[TangerineSDR] DCC discussion list
John Ackermann N8UR
jra at febo.com
Fri Sep 13 10:50:02 EDT 2019
Reference the voltage regulator conundrum. I was looking at that when
designing the synthesizer board that has now morphed into TangerineSDR.
It becomes quite interesting to design power distribution when you have
devices that want a couple of hundred ma at 3.3 or even 1.8 volts when
starting from 13.8-- that's a lot of energy turned to heat.
Where we had gotten with that design was a switching regulator (we were
looking the TI TS30011) to take 9 to 18 volt input and provide really
clean 4V output. That 4V bus would then drive ultra-low noise LT3045
linear regulators to provide 3.3V and 1.8V. Not-fully-finalized
schematic of that arrangement attached. The key was the physical layout
of the switcher to keep the crud well away from the analog components;
potentially even putting it on its own board.
73,
John
----
On 9/13/19 9:47 AM, Phil Erickson via TangerineSDR wrote:
> Hi Tom,
>
> Definitely agree with Option C. Then the user would have a set of
> specs that their +12V would need to meet in order to guarantee an
> internal spur/RFI level of no more than XX -dBc or however it would be
> quantified. So for example, maybe the user gets a menu for how they
> supply +12V vs how the TangerineSDR will perform:
>
> Moderate effort, moderate cleanliness (lowest $$ for power supply; runs
> off site power)
> High effort, maximum cleanliness (higher $$ for power supply; runs off
> site power)
> Battery, maximum cleanliness (medium to high $$ given that this probably
> is a LiFePO4 battery for good A-Hr life; limited run time)
>
> The thing one would watch out for of course is the user who thinks
> that "Battery" means a battery hooked to a charge controller. Our
> experience is that you have to work incredibly hard to get a non-RFI
> generating charge controller, but unless you've tried to do it, not as
> many as you would naively hope seem to be aware of the problem. (In the
> same vein, solar panels are huge HF noise generators when they are
> providing power; after all, they are nice antennas!)
>
> This is all perhaps obvious to those on this list, but useful to state it.
>
> Regarding your Question 2, not sure what the right answer is there.
> The real question is how to characterize the additional RFI that will be
> produced if the user chooses the wrong DC voltage conversion
> technology. E.g. buck/boost converters are cheap but they have a
> switching frequency which can land nasty coherent harmonics, that don't
> average away, square in the middle of the HF bands. Linear regulators
> are of course nice, but they are energy inefficient. Maybe it's better
> to do that voltage conversion design engineering in the TAPR realm since
> how many users are going to be really good at suppressing RFI if you use
> Option 3?
>
> 73
> Phil
>
> On Fri, Sep 13, 2019 at 9:29 AM Tom McDermott <tom.n5eg at gmail.com
> <mailto:tom.n5eg at gmail.com>> wrote:
>
> HI Phil - We certainly will need requirements on power &
> distribution characteristics.
>
> However I think we first may need a plan.
>
> Question 1: do we operate off:
> Option A: 120VAC input (North America)
> Option B: 120-240VAC input (Worldwide)
> Option C: + 12VDC input? [ +12V means in my view +10.5 to +13.8
> VDC, allowing a battery to be the power input. ]
>
> In my view Option C is the easiest for project engineering, but
> requires the user to generate +12V, battery charge, etc.
> Given the possible worldwide AC variables, battery type and size
> variables, etc., it avoids many issues.
>
> If we were to choose Option C then, at the system level then:
> Question 2 how do we create needed voltages:
> Option 1. Data Engine regulates & distributes all the system
> voltages from a single +12VDC (11-13.8V) input.
> Option 2: Separate DC supply derives all the needed voltages from
> +12VDC (11-13.8V) input.
> Option 3: Each module derives it's own voltages from a +12VDC
> (11-13.8V) input.
>
> -- Tom, N5EG
>
>
>
>
>
> On Thu, Sep 12, 2019 at 7:00 PM Phil Erickson
> <phil.erickson at gmail.com <mailto:phil.erickson at gmail.com>> wrote:
>
> Hi Tom,
>
> It is probably good for item 5 to think about whether
> cleanliness specs for the power supply are required. As you
> know, hash on the DC lines could be a major RFI problem.
> (Batteries would tend not to have that issue, hence their
> mention earlier.)
>
> 73
> Phil
>
> On Thu, Sep 12, 2019 at 9:58 PM Tom McDermott via TangerineSDR
> <tangerinesdr at lists.tapr.org
> <mailto:tangerinesdr at lists.tapr.org>> wrote:
>
> I've combed the meeting notes and some other thoughts and
> put together a frist draft of possible DCC discussion topics
> for HAMSCI / TangerineSDR.
> Please review and send me additions, deletions, changes,
> etc. by Monday the 16th and I'll iterate once before the
> conference.
>
> -- Tom, N5EG
>
> *
> *
> *HAMSCI project discussion Topics for DCC 2019*
>
> 1. Need cost estimates for the Clock, DE, RF, and
> Magnetometer modules.
> 2. What is the schedule for the modules, testing, prototypes?
> a. Data Engine
> b. 2-chan RF receiver
> c. GPS Clock
> d. Magnetometer
> e. Other ? SBC, Power supply, etc.
> 3. Each module will have a unique manufacturer serial
> number based on some PROMs that have this capability. Any
> issues with the number or format?
> 4. Do we need to create any videos describing what the
> project is, what the objectives are, status, or other?
> 5. No discussion so far on power supplies, other than a
> request for +12V battery power capable. Do we need a plan?
> 6. HAMSCI 2020
> a. Any more information on the location?
> b. Should we plan a demo of TangerineSDR or the
> completed parts?
> 7. Receive Antennas. Mike Pappas has acquired a
> calibrated filed strength meter, we discussed seeing if DX
> Engineering would let us measure a production lot of
> antennas (10?) to determine the field strength sensitivity
> and variance.
> 8. Do we need a test plan for the system?
> 9. Upload data compression appears feasible (3:1 ?). Do
> we need any study or proposals of how much data we are
> asking folks to upload? Or is this better to determine
> experimentally?
>
> **//___^
>
>
> --
> TangerineSDR mailing list
> TangerineSDR at lists.tapr.org <mailto:TangerineSDR at lists.tapr.org>
> http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>
>
>
> --
> ----
> Phil Erickson
> phil.erickson at gmail.com <mailto:phil.erickson at gmail.com>
>
>
>
> --
> ----
> Phil Erickson
> phil.erickson at gmail.com <mailto:phil.erickson at gmail.com>
>
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