The One-Watt Magic Number.

Started by gil, June 15, 2018, 08:38:19 am

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Trying to make a contact again with my Pixie and maybe 300mW, I recalled most of my past QRP and QRPp attempts using CW. Usually, anything a Watt and above is no trouble at all with a full-size antenna. I even made a contact once from Florida to Estonia (5K miles) using 1.3W! Even my Rock-Mite on 40m seemed to work fine, though the issue was more of a receiving one, because of the lack of selectivity. Then we get down to 500mW, where contacts are still possible, just a bit harder. Below half a Watt things become very dicey, though I have tested 100mW successfully on more than one occasion with Ray 820 miles away. For calling CQ however, one Watt seems to be the practical limit. It gets better from there on up, of course, up to five Watts or so, after which adding power doesn't seem to do much more, at least when conditions are somewhat favorable.

This brings me again to the conclusion that QRP radio designers know their business. Aside from Pixies, Rock-Mites and such, which are fun novelties, great practical radios start at around two Watts. I especially like the SW+ series (ME+ now), and of course, the Weber MTR rigs for QRO operations  ;) I would love to see a surface-mount SW+! Instead of adding current-hungry features, what don't we make radios smaller? We have the technology with SMT components. There should be rigs out there the size of a small box of matches. The limiting factor should be the connectors and controls.

Anyway, just rambling... I think a practical radio should have a minimum of around 2-3W to be safe, with 5W being great. One Watt could get the job done but I would not count on it. Below one Watt you're just having fun, and that's great. BTW the 817 with a less than a full battery outputs 2.5W and people make plenty of contacts with those, even using SSB.

What do you think is the practical power threshold for a CW-mode survival radio?



Some interesting points there Gil - Id really like to see some of the rigs (MTR's QCX's and so on) have the option to redcuce power output.  If all I have is a 12volt battery and the transeiver is putting out 5 watts, id personally like the option to drop the power (and save some battery life ?) on the fly.   I might not always want to reach out to other continents.

As to your question about power threshold for a SURVIVAL radio then I really only need a few hundred miles distance - that might necessitate using a low, horizontal antenna for NVIS or ground wave if im high enough.



I know you are talking about CW as the mode however.....

In 2015 I was building from scratch a Beach 40 DSB transceiver dead bug style on a piece of PCB. This radio was designed by Peter Parker VK3YE, I had just finished the receiver section, and the pre driver, and driver section, but was having problems with final amp going into oscillation, so I disconnected it. It was putting out about 300mw into the LPF measured without the final in the circuit. I was listening to a guy running a special event station aboard the Queen Mary docked in LA Harbor a distance of almost 1000 miles for my Oregon QTH while making the last connections to the mic amp stage with a electret capsule just hanging from some wires on the bench. I kept saying my call while looking at the waveform on my scope, Yep you guessed it, the guy returned my call sign and thanked me for checking into the Queen Mary. He gave me a 57 signal report with great audio. Keep in mind, I was running Double Side Band which means half of my power was going to the opposite side band, so that means I was getting out to S. California on about 150mw. You never can tell where your small signal is being heard. BTW, I had a lot of fun with that radio after I got the final amp section fixed, I made hundreds of contacts including one to Japan, all this on a bout 3 watts.



Quoteid personally like the option to drop the power

Good point, I know of no small QRP rig with a low (lower!) power option... Great idea. It probably hasn't been implemented because of the extra circuitry. Often, dropping voltage will do the trick...

QuoteI was getting out to S. California on about 150mw.

That is amazing Joel. It really shows that sometimes it doesn't take much.

Thanks for your input guys.