Lew G8KJJ 10m delta loop

Earlier this year Lew G8KJJ published this on the Club Facebook Page

The 10 metre Delta Loop described here was inspired by the Pennine Ham presentation and RadCom article by Hiroki Kato, AH6CY. The design is not a copy of his antenna but is a version which fits my specific needs. Currently I have two antennas for the HF bands, a 5 band “home brew” Cobweb and a quarter wave inverted “L” for 40 metres. The two antennas serve my needs well except on 10 metres. Since I don’t wish to take up more garden space with a permanent antenna, the delta loop must be easily erected and dismantled when needed. Fortunately, there is a dead tree stump at the bottom of the garden which can be used to support the 3 metre mast which will be used for the delta loop. This removes the need for guy-wires for the mast.

The design was first modelled using EZNEC software.

The antenna consists of two telescoping aluminium tubes forming a vee with 3mm aluminium wire joining the tubes at the top. The telescoping tubes are repurposed CB halfwave antennas which can be purchased cheaply “on-line”. The advantage of the telescoping tubes is that the delta loop can be tuned to resonance easily. The construction can be seen below. 

The angle between the telescoping tubes is 42 deg. This was found by modelling using EZNEC. 

The Dimensions of the antenna are : - Telescoping tubes:- 4.18 metres, 3mm aluminium wire :- 3 metres. These dimensions were taken from EZNEC and obviously will change depending on location. I found I had to reduce the dimensions in order to bring the antenna to resonance. The SWR was measured at the antenna using a quarter wave length of RG 58 coax and was adjusted to be lowest at the FT8 end of the band. The SWR was 1.4:1 and did not require a transformer.

IN USE

The !0 metre band has been fairly poor in the UK over the last week (week ending Sunday, 11 May) and as a result the number of contacts has been limited. To test the antenna in these circumstances I decided to confine operating to FT8. The most notable contacts were :-

Wednesday 7 May: Brazil, Reunion Island, South Africa

Thursday 8 May: Brazil, Chile, Philippines

Friday 9 May: Namibia

Comparing the Delta Loop with the Cobweb on 10 metres was difficult as I am currently unable to switch the antennas remotely. The reception of FT8 on both antennas suggested that the Delta loop was about 10 db better than the Cobweb. Not a very scientific test!