A simple antenna splitter

By Giovanni Carboni, IZ5PQT


This is a simple antenna splitter I built to connect an antenna to two distinct receivers.



I found the schematic diagram in the excellent article by John Bryant and Bill Bowers on dxing.info. Splitters are expensive if you buy them, but they are very simple to build. I built two of the units called DH-P in the article. The first was built with a binocular ferrite core 43-202 which I had handy. The second is exactly the same but uses the 73-202 core as in the article. Below the picture shows what is inside the brass box of the first unit:




The primary has 12 turns of 0.35 mm dia. enameled wire while the secondary has 8+8 turns of 0.5 mm dia. The reason for the different diameters is just the different color of the wires! But don't try to use 0.5 mm wire everywhere, it won't fit inside the core.
The center of the secondary winding is grounded via a 27 ohm resistor.

The table below shows the results of measurements for the two ferrites. I did not measure the impedance. Notice that an ideal passive splitter has an insertion loss of -3 dB. The table shows that the 73 mix has smaller losses and up to 5 MHz is rather close to the ideal attenuation. At lower frequenceis the 73 mix gives also better isolation, however the 43 mix takes the lead from 5 to 15 MHz. The isolation worsens when the frequency increases and the reason could be due to capacitive coupling between the two outputs. Notice that I have the ferrite cores touching the matallic case, a situation that could lead to unwanted coupling according to the authors of the original article.

Ferrite 43
Ferrite 73

Frequency (kHz)

Attenuation (dB)

Isolation (dB)

Attenuation (dB)

Isolation (dB)

350
1000
2000
3000
5000
10000
15000
-5
-4
-5
-5
-5.5
-9
-10
-25
-26
-25
-25
-25
-24
-23
-2.9
-3.3
-3.5
-3.6
-3.8
-5.0
-6.0
-28
-34
-29
-28
-22
-18
-16
Measured characteristics.


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