...swr is almost flat(with a tuner)...
What is the SWR without
A Hamstick dipole for 40m, when properly tuned for the operating frequency, might be about
10% efficient. That's enough to make contacts in good conditions - it's more radiated power
then when I run my QRP rig at 5 watts - but you'll have best results calling strong stations
when there isn't a lot of background interference.
When operated off the resonant frequency, the efficiency of the system (antenna + coax +
tuner) will decrease. It's probably OK within 100kHz or so of the resonant frequency when
used with a tuner, but beyond that the efficiency can be very low, even though you may be
able to get a low SWR using the tuner.
The first step is to install it properly: ideally both sides of the antenna are insulated from the
support mast, connected only to the two sides of the coax. A 1 : 1 balun at the feedpoint helps,
too. That prevents a lot of stray paths RF paths that can make it difficult to tune.
Then carefully tune the antenna to the center of the desired operating band WITHOUT THE
TUNER. Start with the stingers inserted about 1/2" to 1" into the ferrule. Both sides must
be as close to the same length as you can manage. Check the SWR across the band - an
SWR analyzer is convenient, but you can just measure the SWR at various points to see
if it is resonant somewhere in the band, or off one end or the other. You are looking for
the point of minimum SWR: if it is to low in frequency, shorten the whips slightly and try
again. If it is too high in frequency, lengthen them. If you can't find a dip at all, then either
the antenna is too far from resonance or you have a short or open in your coax or your mount.
Once you get the point of minimum SWR (which might not be 1 : 1) close to your operating
frequency, then you can use your tuner for fine adjustments. Because of the low efficiency,
you're still basically running QRP, so don't expect weak stations to hear you.