Thank you all!

Hmm, let's see...


Radiomaster: new to me, price OK, but not mobile, no AM dampening.

MFJ-1024: I knew that one, rather similar, probably easier to
repackage or fit on a a magmount. Attenuator: very useful!

Sony AN-1: old model, discontinued; as above, but no attenuator (?)

Hyundai Santa Fe: ok, it's built into a car that's not my model, no
SW, no idea what it is. [My old Celica had a hidden AM/FM windshield
antenna already 15 yrs ago, and worked very well, but I stuck a whip
on the side of the sunroof for SW...]

MJ aww-topsy: autopsy? Uh?



Methinks the product I want is still firmly planted in the imaginary
domain!
If I get off my bony butt and build it, I'll share the joy.

Again, if anyone has suggestions for plans (both ELECTRICAL and
MECHANICAL!), here's my dream specs, which I bet would make several
people happy:

- Preamp passband optimized for 3-26 MHz, matching short telescopic
whip (remember, SW-BCL more than ham radio), rolling off steep on
either side. Not that easy, may require a bit of creativity. In my
area, a tight perimeter around the HF passband is essential. Sometime
my car radios don't receive ANYTHING AT ALL because of monstruous FM
overloads.

- Powered by 12Vdc, via thin 50 Ohm coax, RG 174 or similar. Pretty
standard too.

- Mag mounted, for easy installation even on rental cars, etc.
There's a ton of those out there for VHF / UHF / CB etc.

- Power / RF splitter, maybe with attenuator knob.

- Additional step-up RF transformer for matching coax to random-wire
socket on portables (I tried it, it does make a big difference).

Any hints, other than using a glorious J310?