Here's a very simple but effective receive loop antenna for 80m wound on a 35cm diameter crochet hoop purchased at Spotlight.
The tuned part has five turns with a polyvaricon variable capacitor in parallel. There is one turn with a 0.01uF capacitor that goes off to the antenna input socket.
I think the tuning capacitor is about 365pF.
Compared to the radio's whip antenna, signals are stronger and when at the best alignment have lower noise. The other advantage of loops is the ability to null out noise sources too.
When I started this, I thought more turns would be needed so I used computer ribbon cable held in place with Velcro straps.
The tuning range is 1860kHz - 4000kHz with the polyvaricon trimmers all the way closed. (I'll add a little more capacitance so I can cover 160m)
This would be a practical antenna for travel applications and could be particularly useful for nulling out local interference.
I was thinking of building an rf preamplifier but I'm finding that the Degen radio is quite sensitive enough.
The little control box is a potting box with slots cut for the crochet hoop to slot in to it so the whole thing can stand up.
As I'm mostly going to use it with little portable radios I've just gone for a 3.5mm socket for the RF output.
Below is the simple guts of it.
Not pretty and rather brittle, once again a hot glue gun is my friend.