[hpsdr] New Hermes 2M Board

[Tony Hagen]

Hello Helmut,

Please keep the discussion on the list ... very interesting even we cant be 
an active participant

73
Tony

.........................................
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Subject: Hpsdr Digest, Vol 137, Issue 7

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Today's Topics:

   1. Re: New Hermes 2M Board (Larry Gadallah)
   2. Re: New Hermes 2M Board (Helmut Oeller)
   3. Re: New Hermes 2M Board (n3evl)
   4. Re: New Hermes 2M Board (ad0es)
   5. WG:  New Hermes 2M Board (Helmut Oeller)
   6. Re: WG: New Hermes 2M Board (H.A. Meijer)
   7. Re: WG: New Hermes 2M Board (Jim Sanford)
   8. Re: New Hermes 2M Board (Doug Ronald)
   9. Re: New Hermes 2M Board (Shirley M?rquez D?lcey)


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Message: 1
Date: Sun, 9 Jul 2017 20:35:32 -0700
From: Larry Gadallah <lgadallah at gmail.com>
To: Helmut <dc6ny at gmx.de>
Cc: HPSDR Lists <hpsdr at lists.openhpsdr.org>
Subject: Re: [hpsdr] New Hermes 2M Board
Message-ID:
<CAPtFaQv5i7nZ6y3s4hEL7DNu0z5vdds1HL9=5YQp2efOp8hdsg at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"

Hi Helmut:

Thanks for your comments. I think point 1 is quite a bit more complex
than we can address on our e-mail list, but another difference is that
in most cases, we amateurs are dealing with analog modulation schemes,
whereas virtually all cellular systems are now digital, which does
reduce the required dynamic range of a receiver. Nonetheless, I think
we agree that current generation ADCs are sufficient to the task, if
that task is emulating a conventional analog HF radio. Personally, I
am intrigued with the possibilities of multiple simultaneous
receivers, wideband or spread-spectrum modulation techniques (albeit
most are not legal in the amateur services at this time) and so on;
implementing these would involve less decimation and process gain, and
hence would push the ADC dynamic range requirements higher.

For point 2, I should have made it clear that, yes, I was first
addressing frequency stability, which is not the same as phase
noise/jitter. Of the two, I agree that phase noise/jitter is more
important for dynamic range performance. Poor frequency stability is
just annoying, and should be less difficult to solve than getting
better jitter performance.

Cheers,

On 9 July 2017 at 14:35, Helmut <dc6ny at gmx.de> wrote:
> Hi Larry,
>
> I agree with you in a lot points, but would like to correct two items:
>
> 1. 16 Bit, 130 Msps ADCs are more than sufficient for ham radio 
> applications
> and beat most analogue radios. The typical 100 dB dynamic range refer to 
> the
> entire Nyquist zone. You have to add the process gain for narrow
> band/channel operation. Cellular systems- in particular the new 5G- 
> operate
> at frequencies from 0.8 to 39 GHz and they all need an analogue up/down
> conversion into the 'digital' baseband. This architecture limits the 
> dynamic
> range, not the 16 Bit ADC at the IF.
> 2. Don't mix frequency stability over some hours with jitter. HPSDR 
> sampling
> oscillators are VCXOs and PLL-disciplined from a central 10 MHz reference.
> Every designer knows that too much jitter of the sampling oscillator will
> reduce the dynamic range of the ADC performance. A typical phase noise of
> -152 dBc/Hz at 10 kHz offset is fine. Long before Mr. Sherwood and others
> recognized this fact, Walt Kester of Analog Devices pointed to the jitter
> influence in his tutorials.
>
> 73, Helmut, DC6NY
>
>



-- 
Larry Gadallah, VE6VQ/W7                          lgadallah AT gmail DOT com
PGP Sig: B5F9 C4A8 8517 82AC 16B6  02B6 0645 69F0 1F29 A512


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