Maximizing Radio Efficiency

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EEPROM777I
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Maximizing Radio Efficiency

Post by EEPROM777I »

I bought a few cheap RF modules and I don't know how to get the most out of them. The transmitter only sends the carrier at 315MHz. How do I maximize the amount of data that can be transmitted? The spec sheet says both the transmitter and receiver have a data rate of 2.4k bps. I have tried sending just the data I want to transmit and of course on the receiving end I get nothing resembling the transmitted data.

The receivers output goes high when you move a hand near it, so it is appearently very susceptible to outside influences (these were very cheap about $3.00 for the trans and rec). I tried sending different frequencies of square waves and then decoding them at the receiver with a 567 Tone decoder and it works good but this method is slow. Another problem I have with the 567 is that whenever the circuit loses power or power is applied the output turns on like it has received the proper signal. In some cases this doesn't matter because a uC would be programed to ignore this but I got several of these RF modules and I want to make a couple simple remote on off controls and this would cause whatever I choose to turn on sporadically. Any ideas/suggestions? Thanks guys and gals. (Has anyone ever met a girl into this stuff? At the hobby level?).
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jwax
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Post by jwax »

This forum is a great place to meet girls. Or 13 year old boys. Sure.
Sounds like you need to put that receiver in a shielded box first. Also, the data rate is going to be limited by the design of the circuitry, and that was obviously built for cheap.
You can't get 12,000 rpm out of a motor designed for 5,000. For long.
Welcome, by the way!
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Chris Smith
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Post by Chris Smith »

Did you match your antennae’s in and out put?

Are you shielded?

There is a whole science of reflectivity, absorption, interference, attenuation, shape and size for all types of antennae.

ARRL
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jollyrgr
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Re: Maximizing Radio Efficiency

Post by jollyrgr »

EEPROM777I wrote: {SNIP}
(Has anyone ever met a girl into this stuff? At the hobby level?).
Only a couple. The only problem is they were interested in girls too.
No trees were harmed in the creation of this message. But billions of electrons, photons, and electromagnetic waves were terribly inconvenienced!
Robert Reed
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Post by Robert Reed »

You might also try replying to Tatyana or Svetlana. :smile:
EEPROM777I
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Post by EEPROM777I »

Maybe I should refine my question..... (Edit: Well now that I'm done with this post it's not that well refined but maybe I better expressed what I wanted to know)

What is the best way to transfer the maximum amount of data using a transmitter and receiver working at 315MHz with a max data rate of 2.4kbps? Is it as simple as shielding the receiver (and all that goes along with keeping noise to a minimum) and using a uC to do error checking and to handle the data? How am I assured I get all the info? If I just resend the same data a few times how am I to be sure I am getting the right info? Is bidirectional the only way to be assured proper reception of data? Other ?: How do I avoid the turn on pulse of a 567 tone decoder? Whenever I power up a circuit using a 567 tone decoder the output goes low as if it has seen the proper tone. Do I just block out the output using Logic gates or transistors until the power has come on and stabilized? Would it be as simple as building an RC circuit feeding a transistor base which controls one input and and gate so the output of the 567 only carries through after the power has been on for a bit? Thanks.

PS I was only curious about women in the hobby, I'm not here for dating.
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Chris Smith
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Post by Chris Smith »

The antennae is everything.....

Negative or positive defraction in your antennae material?

SWR?

Super cooling, length, material types, molecular dimensions, ballanced size, all equally as important as the lens on a light, and how it will transmit with the least amount of interference.

Imagine trying to see a arc weld using a pair of sun glasses instead of the proper lens?

Too much or too little of any thing can kill it all, as perfection is everything.
EEPROM777I
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Post by EEPROM777I »

Thanks for the reply Chris but reception is not the problem.
Chris Smith wrote:Too much or too little of any thing can kill it all, as perfection is everything.
I'm after perfection. Perfection is out of our hands though only our creator can attain perfection. I just want it close enough to work. No matter how much care I take in shielding and filtering I seriously doubt I would be able to send raw data on the carrier at 2.4k bps. So I am asking what is the fastest method that is least prone to errors. Is the best method a square wave being decoded on the other end? Is there a method that I actually could send just the data to the input of the transmitter (I don't think it's that easy but that's why I'm here)? Thanks for any suggestions.
russlk
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Post by russlk »

High speed modems are able to send 56K over 3kHz phone lines, take a look at how they do it. Phase modulation, but I don't know the details.
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Chris Smith
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Post by Chris Smith »

"Thanks for the reply Chris but reception is not the problem"?


They are the same science, they are not to be dismissed as just a wire, science is everything.

SWR mean more than three letters.

Reflection, conduction, resistance, material types, shape, temperature, coefficient, refraction, etc are all a REAL science, not a "thing" and not just some guess work?

Nonchalant will get you no where, except by guess.

I hope you have plenty of extra time to figure out where you went wrong?

Data, "propagation delay" [signal mixing] and reflection are subjects unto them self.

Gee, I cant get it to send, or I cant get it to recieve?

Hand book....
EEPROM777I
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Post by EEPROM777I »

russlk wrote:High speed modems are able to send 56K over 3kHz phone lines, take a look at how they do it. Phase modulation, but I don't know the details.
Isn't there a difference? Doesn't the modem use analog signaling? My trans and rec are digital. If I'm right I think there is more bandwidth on an analog line up to three KHz than a digital one. Bearing01 don't you design and work with radios? What type? Any ideas?
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Chris Smith
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Post by Chris Smith »

The special word they use is called..."matching".

We have all known the word impedance?

No signal loss, no waste.

Ballanced as possible = power = signal = sucess.

It has its own science....
EEPROM777I
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Post by EEPROM777I »

I'm sorry I don't get it but what exactly are you answering? Seems random to me.
Robert Reed
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Post by Robert Reed »

EEP
My first thoghts were - if you bought a pair of these for $3, pitch them as something that cheap wouldn't be worth the aggravation. But then I thoght maybe you just happened to get a `steal` on something worthwhile. Do you have a spec sheet on these or a web site to refer to? Beyond that, I would speculate that this is an FM system limited to <100mw input power to the Tx final amplifier and is OK for very short range. The transmitter modulation circuit and receivers IF bandwidth are probably limited to +/- 10Khz in order to operate on designated channels without co-interference to adjacent channels. In radio design ,system bandwidth is not related to analog or digital modulation-first comes bandwidth and the the modulation that will fit into that bandwidth. The carrier frequency has nothing to do with the information on it, except: higher carriers are less prone to man made interference, higher carriers can carry larger modulation by virtue of a higher carrier to modulation ratio. In either case, your 2.4 Kilobits per Sec. will easily fit within the bandwidth of your system. One thing I would mention at this point is that in a communication system, the receiver is everything. Quality receievers do not come cheap. But by keeping the overall range short, you can overcome some of the deficiencys that I am sure your system has. Your hand near the receiver should have no effect when the transmitter is idle other than being a horribly cheap design. Proper antennas will help, but I can't advise you on this due to inadequate information - 1/4 wave ground plane,1/2 wave dipole for balanced or unbalanced input, input impedance,etc. Simple antennas at UHF frequencys are not that difficult to construct if you know what you are working into/ out of. As far as your power up/power down problems, they probably could be eliminated by getting into the receiever squelch circuit, but I am betting there is no access on your chip.Barring that access, you could probably build a time delayed sqelch circuit (simple gate) from the receivers out put inline with whatever add on circuit you have installed But the bottom line here is- you need more info on these chips than provided on the post.
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Chris Smith
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Post by Chris Smith »

Im guessing its all "just rocket science" to you?

Good luck?

A world where every thing is very simple?

Try for a Education, not voodoo science?

The Tried and true method?
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