Is a 12-bit ADC a limitation at the solar cycle peak in IARU1?

[Steve Haynal]

Hi Group,

Back in the solar minimum we were debating whether 12-bits would be a limitation during a solar maximum. Are people in IARU 1 finding that 12-bits is a limitation? Just as a reminder:

The HPF on the N2ADR board which blocks AM signals has been the major way of avoiding full spectrum clipping of the ADC. Enable it if you aren't already.

The AD9866 LNA is essential to adjust gain at the input of the ADC for good sensitivity yet avoid ADC overload. Usually a setting of +12 to +24 dB works well. What are people in IARU1 setting this to when the HF spectrum is active? 

Processing gains are real and provide good dynamic range for a single amateur radio band. This is how there is more than ~70dB dynamic range in SDR programs.

https://www.analog.com/media/en/training-seminars/tutorials/MT-001.pdf

73,

Steve

kf7o

[ron.ni...@gmail.com]

Hi Steve,

The limitation of the HL2's 12-bit ADC is most exposed when a nearby HF station operates QRO.  During these situations, I should experiment with some in-line bandpass filters, assuming the other station is on a different band than I want to use, or maybe adding additional in-line RF attenuation for Rx only operation, as the HL2 (plus SDR processing gain) still seems to pick up signals when the built-in attenuation is maxed out.

73, Ron, n6ywu

[Jiri Culak]

Right...I guess its time to add my 5 cents....

I own now in total three Hermes Lite 2 TRXes. (Since I am 99.9% remote, I decided to explore the SDR Route this way) and altough for remote I opted for Flex 6300, but only due to software and mainly smartlink, where little bandwith is needed and i can run on iphone, ipad, etc.,but never ever I came even close to max-out the ADC.

I ran the HL2 in local skimmer mode with 10 RX Slices, conected to Active RX Array, while second was connected to 3el. 40m and only 30m of COAX, listening in from within EU and while I had LY9W,9A1A and simillar big guns reaching -60 / -55dBm signal levels, I was still just fine copying ZL1X etc. I really think when it comes to SDR, that ADC bits are not the only limiting factor - speciall when we can play with ditther and move the whole dynamic range using ATT/LNA to where we wanted it to be at any given moment. 

I wanted to compare so I installed for CQ-WW CW an Red Pitatya clone, with two LTC2208-16bit ADCs running in OpenHPSDR Protocol1. I tried to listen in having a RX Splitter, so delivering same signal to HL2 and the 16bit LTC2208, and again, I just could not find a situation, where the 16bit would work and 12 bit would not. They both performed the same.

So from my point of view - ye LAB Tests might show situations, but in real life - and probably only with XVRTr and VHF/UHF/Micro you can reach such a noise levels and signal strenghts where it can become necessary to have higher dynamic range, but again - even from middle of Europe, I so far managed to hear even in IAR:U Reg1 VHF Contest.

73 Jiri OK2IT

Dne čtvrtek 10. srpna 2023 v 19:00:18 UTC+2 uživatel ron.ni...@gmail.com napsal:

[John Williams]

Do you have a link to your Red Piyata clone?

Sent from my iPhone

On Dec 19, 2023, at 8:23 AM, Jiri Culak <m0i...@gmail.com> wrote:

Right...I guess its time to add my 5 cents....

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[Stephen Seer Snively]

I'm not Jiri Culak, but I would assume the TRX DUO is the Red Piyata clone that runs Thesis. They can be found on several Aliexpress pages, but not anywhere else, really. They often will have a Thesis screenshot as well. Be aware it has only 25mW output and doesn't do PureSignal. 

[Jiri Culak]

On AliExpress or elsewhere is called 

SDR TRX DUO

Jiri

Odesláno z iPhonu

19. 12. 2023 v 15:37, John Williams <jswi...@gmail.com>:

Do you have a link to your Red Piyata clone?

[Jiri Culak]

Hello guys, sorry I’m late but just to clarify

Stephen is right but it will do pure signal since there is a difference and this clone has got two look to digital converters for rx path. Two ltc2208-16 are used. You can either have diversity or two independent receivers, or you can get one input to be your signal. Since it is a low power device, it is up to you, if you’re gonna sample, the signal behind your power amplifier and will use receive input, one or receive input two. 

Jiri

Odesláno z iPhonu

20. 12. 2023 v 23:47, Stephen Seer Snively <scanner...@gmail.com>:

I'm not Jiri Culak, but I would assume the TRX DUO is the Red Piyata clone that runs Thesis. They can be found on several Aliexpress pages, but not anywhere else, really. They often will have a Thesis screenshot as well. Be aware it has only 25mW output and doesn't do PureSignal. 

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[Jiri Culak]

I just thought to show you the LNA / ATT Feature of the AD9866.

Just so you know the setup and test:

1. I am running a CQ in CW with 100W into 3el 20m beam @ 10m above ground using wfview and ICOM 7300

2. I have a Active RX Loops LZ1AQ conencted to HermesLite2 with N2ADR BPF

3. Loops are amplified, sitting about 5m away from the TX Antenna

4. I am listening in on 40m and adjusting S-ATT until I see a that spectrum is clear and no ADC1 overload is being indicated on either Thetis or LEDs

You see on the bottom that from clearly overloaded, to distorted and to clean signal.Yes, the SNR will likely drop a little, but c'mon, being able to listen in without additional SO2R band filters? on 12 bits? This is huge.

Jiri

Dne čtvrtek 21. prosince 2023 v 4:58:43 UTC+1 uživatel Jiri Culak napsal: