Test Report Hamilton Fail-Safe "Certified" FM Part 15 Transmitter

I want one.

Seems as though they copied the SainSonic AX-05B and at least its a clean transmitter.  And now we know what to ask for in field strength for a mile or two which would be 416,000 uVm X 2 and that would be 832,000 uV/M at 3 meters.  As a separate service these numbers was very important to gather.  We'll be submitting that.  Thanks for the tests Tim and again THANKS FOR THE RANGE TEST AFTERWARDS.

At least the SainSonic would do 30-50 Ft on Low Power and was useful at the low power setting.  I wonder what would have happened if someone had an outside antenna at low power what field strength would result?  Maybe they took that into fact when they chose such low field strength with their rubber duck.

FWIW the High Power range was about what I got with the SainSonic (With experimental license).  It too was around 500 mW on high.

Over $150 is way too high for that transmitter whan the same thing is made for around $50 and sold by SainSonic on Amazon.

At least  the power on the low setting is way under powered like the Ccrane which is legal.....doesn't have to be the max. allowed to be certified legal.

The FCC should check once in a while with these certified ones for sale and see for themselves if it's really legal.

The Chinese company just turned down the low setting and left everything else the way it was and somehow got a FCC #.

At least the way Decade did it with the CM-10 they still had made in China on the label, it tuned to 107.5 only and not below 88.1 and had no high power, it was disabled. And it worked at near the limit +or-. Decade had it made specifically to meet BETS-1 rules where this Rangmaster just had the low power function disabled so just radiating from the cabinet would go 6 feet.

Mark

The low power Legal" setting is completely useless. Coverage was *maybe* 4-5 feet at BEST. 

I suppose it would be OK if you left it next to your stereo and plugged your mp3 player right into it when you came home after work or something and listened to the tunes on your big FM stero system. But it wouldn't even transmit across the room.

Useless in low power.  I still maintain it's defective, but they insist it's not.

TIB

Well, like anyone else curious about these things, I opened thie bugger up today and took a couple photos of the two circuit boards inside.  Perhaps those more in the know with these FM transmitters can learn something from them. Maybe recognize some chips or circuits. I see regulators and a modulator. FM is not my thing, and aside from field tests I don't know a lot about them.  I left the photos in high resolution so you can see the details.  If you cliek these links you should get 'em, and click 'em again or whatever you need to do to see the photos in their real size.

and 

I do see the boards are dated 2012, and some numbers there sure look familiar to some other Chinese transmitters I've seen advertised. There is not one word anywhere in the transmitter, on the transmitter, in the manual, or in the packaging about country of origin.  this is illegal.

TIB

Oh, and their antenna is nothing is more than a piece of wire inside the "rubber ducky" outer case. 

TIB

Only thing I see different from the standard CZH-05B(had one a long time ago) is instead of 3 output transistors there are two....for the high setting. The low setting output transistor isn't there which explains the low power on the low setting. The other mod is the RCA input jacks.

Mark

Nice filtering on the power, with the green toroid in an LC circuit it looks like. That will keep hum low. I see the final is a more hefty transistor, for the high power part I guess.

There's a hole in a solder connection by the controller / display board, that wouldn't get past my inspection! It probably would bother boardmaker too, though likely will work okay, but you can touch it up, it would be better.

Thanks for the pictures, pretty well refined boards, with lots of vias for RF, and lasso grounding strips.

One interesting thing I see is a hand-added jumper in the RF section, and below it a trace has been cut, I wonder if that's the mod for low power?

Just another hunk of junk from our illegal friends at CZRF.

832,000 uV/M at 3 meters.

Oh good lord is that mega illegal. I've seen folks fined for WAY less.

I see what you mean about sheer millivolts field strength, and given how easy it is to get power like that with the technology we have now, it shouldn't be a surprise if most units could go over the limit, it's so easy.

There are pressures on all sides, even on the engineers that build the units. They want to build something better and better, and have the technology to do it and they will. Everything else you get in electronics constantly gets smaller and more powerful.

To design a whole system with sharp board design like that, DC and RF filtering, digital frequency control, extruded case, all that seems like overkill for a tabletop product that's intended to transmit just across a room.

The Rules would not seem to be keeping pace with improvements in electronics.

Then you have the world market, and the US, North America, is not the only place that uses small transmitters.

A good idea might be a simple outboard attenuator box, and you could turn a knob and get just the range you need, and it could be designed for extra filtering and to present the correct load to the transmitter's output.

Sure, when younger I wanted to cover the whole town with my Radio Shack FM broadcaster, but it seems that a lot of people have a defined audience, like their subdivsion, dorm, apartment building, and an adjustable box would be a good accessory.