Thursday, February 26, 2009

Safety Code 6

As a licensed amateur radio operator in Canada this is my personal interpretation of Safety Code 6. I am presenting this here for any like minded amateur radio operator who is interested in this topic.


The Radiocommunications and Broadcasting Regulatory Branch of Industry Canada states in "CPC-2-0-03 Radiocommunication and Broadcasting Antenna Systems" (link) that Health Canada has established safety guidelines for exposure to radio frequency fields, in its "Safety Code 6" (link) publication.

"Safety Code 6" states that current studies in Canada and other countries indicate that there is no evidence that a person will experience adverse health effects from exposure to radio frequency fields, provided that the installation complies with Safety Code 6.

It is my responsibility that my amateur radio station comply with Safety Code 6 at all times.

Safety Code 6

Safety Code 6 recommends general procedures for ensuring that exposure of the general public in the vicinity of RF devices is not greater than the levels specified in this Code. A safety factor of approximately 20 to 50 was incorporated with reference to the scientific-consensus threshold for adverse health effects.

Field Strength Limits (Source Safety Code 6)

Within the 3 to 30MHz bands, a person shall not be exposed to electromagnetic radiation in a frequency band listed in Column 1 of Table 5, if the field strength exceeds the value given in Column 2 or 3 of Table 5, when averaged spatially and over time. The spatial averaging is carried out over an area equivalent to the vertical cross-section of the human body (projected area). A time-averaging period of 0.1 h (6 min) should be employed for frequencies up to 15 000 MHz.

src: Safety Code 6

Canada's National Amateur Radio Society (link)

States that while Industry Canada expects radio amateurs to meet the requirements of Safety Code 6, generally most amateur installations will never exceed the recommended exposure limits. There are many reasons for this including the fact that most amateur installations are operated at relatively low power levels (typically 100 watts), are not on a 100% continuous duty cycle and the amount of transmission time is often limited."


From Table 5

From 1 to 10MHz, Electric field strength is limited to 280/f (V/m) and Magnetic field strength to 2.19/f (A/m).

From 10 to 30MHz, Electric field strength is limited to 28 (V/m) and Magnetic field strength to 2.19/f (A/m).

For each band from 80m to 10m the table below captures the E and H field limits according to the safety code 6 definitions.

I assume 200W output from my rig, which is worst case. 100ft of feed line is assumed with 1.3dB/100ft at 30MHz. To get the losses at other frequencies I scaled the loss by the frequency of each band. I assumed a 3dBi antenna gain which is correct for the Cushcraft R8 Vertical. Effective radiated power is 380W to 290W.

Power density is calculated assuming a worst case 3m distance to the antenna.

For PSK modulation I assumed a 50% time averaging over 6 minutes which is consistent with PSK operation, as I listen 50% of the time, and a typical transmission is much less than 6 minutes. On the other hand I assume duty cycle of 100% when I am transmitting. This factor would be less than 100% for SSB
and CW for instance.

Operating Mode Duty Factor
Morse code (CW)
SSB phone
I then calculated the resulting averaged E and H field strengths.

Simply taking the ratio of the resulting field strengths and the limits results in a safety margin over and above Safety Code 6.

A copy of this file is available at Google Docs at link.


Band (m) 80 40 30 20 17 15 12 10
Freq (MHz) 4 8 10 15 18 20 25 30
E Field Limit (V/m) 75 37 28 28 28 28 28 28
H Field Limit (A/m) 0.58 0.29 0.22 0.15 0.12 0.11 0.09 0.07
Transmitter and Antenna

Output Power (W) 200 200 200 200 200 200 200 200
Feed line (ft) 100 100 100 100 100 100 100 100
Feed line Loss (dB) 0.2 0.3 0.4 0.7 0.8 0.9 1.1 1.3
Antenna Gain (dBi) 3 3 3 3 3 3 3 3
Effective Radiated Power (W) 384 370 361 344 335 327 311 296

Distance to Antenna (m) 3 3 3 3 3 3 3 3
Power Density (W/m^2) 3.40 3.27 3.19 3.04 2.96 2.89 2.75 2.62
Averaging (PSK-31)

Time averaging
50% 50% 50% 50% 50% 50% 50% 50%
100% 100% 100% 100% 100% 100% 100% 100%
Resulting Fields

E Field from antenna (V/m) 25 25 25 24 24 23 23 22
H Field from antenna (A/m) 0.07 0.07 0.07 0.06 0.06 0.06 0.06 0.06
Safety Factor

E Field
2.9 1.5 1.1 1.2 1.2 1.2 1.2 1.3
H Field
8.7 4.4 3.4 2.3 2.0 1.8 1.5 1.2

Feedline dB/100ft 1.3

MHz 30


I would state that a Cushcraft R8 vertical at 3m, being fed with a with Rig power of 200W in PSK mode and 100ft of feed line will pass safety code 6.

There are details concerning the Safety Code 6 in the near field which I have not reconciled.

I believe the calculation above to be correct, however all should realize you are accountable for your own calculation, should you attempt to do one for your own station.

Tuesday, February 24, 2009

Buddipole 4NEC2 Model Files

I have found a way to post my 4NEC2 Buddipole modeling files on line using Google Documents.

Eventually I will log many of my design files here for anyone to use.

4NEC2 is available at

Below is a list of the files I have created.

FILE AC_Vbud_40M_09_V01
40m Vertical, (longwhip, 4 dipole arms, red coil)
FILE AC_Vbud_40M_08_V01 40m Vertical, (longwhip, red coil, 4 dipole arms)

Detailed Files:

FILE AC_Vbud_40M_09_V01

Description, LongWhip with RedCoil and 4 Dipole Arms on VersaTee w/ TRSB set to 25ohms (2:1) and 1 8.6m Counterpoise.

This is a new configuration
a) attempting to generate a lower takeoff angle and more gain
b) 40m PSK31 frequency (7.07MHz)
c) Red coil was moved to below the arms and whip
d) Suggested by Ray (K7RFW)

1 fully extended Long Whip
4 22" Dipole Arms
1 RedCoil tapped turns from Bottom
1 Versatee
1 TRSB,(2:1) 25 ohms
1 8.6 (m) Counterpoise

Takeoff angle 30 degrees
Gain 0.0 dBi
SWR 1.6 into 25 ohms

Moving the red coil to below the dipole arms, resulted in a modest loss of antenna gain from 0.6dBi to 0dBi, the take off angle remained the same at about 30degrees. The inductance needed to maintain the antenna at resonance (7.07MHz) was reduced from 15uH (18 turns form the bottom) to 10uH (25 turns from the bottom). Best case SWR was increased from 1.1 to 1.6 as the impedance of the antenna decreased from 22.5ohms to 15.6ohms.

Overall, I would take from this, that is it better to not have the coil placed adjacent to the feed point.


FILE AC_Vbud_40M_08_V01

Description, LongWhip with RedCoil and 4 Dipole Arms on Versatee w/ TRSB set to 25ohms (2:1) and 1 8.6m Counterpoise.

This is a new configuration
a) attempting to generate a lower takeoff angle and more gain
b) 40m PSK31 frequency (7.07MHz)

1 fully extended Long Whip
1 RedCoil tapped 18 turns from Bottom
4 22" Dipole Arms
1 Versatee
1 TRSB,(2:1) 25 ohms
1 8.6 (m) Counterpoise

Takeoff angle 30 degrees
Gain 0.63 dBi
SWR 1.11 into 25 ohms


Sunday, February 8, 2009

Special QSL Cards

Two new QSL cards will be on their way.

For the winter camping "DX-pedition" I made up the card below, it shows the Yurt, and the cozy operating station inside. The globe was generated from Google Earth through Ham Radio Deluxe and the IC7000 radio image complete card.

I've been running the call GC3IAC since the beginning of February in celebration of The International Year of Astronomy. The special prefix call sign starts 1 Jan 09 and ends 27 Feb09 23:59 UTC

VE changes to CG, VA changes to CF, VO changes to CH, and VY changes to CI

I have not posted these in the mail but I will in the next few weeks.