The ongoing quest to reduce QRM – Mains Filter #2


I was using the origninal picture and refrencing off the *EARTH* location post, and not looking at the label (LOAD/LINE) – I have since corrected – afaik no damage done, but good to get right first time if you are using the same filter (FN2030-16-06 FILTER) which has a different layout and orientation to the one used in the slides


Back in May I built this filter for my shack, which provided suitably good results for the time and effort employed. Further to that post G8KVM (Personal “Bern”) posted a follow up link to an updated filter here.

The main difference to this filter was it contained multiple and updated ferrite types as well as a mains-filter. I was immediatly drawn to the idea of further reducing the QRM into the shack as the first filter provided good results.

I ordered the following parts

Large Fair-Rite core 0431177081: MouserFarnell16.47

FN2030-16-06 FILTER, 1 PH, 16A, CHASSIS MOUNTFarnell15.97
CE-TEK  GR17012  IP65 ABS Enclosure – 170x170x75mmFarnell8.79
PRO POWER  PG-11 BLACK  Nylon Cable Gland PG-11 Black – Single Pack, IP68Farnell0.80
Parts Ordered for updated mains filter

I would like to point out that when ordering the mains filter (2030-16-06) the picture on the site is an AC filter. The once I received had DC on it, although the product code was the same.

I was slightly worried about the filter saying DC on it, where this is receiving AC current from the mains supply. Whilst rated for 250V i was not going to take any risks, so setup a test-bed outside, where it was thankfully dry and sunny.

I set about by first running an unplugged in extenstion, plugging the filter into that, and setting up my voltmeter to read AC from the output terminals. There is only one earth on the casing.

I then went back in doors turned on the power and no popping/arcing/fusetripping was observed. I then checked the output on the voltmeter, and sure enough it was good 240V AC coming out the filter.

I then proceeded to complete the winding for the ferrites.

The cable i used was SEL 10 m 2.5 mm Twin and Earth Cable. This very good solid copper wire. I did have to put on some Electrical PVC Yellow/Green Earth Sleeving to the earth-copper as this is bare when it comes out the original sleeve. I didn’t want to use my electric drill for the twisting of the wire, so done this by hand. Whilst physically demanding, i felt it provided safer and better results.

I was then able to twist the cable thru the torids as per directions. I was rather happy with the results, as it was quite tough to get the cable thru the torid and space it nicely.

Having tested for electrical continuity via a voltmeter, i then proceeded to test with a simple electric lamp which worked perfectly well. There was no issue with the wiring on the toroids or the filter.

I then disconnected my old filter and connected the new filter.

I was immediately impressed that i was now picking out more receive signals on FT8 and Wefax images were incredibly sharp.

I had 4 consecutive QSO’s which had never happended to be before, so was my first time manging a ‘pile up’ of sorts !

In summary for the time and expense this is a fantastic additon to the shack and makes me confident that in terms of power-line RF and QRM I have done as much as I can in terms of mains-filtering.

Thank you again to GM3SEK fantastic blog posting and G8KVM for pointing me in the right direction to the updated design !

73’s and see you on the airwaves soon hopefully !

— Appendix page update ! 🙂

Following Phil’s comments I powered down everythign and re-opened the filter as its been a little while since I closed it up.

In the picture below, the mains is the cable to the top of the page, this connects to the line filter, then in turn the ferrites connect to the output of the filter. I think I have got this correct based on the source picture !

Source – – All credits to gm3sek.
Pic of filter following Phil’s observations

Whilst mine isnt as tidy, i think it is correct. Appreciate if you can reply to comment Phil 🙂

The Quest to Reduce QRM – DSP & New PC and more in progress !

  • bit of a longer post today so grab a cup of tea is recommend, else scroll through the page until you get to the bit you want to know about

Several weeks ago I was browsing the local 2nd hand radio shop where my TS690 came from, and amazingly they had the DSP-100.

Kenwood DSP-100 – finding chicken teeth is easier

The DSP-100 is one of the first ever Digital Signal Processors. Kenwood were pretty ahead of the game when they released it. You will see all the filters and features you see in this unit in most modern transceivers, but this is (I guess) about 20+ years old, and are hard to come by. I dont mind saying this unit, 2nd hand was £333 ,which is only £40 different of what I paid for the TS690S, but what it brings to the radio is RF filtered and processed. The promise of ‘hi-fi’ quality SSB, AM, CW and RTTY was too good to pass up. And it looks gorgeous too 🙂

When I first set it up with my TS-690s I connected in my xggcomms Kenwood interface I started running into issues. I honestly believe this is no fault of the xggcomms device, but moreso on how the RS232 signal from the DSP-100 unit is processed and fed into the transceiver. Its fair to say whilst I was overjoyed in having the DSP, alot of what i do requires a good CAT connection to constantly adjust the frequency (FT8 & WSPR), so I reverted back to the Xggcomms interface only and started investigating.

Upon searching, other people had experience similar, but not identical issues. The key to fix this was the IF-232C. This translates the serial input into signals at the correct levels for the DSP & the TS690s.

Up until now I have been using a laptop, which had become increasingly over burdened with USB dongles/hubs coming out of it, also getting the computer to be ‘RF Friendly’ and grounded proved a challenge. The only way i could see to easily and reliably RF was via the USB port, and this little lenovo laptop computer already had *alot* coming out of the USB ports.

With that I decided to get a dedicated full-size ham-radio PC. Nothing expensive or new, in fact I was looking for ‘older’ models with a native DB9 Serial interface so USB to Serial issues would no longer be a problem. This HP Elite 8200 met the specification needs for what I would be using the computer for and was a reasonable price/availablity. I could add all the audio inputs and outputs to the native connectors and also use the on-board serial (or so he thought…)

HP Elite ports – native Serial Port and audio on-board

Having migrated PC i went about installing first the apps I know, namely Fl Digi and FL Rig. I have been using these for sometime for WeFax and love getting the images in. The good thing about reducing the QRM, i can visually see it has been reduced, as I will show later.

I did run into some issues with communicating with the PC, the Serial Port settings had to be changed on the PC also, by now I had also discovered i had ordered the wrong cable from RS Electronics, but have a replacement on the way. I went back to using a USB to RS232C interface for now, which after some tweaking worked. I’m sure I’m not the only person who would still setup a IF-232C, so here are the settings I used between my PC and the RS232C.

Screenshot of Windows PC Running Windows 10 and USB Prolific based RS232 connector

Incase its hard to read on the screen, heres the tabulated form

Bits Per Second4800
Data Bits8
Stop Bits2
Flow ControlHardware
AdvancedLeave FIFO Buffers at max and on
Table of Settings for the RS232 Port on Windows for Kenwood TS690S and IF232C

In the FL Rig for the Serial port the settings are as follows (Select TS450S as the transceiver) :-

PTT via CATEnabled
Retries..Byte intvDefaults
Init (Click)Connected
FLRig Settings
Kenwood DSP-100 with the IF-232C

Now I dont mind saying that I’m still learning, so understanding what filter to use when is very much a case of ‘try it and see’, but i will show a comparison between before I started all the QRM clean up and the acculmation of what I have done so far *plus* the use of the DSP-100.

WeFAX – local QRM is quite clear with the ‘banding’ visible across the otherwise clear image

As you can see in the above image, there is alot of QRM in the picture, the ‘banding’ consistant across the image, in this case probably caused by the Ethernet over Power adaptors, is very clear.

Here is a scan today, same antenna, but will all the additonal work to reduce QRM and the DSP in Receive mode filtering.

Reduced QRM, what you do see is from a fan running because its hot today 🙂

When less electical items in the house are running, namely fans, washing machines and the like here is an example image. Again, this is the same antenna, same external line filters/chokes and the DSP and recent QRM work outcome.

The ice-chart from Hamburg

The ice-chart from Hamburg is the equivlant for me as the last row on the eye-test exam. The letters on it are incredbly small and the details/dots equally so. Whilst with a zoom there is some slight distortion (so more to be gained!) there is a total absence of the QRM which was so present in the first WeFax image shown.

I am adding a MFJ-1026 to the mix now (Thank you Nevada radios, you are doing a great job during the lockdown !) and I cannot thank Steve from Xggcomms enough for the assistance he has given me. I asked Steve for some help on how would I go about connecting both the xggcomms and mfj-1026 at the same time, as they need access to the T/R Control line present on the ACC-2 port. Sure enough Steve was good enough to reply on how to do this, by way of opening up the connector and adding a connection to pin 13 and ground (I used pin 12 for ground).

From Page 22 of the TS690S user manual

I had recently performed an inventory of all the wires/cables,etc I had, so it was easy to find the phono socket I required to connect the back of the MFJ-1026 phono socket to the ACC2 DIN plug.

I first tested the connectivity between socket and plug, to ensure it would work correcly before opening up the xggcomms. I am generally unhappy about opening working equipment in that I could break it and make it unoperational, but as Steve had already offered his support should anything go wrong, i bit the bullet and went for it. Needless to say, it wasnt an easy job for me who doesnt do this type of soldering reguarly.

I had already pre-tinned and checked the continuity between socket and wire on the phono socket, so was confident that as long as I was careful I would be able to add the necessary wires to the respective pins.

I dont mind saying that upon putting the shielding on and checking before plugging in that i found that the case (which should be grounded/seperate) ended up being ‘shorted’ and no resistance was shown on the voltmeter. Undeterred I undone the case and carefully applied a small piece of masking tape across the top pins ‘tucking’ between pins to give some isolation. I apologize i didnt take a picture of this. This had the required effect and that when the casing and flexible connector were restored, the isolation between pins had been restored.

Having completed the cable, the next step is to install an external auxiliary antenna for the MFJ-1028 to match against. I considered several ideas, as in just using a simple end-fed piece of wire, to a range of ‘small’ antennas from Russia that attracted QRM to be used in this way. In the end I decided to get another DX Commander. Whilst I wont totally multi-band this will all 6 elements (in particular 80m requires alot of space) I can setup the 2nd vertical ‘auxiliary’ about 2~3 meters from the ‘transmit’. With this I should be able to ‘phase out’ both any local QRM as well as distant QRM meaning I should not only be able to get out more cleanly, i should also be able to hear and filter those very feint remote signals that currently sit ‘below’ the noise table.

As ever, I will keep posting with my battle with QRM, which I think I am winning one week at a time.

Webcam – some lessons learned !

So having got my webcam up and running with streaming, i had to migrate the streaming server to another PC (in this case a macbook) and relocate the USB cable going into it.

I resumed my daily antenna observations with the inclusion of checking over the camera and re-routing the cabling from the camera so it would be ‘free’ from the mast allowing more length into the ‘shack’

Come the afternoon I’m now perplexed why i can TX and seem to get out well, but RX is non-existant, apart from 18m, which seems odd. I walk the path backwards of changes, of which there have been a couple in the shack with the QRM bonding and all, to try and work out why my reception is so bad.

As i work thru the devices directly connected to the transceiver, no change in reception. I then go out and check the mast, no problems there. I unplug all the connections between mast and and tuner. No change ! What on earth can it be !

At my whits end I relocate the macbook and suddenly see the usb cable from the mac to the camera, albeit on the 2m/70cm mast, it now does have a different ‘vector’ from mast head into the shack.. could this be the source of my problems.

Low and behold, unplugging the mac and the webcam suddenly the channels come alive again. I had created a USB transmit antenna blocking pretty much everything.

I set about removing the camera and cable from the 2m/70cm mast and tidying the cables I had previously disconnected. Full filtered resumed, minus the webcam 🙁

After all this I remembered the advice from the ARRL and Youtube videos “EVERY THING IS AN ANTENNA, EVEN IF YOU CALL IT SOMETHING ELSE”. Hence why my issue had occured, i saw it as a USB cable, but it was an antenna, and blocking my HF.

I probably can fix this, but I’m already battling QRM and I want to reduce issues, not add new ones, so for now the camera stays off, but I was glad of the experience and I could fix and understand the issues.

The Quest to reduce QRM – Bonding

The never ending quest to reduce QRM continued after following the ARRL Grounding and Bonding book and the excellent ‘clean up your shack video’ from RSGB i have been planning to try out what is discussed.

The excellent RSGB ‘clean up your shack’ video

For my ‘shack’ i used the following components, other things like voltmeters and screwdrivers I already had.

GTSE Twin Pack Aluminium Foil Adhesive Duct Tape14.99
Digitus Assmann DN – 19 Earth Equipotential Bonding19.99
Items for bonding

The objective here is to ‘bond’ all the radio equipment together so it has a common earth, therefore not creating a ‘earth loop’ via the earth pin. Also it gave me the opputnity to fix things down and generally tidy the ‘shack’ radio desk up, as I would have to remove everything from the table.

The first step was to apply the duct tape. I check first that it did conduct before sticking it down ! I got the idea to try tape as I didnt want to spend on metal plates and the ARRL book some temp setups use tin-foil and baking trays – so thought this was a good compromise.

The next step was to attach the ‘earth’ bar. I put it at a ‘safe’ location to the back of the table away from where human contact should not be possible and also to give better accessability to the various earth taps on each component. I measured it up and pre-sunk the holes to screw into to make fixing a little easier

I then set about attaching all the earth, or in this case bonding, wires to the bar and positoning my KPO distribution to a place on the table. This had previously been loose and somewhat annoying and potentially dangerous. I measured up the location, pre-sunk some holes and set about attaching.

With the grounding bar connected to the distribution board I set about adding the devices. I checked for voltage first and kept the wires coiled nicely onto the now metal surface.

Comfortable that the right voltage was making it to the distribution board and the position of the feed & choke to the transceiver was good i set about adding the other components to be bonded together.

So i have completed ‘bonding’ all the HF equipment together. I will add more metal tape to the small shelf the laptop sits on and source a USB bond, which I think for the rig will complete the RF bonding of all the devices. I’ll continue to work around the ‘shack’ with more tape and bus-bars to further reduce the RF loops which go through the common ‘mains’ ground, but i’m satisfied with the measurements on the rig for now.

25/5/20 – additon

I’ve since connected the virtual earth directly to the transceiver. This is what the guidelines say to do, and I’m not about to analyse the deltas between the bus-bar and the virtual ground. When I have more experience of measuring and using the Virtual Ground I’ll see if this can be changed, for now i’m following the instructions so the wire from the ‘bus bar’ to the ‘virtual ground’ are directly connected between Tranceiver and Virtual Ground.

QRM & Power Line Adaptors

So last night (11/5 – 12/5) Turned into a bit of a QRM mission. Not exactly sure how, but found myself really getting trying to find the source of a specific hum, as I am gradually reducingt the amount of interference/QRM I am picking up. I started with taking my little AM radio (D-328) around the house buzzing very present. What I wanted to rule out was the utilitys nearby and the garage. Being 1AM and wandering around with a pocket radio should make for amusing footage on the overnight security video from the garage today 🙂 Anyhow, I could pick none up.

I returned home,sure enough the ‘buzz’ was back. So as it was quiet in the house (trust me, we are 24/7 shop here!) i started going thru the fuse box, its an older one, but still thankfully a trip/RCD (?) type box where I can easily flip the circuits. Sadly the circuits are not labelled, which I find quite unprofessional, apart from the ‘light’ fuse. I started flipping fuses and on the 5th one the buzzing on the radio stopped, as did all the mains power to my study and I think the front part of the house.

I set about unplugging everything in my study with the mains back on, hum still there. So I started to research/googling hum between 50 and 500Khz – it seemed so precise, I figured it must be some form of ‘man made’ interferance.

Here is a video of what it sounds like :-

So you can hear it all the way up from 50kHz to a very loud abrupt end at 500kHz. I set about googling as to what that could be, and sure enough found th GM4FVM page on ‘power line adaptors’. I’ve been very careful to remove and limit the use of ethernet in the house now, so suprised that this had caught me out. I immediatly removed the BT Ethernet over Power adaptors I had. This is the result

A longer video with manual AM tuning and a ‘sweep’ of USB

If you are patient enough to have watched the whole video, i congratulate you 🙂 But you can hear the big difference between what a power line adaptor can do to HF/RF in a shack, i.e. completely destroy all but the strongest signals.

This morning I tried out WSPR, the results on receive and transmit speak for themselves :-

wspr map is somewhat busier…

So now its time for work but I think i have taken another big step in reducing QRM in my shack

Next Steps – reduce this hum MORE and MORE

The ongoing quest to reduce QRM !


So I never knew just how much can be done to reduce QRM and where it comes from ! Having bought some ferrite rings and having mixed results, I found this excellent site from M0NWK who thanks to his equipment and setup can really demonstrate how the chokes work, heres the site which also includes a link to the video here

My build was slightly different, as I cant wire in a main tripper, I can wire in an extension in from an existing outlet, I was pleased to see that someone had already asked this question on M0NWK’s page.

I kept the same ferrites as M0NWK but a smaller box and bought a mains filter to which the ferrite-wound would attached.

Heres my part ilst, I use Amazon Prime alot because things arrive quickly and via decent couriers, if I wanted to get this done in less time I could of sourced cheaper, for example the 6 Way Mains Connector can be bought from Richer Sounds cheaper, but I dont know how quick they deliver or who they use.

PartSourced FromUnit Price
Roundcable snap-it core,300ohm 25mm dia
Stock no.: 4669164 (*2)
RS Electronics14.76
sourcingmap Dustproof IP65 Junction Box DIY Case Enclosure Gray 100mm x 100mm x 75mmAmazon6.89
White 3183Y 3 Core 2.5mm 25 Amp PVC Flexible Cable Cut To Length Flex (10 Meters)17.99
Masterplug Heavy Duty 13 Amp Rewireable Plug, 57.5 x 48 mm, Black4.99
Tacima 6 Way Mains Conditioner and Radio Frequency Interference Filter41.92
Permaplug by Masterplug Two Socket Trailing Socket, without Plug and Cable, 13 Amp, White4.04
GTSE 10 Pack of 12 Way 30-76 Amp Electrical Connector Block, 165mm Length, White Terminal Block Electrical Connector Strips 15.49
Heat Shinkalready had
Table of parts used in the construction of filtered mains feed

I started with stripping back some of the 3183Y Flex to bare out the live, netural and earth wires to wind around the ferrite. The heavy gauge of the wire made this quite a challenge, certianly being able to open the ferrite made a big different in creating a well fitting wire to the ferrite. I used cable ties to keep the ferrite and the wires stable.

The Terminal block comes in a massive pack, but its really good quality and will undoubtedly have many uses in the future, so worth having around. I attached these to the ferrite and wires, but not before attaching heatshrink to the wire going into the terminal. This not only looked good but kept the cable tidy.

I then set about measuring the thickness of the coax to make suitable sized holes into the box. I went in thru one side and so the mains feed and outward to the filter strip plug, nicely gapped so the terminal connectors in the box had a good seperation from them.

When drilling the holes I used a regular drill, but fettled the holes with a small round file to get the edges smooth and remove all the excess produced from the drilling.

The choke in its box – right side is the feed in, left side goes to the power strip with further mains filtering on.

Before plugging into expensive radio equipment i tested on a B&Q light to ensure it would turn on and off/and light. (The lid is back on at this point) As this was my first time using this I kept one hand in my trouser(probably short) pockets, but the lights came on and no problems. I then set about putting it into the mains outlet and to connect the additonal filter

Mains filter after the RF filter which supplies the transformer

You will see the parts list contains 2 ferrites, the 2nd one went onto the back of the radio power supply feed directly

Ferrite on the input voltage to the transceiver

As this is 12V DC and whilst can give a nasty poke, a box isnt necessary here.

I went back to the LW frequencies that had previously been plauged by a ‘buzz’ that had now completely gone ! I went onto 80m and 40m and weak stations were getting thru and loud stations were BOOMING.

Whilst this was a fair amount of work, I’m satisfied it has helped reduce my QRM further.

QRM Hunting / Messy Lab

So having got the bhi DIL DSP Receiver, the amount of QRM I was still getting wasn’t good. Although I was slightly tired, i really wanted to solve this issue.

I followed the DX Commanders Youtube posting on QRM here

So i then set about unplugging things around the house, the first thing I found was an electric blanket ! That put out a huge buzz, but there was still plenty of ‘noise’ amongst the signal. I turned everything off in my ‘lab’ and used a car battery to test –

Car battery, less buzzing…

So off a car battery there was a big reduction in noise, so it was something in the powersupply or surrouding room

At this point I used several of these magents and put on the power line in, HF and transformer

I set about winding, but still noise 🙁

By this time, i was still getting less, but still a big interference. I unplugged *eveything* from the transceiver and it stopped ! So it was something being plugged in.. I went thru each device, lo and behold the xggcomms CAT port was the main offender ! By this time it was getting late, and some much needed family time with a few brews and a good film was required to consider the next steps.

After the film and a nice walk of the dog at 11PM (to avoid other dogs/runners/etc) I cam in and started searching for ferrite cores, sure enough amazon had a huge variety, and on PRIME next day, so I ordered think, great i can get these Monday and get going ! Amazingly, even tho i ordered these at 11PM+, they was here the next day ! I was going to tidy the lab up, but set about attaching all the chokes I could to the cables between the mac and transceiver. The difference was amazing…

FT8 came alive very rapidly !

Within a course of an hour, i had made 9 QSO’s on FT8 on 40m, with 3 already confirmed on QRZ ! I was so happy that everything was working really well !

I think I am going to upgrade my chinese power supply which is meant to drive power-strip lighting, which is fine for VHF/UHF (A recommendation from FRED IN THE SHED on 27Mhz) but for HF I will get a decent 30~40 Amp campable linear PSU for the Kenwood to further reduce the QRM.

Now to stop playing on WSJT-X and tidy this place up !

BHI Dual-In-Line unboxing / Saftey

This is where I miss being a amateur radio club, asking advice of seasoned operators. Thankfully I have my long-time IRC and expat friend PA2TG to call on assistance. I asked about eliminating QRM on HF as I was looking at the many different options available, and varying costs.

After reading my email, PA2TG suggested the BHI Dual-In-Line unit for me, which I ordered from RadioWorld who were incredbly prompt with next day delivery! Whilst I wont do a full review yet, here is the unboxing of what looks to be a very worthy addition to the shack !

I also take my responsiblity of being a Amateur Radio Operator seriously, as much as its a ‘hobby’ it is very well taught module of ‘Saftey’ in even the Foundation. Some may laugh at ‘wiring a plug’, whilst I found the difference in fuses and grid types very interesting ! One thing I do take seriously, and check my antennas every single day. One ‘benefit’ of the lock down is that my antennas are staying up longer, and the guying/mounts are amazing, but today I found that one had completely come off ! Under observation I quickly repaired the guy rope and restored the tension to the mast.

Saftey inspection found the pin had completely come out the ground stake, quickly fixed and tension/support restored.

I have been doing other things in the shack, but will right a summary rather than lots of little postings.

Until then stay safe, 73s 🙂