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[hfsig] Performance of 24/192 soundcards? USB Soundcards

Anthony.N.Martin at marconiselenia.com Anthony.N.Martin at marconiselenia.com
Fri Sep 24 11:51:54 UTC 2004


> The problem is: if you have a transceiver with bad DC response
> a receiver  with DFE could still be used. But nobody we a "normal"
> receiver can copy your signal well. So you better go and improve
> your TX to be "compatible"... I would perhaps make sense to have
> something like that in the receiver of  the digipeater to allow
> the users to have a bad DC response.

I agree this could lead to carelessness with coupling the Tx.

The philosophy is interesting.

It has 2 possible conclusions.

* That we should never develop improved modulations as people with
old equipment cannot hear us.

* That we should always transmit at maximum power in case someone
with a small antenna cannot hear us.

I would hope that addressing this problem would enable more
people to use 9k6 that couldn't use it before as it didn't
work for them, and they decided not to buy more hardware.

> Question is: is anybody still interested in 9k6 anyway :-(

It is popular to use less than 9k6 over HF.

I have been asked several times whether I would design a packet
modem for standard FM V/UHF radios for >9k6 using a soundcard and
the standard mic and spkr connections. They always suggest QAM,
but FM radio BW varies so much I think of some kind of rate-adaptive
OFDM where we add or drop carriers accordingly and negotiate with
the other station to optimise throughput.

It is an interesting thought as the existing VHF packet modems
were designed using analogue processing and we have not attacked
the problem afresh with DSP.

As I don't want to spend large sums of money on Microsoft tools that
quickly become obsolete, I'm not likely to do it. Unless Mingw come
up with a driver development kit.

I must admit the AE4JY "pathsim" is excellent, the same program
works on Win-95 and Win-2000 and it doesn't have any driver-level
code of any kind.

Ant M1FDE

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