[TenTec] Moniter

[George, W5YR]

Possibly, Larry, but probably not likely.

Monitors can range from simple audio taps off the modulating audio signal;
to separate monitor systems which usually function to downconvert the r-f
transmit signal to baseband and present the output through a separate
monitor audio amplifier system ; to - in the case of digital rigs - DA
converters and audio systems which emulate the second approach above. 

Usually the first type is a fair indication of what you are putting into
the rig but no assurance of what is coming out. The second type can be a
very good replica of your transmitted signal depending upon how good the
monitor audio system is. The third type can range from fair to excellent,
usually depending upon the word-length of the DA converter and the quality
of the following audio stages.

My IC-765 is an example of the second type and it gives a fair idea of what
your transmitted audio sounds like. The transmit IF signal is taken to
baseband with the BFO signal into a special monitor mixer stage and then
the resulting audio is amplified and mixed into the main audio output
system.

My Kachina digital radio uses a separate DA converter for the monitor
system on the transmit digital data stream at the 40 KHz DSP-processing
level and takes the output to drive the monitor audio system. Early Kachina
models used only an 8-bit DA for the monitor channel and the results were
very poor. An update greatly improved the results with a 16-bit DA
converter and a better audio system.

My Icom 756PRO uses a digital version of the approach taken with the 765.
The main DA 24-bit output from the DSP processing feeds not only the
transmit IF channel - starting at 36 KHz and then mixing up through the
higher IF's until the output frequency is reached - but also feeds a
separate digital mixer which takes the 36 KHz digital data stream signal
back to baseband audio where it is digitally filtered and added into the
main audio output channel.

Of the three, the PRO provides the best indication of the actual sound and
quality of the transmitted audio signal. I have verified this by observing
the output signals in the time domain with a scope, in the frequency domain
with SpectroGram and by careful listening over a quality outboard audio
system.

As most "audio experts" will tell you, however, do not rely upon your rig's
monitor if you *really* want to hear what you sound like. Use an external
receiver with a fairly wide bandpass and ensure that it is not overdriven
and that it is tuned as accurately as possible to you transmitted
frequency. You will still hear only what the monitor receiver passes
through its IF and audio stages so it is not a perfect solution, but it
probably is representative of what most of your listeners are hearing.

I don't know what system your Jupiter uses, but the block diagram will
probably give you a few clues and pointers to the circuit diagrams if you
want to dig into the specific circuitry.

Funny, but in the old days of AM and CW, we seldom gave much thought to
"monitoring" the actual quality and sound of our transmitted signals, other
than soliciting on-air reports, as we still do. I used a WW2 surplus BC-221
frequency meter to monitor my CW signal both to measure the actual
transmitted frequency (!) and to hear the tone of the signal.

73/72/oo, George W5YR - the Yellow Rose of Texas         
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe   
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
Icom IC-756PRO #02121  Kachina 505 DSP  #91900556  Icom IC-765 #02437


Larry B wrote:
> 
> Just been enjoying the moniter feature of the Jupiter. Kinda nice to
> hear ones own voice. I  assume that the other party in the qso hears
> just what I hear when using the moniter feature ? If there was a problem
> in the ssb audio one could hear it using the moniter feature ?