In my case I mentioned that connecting
on receiver Hallicrafters S-85 to the
Coaxial Switch went to increasing noise at transceivers connected
to the Switch. Insulation transformer helped me to remove the
effect. Figure 4
shows design of the transformer.
shows Hallicrafters S-85 on the bench.
Transformer was made with ferrite
ring that I saved from an old Computer PIII. The ring had dimensions
32x16x6 (ODxIDxH). Permeability of the
ring was unknown for me. Transformer had two identical inductors,
each contained 10 turns coiled by wire in 0.5- mm diameter (24
AWG). The inductors were placed at opposite sides of the ferrite
ring. Two lengths of coaxial cable in 20 cm were connected to
the ring. The design was placed in plastic food box.
The transformer was installed
between Coaxial Antenna Switch Protax
CSR- 5G and coaxial cable going to receiver Hallicrafters
6 shows the transformer inside opened food box. . Figure 7 shows the closed food box
with insulation transformer. Figure 2
shows the closed food box sitting beside the Coaxial Antenna Switch.
The insulation transformer allows use the Hallicrafters S-85
without any noise influences to transceivers connected to the
switch. Reception of the receiver was improved with the insulation
transformer. Stations sound clearly with the transformer.
I was mention that there were less noise and clicks in the receiver
especially at lighting and pre storm period.
7 Closed Food Box with Insulation Transformer
5 Hallicrafters S-85
6 Insulation Transformer Inside Opened Food Box
I measured SWR when the transformer
was connected to the 50- Ohm coaxial cable going from Beverage
antenna and to MFJ-259B. SWR was in limit 3…4 up to 4- MHz.
Then SWR was sharply increased and reach 25 at 20- MHz.
However, such high SWR does not hinder the reception. It is more
important for the receiver is to cut low frequencies interferences
going from static, lighting and some home and industrial equipment.
The insulation transformer does it in good way.
73! I.G., va3znw