TM-221 PL tone output level adjustment
 

Surprised no one has posted on this topic yet; here goes:

My Kenwood TM-221 has a problem with the intensity of its PL tone
output level. Mine is too loud, generating frequent reports of "hum"
from others.

I have the original manual with schematic and block diagrams, but no
obvious information indicates where the output tone is generated or
adjusted.

Not being wizardly and knowing there are wizards hanging around here,
I'd like to know what pot needs adjustment to settle it down to the
right level, if one exists. Anyone?

Bonus question: I have the same problem with an Alinco DR-590; if you
can help me with that too, that would be nice.

TIA, KA1IOR

TM-221 PL tone output level adjustment
 

In article .com,
KA1IOR wrote:

My Kenwood TM-221 has a problem with the intensity of its PL tone
output level. Mine is too loud, generating frequent reports of "hum"
from others.

I have the original manual with schematic and block diagrams, but no
obvious information indicates where the output tone is generated or
adjusted.

Not being wizardly and knowing there are wizards hanging around here,
I'd like to know what pot needs adjustment to settle it down to the
right level, if one exists. Anyone?

The TM-211 service manual can be downloaded from www.mods.dk - it has
the schematic and the procedures.

As I understand it, this mobile's tone generator is on a separate,
optional plug-in board, designated TU-3A. The board has a set of DIP
switches (which set the transmitted tone) and a small potentiometer.
It looks to me as if the TU-3A tone board plugs onto the "B unit" PC
board, which is on the bottom side of the transceiver.

The alignment instructions say to adjust VR1 so that the transmitted
signal deviation level (tone, but no other audio) is around .65 kHz
(650 Hz). This is consistent with recommendations I've read for other
radios and seems to be good practice.

Bonus question: I have the same problem with an Alinco DR-590; if you
can help me with that too, that would be nice.

I've been told that in at least some Alinco radios, the CTCSS tone
level is set by a fixed resistor on the PC board (it's not intended to
be adjustable via a pot), and that it's set too high.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

TM-221 PL tone output level adjustment
 

"KA1IOR" wrote in message
oups.com...
Surprised no one has posted on this topic yet; here goes:

My Kenwood TM-221 has a problem with the intensity of its PL tone
output level. Mine is too loud, generating frequent reports of "hum"
from others.

How do you know that this reported hum is CTCSS (67 - 250 Hz) generated and
not 60 Hz from your power supply ? What are you using for a power supply?
A failed LM-723 IC regulator in a linear power supply can cause this type of
problem.

Could you be getting stray RF into your audio chain??

w9gb

TM-221 PL tone output level adjustment
 

KA1IOR wrote:
Surprised no one has posted on this topic yet; here goes:

My Kenwood TM-221 has a problem with the intensity of its PL tone
output level. Mine is too loud, generating frequent reports of "hum"
from others.

I have the original manual with schematic and block diagrams, but no
obvious information indicates where the output tone is generated or
adjusted.

Not being wizardly and knowing there are wizards hanging around here,
I'd like to know what pot needs adjustment to settle it down to the
right level, if one exists. Anyone?

Bonus question: I have the same problem with an Alinco DR-590; if you
can help me with that too, that would be nice.

TIA, KA1IOR

Your Kenwood uses the TU-3A tone board, and there is only one pot on it.
It is VR1 and adjusts the tone output.

All the info you need is found at : http://www.mods.dk/
Service manual included, plus schematic..


Bob N9LVU

TM-221 PL tone output level adjustment
 

In article ,
(Dave Platt) wrote:

The alignment instructions say to adjust VR1 so that the transmitted
signal deviation level (tone, but no other audio) is around .65 kHz
(650 Hz). This is consistent with recommendations I've read for other
radios and seems to be good practice.

Bonus question: I have the same problem with an Alinco DR-590; if you
can help me with that too, that would be nice.

I've been told that in at least some Alinco radios, the CTCSS tone
level is set by a fixed resistor on the PC board (it's not intended to
be adjustable via a pot), and that it's set too high.

Dave & KA1IOR-

I've seen alignment procedures on older commercial radios, where there
was no adjustment. The procedure was to merely verify that the CTCSS
tone's deviation was between 0.5 and 1.0 KHz. I don't know the official
spec, but 0.65 KHz would be a good choice if it is adjustable.

The key is to measure the actual tone deviation, not just rely on hum
reports. Any given repeater may not be filtering out the tone as it is
supposed to. (That same filter should reduce 60 or 120 Hz hum as well.)
A repeater that transmits tone, should be regenerating it, not repeating
the input tone.

It may be difficult to measure the exact frequency of a CTCSS tone, but
you should be able to sync your oscilloscope to 60 Hz line frequency,
and observe whether the received "hum" is drifting or not. (You could
sync the scope to a CTCSS tone generator if you had one.)

Fred
K4DII

TM-221 PL tone output level adjustment
 

I used to have one of those rigs..........I am pretty sure that the TM-221
has encode capabilities out of the box. The optional board would be for PL
decode. As mentioned earlier, there should be a pot for making this
adjustment. If you have the schematic, take a look at the Tx VCO. There
should be two pots that feed the audio to the varactor diode. One of them
will be for setting deviation from the mic input, while the other one will
be for setting the PL level.

Pete

"Robert Kubichek" wrote in message
...
KA1IOR wrote:
Surprised no one has posted on this topic yet; here goes:

My Kenwood TM-221 has a problem with the intensity of its PL tone
output level. Mine is too loud, generating frequent reports of "hum"
from others.

I have the original manual with schematic and block diagrams, but no
obvious information indicates where the output tone is generated or
adjusted.

Not being wizardly and knowing there are wizards hanging around here,
I'd like to know what pot needs adjustment to settle it down to the
right level, if one exists. Anyone?

Bonus question: I have the same problem with an Alinco DR-590; if you
can help me with that too, that would be nice.

TIA, KA1IOR

Your Kenwood uses the TU-3A tone board, and there is only one pot on it.
It is VR1 and adjusts the tone output.

All the info you need is found at : http://www.mods.dk/
Service manual included, plus schematic..


Bob N9LVU