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Amateurs and and U.S. experimental licence holders operating on the LF and MF bands, are limited in the amount of power they are legally able to run. Unlike the HF bands, where maximum power limits are expressed in either DC power input or PEP output, LF and MF operators are required to observe ERP or EIRP limitations. Canadians operating on 2200m are limited to 1W EIRP and to 5W EIRP on 630m.

Although this doesn't sound like much, mustering this amount of effective power can be quite a task on either band, especially on 2200m. This is due to the very poor efficiencies encountered when using antennas that are so small in size compared with what would be considered 'normal'. For example, a typical 1/4 wave vertical used on 40m is about 33' high and with a good radial system can achieve efficiencies in the 80% range, while the equivalent antenna for 2200m would be 550m or about 1800' high ... a little large for most suburban backyards!


The equivalent of a normal 2m 'rubber-ducky' antenna when built for 2200m would be over 600' tall, while one designed for 630m would be around 170' high! A 2" stub used on your 2m hand-held would be the same as a 56' vertical on 630m. Consequently, most LF / MF backyard antennas will realize efficiencies of less than 1% and likely, quite a bit less.

In order to reach the maximum radiated power levels allowed usually requires several hundreds of watts, especially on 2200m, where near kilowatt levels are needed. These small radiated power levels might seem discouraging but they don't account for radio's great equalizer ... propagation. More than anything else, RF loves to radiate, and at times, what can be achieved on these bands with such low effective radiated powers is stunning

It would seem that Industry Canada did us no favors when they stipulated LF / MF power levels to be measured in EIRP and not the, much easier to calculate, DC power input level ... or perhaps they did. I think that, unlike on HF, imposing EIRP rather than DC input power limits puts everyone on an even playing field. Amateurs with lots of real estate and room for a larger, more efficient LF antenna, will be required to run much less power to reach the allowable EIRP and 'stay legal', compared to someone with a small backyard in the suburbs ... the latter can legally generate the higher level of DC input power required to reach the EIRP limits since their smaller antenna is operating at less efficiency. However, determining EIRP is not as cut and dried as measuring input power.

With some fairly sophisticated (ie. expensive) field strength measuring equipment, not typically found in amateur radio operations, ERP / EIRP can be readily determined. This means that for most amateurs,  alternate methods must be used.

Neil, WØYSE in northern Oregon, who runs an experimental 630m station under the call of WG2XSV, has produced an excellent treatise on calculating your station's EIRP level, providing a step-by-step procedure to follow.

In order to determine your ERP / EIRP, you must first determine your antenna's radiation resistance. Two methods of calculating the antenna's radiation resistance for both verticals and top-loaded verticals (inverted L's or T's) are demonstrated, using the physical size of the antenna in relation to the frequency of operation. Once this value is known, the antenna current is measured while transmitting. These two values allow the Total Radiated Power (TRP) to be calculated. The TRP is then multiplied by 3 to yield the EIRP or by 1.82 for ERP. Roughly speaking, 5W EIRP is the equivalent of 3W ERP. Thanks to Neil for this helpful resource.

An alternate method of roughly determining ERP / EIRP values is an interesting new online 'antenna simulator' at the 472kHz.org site. Using known physical sizes along with your ground quality description, the calculator will indicate what total power output is required to produce various levels of ERP and EIRP as well as expected antenna currents, at 472kHz. It's a good starting point if you are either planning a new antenna system or perhaps, repurposing an HF antenna such as an 80m inverted-L or an HF center-fed dipole for use on 630m.

There are also a number of online calculators, such as found here, that will indicate your ERP / EIRP value when you plug in your antenna's 'gain' figure along with your TPO value. Some of the better antenna modelling programs can produce estimates of your antenna 'gain' at 630m and from there it is a simple matter of calculating what power is needed to reach the legal level.

I'm sure there will be a lot more information and discussion about this topic once the LF and MF bands are released in the U.S.A. but in the meantime, calculating your ERP / EIRP levels is not as hard as it might initially seem ... and is likely accurate enough for most agencies overseeing amateur radio activities.
Steve McDonald, VE7SL, is a regular contributor to AmateurRadio.com and writes from British Columbia, Canada. Contact him at [email protected].

Part one of our look at the Digital Modes.

1:05:29

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George Thomas, W5JDX, is co-host of AmateurLogic.TV, an original amateur radio video program hosted by George Thomas (W5JDX), Tommy Martin (N5ZNO), Peter Berrett (VK3PB), and Emile Diodene (KE5QKR). Contact him at [email protected].

This morning I noticed that my last post "A CW contest surprise" is not showing up on the blogs that follow me. I have just been able to see the post that was done 5 days ago on their blogs?? I have not changed any settings and I use Blogger to host my blog. Any info regarding this odd happening would be great!
Mike Weir, VE9KK, is a regular contributor to AmateurRadio.com and writes from New Brunswick, Canada. Contact him at [email protected].

In this episode, Martin M1MRB / W9ICQ is joined by Leslie Butterfield G0CIB, Matthew Nassau M0NJX Andy Mace M0MUX to discuss the latest Amateur / Ham Radio news. Colin M6BOY rounds up the news in brief, and this episodes feature is Operating Portable.

• New UK Ham Radio Guidance
• Easier Ham Radio Authorization for Olympics
• Ladyada Awarded Ham Radio License
• Ham Radio Commutes and Secures West Bengal
• Live Audio on DMR Brandmeister
• Romania Hams Get 5 MHz Allocation
• 50watts for Australian Foundation?

Colin Butler, M6BOY, is the host of the ICQ Podcast, a weekly radio show about Amateur Radio. Contact him at [email protected].

In this episode, Martin M1MRB / W9ICQ is joined by Leslie Butterfield G0CIB, Matthew Nassau M0NJX Andy Mace M0MUX to discuss the latest Amateur / Ham Radio news. Colin M6BOY rounds up the news in brief, and this episodes feature is Operating Portable.

• New UK Ham Radio Guidance
• Easier Ham Radio Authorization for Olympics
• Ladyada Awarded Ham Radio License
• Ham Radio Commutes and Secures West Bengal
• Live Audio on DMR Brandmeister
• Romania Hams Get 5 MHz Allocation
• 50watts for Australian Foundation?

Colin Butler, M6BOY, is the host of the ICQ Podcast, a weekly radio show about Amateur Radio. Contact him at [email protected].

I was reading a fellow blogger Bob VA3QV post about the CQ WW CW 2015 contest and how he did in the contest. It got me thinking to head over to see how I did, I gave a rather part time effort and the conditions were not all that great...surprise surprise. Since moving into the condo I have not been giving the CW contests the effort I have in the past. I entered the contest Single op, QRP single band (15m). I read the results with shock........1st place in Canada, 10th in North America and 29th in the world. I was pleasantly surprised.
Mike Weir, VE9KK, is a regular contributor to AmateurRadio.com and writes from New Brunswick, Canada. Contact him at [email protected].

Amateur Radio Weekly is curated by Cale Mooth K4HCK. Sign up free to receive ham radio's most relevant news, projects, technology and events by e-mail each week at http://www.hamweekly.com.