Sponsored Part 15 fm transmission range
Thanks for the information on that, I was looking at the decade transmitters on eBay, trying to get a deal on one that transmits in stereo. I do have a Field strength meter, but it's really hard to use. I had the best luck with the meter when I took it way away from the city and out to the mountains.as I was getting a lot of interfering signal's in the city. But even in the mountains the meter was really hard to use. 250 microvolts is such a low amount of power, it was hard to get a true reading. The numbers on the meter were bouncing all over the place. And the meter is super sensitive. Even cars driving by 200 ft away would affect it.
It was me that had a Wholehouse 3 and the second and third harmonics were almost the same as the intended frequency and I posted a heads up about this one with pictures of the results. I took the readings beside the antenna(about 2 feet away). The Decade Ms-100, Broadcastvision, are clean and so was the Retekess TR 508. Those CZH O5B and equivalent branded ones only have the label affixed with number on more recent ones. The Retekess TR 508 that me and Artisan tried had the label with certifications. If there was cheating in getting the part 15 certifications the FCC has to go after their own labs that gave it the green light and the company. My findings on the Wholehouse 3 are here back a bit in the posts. I posted pictures of the Wholehouse, Decade, Broadcastvision, and Retekess all the same 2 feet away from the antenna. I'll check and see if I can find it and post the link.
Sounds good, I also have been experimenting with a really cheap auto drive fm transmitter made by scoshe. I got it from Walmart for only 8 dollars. It runs on 2 aaa batteries. I was surprised how good it sounds. Good sound quality and good stereo separation. Itt's very small in size but it works well. I'm getting about 600 feet clear radius without any modifications. And if I add a ten foot audio extension cord to the attached audio line, it will reach 3/4 of a mile radius clear. I tested it with a field strength meter unmodified and it read 50 microvolts at 10 ft. So it has a lot of headroom on the signal strength. It's really sensitive. I can triple the signal strength just by holding it in my hand and my body works as an antenna. It also works really well with an unattached piece of aluminum foil as a reflection antenna. It's really clean hardly any harmonics. The only drawback is it only covers 20 frequencies.. 88 thru 90 mhz and 106 thru 108 mhz. And it's stamped with an FCC part 15 certification number right on the unit.
As for the certification with the Retekess(CZH O5B) or others that is what makes it legal to sell and use and it's not for the user to have the know how and expensive equipment to be concerned with anything other than it went through testing and passed as OK and has the certification ID on the product. It's not up to the user to know how far you should get with 250uV/M@3meters or what that even means as you assume that the company went through the hoops to market a legal product. If there's fraud then that's on the lab and the company that submitted a product for certification. By the way you have a FIM?
Anyway here's a link to my post showing the harmonics of the Wholehouse 3 and the Decade MS-100. The Broadcastvision also was as good as the Decade.
@pete2169 With that Scoshe if you use it as it came certified and you get 600ft, I assume that's on a good receiver or the car, that's OK but if you add 8 ft of wire you now void the certification. Hard to believe that that little thing on 2 AA batteries can reach 600ft or more.
These were made to get your MP3 player to your car radio before cars came with 3.5 audio jacks for this.
Yes, I got 600 feet clear with the scoshe transmitter with a really good car receiver. With the transmitter at ten feet in elevation and flat terrain. I suppose I could get even more coverage area if I elevated the transmitter higher. I was kind of thinking adding a wire would void the certification. I could also get three quarters of a mile coverage radius with an unattached piece of aluminum foil reflector antenna. I have a 20 inch piece of roundf cardboard covered with aluminum foil. If I hang it horizontally about 2 in above the transmitter. It works really good. I was thinking maybe that doesn't void the certification because it's unattached from the unit.
With all this talk about the Decade MS-100 I went to the decade site and debating if ordering would be a worthwhile venture for me...
Yeah that little scoche transmitter is amazing. One time just for fun I attached a 30 inch telescopic portable radio antenna to the negitive battery post with a little piece of lead wire. I taped the antenna so it would stand vertically with a piece of electrical tape. I put it on a microphone stand. And I took it to a ridge 500 ft above the valley floor. I set it out on top of the edge of the ridge overlooking the city in the valley below. I drove down in the valley and listen to it on my car stereo. It worked clear for 2 mi. And listenable for three and a half miles. I was amazed.
@pete2169 This is good that you are finding ways to get unbelievable performance from the Scoshe but we can't really be promoting voiding certifications. The 600ft you get as it comes is amazing for that little thing and within the certification. The foil overhead is a grey area and I don't know if that would be considered a modification as you didn't alter it physically.
The Decade is the best of the bunch quality wise and can last you forever. There's the mono version and the stereo version. Mono will be a better signal for reception. A little less money. The expected ranges shown on the Decade site to a portable and a car are minimum distances not maximum.
Certified for Canada and USA.
One thing that no one is probably interested in (but me). I've experimented with generating RDBS (RDS) via software, and the Decade will pass through the necessary high frequency signals so that a car radio can receive and display the data. The Broadcastvision and the Whole House 3 won't pass those signals through.
There's even an RDS port on the back of the newer Decades so that you can generate RDS/RDBS (for North America) externally via hardware.
You can sometimes get great deals on the Decade MS-100 (mono) used on e-bay. I currently own 2, and picked both up used for C$150 each (in the low 100's in US$). Both were in like new condition and one even was claimed to be new (although I doubted that).
Wow that's really cool that the decade ms 100 does (RDS) I was checking them out online, I want to buy two of them also, 1 mono and 1 stereo model. I'm going to order 1 this weekend. I'm curious to find out what kind of range I'll be able to get with the decade from my 9th floor office, it's about 100 feet in elevation.
@mark. Certification is void by changing the antenna . Putting the transmitter up high doesn't. My car mp3 transmitter has a quarter mile range in the car with no modification. It was imported from China , no certificate to be seen ,either on the box it came in or the transmitter. It wipes out the entire fm band in the car . Doesn't really matter using it in the car because it's moving vs stationary. I bought a cheap mp3 transmitter aa battery powered at Walmartians, around 2008 . It ran the rf output into a rf amp , hooked to an antenna more than 60 feet above ground ...4 to 5 mile range . I used it as my main transmitter for my fm station before I got into part 15 am . I measured it's output at 950 milliwatts. What I discovered was though it went very far , it didn't penetrate into homes very well . Eight on the s meter outside and take the radio into the house down to very weak 2 or nothing at all . Florescent bulbs and Internet put out much interference on fm but not static ....Hiss sound . Beware of illegal broadcasting on FM in the USA ... Especially in or around major cites . They're actively searching for illegal stations . If a person wants real range ...Better do it on AM and stick to the 3 meter antenna ...Going longer decreases range anyway . The AM band in the USA is largely dead . The band is not actively monitored as much ..Besides even within the legal rules using a Talking House withe the stock antenna hanging out the window I was able to reach more than 4 miles , no modifications at all . This is mostly why I go out of the pirate radio operation . Still get out far with so thing that's legal vs taking a risk that's just gonna end up causing trouble. Back in the 70's and up to just beyond 2000 the chances of getting into trouble were far less ...Then came the easy to buy Chinese transmitters ...Pirate radio , something that was rare became a huge problem . Something else happened since decades ago ...Pirates broadcasting over top of licensed stations. ...That set off the current crack down . In the past people would find an empty channel to use ....NOT ANYMORE. ...IDIOTS who went way too far , in some cases operating not just overy a licensed station but operating in some cases over a thousand watts . The best advice now ....Unless you're willing to operate with a range of 600 feet , better to do part 15 am .
@pete2169 The Decade will pass through the RDS frequencies (sidebands at 57 Khz) but you still have to provide the signals.
I modified an open source software program called JMPX to work with Zara Automation (now Salamandra, they're essentially the same). The software generates the RDS signals, using data from the currentsong.txt file created by these automation programs, along with the programming audio. You then just connect the output to the Decade transmitter normally. You have to use 192Khz sampling in your computer audio output for those high frequencies (if it's capable - I ended up using a USB DAC).
Unfortunately, I lost the development environment and the sources to a hardware crash, but I still have the Windows runtimes that I can let people have if they're interested.
The other way to do it is to generate the RDS signals externally, using hardware. You connect the RDS box up to your computer, and software in the computer feeds the data you want to encode to the box. You can then hook up the resulting box output to your Decade (but make sure that it has that RDS input port, I think it's an option). These boxes are expensive, probably more expensive than a new Decade transmitter (they're meant for licensed stations, which ups the price significantly), which is why I went the route I did.
The software solution works perfectly well. I've run it non stop for weeks on a Windows 10 computer with no issues. That's unusual for open source software, as I've found it tends to be buggy.
One drawback using RDS on a Part 15 transmitter is that its range is pretty limited. The combination of very high frequencies which are pretty limited in power, combined with the slow data stream, means that you're only going to get a fraction of the range of your audio. My Decade is also located up high, on the 8th floor of a high rise. Line of sight, to a good car radio, I can get 1/4 to 1/2 km audio range (and that's with a Canadian tuned transmitter, which is more powerful than Part 15). I can only see the RDS data 100-150 feet, sometimes even less, and it takes a while to sync with the radio.
JMPX does allow you to increase the power for the RDS stream, but then that takes away from the audio range.
I just wanted to properly set your expectations. With Part 15 specs you'll get less range.
Wow I just checked out the Decade ms 100s. $580 Dollars for the stereo transmitter. And that's if you can find one. I did see a used one on craigslist for $350 but it's clear across the country from my location. I don't know if I would want to risk that much money unless I could pick it up local. I saw a few used mono decade transmitters on eBay for around $150 to $200. But why would anyone want to broadcast music in mono. I could see it for a talk radio or something. But the whole point in broadcasting music on fm is to have that clean stereo sound