JJ4SDR wrote:Q1: I am just puzzled by the fact that this ADC1 overload issue came up only now, after about 1 week's worth of using Thetis v2.9.0.6 x64/P1?
I have no explanation for this other than perhaps the ATTEN on Tx or Bypass on TX settings were changed somehow during the upgrade.
Q2: Are 50 ohm plug terminators on unused BNC ports on back apron completely redundant?
IMHO they are cheap (literally quite inexpensive) insurance and I use them everywhere I have an open port on all of my equipment. Be cautious about using them on any unused ANT connectors lest you transmit into them.
Q3: Why would "A true condition of excessively high RF power level on the ADC input" rear up its ugly head only now (if that were the cause of the overload indication)? I am ordinarily putting out 1kW on SSB on several bands.
I really don't know. It could be a coincidental change in grounding/bonding/shielding/who knows, or the settings issues discussed above. Other than that I really can't say.
Q4: If enabling ATT on TX doesn't remedy this can I assume that "Crosstalk/leakage poor isolation" is the cause of the ADC1 overload (as I don't use PS at all right now)?
Negative. Unless you've got some sort of internal hardware fault in the ANAN then crosstalk involving the circuitry after the step attenuator has never proven to be a problem, even as far back as the original ANAN-10.
Historical note: on the ANAN-100 and 100D, and in the early 200Ds, the original implementation of PureSignal used the terrible internal crosstalk as the coupling mechanism for implementing feedback! There was no formal feedback coupler in the design! Not until the advent of the Rev. 24 PA/RF board was there an actual internal coupler and switched feedback path.
Q5: Did the TX bandwidth on the GUI with DUP enabled look "normal?" Again, I would think that whoever I am communicating with would NOT see my TX bandwidth being that wide?
Yes, they looked perfectly fine, both DUP on and off. Sadly, that is not "wide", that is normal for un-linearized transmitters of the quality we typically see in amateur radio. Even so, in your specific example your signal is maintaining its desired 3.3KHz bandwidth nearly -50dBc (dB below carrier level), which is really good without linearization. And this will all improve further with PureSignal, of course.
Consider also that, given average band conditions, IMD and other unwanted products are unlikely to be seen/heard at the receiving station if they are -50dBc (nearly 8 S-units down) If you are S9+10 that puts the bad stuff at S3'ish, and most noise floors are truly S3 or above (regardless of what those
nasty Kenwood/Icom/Yaeus S meters say it is).
On this point specifically, anything below -70dBm on the DUP display (DUP = ON) is a "don't care", that part of the signal will never be seen/heard by anyone. I recommend everyone adjust their TX panadapter display to cut off below -70dBm.
Finally, DUP ON is, IMHO, vastly preferred because you are seeing an actual spectrum analyzer display of your transmitted signal, not a digital representation of data going into the DAC, which is what you get with DUP OFF.
I checked to see what the ATT on TX on 20 meters was (I am often there) and I see that ATT was enabled with a value of 31dB which I believe is the MAX value available?
Yes, that's max. and using that much is quite unnecessary. 15dB should usually do it.
I noticed the "RX BYPASS on TX" was unchecked on 40m whereas it was checked on all other bands. After checking that box, the TX bandwidth looks much narrower.
Remember that with DUP ON anything below the -70dBm line is a "don't care", so the signal should not look much different above that in either case.
So, with that box checked, much less ATT is needed on TX as well.
This makes very good sense. That box is not normally checked unless you are using feedback from an external coupler for PureSignal.
With the box unchecked during TX, RX1 is receiving the signal from the internal coupler during TX, and that signal level can get quite high, at 100W requiring some 15dB, give or take, to keep the ADC from overloading.
With the box checked and nothing on the Bypass input then RX1 signal levels will be only those caused by external leakage or internal crosstalk. Putting a 50 Ohm terminator on the Bypass port will further attenuate any external signals.
That said, I do not recommend trying to minimize things in this way. As previously discussed, you want to monitor an accurate representation of your transmitted signal on the spectrum analyzer that we call a "panadapter". To do this select DUP ON, select the appropriate Bypass on TX mode (ON for external coupler, OFF for internal coupler) and set the ATTEN on TX setting as required.
I will migrate to P2 even if that won't have much impact on the overload condition.
It should have absolutely no bearing on the issue. However, fair warning: in very rare instances P2 firmware does not work well on a particular serial number bit of hardware. It's unlikely that will be the case. I just don't want you to think there are any absolute guarantees.
Monitoring myself and hearing the audio in the "cans" and it doesn't sound too bad. Earlier today when I saw the same message come up (I was only listening) and switched to transmit (and MON on) my audio sounded really bad, a horrific buzzing kind of sound.
