Re: Band pass filter

Lawrence Galea

Agree with you.

2mH is too large and it must have been simply for static discharge.

Many moons ago when I used to service TVs I always put a 4 turn air spaced coil across the tuner antenna input.
I used to use a 3 mm twist drill to wind the coil.

The coil would offer enough impedance not to have any effect on TV VHF / UHF signals but would be like a dead short to HF and lower frequencies.

Re our friend's problem, a LPF should solve the problem possibly with the addition of a trap in series between the antenna and receiver input.  

Perhaps as some comfort for our friend re having a broadcast TX causing problems, years ago we had the Deutsche Welle relay station  about 2 miles away and they were running some 600 KW on MW to a 3 element vertical array beaming to North Africa / Middle East and three 250 KW on SW to two side by side curtain arrays that could be steered by phasing lines to + / - 30 degrees (if I remember correctly) with 4 phased wide-band dipoles on each curtain and on both sides of the curtains. They also had a 20 KW SW transmitter feeding a 5 MHz - 25 MHz rotatable HF log periodic array with a 40 metre boom on another tower. A 33 KV supply cable was laid directly from the power station to the radio station.

When it was switched on it would blast in on any untreated equipment, hi fi etc 

Touching any antenna including TV antennas down-lead without grasping it quickly would make a small burn on your fingers and you would see sparks jumping from the feeder to your fingers. 

Cables etc on cranes at the Free-port across the harbour used to act as diode detectors and people could hear the programme being transmitted.

When I was working as a radio operator on board an oil rig just outside the Sues Canal it would come in like a local station not to mention when we were in the Adriatic. No wonder being located on the coast and with all that power and antennas.


On Sat, Nov 16, 2019 at 4:25 PM iz oos <and2oosiz2@...> wrote:

2.2mH is a large value. I guess its purpose be protection against statics. 1uH has is a low impedance at MW providing some highpass but maybe not enough in presence of a nearby station. Try it in any case.

Il 16/nov/2019 04:15, "MVS Sarma" <mvssarma@...> ha scritto:
Great. Simpler idea. Elektor sdr design by Burkhard Kainka  had 2.2mH inductor across antenna

On Fri, 15 Nov 2019, 11:25 pm Miguel Angelo Bartie via Groups.Io, <> wrote:
A simple way to kill BC AM signals is using a 1µH or less in pararllel with antenna input....
Try ... 

73 from py2ohh miguel

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