ATU Default Operation

Larry - W9FLA

Is clearing the ATU memory for a band segment considered
normal after turning the MEM button off?

I have a 6700, reset to the factory default state, and running v2.6.0 SW.  The ATU takes up to six tries to find a match on my 80m net frequency of 3.82 MHz.  Once matched, if I turn the MEM button off, the settings are apparently lost.  Re-enabling the MEM button leaves the ATU in Byp mode and it again requires multiple attempts to match the antenna.  Until a match is found, the “Success Byp Mem” indication is sometimes displayed.  Sometimes it shows “Success  Mem” but the no match is actually made.  Sometimes, no relay activity is heard.  The Tune button must be activated to be certain that a match has been made, even if so indicated!

From both the v2 and v3 SW User Guide:

“If the MEM (Memory) option was selected before the ATU tune operation, the result of the ATU tune operation will be stored in a persistence database otherwise known as a memory and recalled anytime the transmit slice is configured for that transmit antenna port (ANT-1 or ANT-2) and ATU match frequency range.”

Note that I am not choosing the “Clear ATU Memories” option.

George

Larry, your 80m antenna may have very high VSWR at 3.8 Mhz, and that may be why your ATU is struggling to find resonance.  I have that problem with my non-resonant 155' long inv vee on certain frequencies where my Elecraft KPA1500's internal ATU also struggles to find a tune.  Because of that, I bypass the KPA's internal tuner and use an external Palstar HF Auto tuner when using that particular antenna.

I realize this does not address your question about your 6700's ATU, but your fundamental issue may be that particular antenna on 3.8 Mhz.  If your 80m antenna is tuned for the CW portion of the band, you will have problems with it up in the phone band.  Your best bet is to stay down on CW where it is a heck of a lot more fun, HI !

73, George K5KG

George

Larry, your 80m antenna may have very high VSWR at 3.8 Mhz, and that may be why your ATU is struggling to find resonance.  I have that problem with my non-resonant 155' long inv vee on certain frequencies where my Elecraft KPA1500's internal ATU also struggles to find a tune.  Because of that, I bypass the KPA's internal tuner and use an external Palstar HF Auto tuner when using that particular antenna.

I realize this does not address your question about your 6700's ATU, but your fundamental issue may be that particular antenna on 3.8 Mhz.  If your 80m antenna is tuned for the CW portion of the band, you will have problems with it up in the phone band.  Your best bet is to stay down on CW where it is a heck of a lot more fun, HI !

73, George K5KG

Larry - W9FLA

Thanks George.  My 80m antenna has a minimum SWR of about 1.7:1 at 3.675 MHz and reaches about 2.89:1 at my net frequency of 3.82 MHz.  When, after several attempts, the ATU finds a match it reads and stores 1.75:1.

I understand that finding a match may be hard near the specified maximum of 3:1 SWR and above.  The tuning process apparently does not successfully converge each time near this area.  I believe that it once did match on the first trial, but likely have not checked it for some time.  I have run SSB and used the Tune function regularly with the stored MEM settings.

I previously thought that if a match solution was found and stored in MEM, then it would remain in memory and be used when the MEM is again enabled i.e. the button toggles between a stored ATU solution and Bypass.

If I understand Tim's response, this is my current take.

If a match solution for a band segment is stored in MEM, turning the MEM off will require a new ATU search for a match solution after the MEM is again enabled.

This would explain what I see.

73

George

Hi Larry, QSL on the VSWR of your 80m antenna.  The Flex's tuner should easily be able to handle that.  I have a relatively new Flex 6400.  So far, I have used it with resonant antennas, and haven't needed to use the ATU.  When I first put the 6400 on the air, I tried the ATU, and it seemed a little finicky to me at the time.  Since then, I have not needed to use the ATU, or explore it more fully.

73, George K5KG

Larry - W9FLA

With v2.6.0, the MEM function operates as a "Write Only Memory".  The stored 1.75:1 match can be used, but if the MEM is cycled Off, with the desired match stored, this solution is no longer available when the MEM is again turned On.  This then requires multiple attempts to rediscover the correct match.  Indeed, sometimes the tuning process would show "Success Mem" but the SWR value displayed using the Tune function would be the same as when the ATU was bypassed!

Yesterday, I decided to upgrade to v3.1.7.  After installing it, it could not obtain a license.  That evening, I saw the license server problem and, after several more hours, downgraded to 2.4.9.  Now my ATU quickly finds a match, as it did before, and I can cycle the MEM function On and OFF without losing the stored match data.  Sigh!!!