What is the dB advantage of this vs. RF clipping for SSB?
It is a splatter box add-on.
The compression ratio of VoiceMax is fixed at 15:1 with distortion
levels well below 1%.
I suggest you read this for clarification... http://en.wikipedia.org/wiki/Audio_level_compression
Here we go again!
Laura Halliday VE7LDH "Non sequitur. Your ACKS are
Grid: CN89mg uncoordinated."
ICBM: 49 16.05 N 122 56.92 W - Nomad the Network Engineer
|----------------------
RF Clipping is superior to audio compression in SSB transmission. RF
clipping will provide about 6dB improvement over audio compression
alone.
james
> |----------------------
>
> RF Clipping is superior to audio compression in SSB transmission. RF
> clipping will provide about 6dB improvement over audio compression
> alone.
>
> james
Rhetorical question :)
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.
Lots of splatter immediately upon installation.
Actually, if adjusted correctly... no splatter... and 100% constant
modulation.
www.telstar-electronics.com
|----------------
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
>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)?
>
At least Datong made a stand-alone unit. There was an article about
RF-clipping and the Datong unit in Wireless World a few decades ago.
Paul OH3LWR
Huh? How can you do RF clipping outside the unit? Not a chance...
Any unit that's inserted in the mic jack is no RF clipper.
www.telstar-electronics.com
As I said. "Obviously they have to contain 'all the works' (oscillator,
balanced modulator, compressor, clipper, filters, balanced demodulator
etc)."
And, as Paul said, "At least Datong made a stand-alone unit. There was
an article about RF-clipping and the Datong unit in Wireless World a few
decades ago."
But maybe Datong didn't know what they were doing.
--
Ian
They had a lot of company, and the residents here have a very short memory.
Datong was second. Comdel made an RF clipper in the late 60's and early
70's. Mike input and amplifier, mixed up to 455 KHz, sideband generated,
clipped the hell out of it, filtered it with a second filter, mixed back
down to audio with the same LO for injection to your mike input jack. Every
serious contester and DXer had one. Cost more than the receiver.
W4ZCB
That sounds very complex and expensive all right.
Another problem I see is that they only work on SSB.
My customers insist on something small that fits inside the radio and
processes in all modes. The VoiceMax does that with less than 1% THD.
Can't build them fast enough to keep them in stock...
Why do you think that they only work on SSB? Stand-alone RF clippers
like the Datong are independent of transmit mode. They are audio in -
audio out (with a bit of RF magic in between). They should work even on
an audio PA system.
--
Ian
OK, thanks for your input.
LOL... a unit like that (http://www.nu9n.com/deq2496.html) would cost
you at least $300. That's more than your whole station is worth!
Come on... you know how frugal hams & cbers are. Get real.
www.telstar-electronics.com
You mean that old beat up one you got at the garage sale?
I didn't know you ever got that thing working since it was under water
and so rusty inside.
Kudos on your technician skills... fixing up that old dog.
Good to hear from you Laura. You can see a photo of the Voicemax
speech processor in a radio... right before the radio was buttoned up
at http://tinyurl.com/2t2usu
Appropriately, a CB radio, illegally modified. Only a CBer would fall for this
"Speech Processor."
Laura,
Evidently there are many radio operators worldwide that don't share
your views...
Thanks for your comment anyway...
--
fghi003
Yes, VoiceMax is selling well. We are unable to keep up with the
demand at this time. These units are back-ordered until late August08.
sound more like the garbage that fell off of the BACK of the animal while it
was taking a CRAP. OH - wait a minute - "back-ordered" - that is the
convention that you go out and turn-around and order something?
>
Thanks for your comment. In regard to your email... more VoiceMax
modules will be available earlier than expected... around August 1st.
We should have a few left after the back-orders are sent out.
DF4ZS developed a RF speech clipper that fits into the Yaesu MH-31
microphone shell. This mic is used with the popular, tiny FT-817
transceiver along with others and in all speech modes. His clipper has
a SSB IF.
Details: http://jwm.de/afu/0ft817eng.htm
Reviews: http://www.eham.net/reviews/detail/2732 (6)
There are no reviews of the VoiceMax on eham.net while there are 21 of
the W4RT Electronics "One Big Punch" which uses a similar IC and can
be installed either in the MH-31 or inside the case of the FT-817 et
al.
DF4ZS also makes an outboard RF Clipper with adjustable a.f.
compression and integrated noise gate.
If you don't mind tying up a computer to do your speech processing,
VE3NEA developed freeware to work with a soundcard between the mic and
the transmitter that functions as bandpass filter, 7-band equalizer,
noise gate, compressor, and RF envelope clipper. http://www.dxatlas.com/VShaper/
This DF4ZS is a clipping type processor... nothing like the VoiceMax
audio compressor. You are correct, Since VoiceMax is a new product and
there are only about 150 units in use worldwide... so far there are no
reviews on Eham. Thanks for your interesting comments.
www.telstar-electronics.com
That is true. SSB RF clipping is proven to deliver an honest 6 dB
improvement.