The Quest for Power-

[RadioRay]

As you know, many of us use radio transceivers in the 5 to 100 Watts range.  Ham radio advertisers would have you believe that buying expensive equipment with more power is the answer to your problems.  As an engineer and life long ham, as well as a once-upon-a-time government communications consultant, I am here to tell you that power is not generally the solution. 

A little science:  Look at the S-meter on the front of any radio.  This will serve as our measuring tool.


We've all seen those little lines and know that the larger the number, the stronger the signal.  (for the moment we will discuss only signal strength, not signal to noise ratio).  Yes, the higher the number, the stronger the signal - in general.  We also "feel" that -naturally- if we increase our power, even a little bit, it will be more easily understood on the far end - well: yes and no.  The idea that If I double my transmitter power then I double my received signal from S 4 to S 8 is absolutely wrong - here is the REAL math:

Look at that S-meter.  Each one of those 'S-units' represents 6 dB. A doubling of power is only 3 dB.  Therefore doubling your power only gives the receiving station a boost of HALF of one S-unit,  which is generally not even detectable by the human ear, though some might be able to detect the change at a rate slightly over random ... 

Listen to THIS:  To produce an increase of only 1 S-unit on the meter, requires you to double the power and then double it again. 

Let's take the KX3 as an example.  It's rated at "only" 12 Watts maximum output.  Let's call it 12.5 Watts to  make the math easy:

12.5 X 2 = 25 Watts (3dB = half an S-unit)
25    x 2 = 50 Watts (6dB = one S-unit)
50    x 2 = 100 Watts (9dB= 1.5 S-units)

That's right - you could buy an amplifier for over $1,000, to increase your 12 1/2 Watt signal to 100 Watts and ONLY have a signal 1 and a half S-units stronger, though you are burning eight times more power.  Add to this the increased size and weight of your power source, heat sink and etc. - not really worth it. 

The argument is made that "If you're right at the verge of good copy, then that 100 Watts makes all the difference." and this is true, but is also true of 1,000 Watts or 10,000 Watts - right?  It's a matter of what you want to accomplish. If you have that 100 Watt rig, you already have a VERY powerful tool, and frankly, antenna selection is MUCH more important than buying an amplifier. The cost does not stop with 'only' the amplifier either, because usually, every order of magnitude of power increase usually means new BIG power supply, antenna "tuner" to handle the higher power, maybe transmission line and etc. too! the is also the issue that if you have a 'little' RF in the shack at low to medium power levels locking up your computer, getting into your neighbors' viewing of Judge Judy on the idiot box, zapping you when you touch things & etc. , at HIGH power it's going to be a REAL problem...  fixed by more money.

Radio Preppers is a forum primarily dedicated to radio communication during an emergency, especially an extended emergency when we might have to supply our own electrical power.  Unlike ARES/Red Cross/SATERN and other NGO's, we are not primarily focused on being a back-up for infrastructure communications.  We tend to gravitate more toward personal communication (though many of us volunteer for the other as a community service).  Because we are focused on personal/family/small group communications, our needs do NOT include 24/7, high volume low skill requirement comms, as found in cellphones & internet.  With us, it's usually fine to touch base at specific times during an average day, usually while out camping (if there IS call service -wah-hoo, but we make our skeds anyway) some disaster has taken down commercial 'infrastructure' such as during and after events such as hurricanes, blizzards and visits from the Mother In Law.

We've demonstrated what many wilderness QRP'ers already know: that low powered CW is HIGHLY dependable when attention is payed to making skeds based on time of day -v- frequency bands per the distances between stations. We primarily use CW because - on average- there is a system gain of 13 to 18 dB in the ability to copy weak Morse as opposed to weak voice.  Those figures are from various government and civilian studies, matching the ability to convey the same message in voice -v- CW under the same conditions.  Even if we take the lowest of the two figures of 13 dB 'gain' for using CW and apply the basic dB math from above, you see that it requires roughly TWENTY TIMES MORE POWER to convey the same message in voice as is does in Morse over an HF circuit.  Gil & I regularly demonstrate this when we switch to SSB voice, only to find the copy so tough that we return to CW to have easy copy FOR THE SAME POWER SETTINGS. It's simple physics and also anatomy.  It's easier to tell if a weak whistle is on or off, but a weak voice is SO complex, that's it's easy to 'detect' a voice, but miss what it is saying.

So, think 'system gain'.  Slow, steady CW from a QRP rig is VERY effective on a regular basis, while being easily maintainable in a field/disaster environment.  If your goal is to pass messages to/from others when out in the woods, carrying your house on your back (rucksack) or otherwise not having normal infrastructure available, then low power Morse is likely what you should use.




If your goal is  to provide 2mB/sec of websurfing to your local emergency organization, then your going to need a lot more money.

It's food for thought.


de RadioRay ..._ ._

[KK0G]

I couldn't agree more Ray, QRP works and QRP CW works awesome!!

[gil]

Excellent Ray! Thank you for posting.

When I started getting interested in Ham radio last year, I had no idea I was going to go towards small Morse-code-only radios. However, before getting into anything, I always do a huge amount of research. Since my needs were emergency-preparedness oriented, weight and portability were paramount. I always assume the worst, and in many cases, that would mean be on foot, either having to flee, or go somewhere. Honestly, there are much more important things to carry than a radio... Let's see, water filter or battery? Hum... So, unless I can stuff it all in my cargo pants pockets, it's too big... The KX3 for me is a "big" radio!

Voice-enabled radios in most cases (except my beloved KX3), do not fit my bill, and that's that. I had to learn Morse code... I am so glad I did! Like Ray said, twenty times more power. And probably twenty times lighter!

Anyone saying QRP does not work hasn't tried very hard. Anything above 2-3W using CW will get you pretty far. I contacted Slovenia (5300 miles) on 1.3W on 40m! Chatting with Ray 830 miles away is a piece of cake. Sure, some days are harder than others, but it is extremely rare when we don't hear each other, most often due to me not getting up on time or being distracted and forgetting to turn the radio on  ::) (sorry about last night Ray!) Chris and I have had a hard time, but we have heard each-other MTR-to-KX1, so it's probably a matter of trying different bands at different times. That is the key!

I wish we would all try to contact each-other. Mostly in Morse, but hey, everyone is welcome  :) I know how to contact Ray. Chris and Wes know our frequencies, or thereabout... Luck, I'd have to email him through Winlink or use PSK, but hey, it works..  ;D I could probably reach Tim on 2m if I climbed on top of my house with my HT or hoisted my Slim Jim up a tree. Establishing regular "skeds" is a very important part of radio emergency preparedness. Who are you going to trust  if your only source of information is the radio?

Anyway, I'm babbling... You guys have a great day!

Gil.

[KK0G]

In my opinion the key to being highly successful using QRP rigs, especially when operating portable from the field, is CW, this can't be emphasized enough. The inverse of what Ray was pointing out is that you are losing roughly 20 times the power when using SSB as opposed to CW, that's a HUGE loss. During most of the QRP contacts I've had with Ray, Gil and Wes, it's highly doubtful we'd have been able to communicate much less even hear each other if we'd been using SSB.

The real beauty of QRP rigs is the the extremely low power consumption. I built my Elecraft KX1 a few months ago and I'm still running the same 6 AA cells in it that I originally installed; read that again................ 6 AA cells! You couldn't even get a 100 watt commercial rig to power up its back lights with 6 AA cells. When you're traipsing around the woods carrying everything on your back for days, you sure as hell don't want to be lugging around a 40 pound lead acid battery that wouldn't power your 100 watt rig for more than a few hours at most anyway.

I keep talking about the advantages of QRP in the field but they are equally advantageous at home in the shack with your 'big' antennas up in the clear with their gain over field deployable antennas.

[gil]

I keep talking about the advantages of QRP in the field but they are equally advantageous at home in the shack with your 'big' antennas up in the clear with their gain over field deployable antennas.

Not to mention that when you're done, everything can be quickly swept into a small desk drawer..! QRP saves marriages too...!

Gil.

[RadioRay]

You two, being the latest to go on camping trips where you carried loads (in Chris' case, loads of trout being carried home to EAT!) you demonstrated first hand that pack weight is important, even on relatively short hikes in non-emergency conditions.

Receive power draw is MUCH more important than transmit power. As you know, both of your rigs draw between 30-40 mA on receive.  Compared to the standard ham rig which can draw 1.5- 3.5 Amps, just on receive.  Considering that most of our time is in receive mode, either listening or between dits & dahs; receiving is at least 75% of your power budget.  Add to that recreational listening and hunting for stations, and the receive time percentage goes UP from there.

Antennas!  The biggest mistake that I see is people buying a 'cute little radio' and they try to get a little antenna to go with it.  I don't care what you tell the woman in your life, in HF radio: "Size Does Matter"!  The only way that I know of that works to give you a full sized (efficient) antenna that can be carried in a small rucksack is a wire antenna.  You want something with the words "half wave" it in, unless it's a specialty item.  Half wave dipole, End-Fed-Half-Wave and etc. is always a great start, because their 'efficiency' is about as close to 100% as you are going to find on this Earth.  The little antennas at frequencies below 17 meters begin to have efficiencies of 70, 50, 30, 20, 5%. This means that your 5 Watts is actually a fraction of a Watt and because the 'cute little antenna is often close to the ground, you can loose much of THAT from absorption in the ground and surrounding vegetation.

Batteries:  Do NOT go to the woods with a 9 ounce transceiver and a 12 pound battery.  That just does not make sense, unless it's a special application or it's all that you have. I find that three batteries, one solar charging, one charged and one in the set works well for long periods of time in the woods when out of range of resupply.  Two is OK, but becoming a little iffy, unless you can recharge the primary set IN the transceiver while operating, to let the sun power your daytime skeds while putting energy INto the batteries whenever possible and use the batteries for night radio work. 

>>> I prefer skeds when T-storms are not active: mornings through early afternoon, but this is not always practical. 

All things being equal, yes: Morse gets through when voice is so low as to be maybe 'detectable' but not copyable. I know this from personal experience, switching modes on military links and with QRP Buddies at home. The first phrase to learn in voice radio on HF is 'I cannot hear you but I can SEE you!".  ha ha  OK , it's not that bad, but if it's VERY strong signal path sure, go play voice, but in the woods at QRP levels, be ready to run back to what works when the band begins to fade and/or there is interference from meatheads.  Go back to Morse.


My $0.02  worth.  Do correct for inflation.



>de RadioRay ..._ ._

[White Tiger]

This is a very interesting topic - my interest immediately turns to other digital modes in the field?

If I wanted to have a robust prepp network - say one radio set-up for emergency digital communication, in 3 houses, spread out across 10 miles - utilizing CW readers in two houses that have never had Morse training (and don't intend to)...could we still operate that system on minuscule amounts of power?

I'll hang up and listen....

[KK0G]

This is a very interesting topic - my interest immediately turns to other digital modes in the field?

If I wanted to have a robust prepp network - say one radio set-up for emergency digital communication, in 3 houses, spread out across 10 miles - utilizing CW readers in two houses that have never had Morse training (and don't intend to)...could we still operate that system on minuscule amounts of power?

I'll hang up and listen....

In my opinion, no. There are two problems you'd have that I see, first I have yet to see software that reliably decodes CW unless it is absolutely perfect code and relatively free of QSB/QRN/QRM etc. although at a range of 10 miles this problem may not be as bad. the second problem is powering the computer, monitor etc, you're talking several magnitudes of order more power consumption.

I'm not saying it's not possible but it's sort of like comparing apples to oranges.

[gil]

If I wanted to have a robust prepp network - say one radio set-up for emergency digital communication, in 3 houses, spread out across 10 miles - utilizing CW readers in two houses that have never had Morse training (and don't intend to)...could we still operate that system on minuscule amounts of power?

Well, sort of... A reader/keyer like the K42 from http://k1el.com/ will work (no computer needed), but isn't as good as using your brain.. It does add a little battery weight and you need to pack the device as well as a keyboard.. I think it still beats voice, but when the conditions aren't ideal, you might have some trouble decoding. I can decode by ear when barely hearing the signal I am listening to.. An electronic decoder can't do that. Of course, ten miles should be no problem. You can even use CW with a Tech license. But then, you can also chat on 2m.. Morse does get you a bit more privacy though..

The K42 might be a good thing to have if you camp with other people, giving them the possibility to call for help if you are the unfortunate victim of an accident and they don't know Morse code...

As far as antennas in the field, the EFHW can't be beat in my opinion. I use the end-fed tuner from http://betterqrp.com. You do need a tree... I have thought about a weather balloon in no wind conditions, but then you need to pack a gas cylinder, which adds weight.. My Buddistick works well on 30-15m, but as Ray says, you can't beat a wire antenna.

Gil.

[RadioRay]

Morse is excellent for human beings and terrible for machine reading, because machine copiers are generally measuring changes in smplitude e/i if it's LOUDER than the background noise, it MUSt mean that a dit or a dah is being sent.  Machines cannot interpret the grey area between signal and no signal very well in an on/off mode like Morse, or the timing issues of hand sent Morse.

However, other digital modes, such as PACTOR or WINMOR are made to be excellent in noisy and weak conditions and are fully error correcting.  Trying to copy Morse with a reader is going to be dissapointing.

For three house, spread over three miles - I'd go with either VHF packet or VHF winmor, so that you have full error correcting, with a mailbox at each end.  AND I'd set-up for VHF voice using PL tone so that we do not have to listen to ANYTHING be the other stations in our group, untill we choose to do otherwise.



de RadioRay ..._ ._