SA44B (ARM / Pi2 version) for spur hunting

I know there are plenty of uses for the SA44 (and other USB SA units). How are forum users putting these devices to work? I’m interested in a spur hunting device (specifically, amateur radio homebrew transmitter spur and harmonic testing) – to make sure both spurs and harmonics are down from the carrier by the legally required minium.

Would the SA44B (running on a Pi2) be reasonable useful for this purpose? My target frequency range would normally be 137 KHz up to 50 MHz (but not necessarily all at once!).

– Ron

Hi Ron,

I would consider a small windows PC or laptop for best use. There are several restrictions on the RPi2 platform due to driver and throughput issues we have over USB 2. The PC restrictions are very low for the SA44B if you are going to use the API (most PCs will have no problem)

Regards,
Andrew

Hello Andrew,

Thanks for the tip. I’ll probably run it on a PC then. Still, I do like the fact that a Raspberry Pi build is available, in a pinch or for a less demanding situation. A lot of other vendors don’t provide such a thing.

– Ron

Hi Ron,
I’ve had the SA44b/TG44 combo for a few years and it has revolutionised my homebrewing activities. Tuning for ‘maximum smoke’ is now consigned to history and I really enjoy spur-hunting and harmonic measuring when I’m setting up a new rig. The small bandwidths available on the SA44b come in handy for sweeping filters too.
It’s amazing to see how a small tweak of (say) the post TX mixer filter or the LO injection can cause the spurs to change in amplitude over the spectrum and it’s easy to set up a rig for best cleanliness rather than ‘max out’.
I usually set myself a target of -60dBc or better for all unwanted outputs and it can sometimes be a (rather pleasurable) struggle to achieve the last few dB.
Computer here is a Win10 i5 laptop clocked at 2.8 GHz with 8 GB of RAM, but it runs almost as well on my old W7 P6200 laptop @2.1 GHz with 1GB ram.
Hope this helps. I’m sure you’ll find the SA44b very useful – and the price is right!

Andy G1HBE.

[ronaldlees]

Hello Andy,

Thanks for the input. That’s exactly what I wanted to hear. I’ve always had that wishy-washy feeling about trusting someone’s one-time factory test. So, seeing what you’ve written helps the confidence factor (a bunch).

It’s not always the homebrew that I’d like to test. My regular gear will be interesting, plus I’m a kit builder as well. The latest kit uses Si5351A (Qrp-labs). So, it’ll be good to verify (with my eyeballs) that’s as clean as it needs to be.

– Thanks again,
Ron (WB8LZR)

• This reply was modified 7 years, 9 months ago by ronaldlees.

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