VMARS Noise Group


The first screen shows a typical autumn noise floor on a quiet mid morning 80m band with just an ambient noise level, in this instance around S4. The second screen shows the same frequency after a single small LED panel light is switched on, causing the noise floor to rise to S8. An example of just one of the types of interference blighting amateur radio. See the offending light in Section 2.2.2.  Click on either picture to hear the interference caused by the same LED light to the reception of a portable AM station operating from Belgium, over 300 miles away. Very good reception until the light is switched on. The interference kicks in around 30 seconds into the recording.

1. Aim and Purpose

1.1 Noise Floor Investigations

a. To help the society understand the different types of noise that can impact our main VMARS operating frequencies at our QTH’s and portable operations.

b. To help the society in understanding, designing, creating tools and appropriate practices for searching for man made noise.

1.2 Noise Floor Solutions

a. Methods of removing man made noise sources once identified

b. Methods and appropriate procedures for addressing man made noise sources belonging to others including neighbours and commercial organisations

c. WEBSDR’s/remote receivers and use of these (including setting up) for assistance in reception on our main operating frequencies

d. Active Loops: - Designing, reviewing, building and using active loops for assistance in high noise noise environments

1.3 Noise Group outputs

a. Information regarding the Noise Group will be published on the VMARS website

b. Contributions will be made for the Publications Officer

c. An annual Noise Group seminar day for VMARS members with

potential guest speaker, presentations and discussion (Held at Baginton village Hall)

     2.           Types of Noise

                       2.1.           The focus for VMARS (where crystal control is commonly used) is on noise impacting the following key frequencies for users:

                                         2.1.1.           3.615 MHz (AM and SSB)

                                         2.1.2.           3.577 MHz (CW)

                                         2.1.3.           5.317 MHz (AM)

                                         2.1.4.           7.143 MHz (AM)

                                         2.1.5.           51.7 MHz (FM)

                                         2.1.6.           70.425 MHz (FM)

                       2.2.           The common types of noise that can impact users are:

                                         2.2.1.           Switched Mode Power Supplies (SMPS)

                                         2.2.2.           LED lights


This LED light is the cause of the interference demonstrated at the beginning of this page. Note the fake CE mark

                                        2.2.3.           PLT

                                         2.2.4.           VDSL

                                         2.2.5.           Solar PV

                                         2.2.6.           Wind turbines

                                         2.2.7.           Wireless charging devices

                                         2.2.8.           TV’s

                                         2.2.9.           Electric Motors

                                     2.2.10.           Overhead Power Cable

Further valid and detailed information can be found in the RSGB Leaflet, “EMC Advice Leaflet EMC 4: Interference to Amateur Radio Reception” dated September 2019 http://rsgb.org/main/files/2019/09/EMC-Leaflet-4-Interference-to-Amateur-Radio-Reception-v1.0.pdf


     3.             Searching for the man made noise and Tools

                       3.1.           NB: If you are searching for man made noise at your QTH, one of the first tests is to identify the noise on a battery powered receiver, turn off the mains to your QTH and see if the noise level has changed.

                       3.2.           Hand portable battery receivers with loop aerials are a good tool for tracing man made noise, Nowadays these can also be in the form of small SDR dongles with a loop aerial and connected to a mobile phone.

[ Examples of such devices used by members, links or articles to be posted here]

                       3.3.           Finding a source of interference requires a methodical approach. The best approach is to start with the broad view and gradually focus in on specific potential sources. Sometimes it is easier to begin by identifying what isn’t causing the interference rather than what is causing it. Once the obvious things have been eliminated, then the best strategy is to work through nearby devices that could be the cause, searching the possible locations from where the interference can originate, and looking at the characteristics of the interference to help identify it. [Source: RSGB]

                       3.4.           Valid and detailed information can be found in the RSGB Leaflets

                                         3.4.1.           EMC Leaflet 4: Interference to Amateur Radio Reception” dated September 2019 http://rsgb.org/main/files/2019/09/EMC-Leaflet-4-Interference-to-Amateur-Radio-Reception-v1.0.pdf

                                         3.4.2.           EMC Leaflet 16: “Background noise on the HF Amateur Bands” dated December 2017


                                         3.4.3.           EMC Leaflet 14 “Interference from In-House PLT”


                                         3.4.4.           EMC Leaflet 15 “VDSL Interference” dated January 2019


     4.           Technical Solutions to Noise

                       4.1.           Once any man made noise source is identified, one needs to ask the source owner (which maybe yourself) about it’s technical requirement in order to assess whether to simply switch it off or consider a technical “noiseless” solution to the requirement.

                       4.2.            Noise Cancelerhttps://www.youtube.com/watch?v=qNZZ8XwJiYI

[Homebrew designs, articles and products to be shown here]

                       4.3.           SMPS noise suppression https://www.ato.com/how-to-reduce-switching-power-supply-noise

[Homebrew designs, articles and information to be shown here]


                       4.4.           WEBSDR’s

                                         4.4.1.           WEBSDR’s have become popular for VMARS members with some running their own and many using these services as remote receivers with their local transmitters. Good examples of WEBSDR’s can be found here (Search criteria can be applied to find those in UK):

                                                            WEBSDR http://www.websdr.org/

                                                            KiwiSDR https://sdr.hu/

Other internet SDR sites are available

                       4.5.           Active Aerials

                                         4.5.1.           If noise sources cannot be identified or removed, then active aerials are an excellent solution and do not have to be a high cost solution. Active loops for example.can improve reception by up to 3 S points.

                                         4.5.2.           Active Loops:

                                                            Wellbrook Loop https://www.wellbrook.uk.com/loopantennas/(Other active loop manufacturers/suppliers are available)

                                                            Wellgood Loop https://www.george-smart.co.uk/projects/wellgood_loop/

                                                            An Active Loop Aerial for 80m, (Signal Issue 11, April 2009)

[Link to Article]

                                                            Valve active loop amplifier (Signal Issue ??, ??? 2019)

[Link to Article]

                                         4.5.3.           Active Rods/Whips (e.g. mini-whips)

                                                            [Articles required]

                                         4.5.4.           Remote aerials

                                                            [Articles Required]


     5.           Annual Noise Group Seminar (VMARS members only) - Announcements will be made here and in our VMARS Newsletter

Related Links:

1.     Ofcom form for reporting interference: NB: The terms for OFCOM to investigate are that it is free of charge if the source of the problem is external to the property. If the problem is within your own radio system or from something which OFCOM consider to be under your control then they will charge for the investigation at £92.14 + VAT per man hour used.  (MAKE SURE THAT YOU HAVE SWITCHED YOUR PROPERTY MAINS OFF FIRST AND TESTED WITH A BATTERY RECEIVER)


2.     Radio Interference Information - UKQRM (With Groups,IO) https://www.ukqrm.org.uk/

3.     Power Line Technology - https://www.ban-plt.org.uk/

4.     RSGB EMC - https://rsgb.org/main/technical/emc/

     5. Shortwave Listeners Guide -  http://www.listenersguide.org.uk/

Reference Material:
       1. The S Meter - Measuring Signal Strength - http://www.listenersguide.org.uk/swl/measuring-radio-signal-strength/

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