Need Filter parts?  

(This article is also updated with members feedback lower down)


Several people have asked where they can buy parts from for the Filter kit, either because they missed the NARC bulk buy in December, or they want to buy a few extra parts.

The article as described on NARC Live was recorded and the recording can be seen here:


Ian's GM3SEK website with excellent projects - scroll down for the Filter project including the complete slide set of the presentation which shows construction in more detail.


The following are the main components of the kit as specified by Ian along the suppliers you can buy them from which are either used by Ian and or myself when I organised the NARC bulk buy. They are not necessarily always the cheapest supplier, but they are consistent suppliers and all parts are in stock as I write this on 18.1.22.

73 de, David G7URP




CE-TEK GR17012             Suggested supplier:       CPC code EN84544



Cable Gland (2 per kit)

ProPower PG-11 Black                     Suggested Supplier:      CPC code PG-11 Black



Mains filter

Schaffner FN2030-16-06                  Suggested supplier:   Mouser code: 631-FN2030-16/06


Main Ferrite 

Fair-Rite core 0431177081                 Suggested supplier:   Mouser code: 623-0431177081



Smaller Ferrite (2 per kit)

Fair-Rite core  2643167851                Suggested supplier:   Mouser code: 623-2643167851


Tip: Label your Ferrites with their part numbers as soon as you receive them as they look identical to others yet perform very differently!




High temperature flex such as 3093Y 2.5mm is recommended for the filter and this is available from several sources online and locally, eg Screwfix supply 5m lengths as below for collection from a local branch and you will need at least 3m for the filter as described.


Cable update 3.2.22:

Thanks to John 2E0TWQ who shares that Screwfix are currently out of stock but he found it available on eBay under item number 202336536417



David G7URP's buying notes

Note that Mouser has warehouses in Germany and USA but currently if you order over £45 shipping is free and VAT prepaid - the £45 should be exceeded if you purchase the mains filter and ferrites from them all at once.

This information was my experience and is offered in good faith but neither NARC or I can accept responsibility for any errors or problems ordering parts or performance of the filter etc.

David G7URP     18.1.22




NARC Members additional feedback on the Mains filter which came in after the show...


From John 2E0TWQ:

A very useful video showing how to make the filter:

And a surplus filter which might be useful as found on eBay but the seller has a large quantity:



Additional feedback on the Mains filter for NARC members by John 2E0TWQ:
Completed the build this morning add the inline filter to the earth the one i got on Ebay.
This afternoon i have just tested the Mains filter i built and this was on my computer and Flex3000 SDR radio surprised.
Although i did not get the kit at the time of the Narc bulk buy and bought the parts a couple of weeks later i am well pleased with the performance of the kit and the added inline filter to the earth.
I have enclosed some pictures of my build before it was installed.





From Ralph 2M0RHT

I attach photos which I hope help others. It works for me so I must be doing something right. A bit of experimentation does no harm. For me, the + and - go through the filter therefore the earth should do the same. Therefore I constructed my filter as per the photo. Hope this helps others.


 IMG_0761.jpegIMG_0764.jpegIMG_0764 (1).jpegIMG_0763.jpegIMG_0762.jpegIMG_0761 (1).jpegIMG_0759.jpeg




From Malcolm G3PDH:

David,  a very interesting discussion on Wednesday.  

Just to reiterate my points, Firstly there seemed to be debate on some reflectors about which way round the metal can filter went.  I assumed that LINE was the mains in and LOAD the output to the toroidal and output.   
My mains earth connects through from the earth tag on the can filter to the cables going around the toroids and to the mains output from the filter.  I have not connected that earth to anywhere else such as an external earth.
A definitive circuit diagram would be useful and confirmation as to the direction of the can filter.
As I said I don’t seem to have any mains borne interference but decided to keep it in circuit as good engineering practice and it could help with any RF going back into the mains from the TX, particularly the Linear Amp.



From Bob G7JTZ:

Following discussion on the mains fitter /earthing I have took another look at  Solving Urban QRM with Tony G2NF 
Near the end of the show Tony put up a slide Mitigation actions 1 – earthing.
And in it  mid way down it states the following
DO Not disconnect the mains supply earth line use. use the shack mains filter  ideally with an earth- line choke.
Remember 50Hz fault currents elsewhere may prefer your earth in preference to the designated path.
As our filter do not have an earth- line choke you can put A Schurter ACT-1166 E-line choke  16A/20uH  about £12-60.
in the in the in coming earth.
Again this is in the next silde of Solving Urban QRM with Tony G2NF 
From Bob G6PWS:
I have built my filter box within 2 days of getting all from Alan

Wound my cable as tight as I could and just that bit more heated and left for 30mins before releasing stayed good and tight.

Once done it made a remarkable difference S1 down at least so can mark as a 1 from me.

Much cleaner signals coming in especially on top band. Pictures show in working position running just radio power supply and its computer system

Amazing what difference it made! Used other ferrites to wrap onto power lead for computer and coax cables

One problem I had was that I have a outside motion light switch which when I did transmit on 80mts it switch on the outside lights

Which to me was no problem but because our front door has a small window in and the light shone through

My wife got fed up with keep going to the door to see who was there?? Or wasn’t?, But all seems ok now?!