Power Genius XL Amplifier Noise

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Below I have copied with permission some information on the cooling of the RF-Kit 2K+ amplifier.  It uses a pair of LDmos finals and produces similar RF output to the PGXL.  I am most interested in the fan noise specific measurements quoted in the article below.

I often hear on the air or read on the forum comments about how loud or quiet one amplifier is or isn't.  It seems to me that it would be much more valuable to have specific noise db increase measurements as a comparison bar.  Below Bob indicates that the RF-Kit amp is 10dbA higher than his ambient noise when measured 60cm (24 in) in front of the amplifier while running 1500 watts cw and cooling fans on maximum speed.

Is it possible to provide similar specific measured fan noise levels under these same conditions for the PGXL at it's different fan speeds?





"High power solid state RF amplifiers seem to be good at making a deafening amount of audible noise, so how is it the RF2K+ is so quiet? 
I recall almost 20 years ago on a DX trip to activate Tristan da Cunha (ZD9ZM) a friend loaned me a Yaesu FL7000 SSPA.  It weighed 30kg and according to its spec sheet, consumed around 1.9kVA to produce a modest 500W output.  After a few minutes use, its cooling system fully ramped up to make a deafening roar, reminiscent of a jet plane taking off.  At that time the experience convinced me high power amplification was better left to tubes. 
Since then SSPA technology has developed apace but improvements in cooling system efficiency seem to have lagged far behind.  Manufacturers and amateur builders alike have for the most part continued to base their designs upon use of classic extruded aluminium sinks sporting a number of modest height, open fins.  While this type of heatsink can be very effective in sinking heat they are not nearly so effective in giving up that heat to the passing air intended to evacuate it from the equipment enclosure. 
I purchased my first commercially manufactured SSPA 6 years ago and remain its happy owner today. My KPA500 has travelled with me to various DX locations around the world and has never let me down.  I consider it a first class piece of equipment in every respect bar one.  Its fan noise can be deafening.  Without remoting the amplifier, I find its use is only practical with resort to noise cancelling headphones.  This is what I do and will continue to do because the KPA500 has proven itself small, reliable and robust enough to survive air travel inside a standard hard suitcase. 
With the KPA500 in standby and its fans not running, my shack ambient noise level is around 20dBA when measured 60cm in front of the KPA500.  While producing 500W CW output with the cooling fans operating at max speed this increases to above 50dBA.  The KPA500 cooling system is quite typical of those used in modern SSPAs.  It employs a classic extruded aluminium heatsink with 14 fins 185 x 35mm (7.3 x 1.38”) providing a potential 1813 sq.cm (281 sq.in) of surface area over which cooling air may be moved.  A single 90 x 90 x 35mm fan is mounted on the rear of the amplifier blowing air into that part of the enclosure which houses the RF pallet, heatsink and LPF module. 
I carried out the same audible noise test on my RF2K+.  With the amplifier turned on but not driven, my shack ambient noise level measured 20dBA at a distance of 60cm from the front of the amplifier.  While producing 1500W CW output with the cooling fans operating at maximum speed this increased to just 30dBA. 
https://www.noisehelp.com/noise-level-chart.html defines 30dBA as a whisper and 50dBA as light traffic.  That’s a huge difference in noise level.  I imagine most can cope with someone whispering in their shack but many will draw the line at the noise equivalent of a minor road running through. 
So let us return to the question: “How is it the RF2K+ is so quiet?” 
Instead of following the pack and specifying a one piece extruded aluminium heatsink for the RF2K+, Reinhard opted for one assembled using multiple extruded parts to create a box type assembly. This provides for a significant increase in surface area, over which cooling air can flow, while its box construction lends itself to direct attachment of fans providing for improved control of flow. 
Surface Area 
The RF2K+ heatsink comprises 27 vertical fins providing 52 surfaces over which cooling air flows.  Each of these surfaces measures 225 x 85mm or 191.25 sq.cm (29.64 sq.in) but wait a moment.... These surfaces are not smooth aluminium but instead are ridged to provide an approximate 25% increase in surface area to 239 sq.cm or 37 sq.in.  With 52 such surfaces the RF2K+ heatsink provides a massive 12,428 sq.cm or 1,924 sq.in of surface area over which cooling air may be moved.  This creates significant advantage in the disposal of sinked heat.  The RF2K+ heatsink has almost 7 x the surface area of the KPA500 sink.  A similar heatsink to that used in the KPA500 would need to be much larger in a 1500W amp.  Let’s assume the number of fins is increased to 20 and their length increased to 11.5 inches, the surface area available to cooling air would be 640 sq.in only 1/3rd that of the RF2K+ heatsink.  Further increases in size would be met with rapidly diminishing returns as the further the extremes of the sink are from the source(s) of heat the less they can contribute to its disposal. 
Air Flow 
A limitation of the open fin extruded heatsink is that it doesn’t lend itself to well controlled airflow.  In some cases this type of sink is installed with the fins resting upon a plain metal surface to create a box through which air may be blown.  In others the open fin design simply relies upon a high enough volume of air passing through the amplifier enclosure such that enough of it passes over the open fins. 
The cooling system design of the RF2K+ provides for much greater control over airflow.  The 120mm fan pushing air through the sink is directly attached to it ensuring its full output goes exactly where intended – across the fins.  A second 120mm extractor fan and associated decavitation chamber are attached to the opposite (output) end of the assembly.  These reduce the back pressure on the input fan and significantly reduce unproductive cavitation, significantly improving flow. 
A host of factors influence how well unwanted heat from devices is absorbed by a heatsink with yet more influencing how well that absorbed heat may then be dispatched.  The above discussion concerns the RF2K+ approach to the latter and hopefully goes some way to explaining how the “whisper quiet” nature of the RF2K+ has been achieved. 
 
Bob Henderson, 5B4AGN         19-July-2018 "
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John - K3MA

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Posted 2 months ago

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Steven Linley

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I have the rf-kit b26 rf2k plus and yes the fans are very very quiet.
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Tom W3FRG

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I heartily agree, my ASUS Laptop is the nosiest thing in the shack. And, I can't hear that.

The RF 2K+ is so quiet that I have to put my hand at the rear fan outlet to see if its actually running. When the temp hits ~42 deg C, the fans go on and maintain that temp +/- a few degrees.

Tom W3FRG
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Bill -VA3WTB

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To answer your question,,yes it is possible.
I think soon there will be some independent test done on the PGXL. Like the one you posted.
But based on the PGXL capabilities I don't think it will be considered a quiet amp.
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Matt (K0KB)

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It’s like a freight truck driving through a nitroglycerin plant.
(Edited)
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Bill -VA3WTB

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I don't have a Flex amp,,just by talking to as many as 10 people with them find them not so bad.
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Matt (K0KB)

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I don’t know how anyone could find it not objectionable. Mine sits 10’ away from the operating position in an equipment rack and it’s unbearable. I’ve onky spoken with one other owner and they thought the same thing.
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Bill -VA3WTB

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Mat, it sounds like you won't have your amp very much longer.
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Mike W9OJ

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The latest review of the KPA-1500 on eham says it's fan noise is unacceptable. a "fatal flaw." Earlier reviews of the amp says it' not bad at all.
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John - K3MA

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The recent comments are exactly why I made this posting.  People giving opinions with no first hand experience.  Personal opinions about what is noisy and what is not.  Lets see the real measured numbers with comparisons then the subjective opinion can go away and each amp can be compared on a complete set of their pros and cons.  Not just a narrow set of the pros.
(Edited)
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Bill -VA3WTB

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No John,,I do not know who may review the amp,,, all I am saying is I'm sure someone will, sooner or later.
One thing for sure based on what people have told me from using the amp hundreds of hours now, some may find it to noisy and others not so much.
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Jim Runge

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I had the PGXL and the fan noise was unacceptable to me.  I couldn't get it far enough away from me.  My SPE Expert 2K-FA is hardly noticeable.  Both are/were 27" from my head.  Flex was very nice and took the PGXL back and refunded my money.  I know that the PGXL is 1500 watts continuous and the SPE 2k isn't but I don't need 1500 watts continuous, I need a comfortable operating position with minimum continuous noise. 
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Burt Fisher

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I have an IC2KL and it sounds like the Saturn Apollo 11 video above. I thought technology would improve in 20 years for quieter operation. I hate fan noise.
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Kevin N9JKP

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Burt, The technology is there, it costs something to implement and one has to be mindful of the impact of the sound.   My 6700 is the loudest piece of equipment in my shack.  That includes a large computer (that I build, with 7 fans - all Notura which I selected for their cooling and quietness), a Fujitsu split ac unit mounted on the wall almost above my desk, power supplies, UPS, etc.

The argument that one should just make everything remote is just not in the cards for me.  I am hopeful that ARRL might include noise measurement as part of its review.  Once such independent measurements are their hams can factor that into their decisions and the market will react accordingly.
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mikeatthebeach .

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Noctura Fans are worth every cent and Amazing for PA's
https://www.youtube.com/watch?v=btP1LzbwYB4
73 Mike
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Paul

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Another thumbs-up for Noctua fans:

https://noctua.at/en/products/fan

Have used them often. For anyone looking to customise their cooling, they're reliable & very quiet.
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HCampbell WB4IVF

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 I agree that some standard comparative test for noise would be useful, but personally I don’t find the PG XL fan noise in normal mode objectionable at all. Going in I knew having multiple sets of fans for the PS, PA, and harmonic load was going to result in some noise, period.  My backup plan was to move it further away or into another room if it came to that, but I haven’t found it necessary.  The fan noise turned out to be pretty much what I was expecting from some user comments.  In any case, to me the PG XL’s Flex integration, high duty cycle, and clean signal engineering outweighs lower fan noise of some other amps.   It’s a tradeoff of course and no one size fits all.

You could always try one of these....       (-:

     




Howard


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John - K3MA

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Howard, I think the article that I posted indicates that it does not have to be a trade off.  The RF-Kit 2K+ seems to meet all the high duty cycle, clean signal and low fan noise criteria.  It does not integrate with the Flex like the PGXL.  It does utilize several different options to track and adjust to freq/band changes made on the Flex.  However, I doubt that Flex will ever allow a competitor the option of inserting a operating panel in the SmartSDR software like the PGXL.
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k0eoo

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John, the excellent article you reference only deals with the cooling capability of the RF-Kit and not the power output vs. time question.  If available I would like to see some information on the temp vs. key down time at full power for the RF-Kit.  

What makes the PGXL special is its ability to deliver full power over extended time, like running FT8 or RTTY in a contest.  And as Howard mentioned, if you're just rag chewing on SSB in a round table, the duty cycle and temp would be low as would be the fan noise....

(I do not have either of the for mentioned amps, have the Alpha 87A and SPE 1.3kfa so my comments about the noise level of the RF-Kit and PGXL are only based on information I have read.)
(Edited)
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HCampbell WB4IVF

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John, what K0EOO said. 

While I would not characterize the PG XL fan noise at "Normal" setting as low, to me it is acceptable given the other criteria.

Thanks for posting!

Howard
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John - K3MA

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I am not sure that key down is a reasonable test that duplicates what is likely to be a normal use.  Maybe a test that has tx/rx cycle in digital over a period of time would be more of a representation of real world criteria.

I have not done any extensive testing on the PGXL or the RF-kit in this area mainly due to not knowing what a standard test might be.  However, I did run the RF-Kit at 1500 watts using FT8 (15 second TX followed by 15 seconds RX).  The temperature got up to 52C quickly but maintained that temperature.  I ran this test for a total of 30 minutes.

I thought this result was quite good and much more severe than I would normally operate the amplifier.
(Edited)
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Sergey Abrikosov

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Well, the noise level is a big concern for me too.
I have Acom 2000 and it sits about 2ft from me. Most of the time I am listening bands through my speakers and not notice Amp at all. It is very quiet Amp.
I have PGXL on order and really worry that it would be much noisier.
I do not have another room to move it out, so it will be on or around my desk.
One question I have, did anyone suggested to add a water cooling system like used on powerful PC’s? It would add a fan under the desk but typically very low noise fan. The cooling plate could be added to existing heat sink inside of the amp to take a heat out. Of coarse it may void a warranty because modification made, but could help to fight a noise.
Sergey, KN7K
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Matt (K0KB)

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Sergey, first of all ignore the obvious shills who will leave no stone unturned looking for ways to down play issues or up-talk products all while not even owning the product in question or even having seen one operate.

The amplifier is too loud to sit next to you if like me you rarely transmit but want to leave it in operate in case you get the urge and don't want to trip it back and forth from operate to standby to listen

No one is asking for it to be quiet regardless of how much air they move, but for those of us who tx rarely it would be nice to have a mode where the fans don't have to buzz all the time at half speed because we may only transmit for 15 seconds  or a minute and then not again for 15 minutes or an hour and could easily just have fans that ramp up with the heat level in the amp.

My Acom 2000A is very quiet.  The PGXL is orders of magnitude louder than the Acom.

They need to address it.
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Sergey Abrikosov

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Yeah, it is hard to make any judgment without measuremens or detailed reiview. I realize it will be louder than Acom 2000A, but no idea how high noise is going to be sitting next to me.
Sergey, KN7K
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KY6LA - Howard, Elmer

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I think many are missing the point that the PGXL is designed to run remotely so unless you are severely space challenged there is really no good reason to put it next to you where the noise is loudest.


I have a 2K-FA.. I plan to dump it for a PGXL because it can run 1.5KW 100% duty cycle and my 2K-FA will only run 1.2KW @100% duty cycle.


I have been using a Radio Sport Headset for years so Fan Noise just does not exist for me.
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Chris DL5NAM

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Howard, your right. But there also exist PA's they are quiet and can used remote too.

Most Ham's use a PA localy, they work from home QTH. Your are a traveler so noise is not important for you. Also if you a further room where you can place the PA will make every PA silent :-)

But for over 90% of Ham's noise is important.They not use remote mode, PA is placed in shack - 3 feet away.

There was a proposal from a OM that ARRL should check noise + temp and publish this values too.

73 Chris
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Sergey Abrikosov

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Very good point.
Howard, while amp has remote capability, it is not advertised as Remote Amplifier.
And like Chris saying, majority of hams do not luxury of remote operation.
Advertising amp as remote only may affect the sales.
Now, no doubt Flex would love to sale as many as possible.
And I did not order it for testing and returns, but based on limited feedback I getting feeling that I may have an issue with the noise.
As I said I listen a lot through the speakers with Acom2000a sitting next to me, I can call Dx stations for hours until hopefully make a qso and not using headphones unless I am in contest
Sergey, KN7K
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Jim Runge

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I agree. The PGXL was much too loud for my comfort. Flex was nice enough to take it back and refund my money. I will continue to use my SPE Expert 2K-FA.
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Matt (K0KB)

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Jim,

Flex customer support has been the best I've received in any industry I've dealt with.  I wish I didn't need their support so much, but this is bleeding edge awesome stuff.

I think the amplifier would be incredible if they'd do an auto ramping fan starting at 0 or 10% or something.

Glad your expert is serving you well.  I have one on order but hope to never have to take delivery because I hope flex sorts it out.

Best,

Matt
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Bill -VA3WTB

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Chris,,I wish,,but not in the cards for me...
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John - K3MA

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I think it is absolutely incredible that Flex would take a amp back because the buyer thinks it is too loud.  It sure is comforting to know that Flex is firmly behind supporting the PGXL and the customers.
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Bill -VA3WTB

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There are others that will snap it up as soon as it is returned.
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Paul Christensen, W9AC, Elmer

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Water-cooling is a viable option today.  At my home QTH, a 2KW H2O-cooled LDMOS amp uses a small and light copper heat exchanger.  Condensing is assisted by a small pump and a quiet Noctua fan.  

Brick on the key at 1500W and the copper heat pipe exchanger stays under 60 degs. C with very little fan noise.  See my QRZ.com page for an image of the amp.  A pint of clean H2O is needed in a closed system so little evaporates.  Water-cooling works well at high altitudes but might not be a good candidate for some cold WX DXpeditions where any icing must thaw before preparing the amp for use.  But once up and running, freezing wouldn't be much of a concern.

A KPA1500 presently sits at my remote Internet site and it can also be seen on my QRZ page.  The amp does get quite loud during high duty-cycle transmissions like FT8 and RTTY.  Fortunately, it's located 30 miles away, so the noise doesn't bother me at home :-)   With the proliferation of FT8, some of the shortcomings with solid-state air-cooling designs have become exposed.  The KPA1500 RF deck gets as high as 180 degs F.  That's considerably more than the typical stack temperature from a vacuum tube amp.  Apart from that, the amp performs well and PIN diode T/R switching is a pleasure to use.

Paul, W9AC
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Bill -VA3WTB

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I really do not believe Flex made the fan noise loud to drive people crazy on purpose. I do believe that the PGXL is an above average design, everything is made to work a certain way for a good reason that most of us do not know about. Based on pictures and reading and talking to owners there are lots of information and study to do if one want to bother.

The good thing is, all the fan settings are done in firmware. If Flex engineers feel that more tweaking can be made to fan speeds or weather they are on or off then they will likely make more changes. If it is safe for the amp to do so.

The KPA1500 just had an update to the amp functions that tweaks the fans more, and that is after it has been out a few months.
The KPA1500 makes an harmonic noise from the center fan that drives many nuts. The wind goes over a heat sink and makes a pitch noise. Some are modifying the center fan by blocking air flow a little bit on the center fan to stop the noise. I have a good friend doing just that and others are starting to do the same.
I mention this because like the KPA1500 more changes and updates are expected with the PGXL in the future.
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Matt (K0KB)

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Some people get titles next to their names like "Elmer".  I think flex should have an "Apologist" title.
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Bill -VA3WTB

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why?
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Burt Fisher

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I am hopeful someone will do a video like this for the Power Genius. I am guessing no solid state amplifier will be quiet on AM. I have an IC2KL, at 100 watts on AM it sounds like a rocket liftoff. I have an Ameritron AL811H it is quiet, so is my 6400M
https://www.youtube.com/watch?v=T_rG1EJ7Xjc
(Edited)
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Steve K9ZW, Elmer

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I've found my PGXL with production release firmware roughly equal noise-in-shack-wise to the Alpha-9500 it is replacing. 

Other than reading threads like these I've not given it any thought as for noise, as the PGXL meets what I expected.

I've found it less noisy than the SPE 1kW I also had. 

The SPE was relegated to the low shelf, where the PGXL has been okay on the station desk.

YMMV

73

Steve
K9ZW
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Matt (K0KB)

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Steve,

Are you referring to when those other amps rev up to actively cool?
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W7NGA

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Being an anti-contester has its advantages. I can run full legal limit on AM and RTTY all day long using my Alpha 89 and the fans are always a whisper. Of course, I can't change bands without actually rotating a switch and setting two controls, and I do have to wait 3 minutes for warmup ... but then, I enjoy the process and don't find it a bother at all. Old school guy ... still love AM, RTTY, dipping the finals, CW without a computer, ladder line, homebrewing, a QSO beyond signal report and grid square. :)

W7NGA dan
Seaside, Oregon
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Neal Pollack, N6YFM

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Nothin' wrong with any of that :-)

Cheers