I have been in this hobby for 20 years and I have just discovered that RC transmitters vary in their output power. It is not always easy to find these figures but my research so far has found that a JR PCM 10 has a 750mw output, while the JR PCM 9 has 500mw and a Graupner JR outputs at 2W, thats quite a big difference. Were any of you guys aware of this? Do you have any figures for Futaba? Does more output power mean more range or is that obvious?

I think you have been wildly mislead by whoever gave you those figures. The maximum legal effective radiated power in the UK is 100mW, most brands output less than that.

Harry

Agreed. Take care how you interpret bare output ratings like this. There are several ways to measure Tx power and they can give very different numerical answers.
--
Steve

Output power does affect range, but the design of the receiver is the part that makes the biggest difference to range. Two different brands of tx may give slightly differing ranges but they are going to be big range and slightly bigger range. Two different rx can give range of fifty yards or a mile. Choosing your rx is the most critical thing.

H.

Originally Posted by HarryC

I think you have been wildly mislead by whoever gave you those figures. The maximum legal effective radiated power in the UK is 100mW, most brands output less than that.

Harry

The figures for the PCM 10 are stated in the manual. This link http://www.gliders.uk.com/prodinfo.asp?number=G3859 shows the Graupner Synthesised module with a claimed 2W output.

Treat it with a large dose of salt! ERP is the normal measurement and it certainly isn't putting out 2W ERP.

H.

The figures quoted in the manual may be perfectly accurate but are misleading as they do not state the measurement criteria. Tx aerials are relatively short for the frequency we operate on and must be base loaded to compensate and there is effectively no ground plane (plastic Tx case) so a lot of power is lost due to inefficiency.
As has been already stated the maximum Effective Radiated Power allowed in the UK is 100mW.

It's a bit like the claims for output power in Hi-Fi systems. One will claim 100 Watts whilst another will claim only 25 Watts.
100Watts peak into 4 ohms is actually about half the power of 25 Watts rms into 8 ohms. Measurements have to be qualified to be meaningful and comparable.

The figures for the PCM 10 are stated in the manual.

It's either a typo or clever marketing. They appear to be showing the power *input* requirements (12VDC x 150mA = 1.8W), rather than the RF output power. Those two numbers will be miles apart. For sure, effective RF power will be dramatically lower than the deck's raw operating power.

BTW, most USA R/C'ers think we are flying with 750mW of RF. I suspect some would freak if they were aware of the actual power output (it is effectively not much higher than the UK's 100mW). And for some reason, very few folks are concerned with the Rx's performance, despite it being an important component in our application.

Interesting this.

ISTR when 35MHz first became legal in the UK (early 80s), part of the type approval process required that the input power to the Tx's RF section was required not to exceed 1.5W, thus limiting output power to somewhat less than that. This at least was a very easy measurement to make.

Is my memory playing tricks on me - I'm getting on a bit I suppose - or have the regs changed?

David who's getting old and just had to get his 1st pair of glasses

Originally Posted by daleksw

Interesting this.

ISTR when 35MHz first became legal in the UK (early 80s), part of the type approval process required that the input power to the Tx's RF section was required not to exceed 1.5W, thus limiting output power to somewhat less than that. This at least was a very easy measurement to make.

Is my memory playing tricks on me - I'm getting on a bit I suppose - or have the regs changed?

Dunno - maybe just re-written.

OfCom Information Sheet OfW 311 - Radio Controlled Models Para. 4
Frequency : 34.945 to 35.305 MHz
Bandwidth : 10kHz
Use : Air
ERP : 100mW

Some interesting replies and thanks for them, but what is the bottom line, are the claimed output figures to be ignored and are all transmitters outputing the same power?

... what is the bottom line, are the claimed output figures to be ignored and are all transmitters outputting the same power?

In this comparison situation (JR PCM 10 vs. JR PCM 9 vs. the Graupner JR module), they are essentially the same since they all share a common RF deck/module series. Regardless, the effective RF output power will be less than 100mW for use in your country.

Hi everybody(!),

but what is the bottom line

Bottomline #2: Never, absolutely never try to fly with your legal equipment in Europe, if an Oldie from the 80ties is "On Air". The modern receivers happen to be too sensitive, built for 100mW Epirp and especially because of the european small 10kHz channel-separation INCLUDING sideband and "smog" propagation.

Originally Posted by Rudy Vienna

and especially because of the european small 10kHz channel-separation INCLUDING sideband and "smog" propagation.

???

Originally Posted by RaptorNut

The figures for the PCM 10 are stated in the manual. This link http://www.gliders.uk.com/prodinfo.asp?number=G3859 shows the Graupner Synthesised module with a claimed 2W output.

It also says, "Current drain at 12 V approx. 150 mA".

Now since 12 volts times .150 amps = 1.8 watts, as Mr.RC-CAM pointed out, that means that the module is about 111% efficient. Excuse me if I'm a little skeptical about that.