Distance of remote

On the datasheet page 1 I have located the RFout side and I was wondering what is the inductor for? Remove RF noise from VDD? and will increasing VDD increase the range?

Thanks, Jon

The antenna (especially on the receiving end) is probably the easiest thing to monkey with.

My guess is that it provides DC supply current to the output stage.

The output stage is the antenna? There is a dc blocking cap for obvious reasons. It would seem that if I increased the RF VDD that it would supply more current to the antenna and therefor increase the power dissipated by the antenna which should increase the distance?

Not sure. Depends on what they use on the recieving end. If it was simply an op amp or something then possibly but seeing they use SMT I'd still have trouble. Also it would increase the noise and if thats the original issue it wouldn't help much?

Thanks, Jon

VDD

The inductor XL is 50ohms at 350MHz and is used in preference to a load resistor. Idea is that the PA stage can develop an A.C. signal voltage across the inductor of nearly twice the supply rail voltage. Hence 4 times the possible RF power out, as compared to a 50ohm resistor.

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BTW,

"The FSK_ADJ and ASK_ADJ resistors can be adjusted in the

system to optimize output power for each modulation scheme.

An additional 1.5 dB of output power is provided for the lower

bank of channels to adjust for antenna performance. The CE

line allows the transmitter to be powered down completely.

In this mode, the leakage current is typically 0.1 µA."

Which would seem to imply that I could easily change the power... except probably they are using the maximum anyways.

"Jon Slaughter" wrote in news:EOcXh.1189 $ snipped-for-privacy@newssvr22.news.prodigy.net:

I'd play with the receive antenna first.

Ok, looking at the circuit it seems they use

"15 RSET_OOK The value of this resistor sets the output power for data = 1 in OOK mode. A resistor of 3.6 kO provides the maximum output power. Increasing the resistor reduces the power and the current consumption. A lower resistor value than 3.6 kO can be used to increase the power to a maximum of 14 dBm. The PA does not operate efficiently in this mode.

16 RSET_FSK The value of this resistor sets the output power in FSK mode. A resistor of 3.6 kO provides maximum output power. Increasing the resistor reduces the power and the current consumption. A resistor value lower than 3.6 kO can be used to increase the power to a maximum of 14 dBm. The PA does not operate efficiently in this mode."

A value of 3600 ohms for pin 16 and 5*10^8 for pin 15. So it looks I cannot adjust the power any better. I assume the OOK mode isn't used and this would explain the high resistor value unless I'm misreading it. (says 548 on it I think)

I'm going to try and decrease the resistance of the 3.6kohms. IT says the PA doesnt' work well but maybe it will give me enough.

Ok guys, nm. Got it to work(atleast it looks like it). Paralleled a 10k resistor with the 3.6k and it seemed to increase the power a bit more. Works about 80-90% of the time instead of about 1-10% of the time. Might be able to go a little lower but its good enough for now.

Jon

...

Are you saying it works reliably at 50 feet and hardly works at all at 55 ft? If so, then the math says adding less than 1 dB to the total RF power is all you need. But I doubt that would be sufficient - the drop-off seems too steep. I'd pay more attention to your other data that says specific locations in the room are better than others. Sounds like multipath or a local interference issue. How did you conclude its not due to reflections? Have you tried moving the receiver around a bit (like a quarter wavelength)? It might be easier than changing the circuitry if you only need it to work in one seating location.

I've found certain rechargeable appliances can create havoc in the UHF region for distances of 10 feet or so.- any battery chargers in the vicinity (cordless vac, for instance)? Check opposite sides of adjoining walls too.

Steve

Well, I already fixed it last night and now its about 99% reliable. I do not know if what I did is exceptable but it is working much better(for now).

Now if it was reflections I would still have the same issue but it completely gone away. It was just out of its range for the power it was using. Increasing the power increased the range. Was an easy fix but took some time to figure out how to do it. Luckily the chip had the ability to increase the power over its optimal setting and that the remote did not already do that. It was simple as soldering in a resistor which was actually kinda hard since I had to solder in an axial resistor onto a SMT resistor. Wasn't to bad though.

I'm mainly worried about the long term effects of increasing the power. The datasheet does not discuss the consequences. I'm not sure if it will just drain the battery faster or if it could decrease the life of the circuit.