Wednesday, 7 July 2021

BROADCAST INTERFERENCE

HAVE A HEART!

Some time ago I discovered that I had a DeadZone on the 2M band. I could hear people perfectly well across the band but if they moved to 145.400 they disappeared.

I spent a lot of time checking out my shack and sought advice from many senior Hams with advanced licenses. I carried out numerous tests on different radios, different feed lines and different antennas. No one could identify the cause of the deadzone. And so it remained an unsolved mystery!

Well that was until I got my Expert Electronics MB1. Purely by chance, I caught a button on the front of the radio called 'WF' (wide filter) and straight away a HUGE signal appeared, centred on 145.400MHz 😲


Although it was just horrible noise, I thought I could detect the shape of voices, maybe even repetitive beats too. So I switched from Narrow FM to Wide FM and boom, there was HEART FM 105.4 broadcast radio station.

So all that time and messing around trying to solve the mystery of a deadzone was identified thanks to the WF filter option of the MB1. I've no idea what use the WF is for yet, but I'm just glad I caught it by accident.

Living right next to the Winter Hill Transmitter pushing out 5kW on FM probably means I need to invest in a 2m PassBand filter 😂




Thanks for visiting - please take a minute to leave a comment below 

73, Tom, M7MCQ.




2 comments:

  1. Looking at the specs, the LO is running at 20 MHz. Your interference on 145.400 MHz (105.4 + 40 MHz) is probably an image problem. A coaxial notch filter for Band 2 or a band pass filter for 144 MHz would probably sort it.

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    1. Hi John, I thought a 2M band pass filter might help, but when I mentioned that on my Radio Club forum I received this reply....

      "A 2m bandpass isn’t going to help if there is a sproggie actually on 145.400"

      Thanks for the visit John. 73, Tom, M7MCQ

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