My first question is: How do I know that I actually received a Decade CM-10 for the USA market? I bought it right from them, they shipped it to me in the USA, so I assume they sent me the right unit. However, today's tests do not lead me to that conclusion. Is there a way I can actually tell?
I set up exactly as I did in the Whole House 3.0 test. Same field, same equipment, etc. So read that write up if you're concerned about the setup. I used the Potomac FIM-71 meter and corroborated my readings with the Z-Technology R-506. Not nearly as many tests as with the WH 3.0, as fewer options to experiment with (Have to have a power cable, and no power level switching).
Note that the power supply with the CM-10 is required for use, no adapters, batteries, etc are provided. The WH 3.0 I tested with batteries. So any effect caused by having a power cord attached is a requirement with the CM-10. Adding any cord to the WH 3.0 greatly increased it's output, whether audio or power cord, even when not connected to an audio source or power.
All tests taken with the receiving antennas in horizontal polarization.
At three meters the CM-10 gave me 3375 uV/m with the transmit antenna in a vertical position. With the transmit antenna in a horizontal position the field strength at three meters was 6300 uV/m. Clearly both are well over the legal limit of 250 uV/m at three meters.
The power cable for the CM-10 does have a ferrite choke on it an inch or so from the plug that goes into the transmitter. Also the power supply itself is not a wall wart as such, but a lightweight switching supply that has about 3 feet of cord on either side, one to the outlet, on side to the transmitter. There is no continuity from the plug for the transmitter to the power outlet plug. So any counterpoise effect would be with the three feet of cable I imagine.
I did notice that the output varied quite a bit depending on the location of the power cable. By moving it out diagonally from the transmitter the field strength would vary. The readings above are taken with the power cable hanging straight down from the transmitter. Remember, transmitter and receiving antennas are at 7 feet above ground as specified in the meter manuals.
I was clearly expecting this unit to give me much more close to legal limits. I couldn't remember the Canadian limits or I would have tested for them. These readings are not that far off from the WH 3.0 when it has an audio or power cable connected to it. Adding an audio cable to the CM-10 didn't make a noticeable difference, but then again it already had a power cable. And adding either cable to the WH 3.0 made a big difference but once one was added, adding the other cable didn't change things much.
I took my first reading with the FIM-71 and was so surprised I doubled checked the batteries (they're new) and calibration three times, and took the readings three times, all the same, before setting up the R-506 to corroborate. Same readings.
This is why I wondered if perhaps I received a Canadian unit. How do I determine this?
TIB
Tim, I know your expectations, and ours also, were that the CM-10 would come right in on target.
No one expected what you have found.
For the moment we are floating around at sea withoiut oars or sails.
You've got to find some way to get us back to shore!
Tim, did you purchase this directly from Decade in Canada, or from a dealer in the U.S.? I'd contact whomever you purchased it from.
The Canadian limit is 1000uv/m at 3 meters, but your readings are well above that. I am quite surprised.
Was the range comparable to the Whole House you tested previously?
I just reread your original post, and realized that you bought it directly from Decade. Perhaps they sent you a (supposedly) Canadian tuned unit by mistake. Although it's still way too high for even that. I'd still contact them and see what they have to say.
Wow that was even higher than the Whole House 3.0. From 3300 to 6300 I'm guessing that is very close to what you'd expect from the SainSonic AX-05B at high power. So instead of 75% of the population running 6Kuv/m at 3 meters you have oer 95% and if the C. Crane is over I'd say 100% of the transmitter population is over for FM. Either two things are happening. The FCC may be relaxing the rules and it has not been written as such. If so how much? We seen NOUO's in the 6K-7K range. Makes me want to try FM again if I can't get this AM TX to transmit 1/4 to 1 mile. I'd like to know what the uV/M is on a talking house AM transmitter. Really I know we're talking two different bands but it may give us some sort of understanding about range. If 95% is over 250 uV/M at 3 meters one can assume there was a informal rase in the rules or fudge in those rules. We all don't have Patomac FIM 71's and this is not what I expected to happen at all.
Especially when the antenna is horizontal! Could be the meter seems to have a dipole like receiving antenna that is horizontal so when the transmit antenna is also horizontal it's a better match?
Michael @ Decade told me that all CM-10s are FCC compliant and if shipped to a Canadian location they change a couple of things before sending out.
But your tests show way above BETS also!
The MS100 is internally tuned to the right levels, or so we think.
Basically all we, the consumers, can go by is the fact it's certified.
Appriciate you doing these tests with the surprising results.
Mark
I believe that probably 95% of these FM transmitters that are sold are not sold to people who are using them for "broadcasting" and using them for their own uses. So the odds of the FCC getting a complaint and deciding to pursue it are pretty unlikely. They obviously don't drive around scanning the band looking for oddball stations.
I too was certainly not expecting this result as well. I didn't do a range test with a radio this time out, but I had done a bit of a test when I first got it, and just like with the WH 3.0 I was getting just past 200 actual measured feet, in the street, with the transmitter in clear sight from me. That was with the transmitter sitting on at about 30 inches off the ground, so maybe some height would have helped, but again, it was right in front of me. Coverage between the two from that day of quick experimenting had them pretty close in range, but again that's a tough test to call, as choosing a different radio for testing, and minute changes in the receiving whip antenna made a huge difference.
And yes, there is always an increase in reception when the polarization of the transmit and receive antennas are the same. So I expect an increase here. The antennas used for both the Potomac and the R-506 are horizontal half wave dipoles. And my limited experimenting seems to show that polarization is not as big of a factor with a greater distance between transmitter and antenna.
The FCC does NOT actually test these things. We must keep that in mind. The manufacturers send them to a lab to be tested for compliance. These lab tests are submitted to the FCC. On some occasions the FCC may have an issue with some detail, and ask for a change in the design, etc. it looks like only in very rare cases will the FCC ask to actually receive a unit for their own testing. And it appears that the certification process doesn't seem to have any parameters for tolerance in manufacturing.
TIB
If you want to sell your "like new, slightly used" wholehouse at half price and send to me most economical way(Toronto) I'll buy from you.
Mark
I'd be most delighted to sell you the slightly used WH 3.0 for half price + shipping. I need it for a few more days however, as I am going to check actual RF output from the two transmitters before I sell them. Probably get to that in the next day or two. Half price would be $62 + shipping. What is your postal code? I'll figure it out. Do you use Paypal? tim
Basic economy way
Postal code: M6L 3E9 Toronto Canada
Mark
Tim does the Hole House 3.0 bleed the dial at 10 feet? I mean does it wash it really bad? Just wondering. Yea $62 is a really good price especially if the TX is clean in the specturm. A little here and there in transmitting on FM you'd probably be OK with it. Got to be cleaner than the SainSonic I'd imagine. Sometimes wish I'd not have bought it and at least I'd have had a really clean FM Transmitter. Its a less of two evils. But at least if the FCC said I was over at least they would not be as mad as washing the whole dial at 10 feet. That would really get the FCC PO'd at anyone. And its a respect of others issue too with me on the dial wash at 10 feet.
I'm guessing that "bleed" is a way of referring to an overloaded input stage to a radio, which my AMT5000 does out to about 7-feet on some radios.
10-feet isn't bad, as long as the're your own 10-feet.
If you blanked out radios in the whole block it could be bad.
In a completely unscientific test I fired up the WH 3.0 with Christmas music playing through it (Bing sounds mighty good through this transmitter) and stood right next to me late 70's vintage receiver and went through the FM dial and didn't hear Christmas music anyplace but at 92.7, my testing frequency. So, I don't know how scientific that is, it's certainly not a spectrum analyzer, but checked out OK anyway.
TIB
I shifted it into high and still no noticeable bleed anywhere on my home stereo. The result may be different on a crappier receiver, however.
TIB
Cheapest shipping to you in Canada is $13.70.
TIB