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SPE/Flex 6xxx drive control



  • Ignacy Misztal
    edited February 2020
    I have 2k-fa and 1.3k-fa.

    I use 2k-fa with K3. 2k-fa went 4 time for repairs, with at most one due to overdrive. 
    I use 1.3k-fa with 6600. Low power drive mod. Numerous bad antennas and high SWR. Never a problem. Automatic power control for LOW/MID/HI works well. 

    Ignacy, NO9E
  • Tom Worthington
    Tom Worthington Member ✭✭
    edited February 2020
    I just received my SPE 1.5K amp.  I have it hooked to my 6600M with a 3 wire cable as described and with an ALC cable and Hardware ALC is turned on (Version 3.1.8).  All that seems to work correctly but I am just getting started.  The max drive for the LOW setting is 7-10 W depending on the band.  For MID I need about 15 W and about 25 W for the HIGH setting.  I set those in CW mode.  I have been monitoring the ALC voltage with an oscilloscope and it seems to be working as expected; if I raise the drive power or sit close to the output limit in CW mode and then switch to SSB (DX processing) I occasionally see some ALC action.  So far so good. 
    73 and Aloha, Tom, NH6Y
  • Eric Gruff
    Eric Gruff Member ✭✭
    edited February 2020
    FWIW, I had my 1.3K-FA go up in smoke three times with my 6700 driving it. The last time was on the Low power PA setting on 80 M FT8 (probably 600-700 W RMS power) into a tuned dipole with SWR of less than 1.1:1. Half of the RF board was immolated by the heat, but there was no alarm or other warning before I smelled the magic smoke coming out of the amp. 

    I suspect it was more of a heat dissipation issue than a spike causing the LD-MOSFET to pop. I've seen that happen with another SS PA. 

    My opinion is that the SPE PAs should not be used for digital modes, period. The heat dissipation leaves a lot to be desired. My PGXL arrives today, and I intend to baby it quite a bit. I will use my Alpha 9500 and Acom 2100 for the digital modes. They can handle all sorts of insults and just keep on humming along.

  • Lasse Moell
    Lasse Moell Member ✭✭
    edited February 2020
    Using a SSPA and reducing power to baby it may be counter productive, UNLESS the power supply do reduce the transistor voltage. Running less that designed o/p will increase the output mismatch and dissipated power. SPE do reduce the voltage with it's three settings, allowing for a better output match vs power.
  • Pat N6PAT
    Pat N6PAT Member ✭✭
    edited February 2020
    I have a Tokyo Hy Power 450B that's built like a tank. Works great in any mode.  THP amps are always in high demand because they're so rock solid and reliable. In 7 years the only issue I've had with it is a blown fuse.  I sure wish they hadn't gone out of business.

    The only reason I purchased an RM Italy HLA 305V is because the THP amp doesn't do 160. The 305V needs only 2 watts for full power on 160 and is very touchy if you overdrive it.  Not nearly as reliable as the THP.

    Some of these new very expensive amps act like they're made out of glass. One false move and it's back to the factory.
  • Erik Carling EI4KF
    Erik Carling EI4KF Member ✭✭✭
    edited February 2020
    Just my opinion but to me having to change the input power depending on whether the amp is in HIGH, MID or LOW is not good. My 1.5 behaves like that (actually 'behaved' as it is back in Italy after a failure). But my SPE 1.3 takes exactly the same input power to drive it to just under maximum output for all of the power settings, 500W, 1000W and 1300W. There is no need to adjust and no risk of forgetting to reduce input when you change from HIGH to LOW. 
  • Rick Ciotti W3DIY
    Rick Ciotti W3DIY Member ✭✭
    edited April 2020
    Thanks for this feedback. Reminded by SPE US numerous times about many Flex owners with SPE amps who have no issues. Started to wonder about my operating conditions. The ACOM1000, which is my backup amp, is running FB into the same antennas as the SPE and does not require a tuner.
  • Chris DL5NAM
    Chris DL5NAM Member ✭✭✭
    edited February 2020
    your Acom using a PI filter at output !!
  • Erik Carling EI4KF
    Erik Carling EI4KF Member ✭✭✭
    edited February 2020
    If it were true that "..SPE PAs should not be used for digital modes, period" and were effectively not fit for digital they would not be fit for much, given the high percentage of digital operating that now takes place. But their respective user manuals state they are "able to mange all (digital modes) currently in use". Further, Gianfranco I0ZY posted to the SPE Forum that there is no restriction on use for digital modes. False moves are one thing but when they fail through no fault of the user, that is a different matter. 
  • Bill -VA3WTB
    Bill -VA3WTB Member ✭✭✭
    edited February 2020
    And considering that the amps protection circuit is way to slow to protect it from anything. I would see about getting that fixed.
  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin
    edited February 2020
    In comparison, the PGXL is pretty fast about shutting down.  It does it in micro seconds.   

    There is a video on YouTube of Ranko from 4O3A having the amp transmit into a dummy load and then, with the center conductor exposed with a T connector, he uses a screwdriver to totally short the antenna.  

    The amp immediately goes into standby.  No damage.


  • Bill -VA3WTB
    Bill -VA3WTB Member ✭✭✭
    edited February 2020
    I read were Gerald said the PGXL is so fast that a spark can not even be seen with this test. He said before buying any amp do that test first, if it sparks,,don't buy it.
  • Ignacy Misztal
    edited February 2020
    This is not my experience. With low power drive, about 4W for LOW, 6W for MID, and 8 W for HIGH. More on 10M. 

    One way to determine the optimal driving power is to increase drive watching output power, and stop when teh increase is much less than linear.

    For instance if 1 W produces 100W, 3 W produce 290W, 5 W produce 450W, and 6 W produce 470W, 5 W seems OK and 6W is too much. 

    One can drive with 8 W in Low and the amp will work but will be greatly distorting on SSB. Probably no effect on CW.

    Setting different power levels on many bands is trivial with Flex setting in SPE.  
  • Ignacy Misztal
    edited February 2020
    Same was apparently done with SPE 1k-fa. After a series of problems the amp was redesigned. Testing included random short and open at full power.
    Ignacy, NO9E 
  • Rick Ciotti W3DIY
    Rick Ciotti W3DIY Member ✭✭
    edited February 2020
    Yes it is, I have not located a SPE schematic to know how its designed.
  • Mauro HB9FBG
    Mauro HB9FBG Member ✭✭

    Hello everybody.

    TODAY I saw this post after booking SPE 1.5K in February.

    With Covid the delivery will probably be at the end of October but you have given me a thousand doubts ... is it so catastrophic?

    I have friends (who don't have Flex or if they have Flex they have SPE 2k) and they are thrilled. I have the Flex 6400 and have booked SPE 1.5K, no one to comfort me with good news?

    Thanks in advance for any comments.

    73, Mauro HB9FBG

  • I0JBL - Luc
    I0JBL - Luc Member ✭✭

    I have a 6500 linked to SPE 1,5k and works fine. It is possibile band by band to decide the Power input generated by 6500 to avoid any kind of overdrive.

    Best 73 and DX

    Luciano I0JBL

  • Bill AB7AA
    Bill AB7AA Member ✭✭✭

    I have been using a 6700 to drive a SPE 2K-FA for about 5 years with no problem. I drive it to 1.5 KW with about 40-60 watts depending on the band. I do not use the ALC even though the SPE manual highly recommends it. There may be a problem with lesser drive levels overshooting in the Flex, but this is just a guess. I have never had even a hiccup while using the above parameters.


    Bill AB7AA

  • Bob KC9RF
    Bob KC9RF Member ✭✭

    Have the Expert 1.3FA and home brew cable with no issues. Maybe this is just an issue with the 1.5FA. See my post on wiring.

    Make sure you go into the SPE setup for each Amp level and set the desired input to the amp via the menu

    for low, Mid and High. This takes a little bit of time for all bands but is worth it as never have overdriven the amp.

    Mine is the low pad SPE Amp so 10-12 watts will drive it to full power.

    Have run the amp over two years and has worked flawlessly.

  • KT0AM  - Mark
    KT0AM - Mark Member ✭✭

    I've not had any issues driving my SPE1.5k-FA using a 6500 into a Hustler 6BTV vertical in any mode. However, I took great care up front to do a mapping of drive power and mode at the Low, Medium and High settings for each band and at various points in the 80m band spectrum since my bandwidth there is limited (easy to get into high SWR conditions).

    I consult that chart often to make sure that I'm not close to overdriving the amplifier considering band, power level and mode. No magic smoke yet and works like a charm.

  • Ignacy
    Ignacy Member ✭✭

    My feeling with SPE is they work like BMW, very well but may break from time to time. There may be more reliable choices but using SPE is so easy (antenna switch, settable power levels with Flex, pretuning for each antenna separately). My SPE 2k failed 4 times, 3 times covered by SPE warranty and one by credit card warranty. No problems for the next couple of years. After learning of my problems, Gianfranco of SPE volunteered to take it back. I decided to keep the amp, and it was a good decision retrospectively.

    I was cured from tube amps by TenTec Centurion. In one year 2 faults of BK board, one high voltage flashover and a broken band switch.

    There is a problem with digital modes, with guys falling for 50% power just by lowering the drive power as the duty cycle increases. As someone noted, lowering the drive power at same voltage can actually increase dissipation as efficiency plummets. Disisipation power is U * I but output power is I*I*R. So if an amp has an efficiency of 60% at KW out, it takes 1600W W and dissipates 600W. At 50% drive with same voltage, it produces 500W, takes about 1100 W (1600w * sqrt(0.5)) and dissipates 600 W, same as with a KW. With voltage reduced to 35V, the efficiency is restored (more less) and the amp would dissipate around 300W.

    SPE owners have a choice of using the lower voltage to boost efficiency, unlike e.g. KPA1500. PGXL has MFFA, not sure whether this is the same thing as reducing the voltage to maintain efficiency. But PGXL does not have an ATU, which limits its appeal mainly to hams with low SWR antennas (higher level contesters). Personally, my antenna are low SWR except 40m (2 el shorty with 150 KHz 2:1 bandwith) and 160m (80 KHz 2:1 bandwidth). With pretuning by SPE, QSY is instantaneous even on 160 and 40m. No pressing buttons, no turning knobs....

    Ignacy NO9E

  • Chris DL5NAM
    Chris DL5NAM Member ✭✭✭

    There more PA's on market - more silent, with tuner, full remote via LAN, 160 - 6m , 1x TRX and 4x ANT, QSK in 3 mS with PIN diode PTT switching - look for RF2K-S from RF-Kit.de

    73 Chris

  • N5DUP
    N5DUP Member ✭✭
    edited June 2023

    Been a while since anyone has posted here but I wanted to thank all of the posters on this thread. Though I’m not new to SPE Amps, I am to the Flex 6400 and SmartSDR. This thread was IMMENSELY helpful to me in getting my REV 1.0 Expert 1.5K-FA set up with proper RF Pwr levels so it would quit going into Protection mode from INPUT OVERDRIVE.

    I will post the following information that was sent to me from a friend on drive levels but before I do, let me say this, and I learned this from this thread…. The 0-100 RF Pwr: slider is NOT 0 watts to 100 watts, it is 0-100% of whatever RF Prw the radio has and it differs band to band. Use a watt meter between the radio and the amp to verify what rf power the radio is actually putting out at 100% using the TUNE button and then adjust your drive levels according to your watt meter, not the SmartSDR slider value. I found that the radio was putting out significantly more than 100 watts on 160, 80, 40, and 20 meters.

    Thanks again to the OP of this thread and to all the posters.

    Paul - N5DUP

    P.S. Start at several watts under the 30/20/10 MAX/MID/LOW maximum settings

    When the SPE linear is in Standby, you can set the SmartSDR's RF power control where ever you want. When the SPE linear is in Operate, the linear will take over the FlexRadio's drive level based on what you set it for on the linear.

    When the SPE linear is in Operate, just press one of the Left/Up or Down/Right arrow buttons on the front of the linear. When you do this, you will see the "PC:****" appear above where you see "BAND" on the linear's front panel. This is the percent of drive the SPE linear is telling the FlexRadio to use. Basically, for a 100 watt transceiver, 0 to 100% equals 0 to 100 watts of RF output. While the PC:**** is displayed, you can use the same arrow buttons to change the value. The default values used to be 20, 40 and 60 for LOW, MID and MAX outputs of the linear. I think they are different now. Ultimately, the 1.3K-FA/1.5K-FA will need something like 10, 20 and 30 for LOW, MID and MAX. Start out with lower numbers and work your way up to where you want or you see no difference in amplifier output. Again, this needs to be done with the linear in Operate. It cannot be done in Standby. You will also need to make these 3 adjustments for each band.

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