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Author Topic: Linear, Solid State vs. Tube?  (Read 47356 times)
W5SRT
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Posts: 416




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« on: December 22, 2014, 10:35:36 AM »

Very close to making a decision on a quality linear amplifier to keep for the long haul, and I am torn between these options:

1) Elecraft KPA500 (Add KAT500 tuner later if needed)
2) ACOM 1000
3) Something else?

They cost about the same, and I am wondering about the convenience of solid state with automatic band switching, plug and play (120vac 15A), instant-on, and compact size of the KPA500 versus the greater power of the ACOM, maybe better audio quality?, but with slower band changes, warm-up time, tube degradation, biggerness, heavier AC line draw, and whatever else.

Right now, I hang out on nets mostly, do some CQ-rag chewing, and do enjoy making a DX contact when the bands are good.  Transceiver is a TS-590s, and mono band antennas that really don't need an antenna tuner (of course this could change).

Any experiences,thoughts, opinions, blind obsessions, are most welcome.

- Dan
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KD8MJR
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« Reply #1 on: December 22, 2014, 11:14:01 AM »

Once I got a taste of solid state there was no going back to tubes.  Instant Power with no tuning and auto band changes really spoils you.  I also like the fact that I can repair a solid state amp myself without worrying about lethal voltages.  If your an older engineer with lots of tube experience that will not be a problem, but when I was becoming an EE tubes where for the most part already out of the curriculum.

I have had a blast with my Tokyo Hy-Power 2.5KFX, it will do 1500W with ease and you can find a used one for just about the same price as the Acom.  I see that the Elecraft gets pretty good reviews, I just wish they made a 1kw or higher amp.
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“A lie can travel half way around the world while the truth is putting on its shoes.”  (Mark Twain)
W3RSW
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Posts: 606




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« Reply #2 on: December 22, 2014, 11:32:35 AM »

Shhhh, don't tell anyone but Elecraft is about to bring out the KPA-1000.

You already know that the 500 was based on price point and fitting the amp plus power supply in the same case/form factor as the K3.  Hence it wasn't much of a brainer to fit two 500's and combiner in the same K3 sized cab, and place the twice powerful supply outboard in an other cab.

Merry Christmas and Happy New Year; --perhaps the dream'll come true.
« Last Edit: December 22, 2014, 12:10:57 PM by W3RSW » Logged

Rick, W3RSW
M0TTB
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« Reply #3 on: December 22, 2014, 11:42:38 AM »

I made the change to solid state last week, out went the Acom 1500 (owned for 2 years, a 1000 before that), in came an SPE Expert ....my reflex action is still to reach over to change bands/tune up  Grin

If you're a chaser, here there and everywhere on the bands, solid state, or at least no-tune, makes a difference. Besides, I get odd and unpredictable 20-30 min breaks in the shack during the day... leaving the amp on most of the day is a bit of a waste for possibly no qso's in the log.

I know a lot of die hard dx'ers over here have moved to solid state in the last 18 months.
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Andy
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W5SRT
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Posts: 416




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« Reply #4 on: December 22, 2014, 11:46:38 AM »

Shhhh, don't tell anyone but Elecraft is about to bring out the KPA-1000.

You already know that the 500 was based on price point and fitting the amp plus power supply in the same case/form factor as the K3.  Hence it wasn't mich of a brainer to fit two 500's and combiner in the same sized cab, and place the twice powerful supply outboard in an other cab.

Merry Christmas and Happy New Year; --perhaps the dream'll come true.

Hold on just a gull dern minute!  Is this for real???!!!???!!!

Or, are we dreaming hi-hi?
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W3RSW
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« Reply #5 on: December 22, 2014, 12:08:43 PM »

Guess a smiley should have been added.  It'd be real only if Elecraft thought they could get twice the price of a KPA-500 ( which is already fairly pricey for a 500 watt amp.)

But I think it's a viable option for someone;
Perhaps drop the 2d connectors and form fit panels, find a less expensive supply toroid (there should be some economy of scale there in the cubic realm but  offset by combiner costs, etc. )
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Rick, W3RSW
N9AOP
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« Reply #6 on: December 22, 2014, 12:31:37 PM »

Dan,
I had a 811H for 10 years which never gave me any trouble.  I sold it and bought the KPA500 and KAT500 which I use with my K3.  Since Sept. I have used this setup 2 hours a day, 7 days a week and it performs well.  Once you go to all solid state and automation I don't believe you would go back.  I also have a Centurion which I am going to keep.  American hams love power and if Elecraft is going to make and sell a KW unit, it will sell well.  If they could get away with selling a 3KW unit in the USA it would also sell well.
Art
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W8JX
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« Reply #7 on: December 22, 2014, 12:33:26 PM »

Once I got a taste of solid state there was no going back to tubes.  Instant Power with no tuning and auto band changes really spoils you.  I also like the fact that I can repair a solid state amp myself without worrying about lethal voltages.  If your an older engineer with lots of tube experience that will not be a problem, but when I was becoming an EE tubes where for the most part already out of the curriculum.

Solid State still has a way to go and more pricey per watt. As far as instant on, tubes like 572, 3-500 and 3cx1200 are basically instant on. Tuning is not a big deal unless you are technically challenged. It is not big trick to make a amp no tune broad band as there have been a few tube ones that way. You trade broad band for efficiency though. As far as lethal voltages, if you are truly a trained EE being able to work with high voltage safe is not a problem unless maybe you have trouble walking and chewing gum at same time or lack common sense. Tubes are far more forgiving than transistors. I guess PnP amps goes with mail order ham licenses as requirement have been reduced they need to make it simpler for some ops.  
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--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
W9FIB
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Posts: 2531




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« Reply #8 on: December 22, 2014, 12:49:59 PM »

My question is (based on my lack of practical tube experience) why there has never been a controls set up that is fully automatic with a tube final. Seems to me that if a microprocessor can tame high power semiconductor devices, it could also tame a tube(s) just as easy. Or is there some limiting factor that I don't know about?

I deal with solid state control of 4160V at up to 300A every day. But that's at 0 - 400 Hz. So I don't see where it is a matter of the raw power. Is it because of the RF? But there is the same RF in the current solid state amps.

Just curious. (Except for any comment by Mr. Know It All)
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73, Stan
Wisdom is knowledge you gain after you know it all.
W5SRT
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Posts: 416




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« Reply #9 on: December 22, 2014, 12:53:29 PM »

The thing about tuning is that you are keying the amplifier on-air and making the output circuit adjustments.  I hear this frequently on the bands, and it seems rather impolite.  Further, I almost never hear the tuner-upper ask if the frequency is clear, prior to tuning, nor give a call sign at the end of the tune-up.  However, since I am a new ham, I may be a bit obsessed about following all the rules.
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WB2WIK
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« Reply #10 on: December 22, 2014, 01:34:07 PM »

My question is (based on my lack of practical tube experience) why there has never been a controls set up that is fully automatic with a tube final. Seems to me that if a microprocessor can tame high power semiconductor devices, it could also tame a tube(s) just as easy. Or is there some limiting factor that I don't know about?

Guess you haven't looked so hard.  There have been auto-tune high powered tube amps available for many years from several sources.  Best of breed was probably the mighty Henry 8K Ultra, which uses a 3CX3000A7 and is fully auto-tune at 3kW output in the ham bands (best used within legal limit). Wink

The RF Concepts/Alpha 9500 uses an 8877 at 1500W output and is fully auto-tune: http://www.rfconcepts.com/PRODUCTS/New-Products/Alpha-9500-Autotune-Full-Legal-Limit-Linear-Amplifier

So is the current model OM 2500A which uses a GU84B to produce >1500W output power and is fully auto-tune: http://www.innovantennas.com/antennas-a-accesories.html?page=shop.product_details&flypage=flypage.tpl&product_id=391&category_id=38

So was the long-sold but now discontinued Alpha 87A: http://www.rfconcepts.com/REPLACEMENT-PARTS-LISTED-BY-ALPHA-PRODUCT/Alpha-87a-Parts  (it's replaced by the 9500).

I still like the ol' Henry 8K Ultra, though.  It is instant-on and easily runs >3kW output power.  Plug & Play.  Little video demo of one: https://www.youtube.com/watch?v=s_4DJP_M0cg


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KD8MJR
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Posts: 5557




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« Reply #11 on: December 22, 2014, 02:04:34 PM »

Once I got a taste of solid state there was no going back to tubes.  Instant Power with no tuning and auto band changes really spoils you.  I also like the fact that I can repair a solid state amp myself without worrying about lethal voltages.  If your an older engineer with lots of tube experience that will not be a problem, but when I was becoming an EE tubes where for the most part already out of the curriculum.

Solid State still has a way to go and more pricey per watt. As far as instant on, tubes like 572, 3-500 and 3cx1200 are basically instant on. Tuning is not a big deal unless you are technically challenged. It is not big trick to make a amp no tune broad band as there have been a few tube ones that way. You trade broad band for efficiency though. As far as lethal voltages, if you are truly a trained EE being able to work with high voltage safe is not a problem unless maybe you have trouble walking and chewing gum at same time or lack common sense. Tubes are far more forgiving than transistors. I guess PnP amps goes with mail order ham licenses as requirement have been reduced they need to make it simpler for some ops.  

I expected a post like this from you.  It seems that you now follow me around looking for something negative to say.   JX you have lost all relevance on eHam and have become the butt of too many jokes for me to continue wasting my time arguing with you.
Have a good Christmas and try to grow up.


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“A lie can travel half way around the world while the truth is putting on its shoes.”  (Mark Twain)
W9FIB
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Posts: 2531




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« Reply #12 on: December 22, 2014, 02:19:19 PM »

Guess you haven't looked so hard. 

Your right in that I have not looked all that close. Those amplifiers usually don't show up in my price range, so I didn't pay much attention to the details. Thanks for the info! Gives me a place to start looking at their control schemes.

Thanks again!
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73, Stan
Wisdom is knowledge you gain after you know it all.
G3RZP
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Posts: 1321




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« Reply #13 on: December 22, 2014, 02:59:42 PM »

I guess this must be a naïve question. If SS PA stages and SS amps are so marvellous, why is it that when you look over the years at the IMD characteristics in the magazine reviews that when they are so much worse on high order IMD - that which causes the QRM further away - they are so desirable?

A bipolar transistor will inherently be worse than a tube unless major NFB is used [do the expansion of  log (cosf1 + cosf2)], and MOS, especially LDMOS, is famous for its non-linearity. So for an SS station to be really as clean as a last generation tube PA and good tube PA really needs pre-distortion or something like Polar or Cartesian loop feedback.

Convenience - yes. So would discharging raw sewage from St. Louis into the Missouri River, but it would be pretty rough on those living downstream.
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W5SRT
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Posts: 416




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« Reply #14 on: December 22, 2014, 05:11:38 PM »

I assume the solid sate transmitters and linear amplifiers are FCC type approved to operate within the permitted RF envelope, yes?
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