Re: TI-H: RF Linking
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Re: TI-H: RF Linking
>Matthew R Price wrote:
>
>> So far all the discussions have been assuming that we use two
>> frequencies
>> to transmit. Why don't we instead multiplex our RX and TX lines onto
>> the
>> same carrier freq. That way we wouldn't have to deal with the self
>> induced interference of having a transmitter right next to a receiver.
>>
Great idea. But no. Means that two transmitter are running on the same
freq? Nope. Nasty signal mixing occurs using FM, and AM modes will just
intorduce too much noise. You think that noise is bad with two running on
different freqs? Try running two transmitters on the same. Besides, the
reciever will be overloaded because of proximity effects. AND YOU CAN'T
RECEIVE OFF OF YOUR OWN CARRIER WAVE, you merely use it to convey the data.
>> This would also simplify full-duplex transmition and lighten the power
>>
>> load for the device. I'm not an electrical engineer but I do have
>> some
>> basic knowledge;
>
Apparently you don't have some of the facts straight. Re-read whatever
you are studying.
>> I'm not sure exactly what the relationship between the
>> two freqs. should be. Doing this would also provide us with a much
>> cleaner channel.
>
Assuming we do full-duplex, two transmit/recieve sets, the split could be
anything really. If you wanted to REALLY minimize the effects, spread the
transmit/recieve pairs about 10 MHz. Though off the top of my head, I
don't know where that can be legally done. At low power levels, 20-60 KHz
might be enough. It's not like we are running more than 10 Watts. Given
power/size requirements, it'd probably be around 500-700 mW, and with a
decent antenna, could reach about 1500 feet, depending, again, on the
frequencies, and the size of the split.
At 10:18 PM 10/5/97 +0000, Matthew Fogle wrote:
>
>I'e been thinking about what has been said recently and I agree with you
>I think. I have thought up a design that would use one freq and yes that
>will solve a lot of problems but then it will HAVE to have a software
>driver for it. The only way to make it compatible with old link cables
>is to use two freqs because of the async connection. But could we make a
>TSR that would convert this non-ti protocol to TI protocol as far as the
>calc knew I wonder?
>
The only way that we can use ONE frequency is to alternate transmit and
recieve between the two units. Simplex operation would requre a PIC, or
one hell of a hardware driver to buffer and transmit the data. You would
also need a modulator to convert into audio tones, or directly modulate the
carrier with the data pulses (preferred method IMHO). A PIC would probably
be needed, because you need to key the transmitter as well.
Regards,
J. Bender
Joseph C. Bender, N8XRE | AX.25: N8XRE@WB8SWF.#SEMI.MI.USA.NA
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