Why I chose Power Genius XL & First Impressions

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  • Updated 3 months ago

 I just replied to a question I received about my impressions of the PG XL.  Thought I’d share my thoughts with the group so below are my edited long-winded comments;

I haven’t had much air time with it, but so far I’m happy with the PG.  I did a lot of research before finally deciding to go with it.  It was a tough choice between the KPA1500 and the PG.  From what I had read they are both excellent amps.  I flip/flopped between them several times.  Main reasons for finally choosing the PG, in decreasing order of importance to me:

Integration with Flex.  This is really neat.  All you need are power, Ethernet, and  coax connections and you’re in business.  Everything except switching power on/off is done from the keyboard.  I found it super easy to set up, with one exception.  When using the supplied Windows app to configure the radio, a serial number popped up when I selected the radio tab.  I thought the amp auto-detected the radio on the LAN, so I clicked on it, but the amp would not track the radio.  That serial # turned out to be from the radio of a 4O3A user who tested the amp at the factory.  When I manually entered the correct serial number, all was well.  If it wasn’t for that the configuration would only have taken a few minutes as others have stated.  Another minor problem was trying to change the brightness of the backlighting that shows the amp’s state.  Turns out it is a known bug and is in the queue for resolution.    

Headroom.  Based on comments from folks in this group who have run it all day in digital modes at the legal limit, the PG MAY have somewhat more headroom/efficiency than the KPA1500, maybe (as others have stated) due to the choice of PA transistors, harmonics trap, automatic bias class switching between AB and AAB, and/or vapor chamber heat sink.   I haven’t run it at high power yet (except into my dummy load) because I need to upgrade my antenna system surge protectors (which would fire at high power) and coax jumpers.   I’m moving stuff around and changing cabling right now. 

Engineering for clean signals. Use of diplexed filters, the automatic bias class switching, and harmonics trap are supposed to result in cleaner signals than competing LDMOS designs.  Hope this is true.  Future test reports will be interesting.

Fan and relay noise.  I can’t really compare this to other amps, since this is my first one.  I found the noise to be about what I expected from Ria’s comments.  There is noise all right, but it’s not objectionable to me either.  And if it was, I could move the amp further away since I control it from the keyboard.  But I prefer to have it close by because I like to look at what I paid $7K for.  Or maybe not!  (-:    From I read, the KPA1500 is somewhat quieter - it uses pin diodes and has a separate power deck (with its own fans) which can be located further away.  I think the bottom line is what is more important to you, headroom at high power or noise level.  Cooling at high duty cycles at max power takes a high air flow and some noise is unavoidable. 

Compatibility with other radios.  I plan to also use it with my ICOMs since the PG supports the ICOM protocols.  The KPA1500 does this too. 

Tuner.  The KPA has an internal tuner.  The Flex tuner is not available yet and probably won’t be until early next year.  This is not a big issue for me, since I’m getting the Flex tuner free with my 2017 pre-order.  In the meantime I’m using my manual ATR-30, which has the best matching range at high power of any tuner I know of. 

Other comments.  SO2R is not important to me, which is a shame since that’s one of the main features of the amp.  On the other hand, if QSK were important to me I would have gone with the KPA-1500 since it supports QSK via faster pin diode switching (4O3A has stated the PG uses slower mechanical relays for reliability at high power and better isolation).  Also I somewhat prefer the traditional looks of the KPA, but I’ve gotten used to the clean looks of the PG, especially with that great display! 

I’ll be sending the PG back for the 6M fix sometimes soon.   That problem was a little disappointing but these things happen and Flex did the right thing and is fixing it promptly.  The great support from Flex would be another reason for choosing the PG. 

As I said, this is my first amp (50 years since first licensed, geez how time flies!), and I’m having a ball with it playing catchup, time permitting!  BTW, hope Ranko/4O3A publishes his long awaited comparison between LDMOS amps sometimes in the near future.  Also for more reports from other users.

Howard

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HCampbell WB4IVF

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Posted 4 months ago

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Varistor

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I would be very interested if someone would measure the emissions that are leaking out of the amp cabinet. Specifically, the dump resistor used in the diplexer LPF. 400 watts going into it is a lot of power!
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Bill -VA3WTB

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Howard..If you have talked to some people running the XL you will notice how clean they are. I commonly see at least 40db down, that is really good
(Edited)
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Chris DL5NAM

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Howard, good joke 49W :-) :-)
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NX6D Dave

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Don't forget about the 15 dB rule. I think the minimum drive power for 1500 watts out is about 47 watts, under the rule.
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HCampbell WB4IVF

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OK Chris –   49W (+/-) 3% in results in 1500W (+/-) 3% out.  In other words, Bill is correct. 

Agree that accuracy beats precision.   (-:  (-:

HC

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Doug Hall

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NX6D, "The rule" as I understand it is for U.S. amplifier manufacturers, not for owners/users of amplifiers. No? 
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NX6D Dave

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Sounds right to me.  Thanks for the clarification.
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NX6D Dave

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One of the things I like about the PGXL is how quickly it can be started and, with the integration with SmartSDR, how quickly you can change from barefoot to "fire in the wire".  Monitoring FT8 on 6M, every once in a while I see a brief opening to some distant location.  If the amp is on and idling on Standby, I can switch to high power and go after that DX station in seconds.  He reports me at -20 at 400 watts?  OK, I can double that right now and secure the QSO.
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KF4HR

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Howard, reference your comment, "Another minor problem was trying to change the brightness of the backlighting that shows the amp’s state."   Is the Amplifier's display is too dim? 
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HCampbell WB4IVF

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The display is fine.  But the backlighting across the front of the amp next to the display (that changes color depending on whether the amp is in standby/on/transmit/firmware update state) is dim and hard to see in a bright room.  The configuration tab slider to change the brightness is inoperative.   I submitted a ticket and was informed that it’s a software issue. 

(Edited)
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KF4HR

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Thanks Howard.  
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HCampbell WB4IVF

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No problem.  When they fix this I can turn those flashing Federation starship bridge LED’s to warp and really impress my little granddaughters with my shack!   (-: 

Howard
(Edited)
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Roger J. Buffington

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Very interesting thread. Thanks for your impressions and info.
XXX de Roger W6VZV
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HCampbell WB4IVF

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FYI, below are some thoughts by the Power Genius XL designer: 

- Fast protection is certainly something that doesn’t need a lot of discussion. It needs to be a feature of every amplifier. PG XL antenna connector can be short circuited or the antenna disconnected at full power and nothing will happen. Not even sparking. That’s because the protection is fast enough. If you see sparking – protection is slow and transistor is struggling to survive under remaining RF energy and in danger of burning.

Anyone who decides to go for a solid state amplifier should ask for such a test from the manufacturer as a precondition.

- Filters are, of course, the next component that needs to be technically great. Big SWR increases filter insertion loss and increases heating. Somewhere between 1:2,5 and 1:3 SWR it becomes critical.

Filters should be designed for the maximum allowed SWR and the worst impedance case with som*e *additional reserve as well.

Harmonic suppression is extremely important, especially for Multi stations. For that reason, PG XL has duplex filters and suppress all harmonics typically <75dB. This is much better then tube amplifiers. FCC regulations require Harmonic suppression of <43dB which is insufficient for a multi environment. This is why not even the FCC certificate guarantees that the amplifier will be satisfying for a Multi station.  With 70dB harmonics suppression, and some additional filtering, you can easily realize very comfortable operating on a Multi/Multi station.

- Efficiency. For all single tone modes, the efficiency can be controlled in the same way PG XL does – with dynamic VDD modulation. MEffA controls Vdd and makes sure highest efficiency for the given power.

 -SO2R amplifier will become the standard. Today, with Flex Radio and PG XL you have an SO2R setup. In a Multi Op setup SO2R is used for In Band stations that operate on the same band. Also for all the categories where

one signal per band is allowed, regardless of whether it’s on the same or a different band. How much cheaper, simpler and more efficient this setup is doesn’t even need clarification.

 - Finally, the last feature every device today needs, even an amplifier, is flexibility. The technological trend takes us to new stations and accessories connected to the local LAN or WAN networks so the time ahead brings us new possibilities. We already have this and it will become a new standard. Loads of data from various devices in LAN. PTT, inhibit,

frequency, modes, relay statuses, SWR, antenna direction, audio. Basically everything.

 This is why an amplifier must be a part of the system as well. In a future concept it can become a server, client, send data, change parameters remotely etc. This is why an amplifier must be upgradeable and have the option to be completely controlled by software.

 For this reason, PG XL has bias, protection unit and the power supply completely controllable by software, as well as a touch screen display so it could be updated WITH new functions in the future.

 We are heading towards exciting times where station layouts will be completely different and more powerful.

 73 and HNY

 Ranko, 4O3A

 --------------------------------

 I believe his claim of PowerGenius XL 70+ dB harmonics suppression was confirmed in the test report submitted to the FCC.

 Howard






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Stephen Hawkins NG0G

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I operate full break-in almost all the time.  How loud are the relays?  I currently have an AL80B with an external QSK-5.  Before I had the QSK 5 I always felt like I was beating the relays to death when I sending.
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HCampbell WB4IVF

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Stephen -

The relay clicks are there but I don't notice them that much after a while – if anything I think you’d find the fan noise more of an issue.  But if I needed QSK I would probably have gone for another amp with pin diode switching. 

Howard






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Bill -VA3WTB

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They used relays in the PGXL for a very good reasons. For SO2R mode they offer 70db isolation. As high as 2.5kw Pin diodes can not.

And at high power they give a long service life.
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WQ2H - Jim Poulette

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Thanks for the candid report Howard, much appreciated.
73
Jim, WQ2H
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Geoff - W8GNM

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The next step will be to put adaptive pre-correction around the FlexRadio and amplifier combination to drive the IMD levels below 50dB.   This is a feature that the Flex engineers should move up in priority.
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Geoff - W8GNM

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50db is 10dB less adjacent channel QRM than 40dB and well worth striving for.
It really doesn't matter if the exciter/transceiver has very low IMD distortion in its output stage.   The IMD will be generated in the linear amplifier even with LDMOS technology transistors.
I doubt that the combination of the FlexRadio transceiver driving the PG amplifier is actually producing a signal with all the IMD products down 40dB under typical operating conditions.   This is nearly impossible to achieve without fixed or adaptive pre-correction of the system.
ANAN PureSignal APD is typically achieving 60dB with many different kinds of linear power amplifiers.  I would expect Flex to keep up with and excel relative to APD technology that others are offering.  I don't think the introduction of APD should be a top priority, but we have been discussing this for more than 5 years and it is time to move it along as a Flex feature.
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David Decoons wo2x, Elmer

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Geoff

We are allowed to have different opinions. Software changes to the 6000 series software have made the radios a lot cleaner than the Japanese competition and the PG XL is cleaner than other LDMOS amps due to the higher biasing on SSB and MeffA efficiency on single tone modes (cw, FT8, RTTY). The other amp that is very clean is the German Kit amp.

Not sure what Elecraft is using for bias current on the KPA 1500 but I do not believe it is biased as heavy as the PG XL on SSB.

There are a LOT more non-SDR radios on the bands that are worse in IMD performance than SDRs. Even if Flex were to add APD it would be like someone throwing a gallon of fresh water in the ocean. The water will still be salty.

I have personally owned an Anan 100D, 200D and now own an 8000dle along with my 6600 plus a remote 6500 at work. The 100D and 200D IMD are noticeably worse than the 6600 when APD is off. Obviously the Anans are cleaner with it on but the question is, how clean is clean enough?

Again, you are enetitled to your opinion but I am happy with the current performance of my radio and amp. I would like to see Flex continue to add new features which make operating more enjoyable.

My operating is chasing DX, ragchewing, DIGI modes such as FT8, and remote operating. Much easier with the Flex than Anan.

Respectfully
Dave wo2x
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Bill -VA3WTB

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With the harmonic filter in PGXL cleaning everything up out side the set band pass, the radio and Amp together does indeed transmit at least 40db down. I have seen it on Dave's signal when his signal reaches S10 he his very very clean. that is around -40 at s10. So is is not impossible as we have seen.

Flex has already said that APD is on their list to add into SSDR softwar as the hardware is already ready.
But because we are acceptable now and not causing problems to others,,no need to rush.
For me? I would also like Flex to continue with more ground breaking features they have done and have planned.
Pure signal would be really nice to have yes,,I want it. But the way things are right now I'm happy knowing my transmit is clean.

Oh and I notice other companies other Anan who have SDR's in there line up have no plans at all to implement APD, And there sales are doing well.
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Chris DL5NAM

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@Dave

>> the PG XL is cleaner than other LDMOS amps due to the higher biasing <<

OH, you have a test of the PGXL ? Or better much better a PA comparison ? Please show us !



73 Chris
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David Decoons wo2x, Elmer

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Chris. I did mention the German Kit amp you are involved with. You bias the BLF189s at 5 amps and it runs very clean, probably better than the PG XL which is a pair of NXP150H @ 4 amps.

My observations with other LDMOS amps include the Elecraft KPa 1500 which I have seen theee on the air. While I do not know what bias they use of three people I know who have them one is clean running around 800 watts (his normal output) and two were not as clean with comparative signal strength (both driven by non-SDR radios).

The single device LDMOS device amps appear to not be as clean at their rates power out. I can attest the SPE 1.3k/fa @ 1300 watts is not as clean as the PG XL @ 1500 watts. This is due to a number of factors.

I have not lab measurements but just my observations. Again, your RF Kit 2k+ is very clean.

Dave wo2x