• WindomAntennaFD4

Vorläufig / Preliminary, work in progress

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Windom Antenna Fritzel FD4

This web page documents the commercial Windom Antenna Fritzel FD4 measured with the Vector Antenna Analyzer FA-VA5.

On the right side you see a picture of the balun of my Windom-antenna.

One source of buying shows Links #1

If you click on a picture it will be expanded. You can go back to the web page with the back arrow of your web browser.

Technical Data

• Frequency range RX and TX: 80m/40/20m/17m/12m/10m
• Frequency range RX only: ca. 100 kHz to 30 MHz
• max. Transmit Power: 0,2 / 0,3 KW
• Antenna impedance: 50 Ohm (at Balun)
• Antenna connector: PL-plug
• Length: 1x 27,6 m and 1x 13,8 m
• Weight: 1,4 Kg
• Balun Type: 1:6 AMA

Match Box

Without Matchbox it is not possible to get a good SWR on the 15 m band.

On the 80 m band the bandwith with a good SWR is very narrow. So, a Matchbox is needed.

I am using an old MFJ-941B for tuning and power display.

Common Mode Choke

As recommended in an ARRL paper about Windom antenna I inserted a 30 cm long common mode choke (15 x 2 cm Ferrite rings Links #4) 6.7 m below the Balun, see the picture on the right. In order to keep the rings on place, they are covered by a black heat shrink tube, see Links #5.

The common mode choke will help to keep the RF (Radio Frequency) out of the shack, see Links #2,3.

The 6.7 m length coax cable HSR195 (Links #6) should help to improve the horizontal radiation in the way to fill the deep nulls.

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FA-VA5 Charts

With my new Vector Antenna Analyzer FA-VA5 I could see very good, how the matching to 50 Ohm is.

On the 80 m band the bandwith of a good SWR (1:1.04) is very narrow, see the chart on the right side.

So, every 50 KHz deviation needs a different tuning.

The actual tuning setup is in the chart comment:

• T3.5 means Transmitter capacitor set to 3.5.

• I-H means set Inductance switch to postition H.

• A0.0 means set Antenna capacitor to 0.0.

The software VNWA is master calibrated, you can see it in the lower left corner of the diagram with letters MC.

Because the 40 m Band is very small (100 KHz), one tuning setup is sufficient.

The center SWR is 1:1.2.

The smith chart or Smith-Diagramm red curve shows the matching.

The blue curve shows the impedance.

The green curve shows the SWR (Standing Wave Ratio).

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The bandwidth on the 20 m band is wide, one tuning setup is sufficient.

The center SWR is 1:1.4.

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The bandwidth on the 15 m band is wide, one tuning setup is sufficient.

The center SWR is 1:1.10.

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The bandwidth on the 10 m band is wide, one tuning setup is sufficient.

The center SWR is 1:1.21.

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Links

1. Fritzel Windom FD-4 Antenne

2. common mode choke explained

3. Coax Feed Line Common Mode Chokes

4. Ferrit ring LFB095051-000 Laird

5. Schrumpfschlauch 1:2 (9,5 mm auf 4, 5mm), heat shrink tube

6. HSR195 coax cable, loss @ 30 MHz: 6,5 dB / 100 m

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-- RudolfReuter 2019-01-12 11:37:48

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