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Author Topic: Looking for SS HF PA w/QSK...  (Read 9899 times)
OK1RP
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Posts: 155




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« on: November 02, 2015, 08:22:14 AM »

Hi all,

I am looking for highly reliable, compact, solid state HF-6m bands PA with 100% working QSK at around 1-1.2kW heavy-duty output and standard radio interface. Commercial only (no home made) for resonable price. Can someone recommend me any according to own good experiences please?

My favourite model to buy was untill now Acom 1200S but I realized it has no QSK implemented
http://acom.radioamater.cz/acom1200s-leaflet.pdf
...so no way for me on CW.

As the long time Elecraft K3 owner I was also interrested in the KPA500, but there is no enough power as I am looking for 1-1.2kW heavy-duty output.

Any kind of tip, hint or recommendation is appreciated.

73 - Petr, OK1RP
http://ok1rp.blogspot.com
« Last Edit: November 02, 2015, 10:21:46 PM by OK1RP » Logged
DL8OV
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Posts: 769




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« Reply #1 on: November 02, 2015, 01:52:19 PM »

http://www.jumaradio.com/juma-pa1000/

This has the interfacing you require but you will need to ask them about the QSK abilities as they are not mentioned in the specification.

Peter DL8OV
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K7JQ
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Posts: 961




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« Reply #2 on: November 03, 2015, 04:00:09 AM »

The three SPE Expert amps (1 KW and up) claim to do QSK. Never operated one, but check the reviews on this site.
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OK1RP
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Posts: 155




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« Reply #3 on: November 03, 2015, 04:11:04 AM »

Peter,

many thanks. I will check the QSK with JUMA guys...

Do you have own experiences with this PA please?

73 - Petr, OK1RP
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OK1RP
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Posts: 155




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« Reply #4 on: November 03, 2015, 04:19:53 AM »

Hi Bob,

many thanks. I know about the SPE Expert amps. Unfortunatelly I heard about the overheating issues and problems with relays, hi-SWR sensors and reliability in general. Even although the reviews are almost good on eHam I am not sure if it is right way.

I will try to focus on them again. Many thanks Bob,

73 - Petr, OK1RP
http://ok1rp.blogspot.com
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WB4JRQ
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Posts: 4




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« Reply #5 on: November 03, 2015, 06:55:34 AM »

If you have time you might want to check out the upcoming Linear Amp Gemini HF-1K 1.8-50MHz 1kW Solid State Linear Amplifier.
Roger Banks at the DX Shop which owns Linear Amp can give you the details.

Regards,
David
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KA4WJA
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Posts: 893




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« Reply #6 on: November 03, 2015, 08:10:56 AM »

Petr,
If all you're intending to use it for is cw, with your K3, then the actual amplifier IMD might not be of great concern to you...
But, should you ever intend to use it on SSB, PSK, etc., then the truly horrible IMD products produced by may of these new hi-power SS amps (using LDMOS devices, whether from FreeScale or NXP), will inevitably cause significant splatter and interference to others on the bands...  

I am looking for highly reliable, compact, solid state HF-6m bands PA with 100% working QSK at around 1-1.2kW heavy-duty output and standard radio interface. Commercial only (no home made) for resonable price. Can someone recommend me any according to own good experiences please?

My favourite model to buy was untill now Acom 1200S but I realized it has no QSK implemented
http://acom.radioamater.cz/acom1200s-leaflet.pdf
...so no way for me on CW.

As the long time Elecraft K3 owner I was also interrested in the KPA500, but there is no enough power as I am looking for 1-1.2kW heavy-duty output.

Any kind of tip, hint or recommendation is appreciated.

73 - Petr, OK1RP
http://ok1rp.blogspot.com

Petr, understand that my caution is NOT about all SS amps, as the older Tokyo Hi-Power, older SPE-Expert, older Icom PW-1, etc. (all using 50v FET's), are of course not as good as most tube amps in regards to IMD products...but are not truly horrible, as the newer SS amps using the LDMOS devices have turned out to be....

Amps like the SPE-Expert 1.3k-FA (and the JUMA, and the Gemini, and the M-squared, etc. etc...), although marketed as a "1300 - 1500 watt amp", if actually operated linearly, with good amateur practice, in order to keep IMD products low...would actually be a 400 watt amp!

Please see these recent threads were these details are discussed thoroughly...

What HF Amp Has The Best Intermod Figures ?
http://www.eham.net/ehamforum/smf/index.php/topic,104518.msg866058.html#msg866058


Tube vs. SS / Amplifier IMD Tests / Tirode vs. Tetrode vs. Solid-State
http://www.eham.net/ehamforum/smf/index.php/topic,100600.msg866050.html#msg866050



And, two other postings from those threads, as well...


What HF Amp Has The Best Intermod Figures ?
http://www.eham.net/ehamforum/smf/index.php/topic,104518.msg864865.html#msg864865


Tube vs. SS / Amplifier IMD Tests / Tirode vs. Tetrode vs. Solid-State
http://www.eham.net/ehamforum/smf/index.php/topic,100600.msg809648.html#msg809648



BTW, if you look at the multi-page-long spec sheets, you find no mention of IMD / linearity....just hi-power, lots of power gain (25+ db), and hi-VSWR tolerance when used in "pulsed service"....
http://www.nxp.com/documents/data_sheet/BLF188XR_BLF188XRS.pdf



Again, I do wish you well in your search, but just wanted to caution you that many of the newer hi-power SS amps are using LDMOS devices, and these amps have rather poor to truly horrible IMD products....so, if you're ever considering using your new amp on SSB, PSK, etc., this will be an issue for you...
For CW, driven with a K3, it probably will not be much concern..

I'm sorry if my words seem harsh, or if my information leaves you with few options... Smiley



In the US we have many odd sayings / colloquialisms....and I'll paraphrase one here that originally had to do with automobiles ("you can have: Fast, Safe, or Cheap....pick two!")

In the RF World, you can have: Powerful, Clean, or Cheap...pick two!...Smiley

In general, this means:  you cannot get everything unless you have the $$$$....and in our amateur radio world, there are few "hi-end" / "hi-dollar" products....as most are simply "done on the cheap" (another US saying!)


(I hope my somewhat humorous sayings translate well enough??)



73,
John,  KA4WJA

« Last Edit: November 03, 2015, 08:25:39 AM by KA4WJA » Logged
K6BRN
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Posts: 490




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« Reply #7 on: November 04, 2015, 11:22:59 AM »

KA4WJA:

Why is intermod so bad in amplifiers using LDMOS devices?

Technically, LDCMOS transistors seem to perform well in class AB operation, see:  http://www.av.it.pt/nbcarvalho/docs/ci26.pdf

And the ACOM A600S, which uses a Freescale MRFE- 6VP6300H LDCMOS module was tested by the ARRL in August 2015 and found to have very good intermod performance, and was also used in contesting, with "flawless" performance.  In fact, the A600S performed significantly better (intermod-wise) than the Yaesu FL-1000 Quadra amp, which I use, and which uses venerable (i.e. traditional old MOSFET design) MRF150 transistors.  I've never had an issue with the FL-1000.

Any device, solid-state or tube can perform poorly in a bad amplifier design - not so sure it has to do with LDMOS.

Brian K6BRN
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KA4WJA
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Posts: 893




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« Reply #8 on: November 04, 2015, 12:36:17 PM »

Brian,
You are correct that this has more to do with design and running the devices into compression in order to market a "hi-power" amp, cheaply...and conversely, a good design allowing multiple devices to be used, and not running them past compression...


Thank you for pointing out the Acom 600S IMD specs...(I had not seen them!)
The ARRL product review showed the 600S, at 14mhz:

3rd/5th/7th/9th:
42/39/49/55 dB below PEP...

Not bad at all!

(of course still not as good as some of their tube amps, with the Acom 2000a testing out at: 37/60/61/60 below PEP....
or compared to some triode amps, such as the Commander HF-2500, at:  53/56/58/60 below PEP...or the Alpha 9500 at:  45/49/56/57 below PEP...
and for comparison, here's your Yaesu VL-1000 at:  32/44/49/59 below PEP...)



My experience with LDMOS hi-power amps dates back a few years, when I had friends doing the FCC cert testing for some hi-power VHF LDMOS amps....and they were truly horrible (with 3rd order at about -20db(pep)...)
And, then fast forward to this summer with the testing (in the UK) of the SPE  1.3k-FA, with its "3rd order IMD at outputs of 1.3 to 1.5kW to be  -20 to -26dB relative to PEP" (according to the July radCom report)


It appears that Acom's choice of a pair of Freescale MRFE- 6VP6300H's in their 600S allowed them to design an amp that works well, and doesn't have its devices driven past compression....and produces acceptable IMD products!
Kudos to them!!  (and thanks again to Brian, for pointing this out!)

Here's the spec sheet for the MRFE- 6VP6300H's...
http://cache.freescale.com/files/rf_if/doc/data_sheet/MRFE6VP6300H.pdf?pspll=1



73,
John,  KA4WJA

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K6BRN
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Posts: 490




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« Reply #9 on: November 04, 2015, 04:05:30 PM »

Hi John:

Yes, pushing an amp too hard will take it into nonlinear operation, guaranteed, and over-spec of amplifiers encourages it.  I'm not sure that most users realize this.  I've seen a lot of comments that XXX amplifier (including mine) "can easily  do way over its rating".   The cost is distortion - i.e. plenty of intermod.

Sorry about the FL-1000   Wink.  You are right, its not a particularly "clean" amp on the output, at least on paper.  So far no complaints from nearby operators, though.  And it helps that I run it at about 600 watts out SSB (rather than 1 KW) on the higher 50V (high-power) power supply setting.  It should have plenty of headroom at that operating point.

And you are right - its still hard to beat the IMD performance of a good tube amp, largely in part due to the tuned output stage.

Regarding RF power MOSFET and LDMOS transistors, they are regularly sold in modules (the MRF-150s were, too) - sets of two, to support complementary class B or AB designs.  I'm intrigued by the LDMOS transistor architecture because of their better high SWR (high voltage) tolerance.  The traditional MOSFET MRF-150s are an old and proven design, but very vulnerable to voltage stress on their outputs and will fail very quickly from abuse if not well protected.

Regarding the ACOM A600S, the one item I'm curious about is that ACOM rates the amplifier for 100% duty cycle without mode limitations, very close to the thermal dissipation limit of the transistors.  Most manufacturers have a healthy margin against those limits, usually by specifying a duty cycle or lower output level.  Not sure if this means the Freescale devices are really robust or whether ACOM is really optimistic.

All the best,

Brian K6BRN
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K6BRN
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Posts: 490




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« Reply #10 on: November 05, 2015, 12:44:28 AM »

AK!  VL-1000 amp and VP-1000 power supply Quadra system - NOT FL-1000.  My bad.
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OK1RP
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Posts: 155




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« Reply #11 on: November 05, 2015, 02:49:21 AM »

Hi John and Brian,

wow. Thank you very much for sophisticated and deep comments about the SS PAs to you both guys.

Yes, I am the CW op only BUT of course I am looking for clean PA with low IMD spurs too.

That is exactly the major point of my problem in term of finding good PA as John said...looking for the best for reasonable price (I know that it will not be cheap, forget chineese crapies) Smiley

Well Acom 600S is out for me as there is no full QSK as reported some owners. The same is expected for new 1200S model. Even more Acom 600S has not enough power...

The SPEs are out for several issues reason incl. the IMD spurs.

What about the KPA500 from Elecraft? Do you know more details about the IMD and other paramaters please? It is also low power PA > the same level as Acom 600S but there is good working QSK and radio interface system and as K3 owner it will be easy to implement for me. I am looking for 3-5dB Wink but well if there is choice...

I have no detailed refferences for Juma 1000 amplifier > it is short time on the market and there are no reviews from the field as same as laboratory measurement available and I still have no any info about the QSK...

Also I have no more details about the Linear Amp Gemini HF-1K 1.8-50MHz 1kW Solid State Linear Amplifier.

In any case many thanks John and Brian for your hint and suggestions.
Several people in our local radioclub did not understood what is problem to find SS PA with so standard power at around 1-1.2kW out. When I said my requirements including the 100% working QSK, good radio interface, good protection, low IMD and fully reliable then no one was able to tell me any model which meets these requirements...hi.

73 - Petr, OK1RP

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N4MPM
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Posts: 106




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« Reply #12 on: November 06, 2015, 12:45:07 PM »

Icom PW-1 has Qsk and a kw.
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WB8VLC
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Posts: 427




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« Reply #13 on: November 06, 2015, 07:17:55 PM »

I have a homebrew FREESCALE MRFE6VP5300 baby hf/6 METER amp and the imd numbers at 350 watt pep for 3rd,5th 7th order products are -37, -45 and -51 dbc ref to each tone at 350 mA Idq.

Similarly I am evaluating a newer much better part which is in the prototype stage, the PRFE6VP1K5 device and at 1350 watts pep for the same imd products the numbers are -41, -47, -52 dbc at 750 mA Idq.

While this part has respectable numbers even at 1500 watts, the 1350 watt numbers dictate running at this level.

When I was designing with some of our first gen 1 and gen 2 LDMOS devices at the original Motorola PHOENIX facility, unless using the better COM1 facility die which was rare even back in 1997, the IMD numbers were horrid with any of the LDMOS parts coming out of the older transitional MOS-X fabs unless run at ~7 to 9 db backoff.

Fortunately within the past year and a half the Freescale designers (many are from the same old Motorola group BTW from circa 1997) the newer LDMOS devices are orders of magnitude above that available even 2 1/2 years ago.

With advances recently made by the new master, Warren B, these new LDMOS devices are worthy challenges to tubes.

BTW: My two tone test are with 700hz and 1900 hz test tones.
« Last Edit: November 08, 2015, 06:37:31 PM by WB8VLC » Logged
OK1RR
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« Reply #14 on: January 19, 2016, 11:53:01 PM »

There is a big dilemma of most modern rigs, no matter if a transceiver or PA. There is a lot of digital circuitry, powerful processors, complex menus but the antenna switching uses an old fashioned clicking mechanical relay. Only few using PIN diodes. Almost every radio or amp is "full break-in capable" which is not true - at least not at speeds above 20 wpm.

My choice is Elecraft KPA500, although 500 Watts only but absolutely silent.
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