From: Don_R._Moberly.El_Segundo@xerox.COM
Newsgroups: rec.radio.amateur.misc
Subject: User,s report on the *MULE*
Date: 29 Jul 1992 15:05:16 -0700
Organization: UCSD Usenet Gateway
Reply-To: Don_R._Moberly.El_Segundo@xerox.com
NNTP-Posting-Host: ucsd.edu

 EXCERPT FROM THE  *MULE* ADVERTISEMENT

The Multi-Use Link Enhancer, or *MULE*  for short is manufactured by Link Plus
in Columbia Maryland. It is a stand alone, half duplex LINK_PLUS unit that can
be quickly connected to any radio with external cables.

The technology used in the *MULE uses digital signal processing to greatly
improve the "Quality of a radio link". Linkcompex is an acronym for LINKed
COMPressor-EXpander. LINK-PLUS works as follows.

At the transmitter, audio band signals are digitaly processed by LINK-PLUS to
generate a fade-resistant control tone that is slaved to the audio wave form
amplitude, compress the audio waveform and produce a signal that has a constant
amplitude. The composit signal, consisting of the control tone and the
compressed audio signal, is then transmitted.
At the receiver, the composit signal is processed in reverse. The LINK-PLUS
circuity decodes the control tone and expands the audio waveform amplitude to
original speech level. This reverse processing cancels out interference and
noise picked up during transmission (by slaving the interference to the
original spoken voice waveform) and delivers a significantly strengthened
signal. The result is an audio signal that often exceeds that of the best wire
and fiber optics communication systems.

In addition to the technology described above, the LINK-PLUS module has several
unique features that also significantly iimprove the quality of radio
communication.  LINK-PLUS has an automatic calibrattion function which
automaticly adjusts for frequency drift in single sideband systems. It also has
an autosilence function that automticly maintains between keyed transmissions
or pauses in speach. It also incorporates a bypass feature that automaticly
switches of the Lincompex signal processing whenever a signal is received that
has no control tone. This permits radios equipped with the *MULE to communicate
with non *MULE* equipped stations and vice versa.

Although the  *MULE* uses digital signal processing internally,  signals
entering and leaving the unit are analog. Connections  to the *MULE* are made
to the speaker and mic input/output, thru cables supplied by LINK-PLUS.
LINK_PLUS also supplies a high quality speaker and microphone with the *MULE*.

END OF EXCERPT

After operating one of the units for over a month now I feel that I can give a
first impression  of the unit.  The *MULE* does do all the things that the
company claims it can do.  The single problem I had with the unit was after
taking it out of the shipping box and statring to hook it to my rig, I found
three color coded RCA type plugs too hook up, but they were not identified in
the book nor on the connector.  Well a VOM  solved that problem in a hurry.

I have been able to establish linked contacts with units in Maryland, Rochester
New York, Hawaii, and Apple Valley  CA. I have used them on HF as well as V/Uhf
in the sideband mode. I have had three and four way links going on  20 meters.
My conclusions are that the *MULE* realy shines on HF sideband. It is realy
great to have a two hour QSO between Hawaii and California and not have to
listen to the din of tuner uppers, the monkey chatter and all the other
clutter.

The  *MULE* works so well at removing the noise and garbage on the HF bands you
will have the feeling that you are using a local two meter repeater but one
that has better voice quality. The  *MULE in the autosilence mode actualy cuts
out the noise between sylables of speach. Can you imagine operating  CW on 40
or 20 meters and have no noise between dots and dashes. The *MULE* can do this
for you. Using one of these units for RTTY or packet will eliminate all the
retries caused by QRM or QRN.

I have not been able to make any labortory type measurements to see if it meets
all the specs. But I have made a lot of tests comparing the compressor on and
off and the linked signal versis  raw copy without the *MULE*.  The compressor
just by it`s self will boost youir signal 2 to 3 "s" units making the
difference  in whether the other station can copy or not even hear you.

The compressor is of the syllabic-rate type and realy does a much better job
then the hard limiters you find on most of the ham gear. It does not induce
distortion as the hard limiters do. Your signal just simply comes up out of the
noise when you turn on the compressor.

If you are lucky enough to have another *MULE* on the other end of your QSO you
are in for a real treat, with clear distortion free, noise free copy.

In general I would have to say that the unit meets all that I expected from
reading the ads, and far exceeds what I expected in the HF operation. The next
experiment I want to do is link to another *MULE* thru AO13.

If you have a chance to use a *MULE* dont pass it up, The only problem with
using one is that it is so easy to get hooked on it. So try it with caution.

If you wish more information on the *MULE* you can reach LINK-PLUS at (301) 982
1585 ask for Doug Tucker and tell him Don WB6LFC recommended the unit to you.
 Or you can reach me at (310)333 7389 if you would like to set up a sked or
more information.

I would like very much to see this become a standard feature on the ham rigs
put out by the big three and with enough of us getting togather and using this
mode and insisting that they offer it as at least a plug-in option on their mid
and hi end units we will not be happy with them.

This passing off of switched capicitor filtering as digital signal processing
and over charging what is worth  can be swapped out for true DSP with all it`s
programability for very little difference in cost.

Wouldn't it be great to have a rig like the TS950, or FT767 that had a built in
packet modem, digital signal filtering for both voice and data, be able to set
your own parameters for the voice you are listening to and be able to filter
out all the KW tuner uppers, and filter out the LID 100kHz away  over driving
his "linear" by 500%, that is splattering all across the band. The techonoligy
in the *MULE*  today is a long way down the road to being able to do just that
and a lot more.

Even though I sound like a stock holder in the company, I have no affilliation
with LINK-PLUS other than being a very satisfied user of their product.

73
Don
WB6LFC
Newsgroups: rec.radio.amateur.misc