150 watt amp for 10 meters?

[K6CLS]

hey, does anyone have some pointers for a "150 watt" amp for 10 meters? thinking about the 10m contest in December, the low power class allows 150 watts. we are making plans to run from a rare DX, everything will have to be portable (12v powered).

I'd like to buy something but I am open to building a simple circuit. I think we can limit the output power by limiting the drive so flexible on exactly what.

The Ameritron 500W amp (http://www.ameritron.com/Product.php?productid=ALS-500M) is too much power, and too much $$$ for now.

any ideas?
thanks!

Cliff K6CLS

[WB2WIK]

Do you have a QRP rig to drive it (e.g., something that runs about 5W output power on 10m)?

Or, what did you plan to use as an exciter?

[K6CLS]

Yes we can output 5 watts. The Icom 735 runs 5w when cranked all the way down.

[WB2WIK]

I was going to recommend an amp I have which I could sell for a very affordable price; however the IC-735 cranked down to 5W could easily blow up the amp.

It would be perfect with an FT-817 or similar rig that cannot possibly produce more than 5W PEP no matter what you do; that's why I asked.

However, in thinking about your goal: The IC-735 should be able to produce 100W PEP. The difference between that and 150W PEP is only 1.76 dB, or less than 1/3 of an S-unit. Think anyone would really notice? AFAIK the vast majority of operators in the "low power" category are running 100W PEP output power. The League permits up to 150W for those few rigs on the market that can do that without an amplifier (this goes way back to the TS-950S and similar), but in reality there's virtually no difference.

If you're running battery power: The IC-735 at 5W still draws about 4A at that low level (48W consumption); add a 150W amplifier which will draw 25A peak and probably 10A average on SSB (120W average consumption), and you're up to 168W drain on the battery. Instead, if you just ran the 735 at full power, it draws 20A peak and 10A average (120W average consumption), so for losing 1.76 dB in power, you save 48W of battery drain -- allowing any battery used to last longer, or possibly allowing the use of a smaller battery to begin with.

I know personally I wouldn't want the extra 50W if it created any other hardships or compromises in a portable operation. A good antenna system will trump that quickly.

[K1ZJH]

Isn' that a 100 watt rig to begin with? Why do you want to throttleback a 100 watt
rig to drive a "150 watt" amp? What is the brand and model of this 150 watt amp?
Throttling back can be troublesome with rigs that have ALC overshoot problems.

Pete

[K6CLS]

I think you have a good point there. probably get more dBs from optimizing the antenna(s) than from the extra 50W. thanks

[WB2WIK]

I think you have a good point there. probably get more dBs from optimizing the antenna(s) than from the extra 50W. thanks

I think so, too. Without a very good beam, the 10m contest is almost a waste of time. Two or three good beams are much better, if you can aim them in good directions and switch quickly.

My team "won" the ARRL 10m contest in 1982, I think it was. We gave a presentation at the Dayton Hamvention the following year, showing a detailed video of what was involved. What was involved was a 7L 10m monobander at 70' plus a 5L 10m monobander at 80' (different tower, 250 feet away) and a 4L 10m monobander at 35' (on the roof, also 75' away from the other two) to capture the higher angle stuff. I don't think we missed "anything," and were answering the 2000 QSL cards for the next few months that followed.

When the low-powered JA licensees started calling, we heard them all due to the gain and efficiency of the 7L monobander (40' boom) which was built by WA2VUN, W2HWG and myself. If we switched to a dipole or a vertical, we could only hear maybe 10% of them. The "other" 1000 JAs calling could be heard only with the 7L beam.

Antennas are almost the only thing that matters on that band. We ran a kilowatt, but could have made almost all the contacts if we ran 25W; the serious difference is "hearing" them.

[N5TGL]

I think you have a good point there. probably get more dBs from optimizing the antenna(s) than from the extra 50W. thanks

I agree 100%.

[W1QJ]

Isn' that a 100 watt rig to begin with? Why do you want to throttleback a 100 watt
rig to drive a "150 watt" amp? What is the brand and model of this 150 watt amp?
Throttling back can be troublesome with rigs that have ALC overshoot problems.

Pete

This is absolutely correct. I would just use the radio at full 100w and forget trying to bosst the power 50w with an amp.