Double Half Delta Loop (DHDL) Low Band Receiving Antenna

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A few days ago I had the time to build and try a Double Half Delta Loop (DHDL) at our Contest Station ED1R. The Antenna was built within 3 hours and can be deployed / errected within 20 minutes.

The Antenna

The Double Half Delta Loop (DHDL) was developed by George, AA7JV for his Lowband Expedition to Chesterfield (TX3A). It’s a ground independent Receiving antenna which only needs two 10m support poles. Once the wire’s are cut and the Balun build, it takes less than 20 minutes to deploy the antenna.

A detailed description can be found at OK1RR’s website, the DHDL simulation files can be downloaded at TX3A website and IV3PRK’s report about two broadside phased DHDLs is also worth reading.

Double Half Delta Loop

3D View on the Simulation Model

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DHDL in the backyard of ED1R

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DHDL from the feedpoint towards the second pole

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DHDL 1:18 Transformer & Resistor in their enclosures

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Supporting fibre pole in the center at 1,5m

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RF Choke at the base (25 ferrite beats) is crucial

With the specified dimensions, this non-resonant loop is optimized for 80m. On 40m, the Front/Back is too low and on 160m the signals will be very weak. The diagrams below show the patterns for 40m, 80m and 160m.

DHDL Vertical Pattern for 40m, 80m and 160m

dhdl_pattern_horizontal

The antenna’s feedpoint impedance alters between 1000 – 1200Ohm (see below). I built a 1:18 transformer on a Binocular core (Fairrite #2873000202) and terminated the loop with 1000Ohm.

dhdl_impedance

Results

Despite another receiving antenna for comparison, it eliminated very well the QRM we have at ED1R on 80m Fullsize Deltaloop. On 80m I noted a very good F/B while switching between the Transmission antenna and the DHDL. As expected, on 40m the F/B was only marginal and on 160m the Signals were too weak.

Bottom line: The DHDL is a solid performer for 80m. On 160m a preamp is definitely required and on 40m the antenna is not that useful anymore.

A few words of precaution

  • Make sure you don’t listen on the coax cable. Put sufficient ferrite beats on the coax, close to the feedpoint and close to the shack. Ground the cable in 3m distance to the feedpoint.
  • Make sure that metalic structures don’t disturb the antenna. Fences, Towers, Verticals in the close vicinity will create problems and couple into the DHDL. Make sure that these metal objects are at least half a wavelength away. If that’s not possible you will have to de-tune your transceiving antennas – but that’s another chapter
About Tobias (DH1TW)

Self-confessed Starbucks addict. Loves to travel around the globe. Enjoys the technical preparations of Amateur-Radio contests as much as the contests themselves. Engineer by nature. Entrepreneur. For more, follow him @DH1TW

Comments

  1. Alexey Ogorodov says:

    Another master piece, bro… The question is: will it work on 160 with a preamp?

  2. Peter DF1LX says:

    Nice – how was your fullsize DeltaLoop build? Horizontal?
    I use a 40m vertical build DeltaLoop and can use the preamplifier – the total noise is really low compared to a (ok not very good) G5RV – which was existing some time before shreddered :) I will change to a 2 Ele. Delta Loop for 40m – must be a little bit better :)
    Greetings and have fun in Friedrichshafen Peter 1LX

  3. mich on8dm says:

    Hello,

    I v made the antenna before it was published in the 5th edition of the low band dxing book…To make a long story short . The antenna is not working as advertised or published.Even with the best care the antenna is performing in line like a EWE or a K9ay.. The published figures as on Johns LB ding book are wrong.. plots are made on wrong ground and are misleading ..If your lucky you get a bit directivity but that is going to be it….Mich on8dm

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