Micro controllers with UHF transceivers?

Do you guys use that, too?

500mW is a whole lotta power, you can get nearly all the range you want with that. But, no combined chips :-(

But it simply works!

Oh, we live in an RF-crowded environment. Tons of multipath reflections, a local airport runway almost next to the house (you can taxi your aircraft right up to some of the houses here), lots of TV, radio and communication towers on the next ridge because we are on the last mountainous outcropping before the Sacramento plane. IOW this is RF hell, as evidenced by the fact that the usual TV set falls off the rocker without a serious set of custom notch filters in front of it.

We'll test it alright. But as I said this ain't a quite area at all.

--
Regards, Joerg

http://www.analogconsultants.com/

Be careful about those bands: I don't know about other areas but here in the UK the 35MHz and 40MHz are set aside specifically for radio control aircraft and surface vehicles respectively. Given the safety implications of interference on 35MHz in particular I don't think Ofcom would react too kindly if they heard about illegal transmissions on those frequencies.

--
Andrew Smallshaw
andrews@sdf.lonestar.org

Sorry for my misunderstanding.

Over here, we have problems with bears and wolves mainly in rural areas, where they scare schoolchildren and sometimes take some dogs or sheep. It is quite rare that a bear would stray into urban areas.

Paul

Here they do. Bears are usually quite friendly but mountain lions sometimes aren't.

Living together with wildlife is normal out here. For example, we have a fox family giving birth and raising their kits right here next to our house every year. The (late) first owner said that has been the case since when the house was built around 1970. They even don't mind out large dogs, probably just consider them monster-foxes.

--
Regards, Joerg

http://www.analogconsultants.com/

The URL was broken, need to re-join it: .

Is there anything with receive that reaches down to 144MHz (2 meter) band?

Thanks. But same as usual, only TX with uC, not transceivers with uC.

You'll have to study the data sheets in detail, see if it can be goosed down via another master oscillator etc. Most likely not if there are frequency dependent parts inside. The area below 300MHz seems to be strictly discrete and ASIC territory.

--
Regards, Joerg

http://www.analogconsultants.com/

Jim Granville snipped-for-privacy@designtools.maps.co.nz posted to sci.electronics.design:

Not according to the sales critters.

larwe snipped-for-privacy@gmail.com posted to sci.electronics.design:

That was some odd pasting.

Joerg snipped-for-privacy@removethispacbell.net posted to sci.electronics.design:

Now you are talking VHF instead of UHF.

Yes, my dream would always be VHF for this stuff. Unfortunately no chips and the countries on this planet haven't come to agreements there.

--
Regards, Joerg

http://www.analogconsultants.com/

I should also point out that within the UK the license free bands are licensed (with a few exceptions) for transmissions from ground based units only. The details are in OFCOM document IR 2030, last updated about a year ago.

BTW, I haven't seen any discussion of the 458MHz license free band. Is that a Europe only band ?

Simon.

--
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980's technology to a 21st century world

I think that there is a problem in your approach.

You try to do a one/two chip selection before fully understanding the communication requirements. At least this would rule out some frequency bands.

As far as I understand, the only specification for the system is about

100 m range and usability in as many countries as possible.

I think that you should determine at least the following parameters for the communication system:

• data rate needed, both up- and downlink (and hence bandwidth and regulatory limits)

• available DC power both uplink and downlink

• available (antenna) size at up/downlink, for instance a big fixed base station TX antenna at 13.56 MHz might be OK, but the efficiency of a small portable system would be very bad

After these decisions, it might be possible to select among the available bands a suitable one/two chip system.

Paul

It's all pretty flexible in most cases.

Very low, basically no more than a TV remote has to communicate. 300bps would be plenty.

Not a concern, except for the occasional handheld remote. But even there it ain't too important because it can turn itself on/off with bottun presses.

You can get plenty enough range on anything below 100MHz with very short antennas. Done it many times. But the "international" 13.56MHz and

27.12MHz bands are polluted by a lot of fairly rogue transmitters, with some of which I wonder how they ever passed certification.

--
Regards, Joerg

http://www.analogconsultants.com/

Huh?

If it's any consolation, I think the market will be saturated with these devices in 18 months. There is some new European boondoggle going on (at least this one will make money, unlike RoHS). I didn't pay much attention but it is something to do with energy efficiency/ heating.

I wouldn't count too much on such political efforts. We had that here in CA at times, the governor even visited Echelon. But the stuff is so expensive that most everyone stays with the true and tried. Or even goes backwards to older technology to wiggle out of the fossil fuel rat race. Like us when we installed wood stoves.

My faith in electronic controls of heating equipment has sagged after every repair. My favorite gear is the living room wood stove. Except for the blower speed control (which can be disabled) the number of electronics parts is zilch.

--
Regards, Joerg

http://www.analogconsultants.com/

That significantly increases the range. However, the frequency accuracy and temperature stability requirements can become quite demanding and it would be questionable, if a built in crystal oscillator would be stable enough.

Those frequency bands as well as 2.45 GHz are known as ISM (Industrial, Scientific, Medical) bands and they were _not_ intended for radio communication but for e.g. RF-heating of the human body, food and plastics (welding).

Later on, various license free radio communication applications were allowed on this "wasteland" of spectrum and the communication systems had to cope with the ISM usage e.g. by using spread spectrum to avoid the interference from ISM devices.

If you need some degree of protection for your communication system, you should use a licensed frequency band.

Paul

On higher frequencies all you can really do is sweep and then AFC-lock. Else it becomes prohibitively expensive.

That is very much impossible for consumer gear. I remember when we got our first microwave, pretty much the first people in town, and the radio authority folks in Germany had to come out and bless the "installation". That was a substantial roadblock and later removed.

--
Regards, Joerg

http://www.analogconsultants.com/

This is a good system for full-duplex links in areas with low interference. For instance various "Gunnplexer" systems consisting of one more or less stable Gunn diode master station at 10 GHz sends out a constant carrier and the slave station uses frequency locking to lock into that signal and then generates the uplink 100 or 144 MHz above or below the downlink.

However, with half duplex communication, you would have to send a very long preamble before the message to allow locking to the incomming signal. If the data rate is below 300 bits/s, which would require about 300 Hz bandwidth with BPSK, you would need less than 1 ppm accuracy at 433 MHz, which would be quite expensive. With 10 ppm accuracy, you definitively would need to scan the 4.3 kHz bandwidth for the signal. This is OK, as long as the desired signal is the only signal within that bandwidth.

If many similar signals are within that band, you would have to check for correct code, before proceeding into next carrier. As long as the actual message is quite long, you could tolerate a long synchronisation preamble.

Was that on the former 1.27 GHz ISM band or at 2.45 GHz ?

Paul