Re: [Discuss-gnuradio] choosing hardware for demos, ham purposes

[Daniel Pocock]

On 18/05/17 23:16, Raj Bhattacharjea wrote:
> Daniel,
>
> Philip Ballister got in touch with me and thought some of the
> following material might help you out:
>
> https://www.researchgate.net/publication/304346578_Open-Source_SDR_on_Embedded_Platforms
>
> Now to address some of your specific requests:
>
> The only thing I know of that covers 3.5 MHz up to 2.4 GHz, full
> duplex, for a reasonable price, is the LimeSDR. That said, other names
> come to mind for this class of usage, including Ettus B200 series,
> HackRF One, Airspy R2, and the bladeRF. Each of these doesn't meet
> some aspect of what you want. Either the low end of the frequency
> range can't be reached (B200, Airspy, bladeRF), or the device isn't
> full duplex (Airspy has half-duplex T/R capabilities).
>
Thanks for pointing those out and highlighting the LimeSDR option.

Another possibility I had been contemplating involves using one of the
sound-card based solutions for HF bands and something like the B200 for
144Mhz, 430MHz and above.

> I'm not sure what clock stability effect you're concerned with
> (frequency accuracy when tuning?), but this shouldn't be a problem
> with any of the above. If it is, the beauty of SDR is that you can
> correct for these kinds of things in software. There are likely
> carrier recovery / PLL tricks that should easily make sure the signal
> you demodulate is nicely down at zero IF, but of course the technique
> depends specifically on the modulation you're working with.
>

Some examples for the ham radio world:

- on the HF bands (under 30MHz), operating SSB with a bandwidth of about
3-4kHz

- on 2 meters, 70cm, 23cm, 13cm, operating narrowband FM with a
bandwidth of about 10kHz, maybe also SSB

For ham purposes, it is important to maintain frequency stability for
both TX as well as RX.  Are the software solutions you propose only
suitable for solving the problem on the RX side?


> As for PAs, I've happily used Minicircuits components in the past.
> Some models that come to mind after two seconds on their website
> are: LZY-22+, ZHL-20W-13SW+, ZHL-100W-272+, and this is based on your
> frequency ranges. Note however that these aren't typically considered
> portable, as they all have sizable heatsinks and fans, and weigh
> several pounds. Also, some of these have significant output power
> overhead beyond your requirements, and use various power voltages, so
> that's something to consider.

LZY-22+ looks interesting, needs 24V at 5.3A.  The package weight
appears to be 4.5kg though, that might not be suitable for hand luggage
on a flight.

I'd be happy to get something that takes me less power, e.g. from 10 mW
up to 10W (~ 30dB gain) covering 1 - 30MHz.


>
> If it was me and I was taking the show on the road, I'd get a 4U or 6U
> 19" rackmount chassis I can roll around, like the kind for audiovisual
> equipment (Gator, SKB RotoRacks, etc.), and get plates / trays that
> fit this very standard form factor to mount stuff like PAs, SDR, and
> DC PSUs. Matching PSUs with PAs and desired frequency ranges will be
> an engineering trade-off you'll have to consider. Plug 120VAC into a
> power strip in the chassis that's connected to the DC PSUs, and jack a
> laptop into the USB connector that hangs out of the back to connect to
> the SDR and do demos, it's that simple :-)
>


Thanks for this feedback.  Some of my travel involves flying with budget
airlines so I'm trying to come up with something slightly smaller than
that.  Ideally, I carry anything valuable, fragile or essential for the
event I am attending in my hand luggage.  Offsetting the weight of
laptop, laptop PSU and other bits and pieces, I'm trying to come up with
a solution under 5kg, including an ATU.  The ATU I have now is about
0.7kg but I could get something lighter, about 0.4kg.  The battery or a
PSU for radio could go in checked baggage when I fly.

Regards,

Daniel