Small Receive Loop Installation

 I'm just wrapping up the latest antenna farm project with the addition of an active receive-only loop.   This came out of a need to improve my lower HF bands receive capability and help deal with local manmade noise in the neighborhood.  The antenna + preamp combination I chose is the DX Engineering Pro-1B.

The system is located about 250' behind the house in the woods -- away from noise sources and neighbors. The antenna is ground mounted on about 10 feet of electrical conduit, with 2 feet of the mast embedded in a concrete filled hole about 8" across.   To rotate the loop, a Yaesu G-450ADC light duty rotor with the optional mast mount kit is installed about 3' from the bottom of the loop.   Belden 75 ohm quad shield coax carries the RF from the preamp as well as DC to power the preamp.   The Yaesu rotor requires (4) 18 gauge wires, and I found  "outdoor" 4 wire speaker cable (eBay) does the trick economically.

To combat any common mode noise finding its way into the preamp / antenna -- I wrapped several feet of coax (about 8 turns) on a mix 31 ferrite toroid just before the feed line connects to the output of the preamplifier.   All coax and control connections are sealed with layers of Scotch 33+ electrical tape followed by Scotchkote.  (This weatherproofing method has been successful here -- I've just unwrapped connections sealed this way from 21 years ago and they are still pristine.  It takes extra time and can be messy...but well worth it.)

My initial impressions are very positive given that summertime isn't exactly "quiet" on the lower bands.  I'm testing it with an RSP-Duo SDR, and although signal levels are lower than what I'm used to on other wire antennas, the noise levels have fallen more than the signals ==> hence, a better SNR.   These bands have never sounded so clean, and should I see any noise (and I do from some SMPS next door) -- the loop will null that noise out when broadside to the noise source.   So far, so good.

Pro-1B Loop Antenna & Preamp

Mix 31 Toroid at Preamp

Weights for Tree Supported Wire Antennas

I'd been looking for a way to provide continuous tension on a wire antenna, like a doublet or a dipole, that is supported on one or both ends by a tree.   The idea is to run a line/rope from the end of the antenna, down through a pulley mounted high in the tree, and then to a weight hanging from the line; some people use springs to accomplish the same thing.   When the wind blows and the tree moves, the weight would move up and down, keeping more or less constant tension, thus keeping the antenna from snapping.  The ARRL Handbook and Antenna Book have had diagrams of doing stuff like this for decades...but finding a suitable weight can be an issue (besides getting the wire into the tree... that'll be another post...)

I've used a variety of things in the past including buckets full of dirt, cinder blocks, and even "no-weight" by just tying to the tree and hoping for the best, etc. but this time I wanted something that would minimize damage to the tree trunk should it swing into the tree and would be XYL friendly.     Below is what I've constructed from two feet of 2" and 3" PVC pipe, concrete, 12" of rebar, and a lag screw with a loop.

PVC-Concrete Antenna Weight

I mixed up the concrete in one of those plastic storage containers using a 60# bag of Sakrete High Strength mix (although any concrete should do) along with about 2 quarts of water.  After taping off one of the ends of the PVC with duct tape, I filled the pipe up with concrete and then inserted the rebar into the center, leaving about 2" sticking out.   (I had concrete leftover which I used for some driveway patching!)

Once it cured, my son welded the lag screws onto the end of the rebar.  Done.

I haven't weighed them yet, but it feels like about 10 lbs for the 2" pipe and maybe 20 for the 3".   Once I weigh them, I'll re-post my findings.   There's nothing magic about the length and size here, although bigger antennas are going to require more weight to prevent excessive sag.  And in my instance, the plan is to use a weight on just one end of the antenna.

73,

Rush, W4QA

Standard Wire Antenna Approach

2" PVC, Rebar, Lag Eye Bolt