Transmit signal levels on panadapter

K9RX
Posts: 263
Joined: Fri Apr 14, 2017 3:47 pm

Transmit signal levels on panadapter

Postby K9RX » Tue Feb 13, 2018 5:08 pm

re: TX PANADAPTER

This is a slight divergence from the previous thread but it is germane to this topic title:

On TX ... why is it that the displayed TX signal is all over the place relative to the vertical magnitude scale? I have TX PAN set at 0 and -70 .... and a good bit of the time when I TX the peaks are near 0 db or so ... but if I go say to 75 meters they might be at -30 .... and if I go to 160 meters they're at -50 or worse ... obviously if I want to monitor my TX I have to constantly go in and change these settings ... ... if the answer is it depends on the attenuator settings well that seems not really a good reason as the att is obviously known and taken in to account for things like the signal strength meter ... [since its looking at the TX output as brought in through a coupler from the amp output - using PS - obviously that ATT value is also known]

Example: 15 meters, no "receive" ATT in play ... PSA, DUP, ~30W peak is at -40db on the TX pan display (USB) ... turn amp on and run about 800W now its at -20 or so ... tried turning PSA off - no difference ... turn DUP off and it is now at -10. On THIS band if i go to CW it properly shows, properly obviously be the objective meaning at 0 db at the peak, it properly shows 0 db whether the amp is on or not. If i go to 160 meter CW then it shows -80 on the peak for CW and -70 when the amp is on (~35W vs. 800W).

My apologies if this is something I'm doing wrong ... although now approaching a year I feel very familiar with the software.

Gary
K9RX
User avatar
w-u-2-o
Posts: 1628
Joined: Fri Mar 10, 2017 1:47 pm

Re: Panadapter & waterfall settings

Postby w-u-2-o » Wed Feb 14, 2018 1:59 am

K9RX wrote: On TX ... why is it that the displayed TX signal is all over the place relative to the vertical magnitude scale?
It is not "all over the place" if everything is properly in order in your setup.

if the answer is it depends on the attenuator settings well that seems not really a good reason as the att is obviously known and taken in to account for things like the signal strength meter ... [since its looking at the TX output as brought in through a coupler from the amp output - using PS - obviously that ATT value is also known]
All attenuation in the signal path is taken into account by the software, that is not the issue.

Example: 15 meters, no "receive" ATT in play ... PSA, DUP, ~30W peak is at -40db on the TX pan display (USB)[
That seems wrong. 30W is approx 45dBm, less 44dB in the Xtronic coupler, you should see about 1dBm peak on the DUP display.

turn amp on and run about 800W now its at -20 or so
800W is 14dB greater than 30W, so things are going in the right direction, but not exactly the right number. Perhaps you just need to use two-tone or TUN to obtain more exact readings. However, in either case, still not the correct absolute values unless there is some attenuation between the coupler and the radio you have not told us about. OR...you have one of those 8000's where the connections are reversed on the rear panel for PS input and feedback.

tried turning PSA off - no difference
That is correct, it should make no difference.

turn DUP off and it is now at -10.[
With DUP OFF you are not getting a value that is referenced to your output power level. This is just what is going out to the DAC. It has no bearing on DAC reference level, which is what determines RF drive on the 8000.

My apologies if this is something I'm doing wrong ... although now approaching a year I feel very familiar with the software.
Something is definitely wrong. Whether it's your doing or the radios we still have to determine.
K9RX
Posts: 263
Joined: Fri Apr 14, 2017 3:47 pm

Re: Panadapter & waterfall settings

Postby K9RX » Wed Feb 14, 2018 4:32 pm

Thanks Scott.... so I learned one thing - it is not as I had hoped or suspected a relative display - rather you are saying its absolute. I'd lobby for it to be made relative as the "tool" as I had envisioned it is to "see" the TX waveform - not know its amplitude (I have that in several other places) ... but at least now I know it is absolute.

Second: I have to apologize - I stated something that was wrong. I mentioned values seen on 160 meters - 160 is not going through the coupler, it is a different antenna port on the amp so I'm seeing just port to port isolation ... sorry about that...

Meanwhile I will now go back and look at values again to see if i can better determine levels now that I know its not relative.

Thanks again - I'll be back ... hopefully with news that it is operator error ... but so far that is not what it looks like.

regards,

Gary
K9RX
User avatar
w-u-2-o
Posts: 1628
Joined: Fri Mar 10, 2017 1:47 pm

Re: Panadapter & waterfall settings

Postby w-u-2-o » Wed Feb 14, 2018 6:04 pm

K9RX wrote:Thanks Scott.... so I learned one thing - it is not as I had hoped or suspected a relative display - rather you are saying its absolute. I'd lobby for it to be made relative as the "tool" as I had envisioned it is to "see" the TX waveform - not know its amplitude (I have that in several other places) ... but at least now I know it is absolute.
To truly know if linearization is being effective one must monitor the output of the amplifier chain. Therefore you will be subject to its absolute amplitude no matter what. I suppose there could be some sort of automatic display scaling utilized to automatically adjust to match your operating conditions, from QRP to QRO, but alas there is not.
K9RX
Posts: 263
Joined: Fri Apr 14, 2017 3:47 pm

Re: Panadapter & waterfall settings

Postby K9RX » Wed Feb 14, 2018 6:55 pm

w-u-2-o wrote:K9RX wrote:
Thanks Scott.... so I learned one thing - it is not as I had hoped or suspected a relative display - rather you are saying its absolute. I'd lobby for it to be made relative as the "tool" as I had envisioned it is to "see" the TX waveform - not know its amplitude (I have that in several other places) ... but at least now I know it is absolute.
To truly know if linearization is being effective one must monitor the output of the amplifier chain. Therefore you will be subject to its absolute amplitude no matter what. I suppose there could be some sort of automatic display scaling utilized to automatically adjust to match your operating conditions, from QRP to QRO, but alas there is not.


software peak detector with a long time constant and hysteresis ... :>)

more to follow regarding my findings ...

Gary
K9RX
Posts: 263
Joined: Fri Apr 14, 2017 3:47 pm

Re: Panadapter & waterfall settings

Postby K9RX » Wed Feb 14, 2018 7:03 pm

Well I composed a reply earlier today - THOUGHT I saved it as a draft but now its not there ... so here goes again:

The power is as measured on an LP100 (factory calibrated about 18 months ago). Xtronics XDC-4SO with 44 db atten (no added amount)

This is what I'm finding:
15 Meters
40W (46dbm) -16 reading should be: +2
400W (56db) -7 reading should be +12
800W (59dbm) -5 reading should be +15

80 meters
40W (46dbm) -23 reading should be: +2
400W (56db) -14.6 reading should be +12 [I increased the scale on this and the next one to try to get a more resolved value]
800W (59dbm) -13.2 reading should be +15

So on 15 meters I'm off by 18 - 20 db reading too low ... on 80 meters I'm off by 25 - 28 db again reading too low.

This would suggest possibly the XDC coupler is "out of whack" both in actual attenuation as well as flatness of response ...

Gary
K9RX
User avatar
w-u-2-o
Posts: 1628
Joined: Fri Mar 10, 2017 1:47 pm

Re: Panadapter & waterfall settings

Postby w-u-2-o » Wed Feb 14, 2018 9:05 pm

Gary,

While possible, it's very unlikely the coupler is at fault. They are extremely simple and rugged devices, and Dave's design in particular is quite good.

Those readings are suspiciously commensurate with you using the wrong port for feedback. At the risk of stating something that is very obvious, the forward port is the port you need to use, with the amp on the "source" port and the antenna on the "load" port. And the reverse port should be terminated with a 1W, 50Ohm termination.

It would be interesting to see if the radio agreed with the LP-100. Attach the forward port to the RX2/ADC2 input on the radio and see if you get the same measurements as the LP-100.

73,

Scott
K9RX
Posts: 263
Joined: Fri Apr 14, 2017 3:47 pm

Re: Panadapter & waterfall settings

Postby K9RX » Thu Feb 15, 2018 1:10 am

Hi Scott,

I know what you're saying about the likelihood that it is something as simple as the coupler - however if it were wound wrong - maybe someone had a bad day, it would show as a lower signal!

As for the "wrong port". No - its correct... I'm using the FORWARD port. I didn't have anything on the REFLECTED side - I just tried a 50 ohm load - no difference as I suspected. But hold on - you said AMP on the LOAD port? No - that's not right... the amp is the source, not the load. The antenna is the ultimate load ... at least that is how I have it wired and how they're viewed normally. PS: I swapped the sample to the reflected and sure enough it is down when on that port so it is wired up correctly. Although surprisingly only ~23 db down! I'd expect it to be -35?

That's an interesting test you suggest - I'll do that.

be back ...

I get nothing when I connect the forward to ADC2. I did unclick one check box, "gnd RX2 on TX" ... but nothing shows - the display just 'goes away' ... I tried adjusting for a bottom as low as -185 ... nothing. Seems like there was a second check box but i couldn't find it.

Gary
User avatar
w-u-2-o
Posts: 1628
Joined: Fri Mar 10, 2017 1:47 pm

Re: Panadapter & waterfall settings

Postby w-u-2-o » Thu Feb 15, 2018 1:19 am

you said AMP on the LOAD port?
I didn't say that. Go back and read again...
K9RX
Posts: 263
Joined: Fri Apr 14, 2017 3:47 pm

Re: Panadapter & waterfall settings

Postby K9RX » Thu Feb 15, 2018 1:45 pm

wow...... i re-read it multiple times .... I AM losing it :<(

my sincere apologies Scott ...

so back to the issue at hand. Coupler? Not sure what else it could be.

Gary
User avatar
w-u-2-o
Posts: 1628
Joined: Fri Mar 10, 2017 1:47 pm

Re: Panadapter & waterfall settings

Postby w-u-2-o » Thu Feb 15, 2018 2:47 pm

Gary,

I would actually be more suspicious of the power meter. Typical ham radio power meters, even good ones, are not designed to provide accuracy at power levels of 10's of milliwatts, or anywhere less than 1W.

Set it all up again. Forward port of the coupler attached to the PS Input port on the radio. With DUP ON and PS-A OFF on, just pick a single frequency to look at. What do you get for power readings using TUN at various power levels? And, if they are wonky, try attaching the cable to the PS Feedback connector instead. Maybe you have on of those radios with the internally reversed wires.

73,

Scott
AB2EZ
Posts: 94
Joined: Sun Apr 09, 2017 2:29 pm
Location: Princeton, NJ

Re: Panadapter & waterfall settings

Postby AB2EZ » Thu Feb 15, 2018 5:38 pm

Gary

Don't forget to check the SMA jumper cables between the coupler, attenuator(s) and the radio for: connector=>connector center conductor and ground DC connectivity, and no shorts between center conductor and ground.

Stu
K9RX
Posts: 263
Joined: Fri Apr 14, 2017 3:47 pm

Re: Panadapter & waterfall settings

Postby K9RX » Thu Feb 15, 2018 8:53 pm

I think I'm going to have to start printing out pageviews. I sent in a reply a while ago and its not there yet - but your follow up one is. I've had this happen before... strange to say the least.

So - in response to your eariler email - it can't be the wattmeter. I'm showing 16 db difference between the reading and what, based on what you're telling me how it works, the "math" says ... 40W = 46 dbm which displays as -14, atten is 44db which should mean that it shows as +2, a difference of 16 db. So if it were the wattmeter that would mean when it is displaying 40W I would really being running only 1W! Not possible of course .... besides BOTH the amp wattmeter and the LP100 both show the same value within 1/2 W of each other....

also it can't be the cable is wired wrong - it simply wouldn't work at all and PS IS working ...

so that aside I have found something.

So, although I STRONGLY believe that “a corrupt database” diagnosis is in most all cases a wrong one – that resetting it only resets EVERYTHING and if there is something in the settings causing an issue you reset it as well (and the user falsely thinks it was a “corrupted DB”) ... today I tried going to the default factory DB and lo-n-behold it is showing about –0.5 and -1.8 db when I’m using 40W on both 15 and on 80 ... so although not the expected +2 db it is much closer AND they are closer to each other.

So starting with that reset DB I have been adding things back in – nothing changes it – I can turn PS on .... still the same .... I switched to a SSB frequency hitting the band button – tried it again – 40W out (TUN) – displays the same peak at about –1.5 ..... THEN .... when I turn on PS and do a 2 tone test –BINGO! Once I’ve done this – the reading is now at –22 db (TUN, still 40W on the wattmeter)! From here on turning PS off/on again doesn’t change this – forever more it appears to be now at a much lower value AND it appears that it changes as I use the radio - possibly as PS is doing its thing – as if whenever the PS is used it changes how a signal – MY signal is measured/displayed....

I've passed this along to Doug - to see if he could then pass it along to whomever is appropriate ... its either a bug or its a non-documented outcome, one that I would have thought others had seen.

Gary
User avatar
w-u-2-o
Posts: 1628
Joined: Fri Mar 10, 2017 1:47 pm

Re: Panadapter & waterfall settings

Postby w-u-2-o » Fri Feb 16, 2018 12:45 am

Can't say I've seen it here, Gary. Everything is spot on using an Xtronic coupler on my KPA500, on both my 100D and 8000, using either PowerSDR or Thetis.
Joe-W4WT
Posts: 75
Joined: Sun Apr 09, 2017 5:27 pm
Location: Cumming, GA

Re: Panadapter & waterfall settings

Postby Joe-W4WT » Fri Feb 16, 2018 7:33 pm

Hi Gary & Scott,

I thought I would get in here as I've seen this problem for some time. Here is what I see with my 8000 board, protocol 1 with ver. 3.4.7 software and ver. 1.9 8000 firmware.

160m - psa off, tune set to 40w, output panadapter reads -12 with Dup on.
160m - psa off, DEFAULT database load, tune set to 40w output - panadapter reads -5 with Dup on.

I also see a difference here with current database and default database with neither being accurate but default closer.
At 80 watts, PSA off, with default database, I read a -2 with Dup on. Exactly 3 db stronger than at 40 watts so the reading is linear but not correct.

Something does appear to be off.

Joe W4WT
User avatar
w-u-2-o
Posts: 1628
Joined: Fri Mar 10, 2017 1:47 pm

Re: Transmit signal levels on panadapter

Postby w-u-2-o » Fri Feb 16, 2018 8:43 pm

Joe,

It's hard to know what is right or wrong in your case without any context. What is your setup? Barefoot and internal coupler? External amp and external coupler? Which ones? Any other relevant data that would allow us to calculate what the correct numbers should be so we can compare them to the numbers you are getting?

73,

Scott
Joe-W4WT
Posts: 75
Joined: Sun Apr 09, 2017 5:27 pm
Location: Cumming, GA

Re: Transmit signal levels on panadapter

Postby Joe-W4WT » Fri Feb 16, 2018 9:09 pm

Hi Scott,

Sorry, should have included that with the other info. Obviously barefoot at that power level and using the Xtronic XDC-1 coupler with an extra 6db attenuator giving me, I think, 50db of attenuation. With 40 watts at 46dbm, I should read -4 with this setup. I am very close to that after the database reset but still off by one; could be my eyeball though. Before the reset it was way off, as indicated in my previous email.

The main point of my chiming in was to note the difference in my current database vs. the default database as you noted but Scott did not. Not sure why that would be.

73,

Joe W4WT
K9RX
Posts: 263
Joined: Fri Apr 14, 2017 3:47 pm

Re: Transmit signal levels on panadapter

Postby K9RX » Sat Feb 17, 2018 12:46 am

Joe,

Great - now go one step further ... reset the DB .... both PSA and DUP on (they have to be on for this test) ... Move the mouse over the RX panadapter display and right click to get the yellow crosshairs. Go to DISPLAY/TX and set the high at 10 and the low at -25, set the steps at 5 to get a little better resolution. Using the TUN button transmit with 40W and using the yellow horizontal cross hair at the peak of the signal measure what that value is. Note this.

Now click on "Linearity" on the top - get the thin panel to show - click on TWO TONE. Let it run for several seconds. Unclick TWO TONE. Now using TUN transmit again at 40W. Again using the yellow horizontal line with the mouse measure what it now reads?

Gary
Joe-W4WT
Posts: 75
Joined: Sun Apr 09, 2017 5:27 pm
Location: Cumming, GA

Re: Transmit signal levels on panadapter

Postby Joe-W4WT » Sat Feb 17, 2018 3:00 am

Hi Gary,

Following your directions, I see -5db on the first test and -28db on the second after running the two tone/psa test. Interesting.

For grins, I reset the database again and it was back to -5db with tune before using two tone.

73,

Joe W4WT
K9RX
Posts: 263
Joined: Fri Apr 14, 2017 3:47 pm

Re: Transmit signal levels on panadapter

Postby K9RX » Sat Feb 17, 2018 1:38 pm

BINGO!

Gary
K9RX
Posts: 263
Joined: Fri Apr 14, 2017 3:47 pm

Re: Transmit signal levels on panadapter

Postby K9RX » Fri Apr 26, 2019 2:35 pm

Just a quick note - personal settings and suggestions for TX Panadapter settings: Max: 10, Min -70, STEP 5

I believe at least at full power using a coupler the signal on TX is referenced to 0 dbm - this takes that in to account: Using a value of 10 for the top means that the top of the signal is at the top grid line shown and is 0 dbm (there's more 'space' above this that it can go in to - but adjusted as such it will not). Set the bottom to -70. Anything less than this is moot.

Also, at least in the current version of PowerSDR (3.4.9 at the time of this writing) there is a bug in the TX display STEP size - it displays twice the value selected. I'd prefer a displayed increment of 5 ... but can't get it so I set it to 5 which gives a display of every 10 db.

Gary
K9RX

Return to “PowerSDR mRX”