The Fan dipole for 40/20/6m performs well. Now it's time to extend the Fan with more bands.
I want to add dipoles for 80m, 15m and 10m. Making it a resonant antenna for all bands from 80m to 6m (except WARC bands).
Considerations
Adding more parallel dipoles will make the angle at the centre sharper for some the bands (the lower wires). This will affect the radiation pattern. It also decreases the impedance for those bands.
Most Fan (parallel) dipoles found on the Internet start with the lowest band (longest wire) at the top. Bands are added in sequence. Highest band (shortest wire) at the bottom.
Maybe it's a good idea to 'un-sort' the order. By this the longer wires are more apart so reducing mutual influence.
Centre fed antennas fed with coax (50 Ω) will need a balun. I use the 1:1 BU-55 Balun from D-Original.
Limitations
My garden is too small for a full 80m dipole. At one end there is space for 16 meter wire. On the other end 12 meter. Adding a coil in each wire for 80m may look as the solution.
Centre mast 10 meter high. Poles at the end about 5 meters high. So it will be a Inverted V Fan antenna.
The BU-55 balun is specified from 3MHz to 75MHz. Probably not the ideal balun for 80m. We'll see...
Dipole order (top down)
First attempt
The 80m dipole wire will carry the whole construction.
| Band | Length approximate (one leg) | Remark |
|---|---|---|
| 6m | 1,5meter | 'float' on top |
| 80m | 20 meter | support wire |
| 15m | 3,7 meter | |
| 40m | 10 meter | |
| 10m | 2,5 meter | |
| 20m | 5 meter |
Second attempt
10m between 20m and 40m appears not to be the best place. Probably because they are harmonics. In the second attempt 6m is now between the 20m and 40m wires. The 10m band wire is now 'free' on top.
| Band | Length approximate (one leg) | Remark |
|---|---|---|
| 10m | 2,5meter | 'float' on top |
| 80m | 20 meter | support wire |
| 15m | 3,7 meter | |
| 40m | 10 meter | |
| 6m | 1,5 meter | |
| 20m | 5 meter |
Spacing
I will use variable wire spacing.
Spacer is made by cutting a 2cm diameter grey electro tube in four pieces.
Due to the order (shorter wires between longer) spacing can vary (increase) among distance.
80m dipole shortened
The 80m dipole wire(s) must be shortened due to space limitations.
The shortest side must be extended by an coil of about 80uH plus a piece of wire (approximately 2 meter).
The longer leg can be about 16 meter. To short but not much. I will not extend this side with a coil.
Consequence is that the antenna is a bit off centre. But not much.
Making the dipole resonant can (must) be done by cutting the wire length after the coil (leaving the other (long) side of the dipole as it is).
80m extension coil, wire partly hanging down due to limited space. The 40m wire can be used to stabilize construction.
Practice
Made some modifications to improve wind stability. Mainly to prevent twisting.
The Fan dipole performs well (resonant) on all bands without the need of a tuner.
Antenna analyser measurements point out that the dipoles interact with each other. I expect that this will influence the radiation pattern.
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