SWL antenna: Higher but shorter or longer but lower?

[Treehouse SWL]

Question: I've had pretty good reception the past three or so years using a 50-foot wire antenna on top of my backyard fence (about 6-7 feet from the ground) along the edge of our sloped backyard. I also have an MLA-30+, but the long-wire antenna is still better.

The feed line to this antenna broke (actually, our puppy chewed through it), and as I get ready to fix it, it made me wonder about the one other option I have for antenna placement: We have a deck 15-20 feet off the ground, and I could either string a 25-foot-long wire along the long side railing of that, or string about 40 feet of wire along the three sides of the deck.

On the one hand, that antenna would be much higher off the ground than my fence antenna. However, it wouldn't be as long, and it would be closer to potential RFI sources in the house.

Should I stick with my proven antenna placement, or use the higher-up but shorter location?

[Pigmeat]

How about a sloper from the deck to the furthest practical spot on the fence? You would get the advantage of the height, plus it would go to a location you've had success with.

[kris]

     I will repeat the facts after literature and my private experiences:
- the longer the antenna wire, the higher the signal level, the lower limit of the antenna operation
- the higher the antenna, the higher the signal level (important for Mini Whip), the lower the radiation angle of the polar pattern (DX contra NVIS antennas).
- outside the matching range (low SWR) everything changes with the frequency of the signal and the conductivity of the ground under the antenna.
- the problem of self and received RFI noise is even more complex: symmetrical and "on the ground" antennas are quieter than others
To control this: we feed the antenna with a coaxial cable through a matching baloon or antenna boxes.
   Good thing you have access to the VNA and check at least the SWR of the transformer and the complete antenna. Several times I was surprised by the measurements in relation to the expectations, but you get information about what you can improve.
If you have a yard that is 50m long, I urge you to build a Sky Loop antenna.
They have a wide range of good work, high signal level, moderate noise (symmetry),
the height of the suspension is not critical.
    Winter storms destroyed my two large antennas and I am collecting comments to describe the recently built antennas.

[Josh]

I doubt a few feet higher is going to make any noticeable diff in hf work, going longer means more rf is collected and delivered to the rx. That said, if you could put a vertical up that would be a nice addition as oftentimes sigs are better on one polarisation than the other, especially at fade in/out.