to 216MHz 2nd harmonic range from reaching the external antenna.
Some of the designs I've seen, make me wonder why anyone would claim that they cause interference to the air craft bands of VHF television frequencies.
I would love to see studies done on those transmitters, the only problem here in the USA is they are virtually illegal to own, because their RF power output seriously exceeds part 15 FM for the USA and are not certified for any use. But I'd be willing to say, that NOT all of those Chinese FM transmitters are prone to creating interference, that to me is just a myth the licensed broadcasters come up with because those transmitters can be adjusted from 1 watt to as much as 1000 watts.
In almost every case against a person who got an NOUO from the FCC, there is 99 3/4 percent of them that claim the station was causing interference to a licensed station or other service.
Although some cases may be same channel interference, most are about a pirate station interfering with a licensed station on another channel, or the air craft band. Is that really true? Or just a false reason to remove the completion?
Bruce.
Or like RIKA FM who knew they were causing interference and did not care. The 01S was a transmitter I thought about because I could adjust it from 0-1 watt. Id set it to 1mW or till I could reach 800 feet on a car Radio. But there may be times I only want to transmit 30 feet and id adjust the power so my private messing around isn't heard outside my house. Especially just using my stereo like wireless speakers. Its why I wish my tx could do that.
Most of us care about causing interference in my personal belief and want to avoid it at all costs.
Not caring only gets you shut down a lot quicker.
Here is my theory, I personally believe that any transmitter out there AM or FM can be made to stop creating interference.
Even if it does, there are ways to stop that interference if anyone one really wanted to and I am not saying that is done by simply shutting the transmitter off either.
I am in the USA and don't wish to import equipment that may get me into trouble with the Federal Government. But I'd really like to be allowed to do tests on such equipment to see just how junky they really are. But there is a risk factor there I do not wish to take.
I've always wondered what the FCC does with the equipment they seize from pirate stations. Where does it go after they seize it? Has anyone ever asked? Does anyone even know? Or does everyone just not care? I know I'm curious.
I do look over the equipment that is sold by various websites that sell AM and FM transmitters and several show the inside of the cabinet where the audio processing circuit boards and amplifier section of the RF power amp. I see signs of a filter, similar to those band pass filters I see for FM. If there is a 5 or 6 pole filter, and it is designed to block everything above 108MHz, how is there going to be interference to the aircraft bands above 120MHz?
As for spurs, if signs of your signal on another portion of the FM broadcast band is the issue, I know of licensed radio stations in my area that interfere with other portions of the FM broadcast band. This is not always a case of a poorly designed radio receiver, it is a case that at 15,000 watts ERP, your truly going to interfere with something.
Case in point, WBMW 106.5MHz recently went from 10,000 Watts ERP to 25,000 Watts with a move to a new tower location and an authorized power increase of 25,000 watts, you can hear them bleeding over various other parts of the FM band as far away as 15 miles from Stonington, CT. which is where their new tower is located. They were formerly transmitting from Ledyard, CT.
Nothing has been done about that and it still continues to interfere with 107.1 and 107.3MHz.
Now back to those Chinese transmitters, I personally do not believe that every complaint made about interference is 100% truthful. When it comes to a licensed station filing a complaint against an unlicensed station, their most successful complaint is that unlicensed station was causing interference to our listeners ability to listen to our signal, even if that is not really the actual case.
Now as far as WBMW goes, their interference does not interfere with a station on 107.1 or 107.3 that covers the area they interfere with. WAAF on 107.3MHz from the Boston, MA market does not have a 30dBu contour in southern Connecticut and there are no stations on 107.1 MHz that serve this area, one is in Hampton Bays New York and the other is in the New Bedford MA area.
I may be wrong, but without actual testing, we can not be sure one way or another if those Chinese transmitters really actually cause interference.
Now as far as those unlicensed FM or AM stations out there that actually cause interference, what are they using and why don't they look into some type of filtering to avoid this interference in the first place?
Transmission line filters are available for both the AM and FM broadcast bands, they should stop the 2nd and 3rd image from leaving the antenna and they don't cost more than 50 to 130 Bucks tops. Spending that money could save an operator that $25,000 fine for creating interference.
That's my opinion and I'm sticking to it.
Bruce.
I wonder if the new one has the same range?
RE: The clip below from the opening post of this thread:
... FCC Part 15 compliant FCC ID # 2ABT5AX05B7C Low Power -48dbM/500 mW (To adjust power hold down the power button while unit is unplugged then plug power in. Press Down arrow to switch to -48dbM or up arrow for 500mW Click power to confirm. ...
A power of 500 milliwatts is +27 dBm. If the text above is accurate, then the output power of that unit is adjustable over a range of 75 dB (a ratio of more than 31.6 million to 1).
Just to observe that an r-f attenuator or otherwise adjustable circuit of that range and required accuracy would cost far more than the transmitter itself.
So are you saying that the High power is NOT really 500mW (as I suspect)? That would really make more sense as to why the low power was so crappy and I could not go far at all as compared to the Whole House Transmitter 3.0. To me I don't think I am breaking any rules here at all. We'll know for sure when the real tests with the Potomac FM-71 is done. But if the Decade CM-10 is no longer made I wonder if it will also cause SainSonic to have to stop their AX-05B (unless they copy the circuit themselves)? If they want to continue making (or reselling) transmitters they would have to go with Ramsey and assemble all of them and then have each kit certified as a fully assembled unit. So far I see no mention of not making SainSonic on their website. Still I'd like to see the test done to it as I suspect the supplier is HLLY. I don't know how they would have done it in the IC Chip to switch between the high and low like that unless they have two separate routes for the signal to pass. Switch to low power it goes through some sort of resistance. the Transmitter is not that big so there is only so much they could do.
Clip from Reply #58 above: So are you saying that the High power is NOT really 500mW (as I suspect)? ...
I posted nothing that would deny the power values you expressed either in milliwatts or in dBm in your original post. I have no basis for such denials.
All I did is to comment on the difference between them, and to point out the technical difficulty and cost needed to (accurately) produce such a range of output power.
Note that the transmitter output power needed to exactly meet the field strength limit given in FCC §15.239 depends on the configuration/gain/impedance match of the transmit antenna it uses.
A power of about 11.43 nW (0.000 000 011 430 watts) applied to a matched 1/2-wave dipole transmit antenna produces that maximum field. Not much more power than that would be required when using a very short and electrically inefficient transmit antenna -- in almost most cases less than just 1 milliwatt.
So it is unclear as to the reason that some domestic/international manufacturers and their distributors offer (uncertified) transmitters for the FM broadcast band with advertised output power ratings of 10 mW, 25 mW, 35 mW and more for use as "Part 15 FM" transmitters.
Caveat emptor.
Here is another transmitter that claims Part 15.239 specs
http://www.canakit.com/usb-fm-transmitter-kit-ux300-ux300-ca-ux300-ex.html
Only 7 frequencies which sort of kills that transmitter. Otherwise it looks like it is made really well. Since it has a built in sound card the audio quality would be really clean. It use to be on sale for $89 at one time.