Why I chose Power Genius XL & First Impressions

HCampbell WB4IVF

 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

Varistor

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!

Bill -VA3WTB

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

Chris DL5NAM

"See" means you have measured ?

NX6D Dave

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.

Bill -VA3WTB

Yes you can measure on the panadaper

Chris DL5NAM

OK, on panadapter    :-)

Bill -VA3WTB

If a signal is s10 and you see nothing outside the band pass that is very close to 40db

KF4HR

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? 

HCampbell WB4IVF

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. 

KF4HR

Thanks Howard.  

Chris DL5NAM

How many driver power you need for legal 1K5 OUT with PGXL?

Bill -VA3WTB

50w

HCampbell WB4IVF

Right Bill.  49W in results in approx.1500W (forward power) out into a near 1:1 SWR dummy load here. 

Howard

Chris DL5NAM

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

NX6D Dave

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.

HCampbell WB4IVF

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

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

HC

Doug Hall

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

HCampbell WB4IVF

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

NX6D Dave

Sounds right to me.  Thanks for the clarification.

Roger_W6VZV

Very interesting thread. Thanks for your impressions and info. **** de Roger W6VZV

HCampbell WB4IVF

Stephen Hawkins NG0G

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.

HCampbell WB4IVF

Bill -VA3WTB

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.

WQ2H - Jim Poulette

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

Geoff_W8GNM

Bill -VA3WTB

Why should they move it to the top, it already transmits 40db now. At least the amp has already been used with APD

David Decoons, wo2x

Geoff_W8GNM

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.

David Decoons, wo2x

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