Back in the 1990's and 2000's on 160 meters through much experimentation with 1/4 wave length inverted L's I learned that a short fat end fed antenna could radiate a signal just as strong as a tall skinny tower or wire once the low feed point imperdance was properly matched to the feed line. The inverted L's had 65 foot vertical sections, 65 foot horizontal sections with 65 foot long radials lying on the surface of the ground. EZNEC modeling said that the antennas had a near omni directional pattern with the lowest TOA of 25 deg. I also had good results in experimenting with linear loaded 3/8 to 1/2 wavelength inverted L's with no ground radials on 160 meters after the high feed point impedance was matched with a parallel tuning network. The longer the antenna was past 1/4 wave the higher the radiation resistance was and more efficiently the antenna radiated. I had lot's of 160 meter world wide QSO's on CW and SSB with just 100 watts. If my memory serves me well and it usually doesn't nowadays most of the QSO's were on SSB.
Short Transmitting Loop (Google is your friend). They're only good for low power, unless you like artificial lightening. You could start a fire with enough power, if the power amplifier lasted long enough. I have a Pixel RF Pro 1B (Receiving Loop) really great under 10 mHz. I only have room for full size dipoles, but if I had a few acres, I would have Rhombics, the EZNEC model is incredible, but they're not portable, like the loops. AF4RK
Been using large loops for a long time, try to increase internal parameter of antenna system but they are like 560 foot five sided loops. Clearly, you can get even decent results with smaller loops like a 'one ele quad' for example on higher frequencies. But I am always amazed to see the Q on those small loops, my signal is wider then the bandwidth they can achieve!
