QRM

QRM is "man-made interference", as opposed to QRN "natural interference".

Are Compact Fluorescent Lamps (CFL’S) RF Quiet?

By Gary Ryan VK2ZKT

There has been a lot of exchanging of views about these lamps in the press of late and it revolves around the light output and the initial purchase price and are they worth the expense.

I will leave this subject to other’s to thrash out.

In this review I will present my personal findings during a range of experiments I conducted.

I wanted to see if the CFL would add any background hash to the amateur radio bands and in general to short wave and broadcast bands.

For my test set up I used the following.

1 x 500 Mhz RF Spectrum Analyser

1 x Sony portable three band portable radio

1 x Kenwood R600 Communications Receiver

1 x Telescopic whip antenna for the input to the spectrum analyser

1 x Philips GENIE 14 watt CFL (Cool Daylight) model

Test arrangement

The Genie Lamp was mounted on the workbench and the spectrum analyser was located 1 mtr away with the Telescopic whip fitted to the input.

The Sony portable radio and the Kenwood R600 were 1 Mtr distance from the lamp. Short 3 Mtr wire antennas were used.

Obtain a base line

The spectrum analyser was set up and a base line reading was taken in the shack on background noise floor levels.

Test Number 1

The analyser was tuned across the RF spectrum between 200Khz and 500Mhz and the CFL turned on and off to see if any response was found.

Result

The CFL radiated an RF energy pulse that was broadband in nature and lasting for a period of 1.5 seconds at each switch on period. The pulse was up to 5 Mhz in width and at random intervals from 200Khz to 95 Mhz. The intensity was in the order of 15 DB from the base line floor reading

Monitoring the noise on the Sony portable radio on Broadcast AM band produced what sounded like 100Hz power supply buzz that blocked out completely all radio stations outside the local reception area. The Radio station in Kempsey on 531 Khz was completely swamped.

Following the 1.5-second start up period the broadcast band was left with a background buzz of the same type but a slightly lower intensity. The reading on the analyser was in the order of 3 db off the base line.

Test Number 2

The lamp was turned on and off and it was noted that a permanent rise in background RF noise with lamp on was centred on 41 MHZ. The rise was spread either side of this out to plus and minus 5 MHZ. The peak was 6 DB above the noise floor.

Another significant rise was centred on 3.1Mhz in the same magnitude.

Test Number 3

Using the Kenwood R600 the same results were confirmed on the broadcast band and on 3.1MHZ the 100 Hz buzz was very noticeable. Signal strength on the S meter indicated S7.

Conclusion.

CFL’s are not RF quiet and despite having the “C” tick and electrical authority approval they do indeed radiate RF energy.

Remember that for this test I used a well known brand, it makes you wounder about the other less well know types how they would perform in these and other tests.

Also remember that some house holds possibly your neighbours have dozens of these lamps installed, that is a lot of RF been radiated

Personal Observations

I have used one of these lamps in my shack for a period of one (1) month and have removed it. The light output despite all the claims is not the same as a 75-watt light globe and they also contain phosphor and mercury along with the inverter circuit contained inside the base of the lamp. They cost at the very best 3 times that of a quality incandescent globe and I am sure that the carbon footprint to make them is a lot larger.

I have seen Hams use these devices in Magi Lamps. If you are fault finding a circuit how much RF hash are you introducing into the circuit under test and possible into your test equipment as well?

I am also reliably informed that the New Zealand Government has reversed a decision to ban the humble incandescent light bulb in recent weeks.

Propagation and radio wave theory
Propagation	Aurora * E-Skip * IPS * Lightning scatter * Meteor scatter * Satellites * Trans-Equatorial Propagation * Tropospheric ducting
Interference	QRM * QRN
Theory	Electromagnetic Waves * Frequency Wavelength and Period