QRO

Parts for 140W amp

Two items arrived in the mail yesterday afternoon – my EB63 140W HF amp kit and my new-to-me Ameritron AL-811 amplifier.

I bought the amplifier used at a price I couldn’t say no to and am looking forward to putting it through its paces on 80 meters over the winter DX season.

Of course I dug into the box as soon as it arrived. The tubes had been removed for shipping and survived the transit from California. Once installed, the set-up was very easy…almost plug-n-play.

I tuned the rig/antenna for a low SWR on 80 meters, then tuned the amp for 500 watts out as indicated both on my tuner’s bar graph and my Heath wattmeter. Surprisingly, the amp only requires about 45 watts to achieve its full output on 80m. I’ll test the amp on all the other bands but it will probably wind up effectively a monobander on 80m.

The K3’s default transmit delay between keying the amp and applying RF is 8 mS and is adjustable. I had planned on perhaps needing to tweak this value so that the first character of my callsign, a single dot, makes it through without getting chopped, but it appears to be fine as is.

C6AUM was calling CQ on 3506 kHz and a quick “AE5X” sent his way was correctly copied, all characters intact.

Reviews of this amp on eHam are almost universally excellent and, so far, I can understand why. Simple to tune, ample output for a low input and a very affordable way to add a bit over 6 dB to your transmitted signal.

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Construction of the EB-63 will start in a couple of weeks and it will be housed in a Ten-Tec case. Documentation is a bit lacking compared to what QRP kit builders are use to and consists only of this brief bulletin (pdf). No parts placement, tune-up procedure, filter discussion, T/R delay discussion. But don’t worry,¬†Gentle Reader; I’ll document everything here in living color & in the best English someone from my neck of the woods can muster…

In the meantime, I’ll be researching low pass filters for various bands – CCI sells the parts for those in kit form as well but I may have most of the parts necessary already here. Even though this isn’t QRP, Solid State Design and other QRP construction books are worth their weight in gold where this topic is concerned.

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  4 comments for “QRO

  1. Ed
    December 1, 2010 at 7:53 pm

    Hi John,

    I’ll be anxious to hear how you feel about adding the AL-811 in a couple of months, as to whether you feel the investment was worth it and has made an impact, especially on 80 meters. I often feel that I’m outgunned on 80, both from an antenna standpoint and from lack of power. But with a teenager expecting a car soon and then college, I’m feeling the pinch. Sure would love to have had a few extra watts last weekend at times, however.
    73 Ed

  2. December 1, 2010 at 8:12 pm

    Ed, I’m almost sure that if I decide I don’t want it, that I can re-sell it and break even, provided I don’t let the smoke out of it.

    My real interest is just to tinker with something new and I have a lot of years being a QRPer – time to try the other end of the power spectrum. As for the EB63, it’s a stepping stone to the amp I’d really like to build:
    http://www.w6kan.com/ssamp.html

    This is based on another Motorola design, the main parts of which are also sold by CCI. I know absolutely nothing about building amps so will do what learning I can on a cheap one (EB63) and then, if all goes well, move on to the 600W project.

  3. December 3, 2010 at 10:10 am

    John,
    I’ll be anxious to follow your amplifier building project. I’ve been researching options I might add to my Flex 1500.

    I ran across a deal on an AL-811H a few years back as well. It’s been a solid piece of gear and I’m confident I could get what I paid for it if I were to sell it today.

  4. December 3, 2010 at 10:32 am

    Tim, I’ll probably starting it this weekend and am thinking up future applications for it as well.

    For those who have a copy of “Experimental Methods in RF Design”, there are a couple photos of the amp as built by the authors on pages 2.38 and 2.40. Unfortunately though, no narrative.

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