Ben from MBARS provided a useful link to a mains choke he has built recently based on the one in this blog: GM3SEK’s Technical Blog | Notes about current projects and topics, including followups to GM3SEK’s Amateur Radio Technical Notebook
I have several sources of interference to sort out, the main one being the bathroom lights which splatter VHF at S8!
HI Mark
Your posting stirred me into action and I built two for each of the 13 amp filtered socket boxes for my shack. Now I am sure the mains to all equipment in the shack is well filtered. I already had three of the Large ferrites bought from Mouser in 2019. I got the boxes from Rapid and the Schaffner filters and elliptical ferrites from Mouser. I used a 13 amp switch sockets with a larger box. The ferrites wired together only just fitted across the width of the box (90mm). I have 15 mains powered devices plugged in in my shack, so I bought 2 X 10 way Surge protected boards and mounted them on the wall fed from the two filters. Previously I had an 8 way and 2 X 4 ways directly on the mains. I soldered to the filters rather than used crimps.
73 Phil G4OBK
Good job that @G4OBK Phil!
As you’ve mentioned not much room for manoeuvre in that enclosure!
Has it made any difference to your noise level?
I noted that the ICOM IC-7100 that I have recently swapped for an FDM Duo I wasn’t using comes with 2 x SO-239 connectors. The VHF/UHF one can be swapped for an N-Type without any soldering required, so I will do that as my down-feed from the X50N has an N-type connector. I have tried to standardize on N-Type where possible, it connects direct to the FT-857 for example. I plan on following Icom IC-7100 SO-239 to N-Type – M0UKD – Amateur Radio Blog instructions.
If it is to hand could you post a parts list @G4OBK for Mouser?
Thanks, Mark.
HI Mark
Cannot be sure the filters make any difference here as everything in the shack is well ferrited and well grounded to my external earth and ground system in the back garden so I have no severe interference problems apart from occasional static type interference from electrical applicances in people’s home seemingly coming in via the antennae. My next door neighbours fairly new central heating boiler radiates a 16.5 KHz spaced hetrodyne through the HF spectrum which the notch filter deals with if it drops on a station of interest. She is elderly and a good neighbour, she let me in to the house with the KX2 about 18 months ago and this proved that it was the Vailant Ecotec plus 418 central heating boiler that was to blame. Nothing can be done about it - as I am not the customer the firm ignore my emails.
Parts list here:
Mouser
Fair-Rite ferrite clamp on cores low & BB Freq 31 Mat (Bought Jan 2019)
Fair rite ferrite cable cores 43 Full flat cable core (2 needed per filter)
Schaffner power line line filters 16A fast-on (1 per filter)
Rapid Electronics
Hammond RL6465-F Flanged ABS wall mount instrument enclosure 150L X 100H X 90W - box width very tight - only just accomodates ferrite filters when wound.
Schneider Electric GGBL3010S LWM 1 gang 13A switched mains socket
Cable - domestic appliance sized 3 core mains cable - I had that in stock. Clip on ferrite just accommodates 7 twisted turns of that sized cable. Any thicker and you would struggle to get 7 turns through the middle.
Volt drop through filters off load is approx 1 volt when tested. 232V in 231V out.
73 Phil
Dear RFI Expert:
The background noise levels in my shack on the lower HF bands are pretty bad (e.g. S9+ on 160m and 80m). I’ve listened on several rigs and it’s the same, a general white noise and worse during the day.
So, I had assumed it was general atmospheric noise caused by D-layer absorption, lightening strikes and other natural sources. I haven’t done 80m portable for several years [I’ve even cannibalized my homemade 80m dipole to make a ‘high’ bands linked dipole] but Mark @M0NOM informs me that he gets little or no noise on 80m when portable in the countryside. So, maybe it’s not all atmospheric noise.
I don’t think it’s coming via the mains electricity cable to the shack [a small outbuilding a few metres from the house] as the noise is about the same if I use a LiPo for the receiver [and switch all mains appliances off including lights]. I haven’t yet tried moving the rig and antenna feeder out into the garden and away from any mains cables.
There are mains (3-phase?) electricity cables running up the street on telegraph poles but they are 15m from the shack [and much further from most of the antenna wire] and about 8m up which I thought was too far away to be a problem.
Could my choice of antenna be a factor?: a horizontal long wire, inverted-L configuration (22m horizontal at 8m average height, 4m slope to ground and 9:1 UnUn, short earth wire to earth stake, 10m coax to radio/ATU).
So, any ideas where the noise could be coming from?
Hi Andy, I was having noise problems at home on hf but not all the time but still was a massive nuisance…in the shack I have a Yaesu ft101mp through and a Endfed wire 80ft long at 10m high… I found that some stuff in the shack that was on charge and around the house was 90% of the problem.
Hi Mike,
The source of the noise isn’t coming from my house [I powered off the mains at the main breaker and listened to 160m and 80m again on two rigs powered by batteries and there was no decrease in noise]. I connected the rig directed at the antenna [without the coax feeder] - no change.
I walked round the street, passed neighbouring houses and around my garden with two portable Rx’s [my KX2 on 80m-SSB and a Sony portable on MW-AM]. The noise did increase a lot standing under the overhead power cables / telephone cables that run up the street on poles. But that high noise dropped back down when more than a few metres away.
I concluded the noise is probably from many sources and worsened by have an end-fed long wire antenna with an inadequate or no proper ground plane [not possible with my rocky garden]. So, I’m replacing the EF-LW with an Off Centre Fed Dipole (OCFD) which doesn’t need a ground plane. I’ve got the 4:1 current balun and other components to make the OCFD and hope to have it working soon. I’ll do some evaluation on its performance and report back here in due course.
