Combined with an RTL-SDR V3, OpenWebRX+ has produced some interesting findings.
I've tested it with both Decade transmitters (2 different ones) and a Whole House 3. The Decade transmitters produce a nice, stable waterfall signal, and you can clearly see the RDS frequencies (which it passes through).
The spurs that are produced are small, and there is very little if any splatter across frequencies. You get a bit when the devices are over modulated, but it's not really all that significant.
Compare that to the Whole House 3. First of all, the primary frequency tends to move around a bit, as do some of the close in spurs (you can see them in the waterfall moving out from the supposed center frequency, then they are reset and the progression starts again. There is noticeable splatter in the main signal envelope, and several relatively strong spurs about 500 Khz off frequency, strong enough to hear them on the SDR. I'd suspect possible front end SDR overloading, except that this doesn't occur with the Decades.
And if you go into the 'secret' higher power mode (which I did for a few minutes of testing), you get tons of splatter right across the band. Definitely not recommended to use in that mode, even in locales where it might be legal.
Comparing the signal to the Decades, I honestly don't know how these things were certified in the U.S. and Canada. Maybe they used a cleaned up one for the testing with extra filtering. Even though I use the Decades, I kept the WW3 around as a convenient backup, as its form factor is nice and small. But on seeing these results, I won't use it.
In addition to all this, Mark reported a very strong second harmonic when he tested the transmitter with a spectrum analyzer. I didn't even both to do that.
I know there's at least one featured individual using this transmitter over at Hobbybroadcaster. He should get rid of it, and consider the Decade at the very least.
Next, I'm going to try the Broadcastvision AXS FMT, which has a certification number for both the U.S. and Canada.
You are finding out, doesn't matter how, the Wholehouse 3 is a good way to get a visit. The second and third harmonics were way too high and so was the fourth. I didn't switch modes to look up to 950Mz but I'm sure more up there with the 5th 6th 7th and more. That was at regular certified power, not on high! And yes the second was the same strength as the intended frequency depending on the position of the spectrum analyzer.
No way that should have gotten certified. I posted pictures a while back if you can find it.
As Artisan has found the Decade is good and the BVE should be also. The Retekess Tr 508(CZH 05B) that somehow got part 15 certified was clean when I had one for a brief time for testing.
I don't know anything about SDR that has been in conversation as of late but I assume software defined radio when I looked it up it's a way to make your computer a receiver and spectrum analyzer all in one?
This seems to show me some of it..
https://www.hdsdr.de/screenshots.html
As speculated, the the Broadcastvision AXS-FMT has a clean signal in the SDR, both in stereo and mono.
Unfortunately, it filters away the higher frequencies necessary for RDS.
I think Mark is too close to the situation and over estimates the seriousness of Wholehouse 3's spurs and harmonics. Although the transmitter should not have been certified in its poor condition, in the larger geographic picture it would not reach far enough to wave a flag at an FCC roving tiger force.
In my case I have a Wholehouse 2 and avoid using it on the lower FM band because the harmonic splash wipes out all the other stations nearby on the dial, and I want to be able to monitor those stations. But the unwanted junk radiation fades out only a few feet away and would not pose a significant risk to my freedom or welfare. Luckily the device functions properly on the high FM frequencies and can be used.
I was horrified to see the results of the SDR testing of the WH3. But I think some the splatter was the result of the transmitter overloading the front end of the SDR. As I said, I'm going to move the server and SDR further away from the transmitter at some point, and see if the issues still occur.
I really didn't like the way the signal changed frequencies, even though it sounded OK. I actually did see the RDS signals from the WH3, but they were moving all over the place, so it's no wonder that OpenWebRX+ couldn't decode them.
And as a side note, I found that I had to increase the amplitude of the RDS signals for the transmitters that did pass them through so that OpenWebRX+ could reliably decode them. This, despite the fact that my car radio could decode them over 100 meters away from the transmitter. SDR++ had issues with RDS on every transmitter; it managed to get a bit of the data, but I would say they have a problem there.
By more fiddling around with SDR++ Server parameters, I was able to get the network traffic to the SDR++ client to be about 3Mbps. It still isn't low enough to reliably use over the Internet. I've seen network rates as low as 230Kbps (an order of magnitude less) with OpenWebRX+. And it uses commonly available browsers, whereas you have to use the SDR++ program as a client with its corresponding server.
@carl-blare At 107.5 for example, high end of band, the second would be 215 mHz and the third would be 322.5 mHz and fourth at 430 mHz and so on up and up getting into other things in those bands. You are getting into satellite radio and UHF tv and other stuff.
The second and third are just as strong as the fundamental. Anywhere the intended frequency gets to so does the others too so your station can be heard on many places throughout the spectrum.
But you are right that in regular power setting none of it goes far enough that if there's nothing right near you within 300ft or so except residences it probably wouldn't matter unless they are using a cordless phone landline or you are not next to an airport or hospital or someone doing amature radio.
But if you are at the low end of the band like 88.3 for example, the first harmonic would put you just past the aircraft/ communication band and up from there.
Here's a chart of the bands and all the stuff that uses the space where all the harmonics from the wholehouse at the high end and low end of the band get in to.
I don't/can't fault you for using it, it's legal, just saying that there's safer choices.
Here's the bands and what they are used for.... https://www.ntia.gov/sites/default/files/publications/january_2016_spectrum_wall_chart_0.pdf
I'm actually considering purchasing an SDRPlay RSP1A to test it out. The big advantage of it is its larger bandwidth, so you can cover the entire FM band if desired (the RTL-SDR can only do slightly over 2Mhz).
Then I'll have an RTL-SDR V3, an RTL-SDR V4 (it is a different beast, requiring different drivers than the V3), and the RSP1A.
I'm going to do some experimentation with the RTL-SDR V4 on the AM broadcast band, as it has built in direct sampling. It didn't appear to work at first, but upon further research it appears that sensitivity is less with direct sampling (you need to use an up converter to avoid that), and I didn't have the gain high enough (it was set at 0, whereas some of the profiles I've looked at have it set quite high). So we'll see.
I need to back up a little bit because I don't remember whether I looked at harmonics above 108 MHz when I looked at the Wholehouse 2 on a spectrum analyzer.
Also, I only use the thing for brief audio tests and never for long term broadcasting.
Right now I'm using C.Crane FM1 and FM3 for in-house FM purposes, although it would be nice to be able to turn off the stereo. A Decade would be nice.
Fantastic!
I am listening to an SDR-Cast from Artisan Radio at 91.9 MHz and it's beautiful! Old time music blazing away and me able to make some adjustments by remote between here in the U.S. and there in Canada. That is the way to go, for sure!