In message , james
writes
On Wed, 11 Jun 2008 13:36:55 -0700 (PDT), Telstar Electronics
wrote:
|On Jun 11, 8:44*am, james wrote:
| On Mon, 9 Jun 2008 06:25:33 -0700 (PDT), Telstar Electronics
|
| wrote:
|
| |On Jun 6, 4:17*pm, james wrote:
| | On Thu, 5 Jun 2008 16:25:44 -0400, "Tio Pedro"
| || wrote:
|
| |
| | ||"Telstar Electronics" wrote in message
| |
| | ...
| | | VoiceMax is really gaining momentum!
| | | Radio operators all over the world are enjoying the Voicemax
| | | advantage.
| | | Since VoiceMax doesn't use audio "clipping"... your audio is loud AND
| | | clear.
| | | What a concept!
| | |
| | | See what VoiceMax can do for you at
| | |http://www.telstar-electronics.com/voicemax.htm
| | |
| | |What is the dB advantage of this vs. RF clipping for SSB?
| | |
| | |
| | |----------------------
| |
| | RF Clipping is superior to audio compression in SSB transmission. RF
| | clipping will provide about 6dB improvement over audio compression
| | alone.
| |
| | james
| |
| |James is correct... that the RF clipping technique is somewhat more
| |effective. What he fails to mention is that it's more complex... and
| |not easily installed into an existing radio. RF clipping also
| |exihibits substantially more distortion. The VoiceMax installs
| |easily... and provides tangible results.
| |----------------
|
| Actually as easy to design an RF Clipper as an audio compressor. True
| it is a bit more difficult to install. Audio clippers can be external
| to the transmitter and simpler to install and operate. A RF Clipper
| will install as easily as your internal audio compressor. *
|
| Personally I would take RF clipping over Audio compression any day
| with SSB transmissions. If the post filters are good in enough RF
| clipping, there is not significant difference in distortion.
|
| james
|
|But I was under the impression that RF clippers only work on SSB?...
|and the installation involves tearing into the IF section?
|--------------
Correct. An RF clipper an be inserted after the SSB filters or before.
There are versions that do the clipping after the balance modualtor
and before filters. Sherwood did a RF clipper for the Drake TR4 that
was after the SSB filters and had crystal filters to restore the
original bandwidth.
Generally RF clipping is a bit more expensive than audio compression.
Then you get what you pay for.
james
I thought that there were some stand-alone RF clippers. Surely there is
no reason why they cannot be external units, inserted in-line between
the mic and the mic socket (ie audio in - audio out)?
Obviously they have to contain 'all the works' (oscillator, balanced
modulator, compressor, clipper, filters, balanced demodulator etc), but
at least they are self-contained and universal.
Regarding filtering, the main advantage of RF clippers is that they
eliminate the effects of second-order distortion, and only have the
distortion produced by in-band third order intermodulation. For
cheapness and simplicity, if you leave out the SSB filtering (ie do
everything at DSB), you will have at least twice the number of in-band
IM products. But how much worse is this than having SSB filtering?
--
Ian