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Author Topic: 3-500Z Peak Power Concern  (Read 5699 times)

Posts: 13268

« Reply #15 on: October 16, 2015, 05:11:14 AM »

Running an AL-80B on SSB, mostly on 40 meters.  The exciter is a TS-590s and I have the power set at 100 watts, and I am not using an ALC connection.  Usually, in my normal voice levels, I am seeing 700-800 watts PEP.  But sometimes I will see peaks getting close to 1200 Watts.  SWR meter is an Elecraft W2.

Are these high peak going to damages the 3-500Z, or some other components?  Should I make some changes to keep the peaks lower?

Thank you for your thoughts.


- Dan

Dan you are pushing it too hard and will have shorter tube life. Tube is pretty rugged and can handle abuse but it will wear out sooner. You need no more than 60 watts or so drive and anything over about 900 watts out you are exceeding anode current ratings and 900 vs 1200 is about 1 db or in other words no difference in field and seen only on watt meter. 300 more might sound like a lot but in signal strength it is of no real value here. On more thing while a 3-500z is "rated" at 500 watts dissipation, that is in proper cooling with a envelope and pressure cooling thru socket and over tube. With cooling setup in 80b you have to de-rate continuous dissipation rating at least 20 to 25%.  Again it is a testimony to the 500z ruggedness that it stands the abuse it sees for a while anyway.   

Ham since 1969....  Old School 20wpm REAL Extra Class..

Posts: 5595

« Reply #16 on: October 16, 2015, 06:34:58 AM »

If you will search Alpha 9500 and look at the photos you will see a 3528, 3775, and 4135 on the digital display. Occasionally, I would see something off although not quite to that extent. If it was an actual event it should trip some protection circuit in the amp, or if it was a feedline/antenna issue it should do the same. Or, if it was a feedline/antenna issue it should manifest itself some other way eventually and it hasn't.

I know my AL-1500 will handily do 2.5kW (never done on purpose, but by accident!) when driven with 100W. Someone driving a 9500 with a 200 watt rig may indeed be able to get 4kW out at least on peaks.

If being driven with a 100W rig and the meter is bouncing up to 4KW, I suspect the antenna is on the high impedance side and this is causing false power indications. This can happen without reaching the Alpha's SWR trip (remember the amp is supposed to handle 3:1) or grid current trip.
« Last Edit: October 16, 2015, 06:39:03 AM by N3QE » Logged

Posts: 35

« Reply #17 on: October 20, 2015, 10:38:25 PM »

I run my AL-80B at about 700-750 watts output which is plenty.

Posts: 416

« Reply #18 on: October 21, 2015, 07:26:49 AM »

Thanks again, everybody.

I have reduced the drive power to 75 watts, and I run the TS-590s mic gain conservatively inside the ALC meter scale, so the signal out is quite clean.  Power peaks are around 900 watts, but usually in the 400-700 watt range.  Getting unsolicited good-signal reports regularly now.


- Dan
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