Location and evaluation of each frequency

Marker 1: 28.080 MHz (for FT8)

• impedance: 54 + j1.31 Ω (almost pure resistance component, very close to the ideal 50 Ω)
• position: Smith Chart'snear the centerand is in an almost ideal position
• evaluation:
  →directional marker or indicatorexcellenceThe antenna radiates the energy from the transmitter with almost no waste: the antenna radiates the energy from the transmitter with almost no waste.
  →directional marker or indicatorOptimal adjustment state for FT8 operationIt is.

Marker 2: 28.590 MHz (SSB upper limit)

• impedance69.3 + j5.47 Ω (slightly higher resistance component and a little inductance component)
• position: Smith Chart'sright-upper(leaning a little inductive)
• evaluationThe "M" in "M" is a combination of "M" and "A":
  →directional marker or indicatorfavorable: A little far from the center, but within the practical range with no problem.
  →directional marker or indicatorSSB operation is also at a practical level without additional tunersThe following is a list of the most common problems with the

Marker 3: 28.020 MHz (for CW)

• impedance55 + j0.138 Ω (almost pure resistance component)
• position: Smith Chart'sVery close to the centerposition
• evaluationThe "M" in "M" is a combination of "M" and "A":
  →directional marker or indicatorVery goodAligns almost perfectly with the center and has almost no energy loss.
  →directional marker or indicatorIdeal for CW operationsThe following is a list of the most common problems with the "C" in the "C" column.

✅Overall Evaluation and Conclusion

• Smith Chart Overall DistributionSee,28.02 MHz to 28.59 MHzNo major discrepancies in the range of
  All frequencies are ideally located near the center.
• Impedance biasis also small, although there is a slight inductive (upward) shift,
  No additional matching requiredand can be sent efficiently.

Evaluation of 28MHz Dipole Antenna

1. VSWR (Voltage Standing Wave Ratio) Evaluation

• Marker 1 (28.080 MHz / for FT8)
  • VSWR: 1.084→ Very good (almost 1:1 with little waste)
• Marker 2 (28.590 MHz / SSB upper limit)
  • VSWR: 1.403→ Good (less than 1.5, so within the practical range)
• Marker 3 (28.020 MHz / for CW)
  • VSWR: 1.100→ Very good

Conclusion.:

• 28 MHz band.FT8, CW, SSBVSWR is good in all,
  There is no risk of triggering the rig (radio) protection circuit.
• Even at the upper SSB limit of 28.59 MHzLess than 1.5So it can be operated as is without any particular tuner.

2. impedance evaluation

• Marker 1 (28.080 MHz):54 + j1.31 Ω(Excellent, close to the ideal value of 50Ω)
• Marker 2 (28.590 MHz):69.3 + j5.47 Ω(Slightly higher, but acceptable)
• Marker 3 (28.020 MHz):55 + j138 mΩ(Nearly ideal value)

Conclusion.The "M" in "M" is a combination of "M" and "A":

• Close to 50 ohms at all frequenciesThe high transmission efficiency ensures stable transmission without loss.

Evaluation of Return Loss (Reflection Attenuation)

• Marker 1 (28.080 MHz):-27.913 dB(very small reflection = >99% efficiency)
• Marker 2 (28.590 MHz):-15.512 dB(Reflection approx. 3.5% = within practical range)
• Marker 3 (28.020 MHz)The "M" in "M" is a combination of "M" and "A":-26.470 dB(efficiency >99%)

Conclusion.:

• Sufficient at all pointsLow reflectioncan be confirmed,
  Transmit power is transmitted to the antenna with virtually no waste.
• **28.59 MHz (SSB upper limit)** is also in the practical range and can be used without concern.

The following is a list of the most common problems with the

• locusis relatively close to the center of the circle (50Ω), but allcapacitiveI am stopping by the
• Target frequencyTo bring it to the center in,Slightly more coils to increase inductivityIt is necessary to

1.SWR (VSWR) Rating

• Best Score (Marker 1)At 20.930 MHzSWR=1.195
  • Fairly good alignment, but better than the target frequency.Lower Band Limit SideI am stopping by the
• Marker 2At 21.290 MHzSWR=1.700
  • Although close to the center of the band, the SWR is slightly elevated.
• Marker 3At 21.020 MHzSWR=1.258
  • It is near the lower end of the band, but the SWR is good.

→directional marker or indicatorSWR lowest point is at 20.930 MHz and needs to be shifted above 21.000 MHzThe following is a list of the most common problems with the

2.Impedance Evaluation

• Marker 1 (20.930 MHz):45.2 - j6.94 Ω
  • It is almost 50 ohms of resistive component,Slightly capacitive (-j6.94)It is.
• Marker 2 (21.290 MHz):34 - j15.2 Ω
  • Low resistive component, stronger capacitiveTendency.
• Marker 3 (21.020 MHz):46.6 - j10.6 Ω
  • Although the resistance is close to 50 ohms, it is stillcapacitiveIt is.

→directional marker or indicatorPossibility to improve matching by shifting impedance slightly to inductiveThere are

(i)Check resonance frequency

• Marker 1 (7.04 MHz), ,Marker 2 (7.02 MHz), ,Marker 3 (7.18 MHz)Measured at
• resonance pointapproximately7.02 MHzIt is located in the vicinity of the SWR1.566and is not entirely consistent with the

(2)Impedance characteristics

• The ideal impedance is50ΩBut the measurement results show the followingslightly elevatedIt is in the
  • Marker 1:.74.3 + j13 Ω(some inductive component)
  • Marker 2:.77.2 + j9.8 Ω(Slightly off from ideal, but close)
  • Marker 3:.62 + j35.9 Ω(larger capacitive reactance)
• Coil inductanceis slightly larger than that of the other two, suggesting that the resonance is on the lower frequency side.

(iii)SWR (voltage standing wave ratio)

• Marker 1:.1.566(7.04 MHz)
• Marker 2:.1.586(7.02 MHz)
• Marker 3:.1.951(7.18 MHz)
• Around 1.5school (e.g. of ikebana)tolerance levelBut a little more.impedance matchingThere is room to improve the

• Smith Chart has all the measurement points.Right above the resistant componentlocated at,inductive componentis strongly present.
• Resonance point.7.05 MHzTo adjust to the vicinity:
  • Reduce the number of coil turns by one or two turns
  • Slightly extended elements(fine adjustment in increments of 1 cm)