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Re: [Discuss-gnuradio] ham/amateur getting started

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] ham/amateur getting started
Date: Fri, 25 Dec 2015 13:44:56 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0

On 12/25/2015 09:18 AM, Ralph A. Schmid, dk5ras wrote:

First of all, the USRP radios are kind of experimental radios, using them for real ham 
radio operation on antennas will require filters and PAs. "Out of the box" it 
will only be some proof of concept when you create a ham radio application with it.

All 50 ohms, no limitations other than upper and lower border, regarding 
frequency. But connecting a roof-top antenna will most likely not work, due to 
the lack of preselection, you will receive lots of images and other garble.

Ralph, dk5ras.
I think it boils down to "good RF hygiene is still important". Even if you had massive-amounts of excess dynamic range in the digital domain, you don't necessarily have that headroom in all the analog goo that is in front of all the digital "stuff".

When I'm doing RF projects with SDRs where I care about the reliability and consistency of the results, I pre-select with either commercial
  or DIY filters.

In the TX direction (which I don't do much of), you'll almost always need at least harmonic filtering--there isn't a synthesized superhet TX chain on the planet that doesn't have *some* amount of unwanted harmonic and spur energy, and if you're going to be amplifying it, cleanliness of what you're amplifying will not only reduce the amount of wasted power, it will eliminate complaints from other users of the spectrum, and possibly eliminate unwanted visits from the authorities.

Purpose-built radios have already taken care of this, at least in the TX direction, by using output filters that nicely knock-down unwanted mixing products and other spurs. That's nearly impossible to do in a "general, not-designed-for-specific-application" radio like your
  typical SDR.

-----Original Message-----
From: address@hidden [mailto:discuss-
address@hidden On Behalf Of Daniel Pocock
Sent: Thursday, December 24, 2015 13:27
To: address@hidden
Subject: Re: [Discuss-gnuradio] ham/amateur getting started

On 24/12/15 08:31, Marcus Müller wrote:

[1] http://marcus.hostalia.de/sdra/pres.pdf

Thanks for the fast reply, I had a look and I notice you emphasize the USRP
products, you mention the B200 and B210 (the OZ9AEC link I found also
mentioned USRP but didn't specify model numbers)

I had a look at the FAQ[1] and spec sheet[2] to try and find comments about
amateur radio use cases, for example,
- how much TX output power?
- suggestions about use with an external TX power amplifier
- is RX or TX restricted on any frequencies by hardware?
- antenna impedance (50 Ohm?)

and I didn't find any comments on these things.

Looking at the accessory list I found that 782781-01 is a 50 Ohm cable so I 
everything is 50 Ohm?

Even before getting into the software setup, is there any useful guide on
hardware considerations for SDR in an amateur station?  For example:
- power supply requirements
- risk of interference between difference devices in the shack, precautions
- use with other typical amateur equipment (antennas, RX pre-amplifiers, TX
power amplifiers)
- suitability for mobile use-cases, using DC/battery or vehicle power and with a
laptop or even a tablet as user interface

Any feedback or links would be really helpful, maybe they could go in the GNU
Radio wiki Ham page too.

1. http://www.ettus.com/kb/detail/usrp-b200-and-b210-faq
2. http://www.ettus.com/content/files/kb/b200-b210_spec_sheet.pdf

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