I had a horrible possible spur discovery last night just before bed. If it wasn't already a kick in the nuts to have to admit defeat with the FM initiative of more field strength due to the facts that presented itself during intense study and a reality check I found out that my SainSonic AX-05B may not be as nice as I thought it was. Imagine that why is that not a surprise when it rains it pours as they say. Well just before bed and I noticed a slight hum on my TV 3 feet away from the TX. At first I thought it was the mini refrigerator I have in my room for my cans of pop. I turned off the cable box and heard the hum. Shut down my Radio station and at last turned off my transmitter after a whole daytime show lasting till 4AM. Hey hum gone. Oh oh Huston, we have a problem. Danger Will Robinson, Danger! I turned the transmitter back on at the high power setting. Hum comes back. What a kick in the pants. I'm glad this was discovered now instead of a NOUO from the FCC. I remember telling you folks that at high power and at 10 feet it would bleed a boom box but go outside and its gone and everything is normal. Scratching my head and reading about the CZH-15A it all rang in my head too clear. This thing could be doing what the 15 watt CZH-15A done causing spurs on the lower frequencies below the FM band. I decided to switch to low power. Now I fired it up and NO HUM! Problem solved! Yes that is solved I can deal with that but No signal outside my house that is use able for reception not even on the porch. If I am outside and follow the contour of the house I get signal. And get this IT FOLLOWS THE POWER LINES!! What carrier current FM? What did SainSonic do? It has to be inches from the lines but if I walk under the power lines I hear my station till next door as long as I'm outside with the boom box. Does this transmitter feed RF into the lines either accidentally or on purpose I don't know. Is the signal use able inside people's houses? Don't know. I'll need to see when someone buys that empty house next door if they plug their FM Radio in and tune to 87.9 Mhz what will happen. Here I'm talking about carrier current FM and I already have a transmitter doing it and God knows what else. Damn the harmonics or lower spurs arent interfering at low power but imagine what damage this thing could have caused 10 feet away to the neighbor's house in front of me. Not a darn bit cool (I'm trying to keep it clean here as I slam my fist against the desk in anger at a mess I could have caused. I wish I had a spectrum analyzer just so I could see what this thing is up to. That transmitter should be tested by someone just for the sake of part 15ers like me who invest in transmitters when low on cash. I guess I should really had just bought a Talking House AM transmitter with that $54 but I'd always be wanting to test FM not knowing. Folks I know now. Save your hard earned money and if you want FM get something different. Even if you have to buy a scoche and if you have extra wire on it your on your own for you may be over the 250 uVm @ 3 meter rule. We will know if someone has a Patomac FIM 71 to test. I guess Carl can tell us did you get bleed from the Scoche you had keep forgetting the model number. And if my memory serves me right it traveled further than the low power of the SainSonic AX-05B and none of the damn spurs either. Even the Maxell P-13 looked good in review but can only transmit on a few channels. I'd want to modify it to have a digital display. What are your thoughts?
TheLegacy, the life you have entered is the life of a broadcaster, spurs and spikes included.
When I found my Wholehouse 2.0 had wierd spurs which were better or worse depending on what frequency I had it tuned to, it woke me up.
I previously believed that certified transmitters were good and reliable and didn't need checking, but that isn't always true.
The main discovery back when I compared C.Crane 1, Wholehouse 2.0 and Scosche FMT4R was that they all showed the same on the spectrum analyzer, which automatically means they all had the same range of between 100 and 200-feet.
But I have never scanned them all for unwanted out-of-channel spurious oscillations, but definitely plan to do so now.
In addition to the spectrum analyzer for checking, the TECSUN PL-310 and the other models like it can receive the full Japanese FM band which covers the area below our FM band, and my Grundig Satallit 750 has the air-band up above FM, so I have several ways of looking.
We are still on the case gathering data about 15.239 FM operation.
Getting depressed is all right as long as you enjoy it.
Honestly Carl before my rants about FM I sort of knew a turning point might happen and I was getting upset about it. Knowing all you tried to accomplish is about to crumble and your at the sinking ship is not a feeling that is nice. I decided to abandon ship before I drown in a murky mess I was not willing or prepared to continue with especially without all the facts and all. Just not any way I want to proceed. The harmonics with the SainSonic at the high power is perplexing and knowing about Radio and having some experience with a higher power transmitter years ago I just don't think its normal. Maybe some bleed at 10 feet, but coming into the IF of a TV is way more dangerous. At high level anyway the transmitter is showing defects. The ticking sound of the back ground only happens on high power. My guess is that at high power SainSonic is pushing the FM chip too hard to achieve the power of a $50 transmitter. The one I had in Michigan was $200 and that was years ago. Until it burnt out I never seen this. 200 feet would get me to my porch nicely with good sound and I could still monitor my station outside on the swing and Rock out. Might even get to the Library across the street. Could get to the house next door and behind me. Still some use able Range just not ¼ mile. But at the expense of others that won't be worth it. So I want to see what yours does when you test below and above FM. Best Regards.
Allow a story from my early days with ham radio which could have bearing on your TV interference. I owned an excellent RCA XL-100 color TV but it would trash when I transmitted on the HF ham bands. The first thought any ham has when this happens is that there must be a spur or harmonic in their signal. I bought and installed a filter specifically designed to cut off emissions above 50 MHz and this did not help.
After much thought and experimenting I discovered that the ham signal was getting into the IF section of the TV. The clue was that it didn't matter what transmit frequency I used the interference was still there. The IF stage of this TV was contained in a tin box and it plugged into a connector on the motherboard. The box was not grounded to the chassis except through the connector. I added a simple ground strap from the box to the chassis and the problem was solved...no more TVI!
It is possible that your FM signal is clean but it is getting into the circuitry of the TV causing mixing and/or overloading of the circuits. If you can, try changing the frequency of the transmitter from one end of the band to the other. Also, does this interfere with only one TV channel or many of them? If the interference remains with changed frequency or channels then it is likely to be an overloading problem since spurs and harmonics will change with the tx. frequency.
Neil
Maybe late one night I'll try this if 107.5 is cleared up. Its Really close to 107.7 but I'll do a short burst and see if any hum happens. There is a trick with the SainSonic so you don't have to sweep the band (can't understand why these transmitters are not muted until your done). What ou do is Hold the power button down and plug the power jack into the transmitter at the same time. The blue back light comes on and says L or H. Since the H mode was causing the issue I'll switch to H for the test. Next it asks the high frequency you want to stop the scan. I'll use 107.5 Mhz. Then the Low I'll use the same frequency. Pressing power the third time stores it and the transmitter turns off. Turning it back on will transmit on that frequency. Perfect way to set the transmitter without sweeping the band with RF again no one wants to do this if you can find a trick like I did. I'll throw quick carriers less than 10 seconds in the wee hours of the morning and see if I get a hum. If not we know its 87.9 comming in on the TV. It could very well be comming in on the IF for the TV as just the carrier and no audio. It just alarmed me because CZH is really the maker of this transmitter modified by SainSonic. If I still get the issue its comming right into the IF. Now the question is would this happen to a neighbor 10 feet away. The house is right outside my window in front of the TX. So I'd better be clean and not causing any interference or I'm sure to get a NOUO and as I study this is how you get one. Never had one and don't want one. Today the TX was only used on low power as a link for my boom box to hear my laptop as I used the station over the net. I'll see and if I can find the TX is clear I'll go back to operation. Just wish I had a spectrum analyzer though it would make me feel better to really know what this transmitter looks like on the analyzer. If it throws a carrier and you see it all over the band you know your in trouble. Or you see hills in the graph when you transmit other than the one your supposed to see your in trouble too. I learned a little from the Youtube video on the spectrum analyzer. I could get that little dongle and it has a spectrum analyzer on the software. The SDR can be useful as a poor mans spectrum analyzer.
More experiments I threw a carrier at 107.5 at high power and no hum on the TV. Went back down to 87.9 Mhz and hum again. This proves the transmitter is throwing out spurs as I suspected unfortunately. This is at Chennel 3 being received. This again is very bad.
AM can also have spurs and if the transmitter isn't clean you can cause interference in the Ham band just above the AM band...1800 to 2000 KHZ
Mark
The hum the transmitter causes to the TV is slight. I'm probably being overly cautious. After all we were all sitting down and watching TV and it was not so bad you could not watch. Just an observation I noticed. I'll probably still move to AM when I get the money but its something I'd need to find out just to clear my mind. The interference however may be an issue since it was talked about in other sites and one part 15 site didn't allow the discussion for they felt they were trying to be a Pirate not thinking they may just turn the power down since it was a variable setting. I'd really would have wanted to find out if there was a solution that anyone found to it. I guess this is a case where we'll never know unless someone has the proper test equipment and owns a SainSonic transmitter. FailSafe also would probably be close enough since theirs was the CZH-05B and most likely about the same as this one. Anyone notice anything like this with the Decade CM-10? Any bleed or places on the dial other than your intended frequency? I'd like to see if I could promote my station on the new frequency since people drive by and I know sooner or later someone would trip on it and love it and listen on the Internet and tell more friends in this area. This would get me local listeners too which would be quite fun.
More info on the HUM in the TV. I did find out its comming into the audio amp of the TV that is 3 feet from the transmitter. I turned the TV all the way down and you can hear the slight hum. I mean its so small it really don't destract you. You really have to listen for it. It may be as was said before the fault of the TV. Plus the TV is plugged into the same power strip as the transmitter. Now since its transmitting Carrier Current I did check my boom box which does get bleed right next to the transmitter and I hear the hum if I am plugged into the same power strip as the transmitter. In the Kitchen which is the next room I don't hear hum or bleed. So all the RFI seems to be from the RF transmitting into the power strip. Pretty weird huh?
where's the antenna? I've found electronic devices don't take kindly to transmit antennas near them, AM or FM.
At the same time I have been experimenting with FM antennas for the C.Crane transmitter on top of the computer, and then added a 2nd FM transmitter, the computer has totally frozen a total of 3-times.
Should I suspect that the FM signals might be causing the computer to malfunction?
I have now been running for 2-days with the transmitters moved away and so far so good.
Ya, if you're interfering with TV when on a low frequency on the transmitter then you're getting interference on channel 3...if you have a radio that receives TV band audio you can tell this.
People with cable(anolog) tune to channel 3 to get all the stations. Fortunately most people now are watching LCD TVs which won't have this happen.
Sorry you have had bad luck with this transmitter.
The CM-10 does none of this operating at BETS-1 levels. I still have a CRT TV and a radio with public service band and I check . You mentioned the CM-10 in a post so that's why I mentioned here.
The Sainsonic at high power is 500 mW like the other CZH transmitters and with more power the effect on other things will be more if it's not clean.
Mark
And yes the antenna is a rubber duck and its maybe 6 feet from a CRT TV. The cable box transmits on channel 3. And the CM-10 does not do this? This was something I wanted to know. It does sound like they've added some filtering in the CM-10. Wish now I have had the extra money for it. Though could be overpowered for the USA at least its not causing spurs and harmonics. In a few days I'm gonna be trying AM either by Talking House or iAM transmitter. I think its far more safer to play on AM. I don't have the proper equipment not even an older TV sound Radio. I had to sell most of my electronics in 2010 to put food on the table. As I've said I've went without power in the dead of winter. It was either sell and take a loss or freeze to death and starve. I'm still having some issues but not as bad.