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At last an excellent review on the difference between C.Crane’s FM Transmitter 2 and the original FM Transmitter 1:
Total posts : 45366RadioJayAllen’s review site is loaded with goodies. He thinks very highly of PhilB’s AMT3000 from sstran.com
Total posts : 45366We want, Information, Information. Cool sites Carl. I’m glad to see that C.Crane still offers their transmitter. I wonder if the picture is showing the power adjustment pot that people used to talk about?
Total posts : 45366I think it does. If someone were to turn said pot with a screwdriver I wonder if it would go the full 200 feet? I’ve not heard that it would even make the same distance that the WHT makes even with the VR2 pot adjusted to MAX Counter-Clockwise for the FM2’s. Its aasy to do but I’d rather have the higher powered WHT 3.0 with its secret high power mode cuz even at the out of box power it still beats the modified C.Crane. That doesn’t say much for the C.Crane. The Whole House Transmitter 3.0 is still better but both transmitters are still plastic. I’d rather have a heavy duty Metal one.
Total posts : 45366Don’t know how, if both transmitters as they come out of the box, meet the max. allowed by the FCC, with certification, how come the Ccrane only gets 45-70 feet but the wholehouse 3 gets minimum 150 ft. and will go a considerable distance further in actual fact(I have one). If both transmitters have supposedly the same radiated power the coverage should be equal….should it not!
Watched a demo of Tom Web at Wholehouse demonstrating range of the 2 model awhile back and set it up at the 50 yd line on a football field and walked to the end zone with a Eton wind up radio and say “look I’m at the end zone and still a perfect signal”….I know he could have kept walking back a lot more before he lost it.
So….I ask, how can two transmitters operating at the same(?) field strength have such a difference in range? And, this is not doing any hacks or “hidden way” of increasing power….this is just as they come certified out of the box.
Mark
Total posts : 45366I saw the same video on youtube. I searched for “hole house FM Transmitter”+”range” or “sainsonic AX-05B”+”whole house FM Transmitter” or “Whole House FM Transmitter”+”C.Crane FM Transmitter” anyway I wanted to get a comparison of the two and I stumbled upon this. Plus there was another video where someone went in a car and drove 7 houses down his subdivision and yet another that went 1/4 mile away and still got good reception. Now I read a report on both the Sainsonic AX-05B (Set at High Power 500mW) and the report was the Same Range!!! So there is that 1,000 uV/M fudge factor everyone is talking about in forums since the AX-05B is certified and cost less than the Whole House FM Transmitter 3.0. This means that the WHT has to be transmitting at least 100mW to 500 mW at low power into the rubber duck Before switching to High Power. If you had the same connector made to connect the WHT 3.0 to a outside antenna at that rate it would go 1 mile to 1.5 mile at low power. But just on the duck both transmitters will go 1/4 mile. This is before the secret HIGH power mode on the WHT 3.0 which is probably 1Watt (Same as the ST-1A which also is chinese). This tells me that the WHT 3.0 is a FM User CZE-T200 in desguise which has 4 power levels 1mW (Same as C.Crane FM2),10mW 150 Feet),100mW (Sainsonic AX-05B Fail-Safe CZH-05B low power),200 mW(Same reported range before hack on WHT 3.0). So it looks like they simply skipped the two powers in between and when you hold down cycle+mute you jump to 200mW or 500mW. Also you’ll notice that only the HIGH DOLLAR cirtified FM transmitters costing $100+ get to go 1/4 mile on a car Radio as some reported with the Whole House FM Transmitter 3.0 before the high power switch. Amazon talks alot about the secret power mode and the range difference. So its safe to say that its really a FMuser transmitter at a much higher price for the same power. Mystery solved. Only thing they did was to add 75uS pre emphasis to the EQ which was a mod to the audio section of the transmitter. If they had put it into an aluminum chassie like the SainSonic they would have my money. Its why I’m actually considering the CZE-T200 because at 100mW you’d get the same result. If you feel unsafe then keep it at the 1mW or 10mW setting as the report says 10mW goes 150FT in Stereo Hmmm imagine that one. You’d still have a better transmitter than the C.Crane at that level. C.Crane at the hecked power probably is 100mW as its reported to go about 400 FT still less that 1/4 mile without hacks on the Whole House FM Transmitter 3.0. I don’t need a watt meter to figure that one out. I’m sure the 1 mile plus on high power as reported is the same power level as the 1 Watt chinese transmitter costing $200 and I know that is way more than 1,000 uV/M. So there the fudge factor was into play. Plus the Whole House was not sold as a Car FM Transmitter neither is the SainSonic AX-05B but the uncertified FM User one at 200mW was sold as a portable FM Transmitter. So if your transmitter can’t be used in a car the FCC gives the fudge factor everyone talks about according to my shuthing. Ironic isn’t it?
Total posts : 45366I doubt there is a fudge factor at play.
There is some doubt that the Sainsonic is certified, no matter what they advertise on their website. When manufacturers start talking about power instead of field strength, that raises a red flag in my mind. Particularly when they talk about milliwatts, as typical output power for Part 15 is on the order of nanowatts (with a good antenna, admittedly).
Re differences between the Whole House and the C. Crane transmitter ranges – while the rules state a maximum field strength, there’s nothing stopping a manufacturer from releasing a transmitter with field strength less than that maximum (and it’ll certainly qualify to be certified). That is probably the case with the C Crane – from what I can gather in Forums (and from my own experience, as I did own one), there’s a lot of variability in the range you’ll get as delivered (they don’t appear to attempt to adjust each one to maximize that range). If you do decide to use the ‘secret’ adjustment to increase field strength, you just have to ensure you keep within the rule of thumb limits the FCC uses (i.e., 200 feet to an ordinary radio). You’re probably safe with 800 feet in Canada.
Total posts : 45366Well that is what I’m getting at I would not have to hack (open up) the Whole House Transmitter 3.0 and it certainly may go 1/4 mile before that “Secret” power adjustment. If I visit my friends an Canada I could use it there as I certainly would. I never thought C.Crane would not use the max legal power but again companies could use that as a gimick to get you to spend $100’s more on a transmitter. Then again since the FM User transmitter has the 4 power levels I could stay within rules if I went with 1mW (Reported 10 foot) when I’m in the car and use 10mW (Reported 150 Foot on a regular Radio). Still I bet my Sony CFD-S50 is better than most boom boxes as I have a really nice receiver for a ghetto blaster. Still think $125 is a little steep I’ll try and get a refurb of the 3.0 maybe since it too has two power levels like the SainSonic and maybe less harmonics don’t know. That is more of a concern to me at any power level even @ 10 feet.
Total posts : 45366The curves below show the theroretical, free-space field strengths for an FM system compliant with FCC §15.239 (shown in red), and several others.
FWIW, the FCC has issued citations to some operators whose systems had measured signal strengths that could be produced by just a milliwatt or so into a marginal antenna such as a short whip.
Total posts : 45366FWIW, the FCC has issued citations to some operators whose systems had measured signal strengths that could be produced by just a milliwatt or so into a marginal antenna such as a short whip.
Can you post some of those that are 1 milliwatt or less?
Total posts : 45366Can you post some of those that are 1 milliwatt or less?
Below is a list of some FCC “NOUOs” to illustrate my statement in Reply 9. There are many more, but the list is limited to those who could earn their citations using powers of less than 35 milliwatts (mW) applied to the input of a matched, 1/2-wave dipole, over a free space path. The power required in these cases is shown in bold following the respective entry in the list.
Here is one recent example.
http://transition.fcc.gov/eb/FieldNotices/2003/DOC-332404A1.html
The field strength of the signal on frequency 95.9 MHz was measured at 95,597 microvolts per meter (uV/m) at 3 meters, [1.67 mW]
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The ones below are from some research I did several years ago. There are several showing powers of less than 1 mW.
http://transition.fcc.gov/eb/FieldNotices/2003/DOC-310314A1.html
The field strength of the signal on frequency 101.3 MHz was measured at 33,934 microvolts per meter (uV/m) at 3 meters, [0.21 mW]
http://transition.fcc.gov/eb/FieldNotices/2003/DOC-310315A1.html
The field strength of the signal on frequency 88.9 MHz was measured at 1,416 microvolts per meter (uV/m) at 892 meters, [32.4 mW]
http://transition.fcc.gov/eb/FieldNotices/2003/DOC-309813A1.html
The operation on frequency 88.3 MHz was measured at 2,846 microvolts per meter (uV/m) at 154 meters. [3.9 mW]
http://transition.fcc.gov/eb/FieldNotices/2003/DOC-.-309815A1.html
The operation on frequency 101.1 MHz was measured at 3,906 microvolts per meter (uV/m) at 158 meters. [7.7 mW]
http://transition.fcc.gov/eb/FieldNotices/2003/DOC-308807A1.html
The operation on frequency 87.9 MHz was measured at 36,711 microvolts per meter (uV/m) at 3 meters. [0.25 mW]
http://transition.fcc.gov/eb/FieldNotices/2003/DOC-308259A1.html
The field strength of the signal on frequency 98.3 MHz was measured at 1,449 microvolts per meter (uV/m) at 80.5 meters, [0.28 mW]
Total posts : 45366TNX Rich. The last one you posted is like picking fly do-do out of pepper. For 0.28 mW to produce that field strength at that distance make me wonder if the operator was using some sort of gain antenna.
Total posts : 45366Rich’s calculations used the same gain for all the NOUO Field Strength measurements he cited, a power gain of 1.6.
The Part 15 FM (88-108MHz) allowed field strength is tiny, the power required to get there is also tiny. If someone uses a transmitter that is calibrated for micro power use, if the lowest power setting was 1mW (0.001W), and that was accurately the power at the antenna port on the transmitter, the feed line and antenna would need to have a gain of 0.00001875 (-47.3dB of loss) for the radiated field strength to be part 15 complaint. In that case, care would be needed to make sure the feed line and attenuators/pads did not radiate enough to violate the part 15 rules.
Even if a very sensitive radio is used on a channel with no co or adjacent channel interference, getting much more than 750/800 ft of reception range is a clue a transmitter is exceeding the part 15 field limit.
Total posts : 45366For 0.28 mW to produce that field strength at that distance make me wonder if the operator was using some sort of gain antenna.
The equation for maximum free-space field strength vs. distance from a 1/2-wave, center fed dipole is:
E = SQRT(49.2*P)/D
where E is the field in V/m, P is power in watts, and D is distance in meters.
Plugging in the values from that NOUO:
E = SQRT(49.2*0.00028)/80.5 = 0.001458 V/m = 1,458 µV/m.
The reason for the small difference between the field shown above, and the 1449 µV/m field in the NOUO is due to my rounding of the power result when I did my analysis.
Rich’s calculations used the same gain for all the NOUO Field Strength measurements he cited, a power gain of 1.6.
Actually it is 1.64, which is the difference in gain between the maximum power radiated by a 1/2-wave, center-fed dipole and an isotropic radiator.
An isotropic radiator (if it existed) would produce a field of 250 µV/m for a path length of 3 meters with an applied power of 18.75 nW.
A 1/2-wave dipole radiates that same maximum field with only 11.43 nW of applied power.
Total posts : 45366Here next to my keyboard is an FCC certified C.Crane FM1 transmitter with its 11″ antenna vertically extended.
Because the antenna will become incrementally more efficient for each frequency up to 107.9 MHz, for the reason that 11″ is closer to the shorter wavelength at the highest frequency, the transmitter cannot be operating at the maximum allowed certified field strength at every frequency on the band. There will be one frequency, probably at the top of the dial, where the transmitter is closest to the maximum allowed field strength.
When outputing a power that produces the allowed field strength under certification the output power in nW ought to be the same for every identical model, and perhaps the user might have the means to measure the transmitter for that power output level, in which case that power description could be written down and measured from time to time.
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