My Footwarmer Works

Posted on Tuesday, August 13th, 2013 at 7:49 am in

HLA 300 Plus

HLA 300 Plus

I don’t like linear amplifiers and I find my little Yaesu FT857D almost always puts out a hard, clean and clear signal that is good enough. I’ve never doubted the brave little radio would pull me through.

Until Sunday. Earlier the day I worked the Unions End expedition organised by the Adventure Radio Club [click here fore more info] under the callsign ZS3ARC on 40m. It was busy but I didn’t have any trouble to exchange 59’s with Martin ZS1SM and so I was quite chuffed with myself, adding the very rare grid square KG05 to my slowly growing WAGS collection.

Later that evening when the bands closed and they moved to 80m I thought it would be nice to make a second contact. More is better, right? So I called Martin. He was happily chatting away to some other contacts so the band must have been relatively open to him. Here and there he mentioned crashes or interferences but generally he was having good QSO’s.

So I called Martin again. This time I checked my equipment casually just to make sure everything is plugged in and so on. Martin chatted on …

The third time I called Martin he heard something through the noise but he couldn’t properly identify me and stuff, and we couldn’t complete the QSO. By now I realised that this logbook entry was going to take something a little extra, like a few extra WATTS.

Earlier this year I bought a HLA 300 Plus amplifier made by RM Italy from Sams Radio. The price was right, my power supply wasn’t. On a good AHH! it pulls more than 40 Amps and trips my 30 Amp power supply. However at that stage it already bends the needle on my SWR meter past the 300 Watt mark. So the little project was paused, waiting for the arrival of some shekels to upgrade the power supply. And while I was waiting I was happily adding more countries to my logbook using the 50 or 100 Watts of the barefoot radio.

But getting this grid square twice was very very important to me and so I decided to take a big risk. What if I kept my voice lower not to exceed the power limit? Very quickly I plugged the antenna across, the amplifier was already wired to the power supply. I went right down to 5 Watt on my Yaesu FT-857D, I switched the 3dB attenuator on the front panel of the HLA-300 in, tuned 10kHz lower in the band, and did a test call. Disaster! The power supply crumbled under the strain. I will not forget the disappointing click of the trip switch. Sigh. What now!

My antenna is a 80m horizontal loop strung between the trees and it resonates slightly higher up in the band. I pulled out my MFJ-941E Antenna Tuner (also from Sams – thank you Sam!) and pulled the obviously too high SWR down to something a little bit better. By now I was panicking and my hands were shaking so I remember that my settings were not perfect. Next time Sam, please sell me the automatic tuner version! A last check that I’m not connecting the wrong coax cables, and I sit down for a final test. If this doesn’t work …

Just over 30 Amps and 240 Watts and she holds! Lets go! Tune to 3.680 MHz, check my breathing, and wait for a gap. One call (with my eyeballs firmly locked on the ATU power meter) and Martin comes back! Yippee! He gives me a 57 because of QSB and noise but a very readable signal and we both confirm our entries in our logbooks! Crazy how happy I was with that contact confirmed!

Logbook ZS3ARC 80m

Logbook ZS3ARC 80m

Did I learn something from this exercise? Yes: Never ever give up. And that my little amplifier – that most Hams scorn because it is not a kilowatter – has given me a rare contact. What more can a Ham ask for?

1 Comment

  1. Leon - 26/03/2014 at 11:32 am

    Posted on the SARL Forums recently:
    I have been using a solid state RM amplifier “HLA 300 plus” for about a year now, into just about any piece of string I could lift into the air. It likes my G5RV-junior, and it loves the 83 meter horizontal loop that I strung between the trees. I work just about all the bands and the amp is used for SSB only, as I find digital modes don’t need a lot of power. I published a nice blog entry of the first time I was able to work a very rare grid square only because I used the amplifier.

    Generally I feel that it lifts my signal by about 2 S-units from a “sorry I can’t read you” to a “solid copy”, but remember this is anecdotal and subjective.

    On the output side I use a tuner most often than not, because most broadband antennas (such as mine) require a little bit of matching. If I limit myself to 300 watts my MFJ-941E ATU works perfectly, and on 20m and higher I can exceed the ratings if the antenna is nearly matched.

    For driving the amplifier I mostly use my Yaesu FT-857D, but I find I have to turn the output down to 10 watts or so depending on the bands and cables to prevent overdriving the amp. What is really exciting is that my new X1M (5w out)is hitting 265 watts key-down on 40m! On the Yaesu FT-840 I have to turn the RF Power a lot, too. I don’t put in any matching between the Yaesu and the amplifier, but from some reports I have seen one can improve the matching with a very small mod.

    Reports are always “nice audio” but I expect that because the Yaesu gives out good audio and I don’t overdrive the amp. I have been looking for harmonics and other noise but within my limited capability I am not aware of any.

    The only downside I am aware of is that it wants a serious power supply, sucking up to 43 Amps on a lekker whistle. I’ve cut the leads shorter and I’m considering doing some further adaptations, but the fact remains that the output power drops significantly as the supply drops.

    In summary the amp is working exactly as advertised and is making me one very happy ham. More info on my website (search for amplifier).

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