[Elecraft] Antenna Tuner Or Not

[Bruce Beford]

For those that don't know Robert Heinlein:
TANSTAAFL= "There ain't no such thing as a free lunch."

There is wisdom here.

What Mike is saying is that, even though your auto-tuner may find a match to
make the transmitter happy, there may be more efficient ways of coupling
your signal to the ether.

IR losses (Ohms law) within the tuner can eat up a fair amount of your QRP
signal. This loss is higher when the inductor is wound with teeny-tiny wire.
This is the case in some of these small internal ATUs. 

So, bottom line- 

1. The internal ATU can make it possible to operate using an antenna that
presents a wild reactance that must be cancelled out to make the transmitter
"happy".

2. When an antenna system (i.e. feedline plus antenna) requires a fairly
large inductance to cancel out capacitive reactance in the system, this
inductance can be provided by the nifty little ATU.

3. If the ATU has small diameter conductors creating this inductive
reactance, the Ohmic losses in the wire adds up quickly.

4. The smaller the wire used for the inductors, the higher the losses.

5. To maximize your actual radiated signal, optimize your antenna system to
require the least inductance to resonate it. 

6 alternative to 5 (above), you could build an external ATU with a large
roller inductor made from heavy gauge conductor.

7. For most situations, ignore 1-6 above, and just get on the air.

8. No matter what, Have fun!

8-) 73,
Bruce, N1RX


> It *always* surprises me though, that in Elecraft-world all manner of 
> antenna deformity is to be handled by an ATU magic bullet.  Small-
> conductor ATUs are never your friend, if an antenna/feedline could be
> used that doesn't require tuner reactance.  TANSTAAFL!

> 73,
> Mike / KK5F