160 Meters 4 Square Receive Antenna

Project 6 of 7 for October, 2020 – projects to keep sane during Covid-19 Lockdown

Status: Completed

For the virtual Dayton Hamvention this year Contest University had some wonderful online presentations. One was especially interesting to someone who still has countries needed on 160, W3LPL –  “Effective Low Band Receiving Antennas”. A video is still available on YouTube. Frank Donovan, W3LPL, listed receive antennas from the smallest to the largest along with ranking their effectiveness. The best of size, cost, and effectiveness looks like the 4 square high impedance active antenna. DXEngineering offers one in a bundle with all possible parts needed, DXE-RFS-SYS-4S. One is on order.

In Frank’s excellent presentation only one antenna performs better and that is twice as big and only has 1.5 dB Receiving Directivity Factor (RDF) improvement. The Hi-Z 4square appears to be the best bang for buck.

As of today grounds rods to mount the antennas have been made. A 1000′ roll of direct-bury CAT-5 cable is on hand to run power and control signals. A location has been selected about 500 feet north of the transmit antennas. A scheme to reduce the number of control wires so direction can be switched remotely has been invented. This receive antenna should coordinate nicely with the omega-matched tower transmit antenna upgrade this year.

One concern is how far apart to put the verticals for the best performance. The DXEngineering user guide says 135′ or one quarter-wave is optimum for 160. Other references says 80′ or 88′. An email was sent to Frank, W3LPL, to get the word from the master himself.

Hi Mark,
Optimum 4-square spacing for 160M receive is 67 feet.  Wider spacing produces higher signal levels but also higher side lobe levels.


Much more important is maximizing the spacing from resonant 160 metertransmitting verticals, towers more than 90 feet tall power lines andhomes or buildings that may contain RFI sources.   I would try for at least one thousand foot spacing.
Good luck!


73FrankW3LPL

Five hundred feet is do-able but 1000? Hmmm. We’ll see with a site visit tomorrow.

Cable was pulled from the shack to the 4-square site today which is 1000′ away. One thousand feet seems like no problem after today’s site visit. The site is very close to the Field Day site for 2019.

https://w0qlremotebase.wordpress.com/2019/06/07/field-day-2019/

One cable is quad-shielded RG-6 and the other is direct burial CAT-5. One of the CAT-5 pairs will be used for direction control. The other three pairs will be grouped to provide power. Resistance of a single 24 gauge wire 1000′ long is 26 ohms at room temperature. Three wires grouped together will cut the resistance to about 9 ohms (8.77 to be exact). With 1 amp of current the voltage drop would be 9 volts (E=I X R). To provide 12 volts to a device the supply voltage will need to be 21 volts. Fortunately the battery voltage for the new inverter will be 24 volts. A linear buck converter (LM-317 voltage regulator) can be installed at the 4-square end and provide a regulated 12 volts. Per the instruction manual:

The DXE-RFS-3 phasing unit uses and distributes the voltage to power the active antenna elements.
For all four active elements, a nominal +12-15 Vdc at 250 mA current is required.

At only 1/4 of an amp load the voltage drop would only be 1/4 as much or 2.25 volts. If a 13.35 supply was used the voltage at the 4-square would be 11 volts. That might work but might be unreliable. Using a 24 volt supply and a buck converter is a more reliable choice.

Today the ground rods were driven for mounting the verticals. They were measured out to be within 1″ accuracy, using the 67′ side lengths recommended by W3LPL. The sides are precisely east- west and north- south. That makes Europe at 45 degrees the default direction.

Status: 4-square arrived today (some assembly required). The Quad Shield RG-6 cable has been measured out as accurately as possible and cut to length at home for the delay lines.

Next the excellent quality Snap-N-Seal connectors provided by DXEngineering were crimped on.

Tomorrow the cables will be taken to the remote site and connected. The verticals will be installed on the ground rods.

Installed, here is one of the verticals:

This is the hub at the center of the four verticals. The three delay lines are coiled up and strapped to the post. The gray box on the far side contains the voltage regulator (buck converter). The black box in the foreground is the DXEngineering control box.

Inside the gray box is a LM317 voltage regulator or buck converter. It converts the 24 volts input to a 12 volt output. A LM317 is used instead of a LM2596 because the LM317 is linear technology (analog) and does not generate digital hash like the LM2596. This method was chosen to carry 12 volts over a 1000 feet of CAT5 to overcome it’s inherent cable loss. In the picture below the blue/white pair carries the BCD data to switch the relays that control the direction.

Testing to see if the design works in the field shows good results. The gold thing is a 50 ohm resistor which simulates the load of the relay controller. (E = I X R, E = .25A X 50 ohm, E = 12.5 volts).

With the weeds looking very much like vertical antennas a wide shot of the 4 square doesn’t show much. It blends in quite well.

Performance is extremely directional as expected. A station to the northeast that comes in S9 completely disappears when the relays are switched to null it out. Come on winter and 160 season. It will be fun to use this.

Next, FT8 signals on this antenna were compared to the same signals on the 160 meter transmit verticals. Signals are stronger on the transmit antennas but there is no way to null out unwanted signals. A preamp is under consideration to bring up the gain where it will be even with the transmit verticals. The loss in 1000 feet of RG6 may need to be compensated for.

Status: completed (but always looking for improvements). To try to get a little more gain on 160 the jumpers were put in place to peak the response on that band. Gain is still low but it is working as designed.

January, 2021 update: Performance is amazing. A YouTube demonstration should be produced. A preamp was added at the 4 square to overcome the loss in the 1000’ of coax.

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