UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - MW hum - higher frequencies only

agardiner · 17th Jun 2021, 6:41 pm

Hello all,

I don't think this has been answered before, so apologies if it has.

When tuning the MW band at home, I have a noticeable hum on higher frequencies. It is completely clear upto around 1200Khz, then any stations above have hum on them. Very noticeable on Smooth at 1251Khz which is one of the stronger stations, and also on my Spitfire when tuned above 1200Khz, but clear below. Clear again above around 1600Khz. It doesn't matter if the radio is mains or battery powered and it is all sets.

So, I have checked around the house for the usual suspects, but I don't think this is mains hum as such anyway, as the frequency of it is too high; it sound around 200Hz. I don't think it is the neighbours house either, as moving into the garden away from all properties does not reduce the hum.

I live in a rural area, and am blessed with very little RF noise. The house is supplied from a pole with a 3 phase transformer. So - first of all - could this be a phase related hum from the mains supply? Also, talking to Tony from 6V6, he wonders if it could be ground radar from Lakenheath air base, which is approx 12 miles from me.

Any thoughts? It is not a problem, just interested in learning what it might be!

17th Jun 2021, 6:41 pm	#1
agardiner Octode Join Date: Sep 2020 Location: Thetford, Norfolk, UK. Posts: 1,741	MW hum - higher frequencies only - 200Hz Hello all, I don't think this has been answered before, so apologies if it has. When tuning the MW band at home, I have a noticeable hum on higher frequencies. It is completely clear upto around 1200Khz, then any stations above have hum on them. Very noticeable on Smooth at 1251Khz which is one of the stronger stations, and also on my Spitfire when tuned above 1200Khz, but clear below. Clear again above around 1600Khz. It doesn't matter if the radio is mains or battery powered and it is all sets. So, I have checked around the house for the usual suspects, but I don't think this is mains hum as such anyway, as the frequency of it is too high; it sound around 200Hz. I don't think it is the neighbours house either, as moving into the garden away from all properties does not reduce the hum. I live in a rural area, and am blessed with very little RF noise. The house is supplied from a pole with a 3 phase transformer. So - first of all - could this be a phase related hum from the mains supply? Also, talking to Tony from 6V6, he wonders if it could be ground radar from Lakenheath air base, which is approx 12 miles from me. Any thoughts? It is not a problem, just interested in learning what it might be!