SIMPLE RANDOM LENGTH WIRE ANTENNA FOR HF / SDR / SHORTWAVE RADIO
I went to home depot and purchased 100 feet of 14 gauge stranded copper wire with black insulation. ($15) I tied a 5/8 inch automotive socket to a long piece of 20 pound test fishing line and threw it over a 40 feet tall tree branch. I then tied the wire to the other end of the fishing line, allowing me to hoist the wire over the tree branch. I moved to another tree and repeated the same process, thus hanging the wire as you see in the diagram above.
I ran a small length of RG-58 coax out the window of the house, that was just long enough to make it to the two existing ground rods next to the house. I soldered the 100 feet length of wire to the center lead of the coax and insulated it with electrical tape. Using a simple hose clamp and a small length of wire, I connected the outer copper braid of the coax to the ground rods.
I went inside the house and connected the antenna to the SDR radio and started tuning around the HF portion of the radio spectrum. The noise floor / static level was a very high S7. Reception was decent, but, due to the high noise level it was a poor antenna. I concluded that the antenna was lacking an effective counterpoise, as the ground rods alone were not working well.
I connected a 5 feet piece of wire from the coax braid / ground rods connection to the water spigot on the east side of the house. I then connected a 35 feet piece of wire to the coax braid / ground rods connection and connected it to the water spigot on the west side of the house, as seen in the diagram above.
RESULTS / PERFORMANCE
By adding the extra counterpoise wire connections to the water spigots, the noise floor of the antenna dropped from a noisy S7, to a very quiet S3. I tuned the SDR receiver to WWV on 5MHz and was surprised by the strong S9+15 signal. I then tuned to WWV on 10MHz and received a strong S9+10 signal.
I tuned around various shortwave radio bands on HF, as well as 80 meter (3.8MHz) and 40 meter (7.2MHz) frequencies, finding these bands to be littered with clean sounding S9+ signals. I found it very impressive that this antenna was receiving very strong signals, on top of a very quiet S3 noise floor. I found more than a few shortwave and ham radio stations that were pounding in with S9+20 signals.
Now for the true test of the antenna. A random wire / long wire / dipole antenna can easily perform well from 1MHz to 20MHz, but, performance often suffers from 25MHz to 30MHz. I tuned the SDR receiver to 27MHz CB radio and was shocked by the results. The performance was as good as a ground level resonant 27MHz 1/4 wave dipole or CB radio magnet mount antenna. Local base stations were coming in with ample S7 - S9 signals. Truck drivers ten miles away were coming in with ample S5 signals. Very impressive.
There is a security camera half a mile away from my house, with an attached 49MHz wireless microphone. It's been running for years. In the past I have built a resonant 49MHz vertical dipole antenna and a resonant 49MHz ground plane antenna, in an effort obtain a better signal on this wireless microphone. The best signal I have ever received was S8.
This simple random wire antenna is receiving that 49MHz wireless microphone signal at S9+5. I find this to be baffling, being that this is theoretically the worst antenna to receive a signal that is nearly 50MHz. It seemingly defies explanation. I suspect it has something to do with the short vertical stub at the end of the long wire.
As a SWL (receive only) HF antenna, it easily outperforms a G5RV Jr. antenna. In one instance it was receiving WWV 2.5MHz, 5Mhz, 10MHz and 15MHz at the same time, all frequencies with S9+ signals. Day and night the shortwave and ham radio bands are littered with S9+ 20 signals.
Like most antennas this antenna has a downside. For whatever reason, this antenna is a bit meek on 20 meter ham radio. (14MHz) Known stateside S9+10 stations often come in at only S9. However, it does do quite well on 20 meter DX, as I did receive several stations in Europe with S5-S8 signals. A small price to pay for a $15 antenna that does so well in many applications.
This antenna is an all around good performer from 1MHz to 50MHz. I have yet to encounter an S9+40 signal that one would receive with a G5RV antenna, but, G5RV and G5RV Jr. antennas are certainly more noisy. (higher noise floor)
I have been experimenting with shortwave radio wire antennas since I was six years old. This is one of the best anti theory antennas I have ever made, as it seemingly defies technical explanation. It accidentally works very well over a wide range of applications. It's a testament to the fact that crude experiments can sometimes trump math / antenna theory.
I encourage others to run their own experiments and ignore math / antenna theory at times, as the outcome can sometimes be surprising.
SIMPLE RANDOM WIRE ANTENNA
There are rare instances where the theoretically worst wire antenna design, works as good or better than the best antenna designs. This is one of those instances. Enter the crazy world of the simple random length wire antenna.
SIMPLE RANDOM WIRE ANTENNA IN ACTION
SIMPLE RANDOM WIRE ANTENNA