Issue #4 - Tuning Up a Kilowatt

Please join us for discussion on the tuners described in Issue 4 of Trials and Errors, or on any topic related to Issue 4 or "Trials and Errors" in general! Here's the link in case you missed the article. Thanks, Dave W7DGJ

 

I have my AT5K at the ready: One Kilowatt IN, 248 foot LOOP on output.
Capacitors are set at maximum...... Ready for discussion/

 

Sounds like a great setup. I wanted automatic tuners for this article, and under $1000 (all under $800 here). Lots of AT5K's out there and with a good rep.

 

I don't understand the 'trend' to blast out 800 Watts to 1.5 KW. With the solar cycle nearing it's peak and propagation so good lately I have been happy to put away my 100 watt radio and use one of my 5 watt QRP radios. I'm having a lot of fun with it and continue to participate in network groups even with just five watts. Those that I talk to can hardly believe that I'm using just five watts and a wire. As far as antenna tuners go, I don't need an automatic tuner. A couple of knob adjustments is all it takes, when I might need to use a tuner at all. I use an antenna that is resonate on all bands so I only need a tuner if I venture way off to one end of the band. Then I only need to nudge the SWR down a little with the tuner.

 

Hi Gary! You're right about improving conditions. But even with that being the case, there's one heck of a hard time for someone trying to break through a pileup with a QRP radio or even a traditional 100 watts. Some "nets" like the Activity Group will focus on giving QRP stations a break -- I like that. They always give QRP operators the space to jump in and get signal reports, and some are very, very loud! But an exec at a major retailer told me that linear amps are selling well, and always on backorder, because hams want to pick up their power output. For me, I don't want a single "manual" control to deal with . . . I want every process optimized and automatic. That's just the way I am. . . Had a tube amp for a long time and got weary of the whole process. I like to be able to move on a dime, to change frequencies and bands and be on the air in a split second. As far as QRP goes, a coming issue of Trials and Errors focuses on the QRP life, as it is a WHOLE 'NOTHER way of thinking about doing ham radio! Dave

 

@W7DGJ
Loved the article, but I'd have to say that 800-1k watts feels like overkill for this cycle, at least so far. That being said, there's nothing wrong with blasting out the legal limit and getting 59s all the way to hong kong.

100 watts works pretty well for me, but it's not like I have a choice, the amps and tuners that are popular right now are about as much as my whole rig. I also like the feel of adjusting knobs for the optimum SWR, even if it takes a minute or so. I guess i'm more of a tactile guy.

Just my 2 cents. I'm liking the articles thus far, keep up the good work!

 

Thanks so very much — love the feedback!

 

I didn't feel financially inclined to take such a huge plunge on a 1Kw or more amp, plus knowing that the investment in such an amp would require some upgrades beyond my simple wire antennas, to fully realize the potential of my investment. But luckily, a local ham in town had completely rebuilt, renovated, and upgraded an older Heathkit SB-200 linear amplifier, and sold it to me at a very reasonable price.

Testing the SB-200 at his shop before purchase showed the amp could put out close to 800 watts safely. My current setup utilizes an MFJ-994BRT remote tuner out at the antenna base, which is only rated for 600w max, so I usually keep everything set so I'm only pushing 450-500 watts down the line. I do have to bypass the amp when I switch bands, sending a 10w carrier signal to get the MFJ initially set, but once it's settled in I can flick the power back up.

So far I've been happy with this arrangement. I think my only dissatisfaction is that the amp doesn't operate on 30m or 17m bands. I've read there are mods that can be done to add these bands to the mix, but I'm not going to mess with it....it's not really that important not having them available. And even since getting the amp, I still find a lot of enjoyment just working the bands 100 watts "barefoot", maybe just switching on the amp for the more distant stations.

Great article....thanks.

 

Thank you for your note Brando. Your shack looks great. The SB-200 is one of the most famous pieces of Heathkit ever to come out of that company. It's a great tube amp. I used an Ameritron Al-80B for a time before I went the solid state route. It was also a workhorse. But, as these things age (me too) I got more and more inclined to automate everything. The SS amp was just so nice because of the bandswitching feature, and so many protection circuits. I'll be writing about my Amp explorations soon . . . Your genuine "thanks" made my day. Dave, W7DGJ

 

My hamfest t-shirt.

 

I can often HEAR, and easily copy stations running five watts, and sometimes a single watt.
I USUALLY use a kilowatt when serving as Net Control, not for my benefit but to make it possible for those operators in high RF noise environments to participate.

I LISTEN for QRP, but run a Kilowatt for the convenience of OTHER operators, you see.

 

Don't forget to remind folks that those Auto Tuners have a MUCH lower power tolerance for FM, RTTY, FT8 etc. I think that the
LDG 1000 ( I have a 600Pro and used a RT 600 for years ) has a max of about 250W . Your tuner has a higher risk of failure if you are matching difficult
loads - for example a short ( less than quarter wave ) wire on 80 or 160 M. I use a MFJ 998RT at the feedpoint of my antenna. Many of
the 100W auto tuners will only tolerate 25 W of FT8. After 50 + years as a ham on HF - I consider the autotuner one of the greatest inventions!

Tuners have an easier time of matching higher impedances than lower and have much lower internal losses (that generate heat ) doing so. If you
are running high power and see your SWR start to creep up - better check your system for heating of cores, baluns, UNUN etc.

Avoid the common mistake of ( for example ) building a 40 M dipole with a 1:1 Balun and trying to force it to work on all the HF bands with a tuner - especially
one in the shack.

Have fun!

 

MFJ tuners handle full rated watts.

If you want to run high power with high duty cycle modes, with an auto tuner, get an MFJ.

 

"MFJ tuners handle full rated watts."

Yes the MFJ also drops their rating for rtty and FT-8 like everyone else since MFJ didn't get any clearance from god to change the laws of physics.

 

I find a great difference in the way that QRP operators consider the hobby. Much more zen-like than the SSB full-legal-limit operator. Dave