80 Meter Dipole upgrade

19 Feb 2019.  upgraded the 40m dipole to 80m by adding two 30’4″ lengths of #30ga stranded wire.  It took a couple of stages but the job is done.

SWR at rig end from the 4:1 balun
80 3.88  4.5
60 5.35 11.1
40 7.04  24
40 7.18  24
30 10.1  5.3
20 14.0  6.3
20 14.2  7.0
17 18.1  1.6
15 21.2  4.0
12 24.9  4.9
10 28.2  2.7

SWR at rig end from the twinlead before balun
80 3.88  28
60 5.35  2.4
40 7.04  > 30
40 7.18  > 30
30 10.1  18
20 14.0  2
20 14.2  2
17 18.1  3.5
15 21.2  3.4
12 24.9  9.3
10 28.2  2.7

With the 4:1 Balun
The Kenwood TS590SG can tune  80, 30, 17, 15, 12, and 10  meter bands.
The MFJ-901B tuner is needed for 60, 40, and 20 meters.

Materials: 30awg wire – white teflon coated  for the west leg to blend with the building, black silicone (200 F) for the E which is more invisible in the air.  U shape, first 30′ on both sides then just folded/dropped to fit in.

Construction: original PC board T support with two hole strain relief – this design has held up well since the beginning.  The original 30 ga single copper conductor wire became brittle over time and had to be replaced.  The stranded should be a bit stronger and more flexible.  I made a splice board with copper clad board – two hole strain relief design, 1/2″ by 2.5″ copper sheet jumper taped in place on the west side, antenna wire  soldered to the copper plate.  The jumper is soldered on the E … originally the idea was to use the copper sheet as a switch conductor to easily remove the 80m stub – this is impractical for permanent installation.

Performance : so far so good, definitely louder on 80m, suspect 40m is compromised.  The balun observed to heat up to 140F after operating for a while long 100w FT8, runs cooler on other bands so need to be careful on 40m.

Is the end fed now better on 40m ?   2/21/19  –  it works pretty well and may be outperforming the dipole … several factors including EF wire orientation (NS (ef) vs EW {dipole} )  of highest current segments and height may affect this too!

135 foot Length
The ARRL Antenna book lists a 135′ doublet recommended length … this length may work better than 120 with much lower 80 and 40m SWR before the balun (the 1:1 , i.e. no transform, swr)

135′ dipole SWR at rig end from the 4:1 balun 
 λ     f 
80  3.5       5          4
80  3.88     4          5
60  5.35   14          12
40  7.04   25        24
40  7.18   25        24
30  10.1    2           1.6
20  14.0    9           8
20  14. 2   9           9
17  18.1    5           5
15  21.2    3           3.4
12  24.9    4           5.4
10  28.2    3           2

 

~ by marksun on February 21, 2019.

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