From: gkd@wpi.WPI.EDU (Gregory K Doerschler)
Newsgroups: rec.radio.amateur.misc
Subject: Re: DJ-580T problem with audio drop out using T-SQL
Date: 14 Sep 1992 05:17:19 GMT
Organization: Worcester Polytechnic Institute
NNTP-Posting-Host: wpi.wpi.edu
Keywords: Alinco DJ-580T problem tone squelch


The tone squelch decoder on the DJ-580 has several peculiarities which
I've noticed:

1) When receiving in the tone squelch mode, the tone squelch decoder
remains "open" for two seconds after the incoming tone-equipped signal
ceases.  This in essence means that the radio is in carrier squelch mode
for two seconds until the tone squelch decoder "resets."  This could
actually be construed as a feature, since it allows the user to 
automatically monitor the frequency between transmissions for any
non-tone equipped signals.

2)  When in the tone squelch mode and receiving a non tone-equipped signal,
the speaker will remain silent.  However, if a stronger tone-equipped signal
appears on the frequency while the non tone-equipped signal is still present,
the decoder waits two seconds before opening up on the tone signal.  This
means that you miss the first two seconds of the tone transmission.  Note
that the same thing happens if you leave the squelch "open" while in
the tone squelch mode.  The radio sees the open squelch as a non-tone 
signal.

3)  As the manual points out, the tone squelch function only works on
the main band.  The sub-band goes into carrier squelch mode, even if
it had been programmed as tone squelch.

4)  When switching the main band from VHF to UHF or vise versa by
pressing one of the band buttons, the radio does not read the PL
tone frequency programmed into the new main band until the user
performs some additional function on the new main band.  This function
can include transmitting, changing the frequency or memory channel
by rotating the tuning knob, pressing the up/down buttons, or setting
the radio to scan; switching from memory to VFO or to call
channel (or vise versa), or pressing <FUNC>TONE followed by the
main band button again.  

    EXAMPLE: Enter a frequency of 446.000 in the UHF VFO with the
    Tone Squelch activated.  Set the tone to a frequency of 88.5 Hz.
    Now press the VHF button and enter a frequency of 146.52 in the
    VHF VFO with the Tone Squelch activated. Set the tone frequency
    to 100.0 Hz.  At this point, the radio is recieving on 146.52
    MHz in the Tone Squelch mode with a tone frequency of 100 Hz,
    and in the carrier squelch mode on 446.000 (since UHF is 
    currently the sub-band).  Now press the UHF button to make
    UHF the main band.  This causes 146.52 to revert to the carrier
    squelch mode, and 446.000 becomes tone squelch.  However,
    the tone frequency on 446.000 is 100.0 Hz (which had been pro-
    grammed into the VHF VFO) rather than 88.5 Hz (which had been
    programmed into the UHF VFO).  To get the radio to switch to the
    UHF tone frequency of 88.5 Hz, you must perform one of the functions
    mentioned above.  (This problem would still be experienced even
    if the Tone Squelch mode was not used on 146.52 MHz as long as
    the frequency which the 2 meter tone were set to was not 88.5 Hz.)

Note that if the battery save feature is active on the main band and
the frequency remains quiet long enough for the feature to kick in,
the radio will also revert to the correct tone frequency.

5)  If using the radio in crossband repeat mode, the same tone
frequency should be programmed into both bands when the tone squelch
function is used.  If the tone squelch function were used and different
tone frequencies were set for each band, activity MUST alternate
back and forth between the bands.  The radio will not hear the
second of two consecutive transmissions on the same band.
(This condition is related to (4) above.  The "main band" appears
to kick back and forth when in crossband repeat.)

6)  When scanning memory channels programmed in the tone squelch
mode, the radio will stop scanning on any non tone-equipped signal,
but it will remain silent.


Getting back to the problems mentioned in the newsgroup, the two
second dropout experienced when the main band was switched while
a tone-equipped signal was being received appears to be related to
(2) above.  The radio may see this condition as a tone-equipped
singal being received while a non tone-equipped signal was
already present.  If the tone-equipped signal disappeared when
the main band was switched and did not reappear after two seconds,
the problem would likely be related to (4) above.

In the case of the radio muting a tone-equipped signal during
mid-transmission when in the tone squelch mode, I suspect that
the tone on the signal was either too weak for the decoder to
sense or it was off frequency.  This happened to me a couple of
times when I was using the '580 to monitor a group of handhelds
operating on 151.895 MHz.  One of the handhelds did not reliably
activate the tone decoder in the '580, even though the decoder
on a base station operating on that frequency had no problem 
with it.  (The other handhelds seemed to hear it OK too.)

These problems are somewhat peculiar, but are not really crippling
to the operation of the tone decoder.  I find that it does help
to understand what is happening though.

                                          Greg