6000 Series ATU Memory Bandwidth Adjustment

Ken - AE8I

The FLEX-6000 Signature Series SMARTSDR Software User Guide (v. 2.3.9) states on page 93 that "for high Q antennas that have a very narrow low SWR range, ATU memories can be saved every 10 kHz for a very granular ATU memory profile for that antenna." 

I am unable to find further information in the User Guide about how 10 kHz is chosen, as opposed to the default +/-100 bandwidth. Am I therefore correct in assuming that this is a decision made automatically by the SMARTSDR software, as opposed to it being a user-configurable feature?

David-N5PSM

I am also interested in this subject as I use a "Long-Wire" antenna while traveling.

Geoff AB6BT

I have not tried this, but can't you just save a new ATU memory entry every 10 KHz?

Ken - AE8I

Yes, I have found that a new ATU memory entry can be saved at any distance from the last entry, be it more, less or exactly 10 kHz. The software does not affirmatively prevent this from being done. This, however, only tangentially addresses the concern which caused me to post.

As the User Guide alludes to, I’m using a high Q antenna. My concern is this. Let’s say I have two frequencies that I want to assign to the ATU memory. They are 75 kHz apart and require vastly different L/C values for acceptable SWR. If the ATU memory is at the +/-100 kHz bandwidth, will the second ATU memory entry overwrite the first, making it necessary for me to actuate the ATU again when I return to or near that first frequency? And if so, can the 10 kHz bandwidth be operator activated to alleviate this problem? If not, when does the software “decide” to switch from +/- 100 kHz to 10 kHz? Is it when the operator makes multiple ATU memory entries in a very narrow frequency range, when the software recognizes vastly different L/C values for frequencies in close proximity saved in ATU memory, or does the software make the decision for some other reason?

I understand that some of these questions could be definitively answered by making a careful accounting of SWR values gathered for multiple ATU memory entries accomplished across a narrow range of frequencies. But before I took the time to do that, I decided to post here to see if anyone could supply the answer for me.

   

Geoff AB6BT

I think I see what you are saying but isn't the question answered by this (Page 91):

ATU Match Frequency Range – After the ATU has found a successful match, the inductance (L) and capacitance (C) values are valid for a 200 kHz frequency span centered at the frequency the ATU tuning operation was initiated, or +/- 100 KHz. Once you tune the frequency of the transmit slice beyond that range, the ATU will be put into Bypass mode. The only exception is if there is another previously saved ATU memory frequency contained within that ATU Match Frequency Range and you have ATU memories enabled.

Edit: And this as you noted:

Also, for high Q antennas that have a very narrow low SWR range, ATU memories can be saved every 10 kHz for a very granular ATU memory profile for that antenna.

Ken - AE8I

I read the last sentence you’ve highlighted from the page 100 paragraph as I reviewed the section on ATU functions, but at that time did not feel it adequately addressed my questions. But upon further review, prompted by your posting Geoff, I think it does. Thank you.

Therefore, to restate what might be obvious to almost everyone except me until your posting, the sentence you highlighted is saying that if I commit a frequency to ATU memory and move beyond 100 kHz away, I must repeat the operation to save this second frequency to ATU memory, as this newest frequency is beyond the memory range. I have always understood that. If, however, I save a new frequency within 100 kHz of the previous, the settings for this new frequency are saved, without overwriting the first ATU entry. And so, I assume the 10 kHz bandwidth is called out in the User Guide to explain there will be no overwriting if the second frequency differs from the first by as little as 10 kHz and as much as 100 kHz. If ATU memory data never overwrote other data, no matter what the difference in frequency, then the 10 kHz statement in the User Guide would not be necessary. Hence, overwriting must occur at less than a 10 kHz bandwidth when saving ATU data in memory.

Geoff AB6BT

I wonder what happens if you try to save ATU memory settings at 5 KHz spacing?

Ken - AE8I

That is already on my to-do list for the near future.