Теме: Радио-аматеризам | Радио-техника

Build grid dip meter adapter coil for antenna analyzer

Скраћена веза: http://pedja.supurovic.net/veza/8706

Antenna analyzer like MFJ-259, MFJ-225, MiniVNA and similar may be used as simple grid dip meter for measuring coils, traps and capacitors. All you need is grid dip meter adapter coil which you may buy (costs for MFJ adapter set is about 30 USD) or make it by yourself for few USD.

If you want to build on your own here are dimensions of original coils sold by MFJ.

Small coil for short wave frequencies: coil diameter 15mm, coil length 15mm, 30 turns of 0.5 mm copper wire wound on PVC tube. Coil inductance should be about 3.6μH.

Large coil for HF frequencies: coil diameter 50mm, 2 turns of 2 mm copper wire, free standing.

For VHF frequencies: coil diameter 15mm, coil length 15mm, 4 turns of 2 mm copper wire, free standing. Coil inductance should be about 0.2μH.

Here are coil dimensions for more precise frequency range usage:

Frequency Diameter Turns Coil
length
Wire
diameter
Inductance
HF band (small) 15 mm 30  15 mm  0.5 mm  3.60 μH
HF band (large) 50 mm 2 2.0 mm
VHF band 15 mm 4 15 mm 2.0 mm 0.20 μH
 1.8 – 4 MHz 15 mm  65  20 mm  0.3 mm  35.00 μH
4 – 10 MHz 15 mm 25 13 mm 0.5 mm 7.00 μH
10 – 27 MHz 15 mm 10 10 mm 1.0 mm 1.30 μH
27 – 70 MHz 15 mm 7 30 mm 2.0 mm 0.30 μH
70 – 114 MHz 15 mm 4 20 mm 2.0 mm 0.13 μH
114 – 170 MHz 15 mm 2 6 mm 2.0 mm 0.07 μH

I have built larger one turn coil with diameter of 80 mm (2 mm wire diameter) as I needed to measure larger traps, and it works fine for whole HF band.

MFJ uses cinch connectors (RCA) so additional connector adapter is required to attach them to antenna analyzer. You may use other connectors for your build.

I got this data from Bedienungs- und Abgleichanweisung für Antennenanalysator MFJ-259B / Vectronics SWR584B, Version 1.4 von DK1NB.


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