PureSignal performance on 6M

K9RX
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PureSignal performance on 6M

Postby K9RX » Mon May 07, 2018 2:31 pm

Scott,

Thanks for redirecting me ... I remember reading this some time ago but at that time didn't have anything other than a casual interest.

So - looking at the schematic. Alex isn't used for TX! THAT was my confusion and why I kept saying "if OFF FCC certs would not be met". It is only a, as you note here and as I have confirmed going over the schematics, a preselector.

Also - reading what you have here - so if one does nothing but turn ALEX off on the front - or set MANUAL instead of FIRMWARE on the BPF1/LPF1 page, items 2 and 3 are exactly the same - correct?

If so then why do I see a change in my IMD performance when I turn ALEX off? If nothing is different - if the same filters are in place - why is it that my 2 tone test shows -12db with ALEX ON and -31 with it OFF (25W, PSA off)? My apologies for being what must have seemed discombobulated since it hasn't been answered - that is the question I've been trying to get addressed so far to no avail. [this is still about ALEX - but regards testing on 6 meters using an 8000DLE]

if not the same what else is different that could again address why for me turning ALEX ON makes the IMD much worse?

Gary
K9RX
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Re: Preselectors, the ALEX button, and RX2

Postby K9RX » Mon May 07, 2018 9:59 pm

Scott, Warren & Doug,

Ok .... so I upgraded, again, to version 2.3. If you recall I went back to 1.7 because i had an issue with CW where the TX wasn't well defined (see other forum post).

So again this relates to Alex and it being on or off. I've not had anyone state why turning it off, setting it to "MANUAL" on the BPF/LP page, which if I understood Scott's leader in this thread - made no difference compared to having the default "FIRMWARE" checked..... here are my new results - quite different from previously listed on the Yahoo ground where worst case with ALEX ON I was seeing an IMD of -12 (2 tone test)... but the same results in that turning ALEX ON or OFF directly impacts what I see and get.

Version 2.3, LP100, LNA bypassed, 6 meters (I just found out TAB doesn't work here in this forum like it did on Yahoo so hopefully this lines up):

Code: Select all

PWR   IMD      PSA      ALEX   TX Disp peak   ATT
25W   -42      OFF      OFF   -21            14
25W   -63      OFF      ON    -59            14
25W   -61      ON       OFF   -21            10   (Feedback is green, Correction is green)
25W   -80      ON       ON    -59            0   (Feedback is red, Correction is yellow)
75W   -31      OFF      OFF   -18               (had to manually set to 14 as was getting yellow OL indicator)
75W   -44      OFF      ON    -52            14
75W   -62      ON       OFF   -19            14   (Feedback is green, Correction is green)
75W   -76      ON       ON    -52            0   (Feedback is red, Correction is yellow)


Note I tried using the supplied PS jumper to go direct within the radio - saw no difference on the one test where I tried it. Ext coupler is Xtronics.

So - much better - I've no clue why I was getting -12 yesterday using version 1.7 firmware ... I AM careful and it was real.
questions:
1) WHY am I seeing such a huge drop in the displayed TX signal (DUP of course is on), as much as -38db, when ALEX is on?
2) NOTE: on 15 meters just as a test I see no difference in the displayed TX signal with ALEX ON or OFF... as I would have expected.

Now on to see if the CW is corrected. Note just to be sure, since I found out there is no embedded error checking, checksum, or what have you in the files or after the transfer (which is standard practice in the industrial world - some form of file/download confirmation) ... and since version 2.3 didn't work I deleted it and redownloaded it. Note that ALSO version 2.3(N1GP-beta) didn't work as well so this unlikely was the problem but what the heck...

Gary
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w-u-2-o
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Re: PureSignal performance on 6M

Postby w-u-2-o » Tue May 08, 2018 3:37 pm

Gary,

I split this from the "how to use ALEX" topic because it is worthy of its own topic.

I also took the liberty of fixing your table so that it is readable. You can use tabs within the "code" tags.

First, understand that with ALEX OFF, the settings in Setup > Ant/Filters > BPF/LPF rule. When ALEX is ON the receiver uses hard-coded firmware defaults for its settings.

Doug said that the firmware sets "Disable 6m LNA TX" automatically starting in firmware v1.9. Your results imply that you have not checked this box in Setup > Ant/Filters > BFP/LPF. If it was checked, then the results should be the same, ALEX on or off. So that would explain the differences, if true.

The good news is that PS is clearly working now.

The other bad news is that you seem to be lacking sufficient feedback signal level when ALEX is ON. This is another problem that needs to be resolved. But first let's resolve the Setup > Ant/Filters > BPF/LPF problem. Please post two screen shots of what that window looks like, one with ALEX ON, the other with ALEX OFF.

73,

Scott
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Re: PureSignal performance on 6M

Postby K9RX » Tue May 08, 2018 11:40 pm

Scott.... I'll get back to you tomorrow. I had composed a response but was waiting for more info (talk to Doug today) ... and while waiting apparently the forum timed out my login and didn't warn me of that before I hit "SUBMIT" ... then prompting me to log in (again) so I lost it all.

g.
K9RX
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Re: PureSignal performance on 6M

Postby K9RX » Wed May 09, 2018 5:59 pm

Scott,

Ok .... so first the responses/answers to your post are: yes I had the Bypass TX checked as I had indicated and the only thing that changed on that BPF1/LPF page was the selection of Firmware when ALEX ON was selected and Manual when ALEX OFF was selected - as you had detailed and expected. NOTHING else on that page changes and no other boxes are checked. The 6 meter filters were selected in both cases albeit grayed out ... thus no picture necessary.

I talked to Doug on the phone yesterday and he did some testing. He was able to confirm that when "Firmware" is selected and one is on 6 meters that NO filter was being selected! Thus a bug. He's turned it over to the firmware guy(s) to correct as needed. Apparently this "Firmware/Manual" stuff goes away (the Firmware selection) in Thetis. So I'll just leave Alex off at all times.

So we're good to go.

Gary
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w-u-2-o
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Re: PureSignal performance on 6M

Postby w-u-2-o » Wed May 09, 2018 6:46 pm

Allow me to pile on by saying automatic firmware control of anything is a bad idea in an SDR. Everything should be software controlled. In this case firmware should just be passing through the software commands to select filters and pre-amps appropriately.

I can confirm that this is indeed the case in Thetis. I do miss the ability to bypass the preselection in the main console UI. I have actually taken to leaving all preselection filtering off. I have no local broadcast stations, nor any nearby ham neighbors, nor am I in a contest environment with bad co-site transmitter problems. In short, not needed 99% of the time here.

73,

Scott
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Re: PureSignal performance on 6M

Postby K9RX » Wed May 09, 2018 8:45 pm

ok.... just to be sure I don't think Doug was saying that the filter was bypassed - I think he was saying nothing was done - i.e. there was a "disconnection" from input to output in the RX chain while transmitting. That is the only way I could see, the radio could exhibit 30 - 40db reduction in signal level with ALEX ON. If it were simply bypassed the signal would have gone UP a small amount due to the losses in a muli-pole filter when there.

So if I understand properly the MANUAL selection still keeps the BPF filters inline as needed for each band/segment ... also this was only in TX.

Gary
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w-u-2-o
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Re: PureSignal performance on 6M

Postby w-u-2-o » Thu May 10, 2018 2:29 am

K9RX wrote:So if I understand properly the MANUAL selection still keeps the BPF filters inline as needed for each band/segment ... also this was only in TX.
If you don't have bypass selected, and if you have not manually selected a filter configuration, then yes, this is correct. This is true for RX and/or TX, depending on the settings you have configured.

Again, referring to my "how to use ALEX" topic, the "manual" setting (ALEX OFF) is no such thing--it is more properly labeled "software controlled" as opposed to firmware controlled. And it has its own set of limitations. When in software controlled "automatic" mode (ALEX OFF), it will not respect the VFO B setting (firmware controlled is no different).

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