ADC2 Overload! Condition?

[KA9UVY]

Turned on my radio today and did a single 2tone adjustment, started getting an error message (ADC2 OVERLOAD!) sometimes in RED and sometimes in yellow but quite frequently flashing on and off.. Never had that error since getting the radio 2 weeks ago.
Anyone else experience this? What could be causing this? What can I do about it?
Will this damage my radio?
Late model Anan 7000DLE MK2 but says 3
FW v2.1.12 Potocol 2
Thetis pre-release 2.9.0.8 on Win 10 I7 16G Ram PC

[KA9UVY]

I believe I figured out what was the cause of my ADC2 overload, I was on 10 meters observing this issue and I have a local 3/4 mile away high powered CB operator, as I tuned down from 29 MHZ AM I found that He was talking on 27 Mhz and the Overload error was tripping every time He keyed his transmitter, also noted that the RX took a bit to recover after the end of his transmission.
Since the antenna and filter selection seems to be the same for 10 and 11 meters I'm not sure what I can do to mitigate the overload from a strong local signal on 11 meters when on 10?
Any suggestions for settings, AGC or DSP that might help?
Looks like I might need to purchase a 10 meter band pass filter for this radio to protect it's front end from overload.
I did not see the error on 15 meters or lower but didn't check 12 meters, I'm sure it was getting hammered as much as 10 was.

73, Robert
KA9UVY

[K1LSB]

Increase your ADC2 S-ATT value to 15 or 20 or so.

Mark

[KA9UVY]

Good morning Mark, Thanks for your advice but could you please tell me where that setting is located? I've only been running Thetis and the Anan for a couple of weeks and I can't put my finger on that setting?
Where to find it, and what does it do?
The guy is on again this morning and it certainly looks like that is the root of this issue, I pulled up the Wideband display and can see his spike on 27 Mhz is in step with the Overload error on screen.

Thanks, 73
Robert

[K1LSB]

Robert,

See the pic attached, the two yellow arrows on the mid- and lower-left portion of the screenshot are pointing to the S-ATT attenuation settings.

The upper arrow is pointing to ADC1 attenuation, the lower arrow is pointing to ADC2 attenuation.

Mark

S-ATT.jpg (1.89 MiB) Viewed 2389 times

[KA9UVY]

OK Mark, That attenuates wanted signal as much as out of passband signal, correct?
Not really wanting to loose performance on wanted signal here, is there not a better solution to out of band pollution?

Thanks, Robert
KA9UVY

[KA9UVY]

If I am reading the Wideband graph correctly This guy is hitting -70 Dbm peaks.
I may need to come up with a trap of some kind to protect this radio?

Robert
KA9UVY

[K1LSB]

OK Mark, That attenuates wanted signal as much as out of passband signal, correct?
Not really wanting to loose performance on wanted signal here, is there not a better solution to out of band pollution?

Thanks, Robert
KA9UVY

The raw S-meter strength of any particular signal of interest isn't what's important, rather it's the Signal-to-Noise (S/N) ratio that determines the actual readability of a signal. Attenuating the energy being received by the antenna simply reduces the strength of everything being delivered to the ADC equally, including all of the radio signals and the received noise, so the S/N ratio remains unchanged for any given signal in the band (as long as the noise level of the attenuated signal is still greater than the noise floor of the radio itself, which can easily be determined by simply disconnecting the antenna).

As proof of that, look at both receivers in my picture above. The upper receiver is on a tuned dipole and the lower receiver is on a wideband active mag loop, which doesn't capture anywhere near as much energy as a dipole. But look at the PBSNR meters in the upper middle portions of the screen. Those meters show nearly equal S/N ratio for both ADCs, even though the S-meter signal strength of ADC1 is at least 10dB higher than ADC2 (which can be easily seen on any of the several pairs of S-meters strewn about my console, lol). In short, attenuating a signal doesn't adversely affect the readability of any signal at all. As long as a signal is above the noise received by the antenna it will still be the same relative level above the noise after everything is attenuated.

Go ahead and dial in some attenuation and see for yourself that the readability of any signal isn't affected at all.

Mark

[KA9UVY]

Hello again Mark, I follow your comments pretty much all the way but in the back of my mind attenuation equals noise floor... Been thinking that way all of my Ham tenure. Worked weak signal UHF for years and coax loss + connector loss is always added to noise floor.
Guess what's really important is always as you say S/N ratio but easier to achieve enough signal to demodulate over a LOW noise floor, correct? I have no control over the signal I'm trying to hear but I do have control over the noise floor to some extent, coax loss, local noise generated near my receiving antennas etc.
I did find a way to turn on the step function so at least the ATTN doesn't go 10 db at a time, I will experiment and see how much attenuation is needed to keep the offending signal from overloading the ADC.
Just looking at the WB display makes me scratch my head since I have a ton of spikes showing between 14 Mhz and 30 when on 10 meters but while ago I had a QSO on 160 with a local and all of that region of the spectrum was totally attenuated by the filter in the Anan.
Watching the WB graph is interesting and it seems as though the same filter is in use from 12M-10M and even in the 6 meter band those signals between 14-30 are quite visible here.
The signals would be attenuated more if I used separate antennas I guess but a Hex beam is employed here from 20-10 and a multi sloper is used on 160-40 so I'm sure that aggravates the situation... Maybe I will have to kick a tuner in to act as a band pass filter ?
So much to learn here.
Thanks again, 73
Robert
KA9UVY

[K1LSB]

Robert,

You're overthinking it. Even after attenuating the signal coming in from the antenna, as long as the noise level is still above that of the machine itself (which can easily be determined by disconnecting the antenna -- if the noise floor drops then the noise level coming in from the antenna is the limiting factor, not the radio's front end noise floor) then there is absolutely NO degradation of the S/N ratio, and even the weakest signals that are being received are still just as readable as if no attenuation had been applied at all.

Your experience with UHF is valid but simply doesn't apply at HF noise levels, due to the fact that VHF/UHF noise levels are typically much lower than the noise levels encountered on HF.

If you haven't already applied 15 dB of attenuation to your overloaded ADC2 (and then disconnected the antenna to verify that the noise floor does indeed drop further) and visibly seen the results for yourself then you're never going to understand what I'm talking about.

Mark

[KA9UVY]

I just saw this post and with 15 db ATT on I can very slightly see the waterfall change when I pull the antenna off. -108 to -128. Does that mean there is still 20 db of wiggle room? I put in 30db of attenuation and now unhooking completely yields same -108dbm on 10 meter AM. Good grief, I'm gonna have to let that soak in for a bit Mark.
Thanks again
73, Robert
KA9UVY

[K1LSB]

Yes, now you're actually witnessing what I was referring to. If the noise floor drops when you pull the antenna then the attenuation isn't having any negative effect on any signal that's above the band noise.

Mark

[K1LSB]

Robert,

The only reason I advised you to dial in 15-20 dB of attenuation was so we could suppress the strength of the offending nearby signal sufficiently to get rid of the ADC Overload condition. If 5 or 10 dB of attenuation will suffice to accomplish the same thing then there's no need to run more attenuation than that. Whatever level of attenuation is sufficient to correct the overload condition is all you need.

Just wanted to clarify that for you.

Mark

[KA9UVY]

Ok, Thanks Mark, been experimenting this evening but haven't had the local on yet...will try and find a place to set it... This radio is amazing in many ways, actually retains ATTN settings per band!
Hope to catch the signal on and find a happy spot for my ADC. Strange I haven't caught anyone on 10 Meter AM since I got this radio and activity had really been picking up when I was using my Kenwood. I have talked to a local on there and it's not deaf but not sure how good it is on 10 or 6 meters.
I remember my Flex 5K ( a decade ago) was poor on 6 meters and you could insert a preamp in the loop for RX only, does this radio have that ability ? Lots of connections on back but not seen clear documentation on hooking up transverters or optional preamps and filters.
Guess that's another thread..
73, Robert
KA9UVY

[K1LSB]

The radio appears to have a 6-meter preamp (Low Noise Amp) that you can enable or disable but I've never used it so I can't attest to its functionality:

Capture-3.jpg (151.26 KiB) Viewed 2271 times

Mark

[KA9UVY]

Mark, looking at the form you have open in setup, I wonder if I could tweak the lower cutoff freq on the 12/10m filter to just above 27.5 mhz? Would sacrifice the 12m reception but might mitigate the CB overload when on 10 ?
Robert
KA9UVY

edit: wouldn't let me cutoff above 24 Mhz,

[K1LSB]

Robert, I've never fully understood the function of those filters, nor the operation of the Bypass/55 MHz BPF.

However, I will report that the effect I'm observing on RX2 of the 6m LNA and the Bypass/55 MHz BPF are not at all what I was expecting.

Sorry I'm not of any help to you there.

Mark

[w-u-2-o]

Mark, looking at the form you have open in setup, I wonder if I could tweak the lower cutoff freq on the 12/10m filter to just above 27.5 mhz? Would sacrifice the 12m reception but might mitigate the CB overload when on 10 ?

The bandpass filters which comprise the preselector in the ANAN hardware are not adjustable. Go to the schematic section of the forum and download an RF board schematic for the ANAN-200, it is almost exactly the same as for the 7000 for which the RF board schematics are not yet allowed to be publicly posted (but can be obtained from the factory on request).

The numeric fields on that setup screen tell the software which fixed, non-adjustable, hardware bandpass filter to select when the receiver is tuned to that frequency range. This feature is a leftover from the very early days of the openHPSDR project (the PowerSDR days) when people were rolling their own filter boards. It probably no longer has a place or purpose with any ANAN series hardware. It is best left alone.

The bandpass filters in the preselector are only third order, therefore have limited ultimate out of band rejection, and thus are of limited usefulness against a very strong, out of band signals.

Increasing the step attenuator is the way to go, as already described. The noise figure of the basic ANAN receiver design has never been formally measured AFAIK. However, if you use a dummy load, set S-ATT to 0dB, and measure the noise floor in dBm/Hz, then compare that to the theoretical thermal noise floor of -174dBm/Hz, the noise figure can be estimated to be around 17dB on 10M. Not spectacularly good, but typical for an HF receiver.

For every dB of attenuation you add the noise figure will increase (get worse) by 1 dB. You can easily see this effect if you have a dummy load. And Thetis makes it easy to measure as Richie conveniently added a noise power spectral density readout on the second page of the info line.

Capture3.JPG (32.04 KiB) Viewed 2177 times

As long as you don't degrade the noise figure by more than the band noise you are not going to hurt receiver performance. This is why when you take that dummy load off and attach a real antenna you don't see any changes in the noise floor until you start cranking in quite a bit of attenuation.

Adding attenuation can improve receiver performance by optimizing ADC dynamic range. Indeed, my standard practice even without interfering signals is to increase S-ATT until I see the SNR of the largest signal on the panadapter start to drop, then back it off 2 or 3 dB. Having an attenuator adjustable in single dB increments is yet another way our radios work better than others, which typically only offer 10 and 20dB steps.

[KA9UVY]

Thanks for the information regarding the filters in the Anan, and the attenuator advice.
Since " The bandpass filters in the preselector are only third order, therefore have limited ultimate out of band rejection, and thus are of limited usefulness against a very strong, out of band signals."
I wonder if you could direct me to an informational post on how to insert a preamp or filter into the RX signal path?

I remember a Decade ago when I ran a Flex 5K and you could select an in and out connector for such a purpose. I haven't had any luck so far with an RX antenna switching in or out. I can set it up in the antenna selector and it is connected but the green RX ANT button in the center top of Thetis doesn't seem to do anything... I can only switch it in and out with the antenna selector matrix.. I can switch it out at the bottom of the Thetis screen where you can select only 1,2,3... I placed my RX antenna on EXT1 in so maybe I should have it in another port?
Another Thread perhaps..?
I have looked at a few manuals on the Anan website and can't say I'm having a lot of luck following them... Is it true that my radio doesn't have it's own manual? They seem to have encompassed the high power and computer equipped models with it and it's clear as mud to me when they bounce back and forth describing connectors and such that aren't on all three models.
Maybe they could color code each radio models section or something to help... Think I learned more from the 200D manual than anything else I found on there.
Thanks for all your guidance, I't clear you have answers and boy do I have Questions! After 10 years away from SDR TXCVRS I have a lot of catching up to do.
73, Robert
KA9UVY