Good morning everyone.  I just thought I would post this, but some of you
may have figured this out, but I have discovered something rather
interesting with PL tones and DPL that is worth noting. The other day
 I was playing around with the THF6A and a Motorola Expo that I know is set
to 103.5 Hz PL, and I have noticed that each repeater especially when it
comes to business and public safety and some ham repeaters all have a
distinctive hum to them that is at another pitch.  I set my THF6A to 103.5
Hz, and monitored my transmission with a scanner I have, and discovered
that the hum  sounded just like that of the Expo.  Then I got to playing around and
noticed that the pitch of the hum your radio puts out that for some may be
hard to hear will increase as you increase your PL freq.  Also, a DPL has
a quiet rumbling sound when you key up and monitor, but I just thought it
was worth noting here.   If anyone has  any questions please feel  free
to ask.