[Elecraft] low-noise 40m RX antenna?

[Ron D'Eau Claire]

I have a 2nd rx jack awaiting an alternative receive antenna too. One
antenna that I am considering is a small receiving loop that I can
rotate to null both QRN and QRM. The other is a subsurface (underground)
antenna. John Heys G3BDQ in his little book "Practical Wire Antennas"
discusses work with these. Of course they are no great performers on
transmit producing signals about 16 dB below a "normal" dipole, but for
receive... here's what G6PG reported, "...reduced QRN to almost zero and
allowed the reception of shortwave signals almost as efficiently as did
his elevated wire."  

All the reports seem to agree that the QRN is greatly reduced using an
antenna on or underground.

The antenna Heys discusses is a dipole, but very short by "normal"
standards because of the loading effect of the earth. A 5 MHz dipole
used by W0YBF was only 46.6 feet long, compared to 93.6 feet for a
resonant dipole above ground. 

DeMaw also reports very good reception with 'on-ground' antennas. In his
book, "W1FB's Antenna Notebook" he describes using an on-ground antenna
consisting of a length of 50 coaxial line terminated at the far end with
a 51 ohm resistor. A less-expensive alternative that worked as well,
DeMaw writes, is a length of speaker wire terminated in a 220 ohm
resistor at the far end and a 4:1 balun at the rig end. DeMaw wrote,
"Even a random length of wire placed on the ground is often quieter than
the transmitting antenna." 

What all of these antennas have in common is the need for a preamp
-something in the order of 20 dB -- just what the K2 has already
built-in and ready to go to work on the lower bands.

And, with these, if you did encroach on the power company's easement a
bit, you wouldn't have to worry about a hot line falling on your antenna
in the event of an accident or of them tearing anything down (Now,
tearing your antenna UP might be a problem if they dig trenches...). 

Ron AC7AC
K2 # 1289

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Since the K2 has a separate RX antenna jack (on the K160RX module), I'm
thinking about putting up a low-noise receiving antenna for the low
bands. Unfortunately, to get enough wire for a Beverage antenna, I'd
have to sneak something along the fences in the power company easement
behind my house. This leads me to wonder about other possible low-noise
antenna solutions that might take less room (tuned loops, etc.). 40
meters is the band I'm most interested in.

Any suggestions? I think this topic might be of general interest for
weak-signal DX and QRP work on 40, but you seldom hear any discussion
about low-noise antennas outside of their application to 160 meters.

tnx
Wayne
N6KR