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Author Topic: Any News on the new Legal Limit Amps from Elecraft and Flex  (Read 24643 times)
N2RJ
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Posts: 2100




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« Reply #90 on: June 19, 2017, 07:56:39 AM »

For those asking about the devices used in the KPA1500, this from from a recent Elecraft newsletter:
"For those who have asked,  we are using two 1400 W BLF188 LDMOS FETS mounted to a large 3/8" thick copper spreader in the KPA1500. This yields 2800 W of device dissipation, providing lots of headroom for the amp."

73 Dave

That seems like a rather odd choice given that the more recent 1.5kw 1K50H is available, and is essentially a drop-in replacement. Two of these are in the Flex amp.
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NO9E
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Posts: 888




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« Reply #91 on: June 19, 2017, 09:36:58 AM »

Quote
Here are some MTBF values;

60C   105,000 years
80C     20,600 years
100C     4,800 years
120C     1,280 years

Perhaps 300 years at 140C and 70 years at 160C.

With Rasberry Pi or similar, the excuse of "heavy duty" engineering is gone. Just put sensors on SWR, currents and spreader temp, and react in microseconds. Perhaps this is what these amps will do.   

I am particularly excited about the 4O3A amps as it is designed to adjust parameters for maximum efficiency = minimum dissipation.

Ignacy, NO9E
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W3RSW
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Posts: 606




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« Reply #92 on: June 19, 2017, 10:52:52 AM »

The BLF 188's look pretty decent to me.
http://www.ampleon.com/documents/data-sheet/BLF188XR_BLF188XRS.pdf
A pair is certainly adequate.

Also the 3/8 copper spreader is only the first heat dissapation point.  I think a matching or larger footprint by 'X' depth and 'N' number of fins aluminum sink/radiator with powered fans is the remaining part of overall dissipation requirement.  Grin

I'm sure Elecraft has wrought a decent design. The competition will be interesting.
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Rick, W3RSW
N2RJ
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Posts: 2100




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« Reply #93 on: June 19, 2017, 05:27:19 PM »

The BLF 188's look pretty decent to me.
http://www.ampleon.com/documents/data-sheet/BLF188XR_BLF188XRS.pdf
A pair is certainly adequate.

It's an older design, 3 years old already. The 1K50H is new, as in last year. It's an easy drop in replacement. I would hope that "BLF188XR" is just a generic term for "50V LDMOSFET" and that Elecraft actually uses the 1K50H.
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W7VO
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Posts: 313


WWW

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« Reply #94 on: June 22, 2017, 07:55:29 AM »

The warm glow of a pair of 3-500Zs are always reassuring on a cold winter night of contesting. A warm glow with a set of MOSFETs would have an entirely different meaning......

73;
Mike
W7VO
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W9FIB
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« Reply #95 on: June 22, 2017, 08:08:21 AM »

To me a warm glow from any device/component is energy being wasted as heat and light.
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73, Stan
Wisdom is knowledge you gain after you know it all.
K6AER
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« Reply #96 on: June 22, 2017, 07:39:18 PM »

On a cold night the amplifier has no wasted energy . When my wife wanted to work in my radio room she would turn on the amp with 3-500's for heat.

In reading this thread I still have not seen any real numbers on pre-disposition IMD. Amplifier efficency for tube or LDMOS 2 KW amplifiers is well within the normal operating needs of the averagame ham.

At 1.5 KW SSB,  my tetrode amplifier averages 35 degrees C exhaust temperature  an drops to 26 degrees in about 2 minuets at rest.

At Dayton Flex had their IMD  reading specifications which were about 40 dB for 40 and 20 meters on the 3rd and 46  dB  on the 5th.  This is all hams will need in actual operation.

Cost is the biggest factor marketing amplifiers. Most hams have about a $3k limit.
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N2WQ
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« Reply #97 on: June 23, 2017, 03:11:46 AM »

The BLF 188's look pretty decent to me.
http://www.ampleon.com/documents/data-sheet/BLF188XR_BLF188XRS.pdf
A pair is certainly adequate.

It's an older design, 3 years old already. The 1K50H is new, as in last year. It's an easy drop in replacement. I would hope that "BLF188XR" is just a generic term for "50V LDMOSFET" and that Elecraft actually uses the 1K50H.

This is empty "specs talk". First, there is nothing wrong with the BLF188. It's a well understood design.  Second, the 1K80 is a much better choice because it's higher drain voltage, which makes the output transformer easier to implement and gain better overall system efficiency.
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N9AOP
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« Reply #98 on: June 23, 2017, 10:39:56 AM »

Regarding IMD--At the last hamfest I was at, I asked about 40 different hams what their thoughts were on products of amplifiers.  Most did not know much about IMD and the rest simply didn't give a shit about those products being produced by their amps.  Their thought was that if the FCC approved the amp, it was just fine.  I also talked to 5 owners of OM power amps and they said they usually ran them above legal limit.  Their thoughts were that if you were not supposed to run over legal, they wouldn't sell those amps over here.

Right or wrong, that's what my fellow hams said.
Art

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ZENKI
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Posts: 1648




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« Reply #99 on: June 23, 2017, 04:47:45 PM »

Thats why we need  a set legal standards much like the ITU standards to be applied to the ham service.

We just have to admit that the vast majority hams today are appliance operators who are not technical people who can be entrusted to  follow good engineering practices. When appliance operators operated commercial radio stations they had to employ  broadcast engineers to run their transmitters in a compliant manner. Many hams  are not technically proficient and thats why we need regulations to allow these appliance operators to enjoy their hobby without causing unnecessary and harmful interference to others.

 Nanny state laws comes about because stupid people force governments to act. Is it a surprise that the ham service cant even regulate itself in a technical light  that maintains standards with good engineering practice? The issue of transmitter IMD is a case point. Hams who think that its their right because they bough a radio and amplifier, think that its ok to cause interference. These same people who argue against regulations are the ones who buy radios with  strict limits on harmonic output. Does harmonic radiation level laws affect your enjoyment of your hobby? No it does not, I dont know why these same stupid hams think that a minimum set of IMD regulations  is going to  somehow kill off ham radios and amplifiers or cause the price to increase. It  just making excuses for CB stupidity and manufacturers who want to turn the ham radio service into CB commodity market where everything has the worst engineering standards and practices.  A good example is the new Yaesu FT-891  which has 3rd order IMD levels of -20DB below PEP. Thats minus 14 db in the old measure. Most CB radios would measure better and hams are buying this garbage from Yaesu!


Regarding IMD--At the last hamfest I was at, I asked about 40 different hams what their thoughts were on products of amplifiers.  Most did not know much about IMD and the rest simply didn't give a shit about those products being produced by their amps.  Their thought was that if the FCC approved the amp, it was just fine.  I also talked to 5 owners of OM power amps and they said they usually ran them above legal limit.  Their thoughts were that if you were not supposed to run over legal, they wouldn't sell those amps over here.

Right or wrong, that's what my fellow hams said.
Art


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N2RJ
Member

Posts: 2100




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« Reply #100 on: June 23, 2017, 06:56:26 PM »

The BLF 188's look pretty decent to me.
http://www.ampleon.com/documents/data-sheet/BLF188XR_BLF188XRS.pdf
A pair is certainly adequate.

It's an older design, 3 years old already. The 1K50H is new, as in last year. It's an easy drop in replacement. I would hope that "BLF188XR" is just a generic term for "50V LDMOSFET" and that Elecraft actually uses the 1K50H.

This is empty "specs talk". First, there is nothing wrong with the BLF188. It's a well understood design.  Second, the 1K80 is a much better choice because it's higher drain voltage, which makes the output transformer easier to implement and gain better overall system efficiency.

The 1K5 is essentially a drop in replacement and gives more headroom, even
SPE is using them now. There is also the issue of parts availability. Using a more recent device assures longevity of replacement parts supply. There is no reason not to use it, especially when it's about the same price.
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K9MOV
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Posts: 106




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« Reply #101 on: June 23, 2017, 07:07:08 PM »

Like it or not--- ZENKI is 100% correct on this subject.
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SM0AOM
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Posts: 261




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« Reply #102 on: June 24, 2017, 04:07:04 AM »

We just have to admit that the vast majority hams today are appliance operators who are not technical people who can be entrusted to  follow good engineering practices. When appliance operators operated commercial radio stations they had to employ  broadcast engineers to run their transmitters in a compliant manner. Many hams  are not technically proficient and thats why we need regulations to allow these appliance operators to enjoy their hobby without causing unnecessary and harmful interference to others.

My solution to this problem would be an incentive licencing programme where applicance operators are limited to power levels commensurate with their actual knowledge, say, 10 or 50W, and higher power privileges are only granted to those that can show the necessary engineering knowledge.
technical investigations
It is against the spirit of the ITU Radio Regulations to give vast privileges to people without the proper knowledge.

Once were radio amateurs considered to form an elite among radio hobbyists due to their interest in:

"A radiocommunication service for the purpose of self-training, intercommunication and carried out by amateurs, that is, by duly authorized persons interested in radio technique solely with a personal aim and without pecuniary interest."
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K6AER
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Posts: 5745




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« Reply #103 on: June 24, 2017, 07:27:46 AM »

This is done in Japan.
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W3RSW
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Posts: 606




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« Reply #104 on: June 24, 2017, 08:00:36 AM »

N2RJ,
Both amps are using two output devices in PP, essentially eliminating even harmonics as well as more than adequate at 1500 pep., still quite linear at 2000 pep.  Granted not quite so linear at the purported 2800.  

Regarding longevity, the 1k50 itself is about to be supplanted.  Grin

And if they're drop-in and if BLF's becomes scarce then drop in newer and reset the bias, etc.
By that time a replacement probably won't be the 1k50.

So we're all waiting with bated breath for 1k100's .  --Very friendly to you and comradely laugh. Is there an emoticon for that?
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Rick, W3RSW
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