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Living Life on HF – The Age of Power

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Now that the FCC has dropped the code requirement a few people may find themselves with HF privileges that they otherwise would not have. So maybe they will venture on to HF. HF – “here lives dragons” – written on medieval maps of unexplored territory; what will you find on HF?

Living life on HF you might get the idea that you need more power – a common theme. When finesse and skill fails – when 100 watts is just not enough – you just need to get more power. Or, at least, that is what “they” want you to think. More power – “that’s the ticket”.

More POWER – How to get it

In this day and age if you want more power you can just go out and buy it. You can buy RF Power from a commercial retailer like AES – we suggest that route over eBay.

The basics of what you need.

It’s not that complex.  Here are the basic things that you will need

Exciter

We have a bunch of radios here and we try to use all of them at one time or another. Our favorite of late is our 30+ year old Kenwood TS-830S Hybrid snagged off eBay. We have more modern rigs like the Icom 706 MKIIG, a Yaesu FT-847, a Kenwood TS-950S, and a few others. For our setup here well use the good old TS-830S tube rig and the more modern Yaesu FT-847.

Exciter connections

Your task will be to make or buy a connector for your radio of choice that will key (activate) the linear and let the linear manage the output of the exciter (ALC). Some connectors are simple as a RCA plug; some are complex multi-pin jacks that mate with a connector on the back of the radio. Beyond this you will need a simple segment of coax to connect the RF output of the exciter to the input of the linear.

Linear – the “kicker”

Click for larger images

We made a choice of the Ameriton AL811H 800 Watt Linear. We made this choice as it was the best bang for the buck. At about $750 it’s about $1/Watt. In addition, the AL811H works fine on 110V. As you go up the ladder of tube linears you will eventually find that you will need to run these on 220V. Solid state linears are easier to use but are more expensive and require high amp power supplies. We went with the tube linear since it glows in the dark and its “old school”. We like old school. Old school and the glow of the tubes in the dark add to the ambience of role-play on the HF bands – pipe and smoking jacket optional.

Tuner

It’s good to go with a tuner on the output of the linear. Tuners that handle power more than 100-300 watts get increasingly expensive. We have a MFJ Roller Inductor rated at 3,000 watts. The metering on this tuner is convenient. It has two scales 0-300 Watts and 0-3,000 watts; so that is perfect.

Making the connections

Probably the hardest task you will face is to get the connectors for your particular radio that will key the linear and let the linear control the ALC of the radio. Some manufacturers include a connector for “remote” or “accessory” jack on your radio. You might face a soldering job on tiny pins. Or, you might not have the connector and have to hunt it down. The easy way out is to go to eBay and buy a cable from someone willing to hunt down the connectors and solder tiny pins for you at a price. A ready-made cable is about $10-$20. In our opinion, a ready-made purchased cable is well worth the price given the hassle of making one of these cables.

You wont listen to this… and you may be sorry .. but don’t forget the ALC connection. For radios that dont have an explicit external power control you are going to need this connection. The Kenwood TS-830s does not have a power control and the output of the TS-830s will exceed the recommended input limit of the AL811H linear. The TS-830s will put out 100+ watts while the max recommended input to the A811H is 70 Watts. In addition, depending on your circumstances, you might not want or run 800 Watts. If your radio has no power output control, and you dont want to control the power via the mic gain (not recommended) and/or the Car control you need the ALC.

The magic of the ALC feedback from the linear to the radio is that the linear can tell the radio to “back off” on the input power. Use of the ALC line is the recommended way to limit the exciter output to the linear.

That just leaves the keying circuit. Bottom line on this is that the linear has a physical relay circuit that activates the linear. Your radio linear keying line simply completes the circuit on the relay causing it to be energized which in turn gets the linear doing its thing. Some radios have physical relays that key the linear and some have transistor switches. If your radio uses a transistor switch then the only thing you need to worry about is how much current this transistor can sink without blowing. The AL811H has a low current keying circuit and it’s not an issue with the radio we have in our example. Our TS-830S has a physical relay the keys the linear; the Yaesu FT-847 has a transistor switch.

Putting it all together…

Its all pretty much plug and play. Use a good grade coax and route the RF from Radio to the Linear to the Tuner and then to the Antenna. The radios keying line and the ALC connect to the linear at the appropriate marked jacks. See the picture above.

Adjusting the ALC

You will note there is a pot on the back of the linear. The pot controls the amount of feedback from the linear to the radio. The more feedback the more the radio will “back off” on the power. This is how you can adjust power on a radio that does not have a power control – like the TS-830S.

Suppose you want to run max 400 watts from the linear. Here is how to do this. Turn the pot fully clockwise. This is max negative going ALC. If all is hooked up properly, the radio, no matter how high the power setting should show minimal power out. In CW mode, key the radio and slowly rotate the ALC pot on the linear counterclockwise until you see the power you want on the meter (Note: check the power out on the rig meter and power out from the linear into a dummy load. Glock gets about 10:1 – 30 Watts in gets 300 Watts out from the linear). This is your ALC setting for this radio. Other radios have different responses to the negative ALC feedback so you need to reset this if you swap radios.

Tuning up the Linear.

Tuning up a tube linear may seem a daunting task as first. But after you get the hang of this it second nature and can be accomplished in about 20 seconds. We won”t go into how to do that here at it is fully documented elsewhere.

In the World of Power…

You might ask what is 800 Watts worth compared to 100 Watts? You might be surprised. It sounds like 800 Watts is a lot but in the world of Decibels, S meter readings, and fantasy role-play – things are not what they seem.

Consider this. Every 3 dB is a doubling of power. One S-unit is 6 dB. Starting at 100 Watts and doubling it we get 200 watts; double that to get 400 watts; double it again to get 800 Watts – the full power of the AL811H. From 100 Watts to 800 Watts is 3 x doubling of power. That is 3 x 3 = 9dB. 9 db is 1.5 S-units.

So, for all that trouble you got +1.5 S-units at the other end. So if you got a signal report that you were S7 with 100 watts you will get a S8+ with the linear flat out. Is that worth it?

Look at it a different way. Suppose you get a signal report of S9 running 100 watts. Suppose we went the opposite way and diminished the power by 1.5 S-units. Now you are S7+. How much power does that represent?

If you can be heard at S7 think about this. If you can be head at S7 then you can be heard with about 12 Watts (100/2=50W; 50/2=25W; 25/2=12.5W). If you can be heard with 12.5 watts why would you need 100? If you can be heard with 100W why would you need 800W? What real difference does it make?

Try the experiment for yourself. Next time you are on HF running 100W and you get a signal report of S9 or better back down the power to 10W or less and see if you can still be heard. It is likely that you will be. Now you nearing a different realm – QRP – where less is more.

How much are you willing to pay?

Is the linear and the tuner worth the cost? You will have to judge for yourself. The AL811H is about $750. A tuner capable of handling 800+ Watts is about $400. Plus add some good coax. Is 1.5 S-units worth $1,000+?

Want to take it to the next level? Double the 800W to get 1.5KW. That is the extra .5 S-unit beyond what you have with the AL811H. Next step up in the Ameritron line is the AL-82 at $1,500 – twice the price of the AL811H plus you will need to run that on 220 Volts. Is 2 S-units over base power of 100 Watts worth $2,000 (linear + tuner)? Based on what you hear on the air, would that make a difference to the receiving station?

Will it make a difference to your neighbors that you are now running 1.5 KW from your backyard vertical antenna into their telephones, audio equipment, and home theater? Sure it will – think about it.

If you want to run power then the first 800W makes the most difference and the AL811H is the most cost effective choice at about $1/Watt. But keep in mind that it’s only 1.5 S-units on the receivers end. Propagation is everything and if that is not in your favor no amount of power will help you.

Those guys running 2,000 watts over 100 watts will only push your S-Meter 2 S-units and they probably have $2,000+ invested in that effort. Is it worth it? Up to you to decide. Your wallet needs to be at least as big as your ego.

Ham Radio – the Good Life – Everything a Ham Radio Operator could want.

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Written by frrl

August 3, 2008 at 6:05 am

3 Responses

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  1. A good description that would be very helpful for the Amateur seeking to upgrade from 100W to the maximum permissible in their jurisdiction. There is one error however that requires correction, and that is the confusion between a doubling of power [3 dB power increase] and the subsequent increase of one S Point at the receiver.

    The S Meter is not calibrated in power units [the watt] but in volts. Recall that dB = 10 log (p1/p2), but when the power is expressed as v^2/R, then substituting this into the formula, and simplifying according to the rules for log expressions, gives dB = 20 log(V1/V2). Thus 3dB power increase corresponds to 6dB on the S Meter.

    Hence in the example where 100W is doubled 3 times, there is 3 x 6dB increase = 18dB response on the S Meter. The S Meter will read a full 3 S points higher. If the S Meter was reading S9 for a 100W signal, and the power was tripled, the meter would show ‘close to’ 20dB over S9.

    Chris VK4YE

    Chris Bourke

    February 12, 2015 at 3:38 am

  2. This is a great post. thanks for doing the eye opening #’s

    KF7ASQ

    June 23, 2009 at 11:14 pm

  3. Excellent article!! What you said cannot be more true.
    Is running 1.5kw really worth the money but then again some like to have bragging rights… oh well.. to each its own.

    Randy

    May 2, 2009 at 11:14 pm


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