Many thanks to Scott (KK4Z) who shares the following post from his blog KK4Z.com:
There is always a lot of talk about QRP vs QRO, 5 watts vs 10, ad nauseam. So today I thought I would run the numbers and see what the real deal is. First we need a few definitions. An S-unit in general terms is the minimum change in signal strength to be just noticeable (k3wwp.com). In more technical terms it equates to approximately 6 db in change. The decibel (dB) is a logarithmic number. Each 10 dB represents a factor of 10 difference. This may be a little out there for some so we will cut right to the shortcut. There are two types of logarithms. For calculating dB, use the common logarithm which is base 10. To see if your calculator uses the right one. Punch in 100 and then log. The answer should be 2 which equates to 10 to the second power which equals 100. This is not a technical paper but an entry way to see how changing the power levels affect the signal level of your transmitting signal. As you guessed, it is not linear.
Let me introduce an equation:
Where Power P1 is the power you wish to evaluate and reference power P2 is your starting power. Let’s take going from 5 watts to 10 watts. The equation would look like this:
We take 10 and divide it by 5 which give us 2. Then we hit the log function on our calculator which gives us 0.301. Multiply that by 10 and you have about 3 dB in gain or about one half of an S-unit (remember 1 S-unit is equal to 6 dB). Let’s do one more by hand and tackle the QRP/QRO debate. How many S-units will increasing power from 5 watts to 100 watts give you? The equation looks like this:
Take the 100 and divide by 5 to give you 20 and then hit the log function to give you 1.301. Multiply by 10 for 13.01 dB. Divide 13.01 by 6 dB and you have 2.17 S-units. Going back to our definition that one S-unit is the minimum change in signal strength to be just noticeable shows that going from 5 watts to 100 watts is not that great of a change.
Let’s let the other shoe drop. What about going from 5 watts to 1500 watt? That will give you 4.13 S-units of gain vs 1.96 S-units going from 100 watts to 1500 watts?
This gives you a fairly easy equation to help you evaluate your needs based upon empirical data. Running 20 watts over 5 gives you 1 S-Unit. Using less power means less drain on the battery for longer operation. This is only part of the equation. Propagation, antenna, mode used, and station efficiency all play a part. Have fun and maybe don’t toss the QRP radio yet. 🙂
Many thanks to Scott (KK4Z) who shares the following project from his blog KK4Z.com:
Paddle Mount for the IC-705
I kinda like the idea of being able to mount your paddle to your radio when operating portable. You can use the weight of the radio to help prevent the paddles from moving around and it frees your off hand for other tasks. We see examples of this with the Elecraft KX series of radios and there are some adapters for radios such as the Yaesu Ft-817/818.
I really like my IC-705. It is probably my best radio for POTA/potable operation. I think the only time I would leave it home is if weight became a problem or I needed to exercise one of my other radios. Recently, Begali came out with a mount to attach their Adventure paddle to the IC-705. It is a sweet set-up; however, the approx. $400 USD price tag got me looking for other alternatives. I have nothing against Begali, I own three of their paddles, and they are superb instruments. I think I wanted to tinker, and this gave me a good excuse.
For paddles, I have a set of Larry’s (N0SA) SOTA paddles. I love these paddles. When I go on an activation/Portable Operation, I bring these and my Begali Travelers. If I was going to do a SOTA activation, I would just bring Larry’s Paddles. Next was a trip to Tractor Supply Company (TSC) for a sheet of 16 ga. Steel. That set me back $16. I cut it to 3″ by 3 1/2″ using a cutoff wheel on my grinder.
I already have a stand I made out of 1″ x 1″ angle aluminum so I cut this to fit behind it.
The blue on the metal is Dykem Blue which is a layout fluid. In creating this project, I am only using hand tools. Power tools consisted of a grinder with a cut-off wheel. a hand drill, and my trusty Dremel tool. Here is a picture of me giving the mount a rough finish with a file. Continue reading Scott Builds a clever Icom IC-705 Paddle Mount→
Recently, I have had the desire to try my hand at winding toroids. They have always been a mystery to me. Today’s project is winding a toroid for 40-10 meters. My target antenna is one I learned from Thomas, K4SWL. It is a random wire antenna that is 29.5 long with a 17 foot counterpoise. It is a great antenna and works well at park campsites. I either string it up in a tree or I use my 20′ B&M fishing pole.
Thank you for sharing this, Scott. I’ll be the first to admit that I can hardly take credit for the antenna design as it’s been out there for ages, but I do love this simple antenna and it has become an invaluable member of my field antenna arsenal.
I, too, have been planning to build a 9:1 UNUN and pair it with the speaker wire antenna just to make that match a little easier.
Thanks so much for sharing this and your excellent build notes!
I love this pack, Scott! I’ve never owned a proper waxed canvas bag, but I’ve heard so many good comments about them in terms of comfort and longevity. Like Red Oxx, the Filson brand is well known for quality products.
I like how you mounted your N0SA SOTA paddles to the clipboard so that they can be easily pivoted for transport.
I also like those POTA/QRP cheat sheets. I have those in my KX1 kit, but none of the others. I need to make some with QRP calling frequencies and the 60M channels (which I always forget in the field). Thank you for the tip!
Cutting an exercise mat to make a padded seat for the field is incredibly practical. That would also serve to pad the back of the pack and, as you point out, make sitting on wet ground much more comfortable!
KK4Z’s Discovery TX-500 Pack List
At my request, Scott very kindly provided links to the gear in his field kit: