The big thing that having the tuner set to work in receiver mode does 
is to serve as an additional noise filter. It does so by narrowing the 
amount of spectrum which includes both signal and noise that hit the 
front end of your receiver or transceiver.

If you really want to hear what I'm talking about, connect a manual 
tuner and ten or fifteen feet of antenna wire to one of the hand held 
DC to Daylight receivers such as those in the THF6, Icom T90, and 
other vhf hand held rigs. You adjust it by tuning for maximum received 
signal as indicated by the audio signal processor that is between your 
ears. You will be surprised with the result.

My THF6 is pretty worthless on shortwave without such a tuner 
arrangement.

So, if you are using the internal tuner of your hf rig, set that tuner 
to work on receive too. Then, if you want to tune way out of the 
normal band width of your antenna, simply turn the tuner off until you 
are ready to transmit or listen within the ham bands again. The 
difference won't be as dramatic as for the hand held units which have 
no front end filtering at all, but you will still notice some 
improvement in signal Vs noise.

Most external manual tuners  live in the receive mode at all times.

Some, probably all, of the external automatic tuners can be set to not 
work in receive mode if you find that you don't really notice a 
difference.


----- Original Message ----- 
From: "Howard Kaufman" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, March 28, 2010 6:25 PM
Subject: ts480 test


I don't trust my observation, so I'd like somebody else to test it. 
After a
day of experimentation, I think that using my ts480 with an external 
tuner,
provides a better signal to noise ratio after tuning the antenna, than 
does
bypassing the external tuner and using the internal tuner.  I don't 
use the
internal tuner on receive.
I'd like an observation and an explanation.  Seems surprising to me.
H T Kaufman MSW LCSW
Adaptive Technology Instructor


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