Operation inside a building is always tricky. You don't know how the wiring / ducting
in the walls will affect the antenna, and performance will be greatly dependent on
the building materials used. Being able to get an antenna outside - putting it on your
balcony, sticking it out a window, or running coax out to an antenna on your car - is
likely to give much better performance. Hotel rooms are often plagued with electrical
noise, making it difficult to hear much of anything.
It isn't difficult to wind a loading coil to use with a telescoping whip of whatever length
you can find: there are many such designs available, both commercial and home-made.
For use in a hotel room, you'll need to be able to work in a height less than 8', and 6' for
a vertical is probably more practical (to avoid proximity to the ceiling, which may contain
wiring, etc.) Efficiency of such an antenna can be reasonable on 20m through 10m, but
drops on the lower frequencies. You'll need at least one radial for each band you are
going to operate, which can be laying on the floor.
The most successful operation I've managed from a motel was where I could step out
on the balcony on the top floor and toss a wire over the peak of the roof. Another
time I made a grappling hook out of a wire coat hanger and tossed it out the window
into the rain gutter across the alley. If the window frames are aluminum they are
often all bonded together and make a good ground plane for a whip antenna stuck out
Unfortunately, many hotel windows don't open, and you need to take a different
approach. For 10m I'd try a dipole strung across the room - it certainly is cheap
and can be made from light wire. You'll either need adjustable ends or a tuner,
however, as you can't count on the resonant frequency when installed indoors.
Where you can't get a full length antenna, you can fold the ends around. A small
antenna with the ends already folded up is the "Notebook Antenna":http://www.n5ese.com/notebk_ant.htm
Probably the simplest approach is to make such an antenna that resonates close
to 40m and feed it with twinlead to a tuner - that should work up through 10m.
Another option is some sort of small "magnetic" loop antenna. Here is a homebrew
, and there are also
commercial ones available. Such an antenna should give good results on 20 - 10m,
and some versions will tune as low as 40m, though efficiency will be lower.