The price of a solid-state watt

As Elecraft gets ready to release its KPA500 solid state amplifier, I’ve been comparing similar amps from other manufacturers. According to a recent posting to the Elecraft reflector by Eric Swartz WA6HHQ, the KPA500 will be around $2000 for the kit version.

That’s “kit” as in solderless K3-style.

In the meantime, as I (and others) do the age old dollar-to-benefit analysis, it’s interesting to note what’s available as the trend in amplifiers ever so slowly migrates toward solid state.

Amplifier    

Price    

Power    

$/watt    

       
Ameritron ALS-500 $1,100 500w $2.20
Ameritron ALS-600 $1,600 600w $2.70
Ameritron ALS-1300 $2,900 1200w $2.40
THP HL-550 $2,950 550w $5.40
THP HL-1.2 $2,600 750w $3.50
THP HL-1.5 $3,500 1000w $3.50
THP HL-2.5 $6,000 1500w $6.00
Elecraft KPA500 $2,000 500w $4.00

A few months ago, I purchased my first amplifier ever – a 500W Ameritron AL-811 (tubes). I bought it used and paid 60 cents/watt for it. The additional power has been noticeably beneficial – I’d wondered prior to using it if I’d be able to tell in my normal routine of DXing.

I can.

My original intention when buying it was that I’d use it only on 40 and 80 meters. Wrong!

Several recent DXpeditions have been active on 15 and 17 meters – bands that are only beginning to open, perhaps for a few hours a day. Those DX stations have, at times, been merely a whisper – likely unworkable at 100 watts. To even copy them at all requires all the finesse the K3 is capable of and known for, so the extra power was probably the difference between logging the contact and not.

What I don’t like about the amp is that 1) changing bands requires re-tuning and 2) the T/R relays are as loud and clunky as you’d expect QRO relays to be.

A solid state amp is looking attractive and I’m sure I can sell my AL-811 for what I paid for it.

500 watts makes a real difference over 100 watts. 7 dB mathematically; additional band-countries operationally.

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  6 comments for “The price of a solid-state watt

  1. February 10, 2011 at 2:49 pm

    The same arguments that QRP’ers use to support the use of low power also work to support the use of higher power. It’s true that 100W only gives you approximately a 2 S-unit advantage, so if the other station copies your 100W signals at 599, he’ll be able to give you a 579 at 5W. But what if he’s copying your 100W at 559 on a band with QRM and QRN? 5W may not cut it. I know I’m preaching to the choir on this one John.

    I can see how the 7dB increase from 100 to 500W can make a noticeable difference for you. Given that you’ve noticed this difference, have you considered going for the full legal limit?

    • February 10, 2011 at 3:14 pm

      I have Dave but the next 500 watts is significantly more expensive than the first. Also, I’d need a 240V outlet here in the shack, so there’s an electrician at, what – $75/hour if I’m lucky. Plus the antenna tuner would need to be upgraded, etc.

      On the other hand, my heating bill might decrease!

  2. February 10, 2011 at 10:17 pm

    John, I remember your post when you got the amp and I remember posting a comment wondering if you’d find that it made a difference for you. I’m glad to see a followup, and I figured your experience would favor the amp’s usefulness. It’s hard to argue with the extra punch. I am a little surprised at your findings on the upper bands, I’ve never really felt that I needed more than 100 watts to (eventually) make the QSO on those, but with my relatively low antennas, you may be hearing a lot more than I am, especially with the K3. So, for now, my focus has to be on improving my antenna situation, as it should be. But one day I hope to go QRO as well. As you know, as your DX total climbs, those remaining entities are on much less frequently and you have to make the most of those rare opportunities. Extra power would be nice. I’ve heard you a few times on 40 and 80 in the past weeks and, although I’m not all that far away from you, your signal definitely had a punch to it. I was assuming you might be running high power.

    Elecraft was represented at the Richmond hamfest last weekend, but they just had a K2, a couple of K3’s and some of the smaller items. I was wondering if they might have an amp, but nothing yet.

    73 Ed

    • February 10, 2011 at 10:36 pm

      I remember you asking me that, Ed. I’m almost certain now what I suspected back then – that with my old rig, an FT840, its 100-watt output was sufficient for its receiver. With the K3’s APF, I really can pull signals out that would otherwise be uncopyable – and I’m sure they would be deaf to me as well if I were using 100 watts. I was at the point of hearing stations that I couldn’t work and that’s a frustrating position to be in. 500w seems a good match to the K3’s receiver.

  3. Dave Cuthbert
    February 25, 2011 at 9:42 am

    When comparing amp prices the street price should be used. For example the ALS-1300 is $2400 at HRO making it $2.00 a watt.

    I’ve had tube amps and I’ve had SS amps and SS is the way to go. I have an ALS-600 and an ALS-1300 (The ALS-600 goes up for sale soon).

    Why are SS amps generally more expensive per watt? They have power supplies that are 50% bigger and that costs 50% more. A SS amp is not inherently less efficient but the efficiency is optimized for around 75 ohms. This is to enable the amp to deliver rated power over a 1.5:1 VSWR range or 33 to 75 ohms. While the SS amp efficiency might be 65% into 75 ohms it is 44% into 33 ohms. A tube amp can always be tuned for maximum efficiency over this VSWR range and hence has an efficiency of 65% or more. So, the SS amps needs a power supply that is 65/45 = 1.5X bigger.

    • February 26, 2011 at 4:05 pm

      Thanks for that info, Dave. I did try to use consistent sources for the prices but was not able to do so across the board. Also injecting a bit of inaccuracy into the mix is the fact that some manufacturers specify power for both CW and PEP; others do not.

      I agree that SS is the way to go, at least in the case of a CW op who wants to maintain QSK operation. I plan to be one of the first to purchase Elecraft’s KPA-500 as soon as they hit the market.

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