> What is the best length for a T-type longwire used with a 
> radio whose
> freq. range is 2.5-6mHz?
 
  No simple answer. :-)
 
  You have too wide a desired frequency range to use just one dipole antenna 
efficiently on all you mentioned. I would say offhand to use an antenna that 
will adequately work on 2.5 MHz, and also use a tuner matching box to be able 
to "tune up" on the other frequencies.
 
  Now, if you want to just _listen_, that's a different story. I was 
presuming that you had a transmitter. (grin) A good long wire of at least 50' 
will work. :-)
 
                                                        _Ray_
 
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