What are Canada's "experimantal" radio frequencies

[theimperia]

Hi everyone!

Lol, I built an FM transmitter (audioguru's Mod3) and connected it to a half-wave dipole. Turned it on (on an empty frequency, 100MHz) and left it on for about 20 minutes. Distance was about 200-300 meters.
The next day, I've seen a truck with a huge dipole on the roof driving back and forth on my street (the transmitter was off by then) No kidding.


The question is: what are the "legal" frequencies that can be used to experiment? Let's say I build a receiver as well, at what frequency should I build it to make sure that "RF cops" don't show up at the door.
Maybe you know a link to a website (official) that'll explain that (I tried CRTC, but no help from their website).
This is for Canada...


Thanks for your answers,
TI|CP

 

[audioguru]

He, he. :lol: The RF cops nearly gotcha. They were probably looking for me!

All frequency charts that I've seen apply only to Americans. I don't think us Canadians have any frequencies available for our tests.

I don't think that Canada's RF cops are scanning the waves. They probably responded to a complaint from someone or a lot of people having interference on a legitimate station's frequency, like 99.9MHz.

I chose a frequency for my tests that was used by a low-power foreign language station. If any listeners complained to the RF cops then they hopefully couldn't be understood. :lol:

 

[theimperia]

All right, FOUND IT!!!

Actually, this hole RF stuff is under Industry Canada:

**broken link removed**


They got several useful docs:
RF Spectrum Table in Canada (for 2004):
http://strategis.ic.gc.ca/epic/internet/insmt-gst.nsf/vwapj/canadiantable-e.pdf/$FILE/canadiantable-e.pdf

Low Power License exempt doc:
http://strategis.ic.gc.ca/epic/internet/insmt-gst.nsf/vwapj/rss210.pdf/$FILE/rss210.pdf

License exmpt conditions:
https://strategis.ic.gc.ca/epic/internet/insmt-gst.nsf/en/h_sf01906e.html

I'll keep reading, but those are most important ones.

Take care,
TI|CP

 

[audioguru]

Hi The Imperia,
Oh, oh! My transmitter is about 1000 times too powerful. :lol:

 

[theimperia]

lol, in your face, RF cops

How do you actually measure the power output of your transmitter? Is there another way than a field-strength meter?

BTW, did you notice that there's nothing allocated beyond 275GHz? We could use it (to shoot at people's brains, lol).

But still, it says that Commercial FM band isn't reserved for anything (I mean, you can use your transmitter in that band. As long as it's 100 mW). I'm gonna read those docs again, and probably bother RF Cops (aka Industry Canada/Radio Spectrum division), to make sure about that... I just need to receive sensors in a 200 meter radius, in a forest...

TI|CP

 

[audioguru]

Hi The Imperia,
Canada's rules and regulations conflict about how much power is allowed on the FM broadcast band.
In one document the limit is 300nW, which is 0.3mW. On another document it is a whopping 1.0W!

I just assume that my transmitter is 50% efficient. Therefore when it draws an operating current of 56mA from a 9V battery, its total power is 504mW and its RF output is calculated to be 302mW.

275GHz is way above microwaves. I don't know any transistor that can work so high and wiring at those frequencies should be done by a plumber. :lol:

 

[chemelec]

The REAL BOTTOM LINE: If it Interferes with Anyone, It is Illegal.

The Problem with All these Simple, Coil Transmitters is Harmonic Radiation at multiplies of the origional frequency. Crystal Control is Better.

The best frequency to just play is the CB Band. (27Mhz) they Seldom Bother Monitoring it anymore.

And Output Power has Little to do with Battery Current Draw. It will definately be Much Lower than that.
In Addition to Legal Power Limits in Canada, There are Antenna Limitations.

Hope this Helps.....Gary

 

[Nigel Goodwin]

And Output Power has Little to do with Battery Current Draw. It will definately be Much Lower than that.

Well output power has obviously got a GREAT DEAL to do with current consumption, in fact the usual way of specifying RF power is to give the DC input to the output stage. This is very easily measured, unlike the actual RF output - which really needs to be measured as ERP (effective radiated power), which takes in to account the gain of the aerial system.

Estimating the RF output as 50% of the total power consumption sounds a reasonable estimate to me?.

 

[audioguru]

Except I can't divide by two accurately!
Half of the total power of 504mW is 252mW of RF power output. :lol:

 

[chemelec]

Well I Somewhat Disagree, Because of the way you Origionally Worded it. Total Battery draw Also includes: Mic, Preamp, Regulator losses and Modulation Circuits. Can be Substantial on more powerful transmitters.

usual way of specifying RF power is to give the DC input to the output stage.

But Yes, I Do Agree with this. And I also agree this is about half of that power.

It should also be pointed out that Actual power is dependent on Proper Impedance to Antenna Matching.
"Standing Waves" can reduce Actual output power to Nothing.

Remember that a lot of guys on here do not have much Electronic skills.
Sometimes Careful Wording is Really Important.

Take care.........Gary

 

[Nigel Goodwin]

Well I Somewhat Disagree, Because of the way you Origionally Worded it. Total Battery draw Also includes: Mic, Preamp, Regulator losses and Modulation Circuits. Can be Substantial on more powerful transmitters.

Modulation circuits only really apply to high level modulated AM transmitters, where you require high power for the modulation. In an FM transmitter the modulation requires only a very tiny amount of power, as do all the other sections you mentioned. By far the most relevent circuit is the output stage, all the rest will be fairly insignificant - particularly as we're 'guessing' at 50% efficiency!.

In the context of this thread, about simple FM 'bugs', the total current drawn is near enough the current drawn by the output stage (unless there are SERIOUS design errors in the other stages?).

 

[theimperia]

But anyways, if you approximate the power taken from the battery as the power consumed, then it's gonna be the AT MOST value. Since other circuits also consume some current, then the actual power will be lower. But, say, if you disconnect everything except the oscillator and the output stage, then that's pretty much the power it'll output (well, half of it if 50% efficiency).

BTW, why it's 50%? Just a shot-in-the-sky value?

 

[Nigel Goodwin]

BTW, why it's 50%? Just a shot-in-the-sky value?

Yes, a class C output stage should be more efficient than that, but guessing at 50% allows for the rest of the stages as well.

 

[audioguru]

You know what? I think that the output RF amplifier transistor in my FM transmitter does operate in class-C and is much more efficient than only 50%.
The transmitter is using 504mW from 9V. A little TO92 transistor gets pretty hot at 250mW or 300mW. My output transistor is biased on hard but barely gets warm. When I kill the oscillator it gets very hot! :lol: