Every mW can matter when using legal CB and HF ham bands phone modes

Most people know, in short, that significant changes in TX power are required to make a noticeable difference to RX stations S meters and so this is not a write up going over known mathematical formulas easily found elsewhere. What this is, is just a few notes with explanation of why squeezing every mW of TX power out may help you to be heard and what you could do to achieve this.

In his book "Minimum QRP: Doing more with under five watt amateur radio" Peter VK3YE presents an S plotted graph and describes his experience of using various TX powers up to 100 W. He, like other people have found that dropping TX power from 100 W just a little that no one noticed. Dropping a little more and most people still heard him. Similar drops in power further down the graph made a more significant difference in who heard him. The S graph flattens out again when reducing in the same steps when into mW levels.

I have recreated his graph as I don't have permission to copy and paste it directly from his book. It's a close representation of his and his findings. Additionally, I have put some notes on it regarding compression (notes about this below).



Look at the percentage change of people that could hear him when lowering from 100 W to 50 W (halving power).. not a big change. Compare that to the percentage that could hear him when lowering from 10 W to 5 W (again halving power).. a much more significant amount of people.

Obviously, there are a huge number of other variables that are at play when trying to get yourself heard, e.g. propagation, antenna types, location, operation technique etc etc, and bands being worked (his findings were logged using 7MHz btw). But, when restricted by 10 W power levels (foundation licence) or 12 W CB levels (SSB mode), should his findings be ignored?

Physical practicalities and costs will mean a lot of people will not be bothered by the findings, and I still heartily agree with the words "any radio is better than no radio and any antenna is better than no antenna". So much fun can be had with so little and little cost. But his findings do show very small gains in output TX power may just be enough to make the difference between being heard or not. So maybe contentious changes like the following will help to get heard:

- Swapping out your RG58 for RG213 is actually a good idea. Or reducing the coax length and swapping it all out for LMR400.
- Removing all inline coax devices like meters, coax joins and switch boxes to gain you a fraction more TX power to your antenna.
- Ensuring your antenna is perfectly resonant and not using your inbuilt ATU to ensure max TX power is utilized.

Some people might like to try examples I have given like the above, but as I said because of physical practicalities and cost many won't. For myself I am using RG213 at home, but I can't shorten the length much more and I am not going to pay out to exchange it for LMR400. I keep my inline coax devices to a minimum, but keep one meter inline always to make ensure the station is functioning correctly and legally on TX.

One thing that does significantly assist in being heard though, when using SSB primarily, is using properly setup speech compression (David Casler on youtube has at least one video that explains this well). Increasing average power by 20% can up the percentage of listeners you are heard by significantly when using PEP power allowed by us (see the notes I put on the graph above). My own findings have shown me that switching in or out compression can make the difference of making a contact or not. Peter's words to me regarding this were short and clear and backed up my own findings "Clean compression will improve readability when your signal is marginal. Every bit helps at low power."

This was just some waffle and food for thought and discussion, and not intended in encouraging unnecessary spending or people peaking their 4 W CB's out to 6 W and burning them out quickly etc. But maybe if you are looking for a new radio you might want to look for one with compression built in, or if a new mike then one with compression features…

Nice write up Neal and an enjoyable read. Well done.

As you say there are some contentious points raised and the common 'coax' issue is one I've managed to avoid arguing about. If people are happy to buy more expensive coax, change SO/PL-259 to N-types etc. then good for them and I hope it all serves them well.

You may remember that I ran a multiple dipole fan array previously all hooked up via coax which was great on their resonant frequencies. However once I strayed away from their resonance or even tried to achieve other band usage via an ATU the performance was not as expected. Most told me "what do I expect" and pointed out the fruitlessness of utilising ATU's, matching or coupler circuitry due to losses, SWR problems etc.

But if "resonance" was the golden key then how come everyone was happy with their 5/8ths antennas or collinear type antennas?

Sure enough if you 'open up' or disassemble one of these antennas you will often find inductive coils and small capacitors all in the name of providing a match to the 50 ohm coax feeding it. Not much different from the capacitors and inductors used for matching in an ATU then?
(There are still debates as to whether this should be done at the antenna end with the 'coax' still being the issue.)

I had started exploring ladder line fed antennas, namely "doublets" and was met with a barrage of "Oh No!" and some quite angrily so. Apparently all those radio enthusiasts from old were quite wrong in their assumptions and the use of archaic devices and means such as ladder line was totally 'outdated'. Yet many DX records from those old timers remained so for many a decade unabated or beaten by modern methods.

Surely there must be something in it?

It was after being given some confidence by one of the members here at Charlie Tango, (The DB), also reading an article here :- Non-resonant vs resonant antennas that I explored these options further.

I'm still exploring them, still figuring out the best methods to provide 'balanced' loading but so far enjoying the results I'm getting. My 44 foot doublet favoured by eminent scholars such as Les Cebik is serving me well and considering the multi-band functionality I am enjoying I would hardly call it a 'compromised' antenna.

Some will continue to argue this and that's a very good thing when done sensibly, for then we may come to finally herald the truth or even multiple truths.

I just like that the arguments for older antenna technologies means I can build or homebrew feeders, matchers etc. whereas the arguments for 'modern' technology and 'coax' means that I have to buy stuff, then buy more expensive stuff and so on.

So just on that basis alone I don't bother arguing about it. Each to their own.


I agree completely on correctly applied 'speech compression' for SSB use which is why my old Yaesu FT290R now sports a 'homebrew' mod to enhance the SSB audio at the RF side of things rather than distorting the original AF signals. Makes the little 2.5 watt output of that little radio sing gaining reports of greater legibility despite low S readings.

Same can't be said for the terrible 'processor' on my Yaesu FT757gx but I'm hoping to mod that up with a similar process as I used on the FT290.


I do love a bit of QRP and hence why I'm totally happy with my Foundation level licence squeezing radio enjoyment from every meager Watt I have available. For others 'progress' up the licence system to gain more Watts, purchasing linears and placing antennas atop their house you can see from space is their thing.....and I'm very happy for them.

Enjoy your radio, no matter what.


Brilliant stuff again there Neal and got the 'juices' going. Awesome stuff and worthy of a 'Thanks'.
(As you know I'm a fan of Peter's work and nice to see others enjoying his words also.)

All the very best,
Victor

Sort of agree with this but for Rx reasons more than Tx having weak signals coming in makes sense to run as smooth as you can where as Tx you can just up the power and as a foundation holder that would be at the aerial so if you’re running long lossy coax with lots of joins and in-line crap adjust your output accordingly so as you still get 10 at the aerial might mean you need to run 15/20 whatever to achieve this.

On a coax note again it’s not just a tx thing if you want to run cheap poor shielded Rg58 be my guest but it will be subject to more spurious Rf and interference than better shielded stuff

Great article and thank you. i really would love to see some serious qrp efforts in the 11 m band...but i'm out numbered by the big boys (from here and the U.S) on all frequencies. on a quiet channel, clean modulation and a good beam antenna works wonders.
thanks!