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

Anthony.N.Martin at marconiselenia.com Anthony.N.Martin at marconiselenia.com
Mon Sep 27 15:06:05 EDT 2004

> Bad idea (to use the standard mic connector). Been there, done that.
> The problems are:

> * most mic connectors are followed by an AGC/limiting circuit, which
> introduces nonlinear distortion

A bigger problem I've just thought of is the hard audio bandwidth
limits applied by filters in many of the CTCSS chips; 300Hz to 3kHz.

> * some (most?) handhelds do not disconnect the internal microphone when
> you connect an external one, so any ambient noise gets transmitted along
> your modulation signal

Well that's just broken. You couldn't even use that with a headset
in your car. I've seen some very cheap PMR446 and CB handhelds and
I've not seen this. Return to supplier. Problem solved. Next.

> The best I could get was about 4.8kBit/s, and that was pretty fragile.

What did you try?

I suppose that if we want to develop higher-BW more spectrum-efficient
modulations for V/UHF 12kHz channels we have to design our own digital
I/Q transceiver.

Another subject:
Have you seen this digital HF transmitter-on-an-FPGA?


This email and any attached files contains company confidential information
which may be legally privileged.  it is intended only for the person(s) or
entity to which it is addressed and solely for the purposes set forth
therein.  If you are not the intended recipient or have received this email
in error please notify the sender by return, delete it from your system and
destroy any local copies.  It is strictly forbidden to use the information
in this email including any attachment or part thereof including copying,
disclosing, distributing, amending or using for any other purpose.

In addition the sender excludes all liabilities (whether tortuous or common
law) for damage or breach arising or related to this email including but
not limited to viruses and libel.

More information about the hfsig mailing list