On 2026-06-30 12:07, Urban Hakansson wrote:
Hello usrp-users community,
I am evaluating hardware options for a project operating across the HF
band (specifically 1–30 MHz). We are deciding between adapting an
X300/X310 with a UBX daughterboard or stepping up to the USRP X410.
While we know the X410 covers this range natively, its 4 TX/RX
channels are more than our project requires. We are trying to
determine if the X410's lower frequency floor provides a massive
real-world performance leap over a filtered UBX system for a 1-channel
or 2-channel deployment.
I have been reviewing the Ettus KB application note: "Experiments with
the UBX Daughterboard in the HF Band." The document shows that with
careful flow-graph design and external pre-filtering, the UBX delivers
quite good HF performance despite its nominal 10 MHz limit.
I have a few questions for anyone who has pushed the UBX into the HF
band or compared it to the X410:
1.
Pre-Filtering Selection: The KB note mentions an FM-trap and
3-pole LP filters but does not name specific parts. I am looking
at Mini-Circuits components to build this front-end filter chain.
Has anyone successfully deployed specific Mini-Circuits part
numbers for this exact UBX setup?
Examples: Mini‑Circuits VLF‑45+, Mini‑Circuits NSBP‑108+,
Mini‑Circuits ZX75LP‑50+.
I'm the guy who wrote that app-note, years and years ago now. I can't
remember which pre-filters I used, and they weren't mini-circuits, but
I'm sure they have
close to what you need. For the FM-trap, I used a consumer
part--typical in the CATV/SATTV market--literally available on Amazon
last time I checked. If you search
on "FM bandstop" you'll find several examples.
1.
2.
Unpublished Performance Data: Does anyone have characterization
figures, noise floor comparisons, or empirical data regarding UBX
performance specifically between 1–10 MHz when bypassing/working
around the LO constraints?
I didn't gather any detailed performance data at the time. Noise
figure won't be horrible, but I'll point out that for over-the-air
operations in most of HF, you aren't
limited by receiver noise, but rather galactic background noise,
which can, at the lower end, be equivalent to about
50,000-100,000K---MUCH larger than you'll
find in the front-end of ANY modern receiver.
1.
2. UBX vs. X410 Direct Sampling: In practical HF deployment, how much
dynamic range or noise figure advantage does the X410’s
direct-sampling architecture buy you over a UBX using DDC
workarounds and aggressive external filtering?
This I don't know. It certainly is the case that for HF over-the-air
operations, high dynamic range is a requirement, because you can have
very loud signals right at
the edge of your passband. I'll note that the receive-path ADC is
14-bits on an X310, whereas on the X410, it's only 12-bits. This
lowers your dynamic range by
about 12dB, typically. I don't have access to the schematics right
now, so I don't recall whether there are any pre-amps in front of the
ADCs on the X410. If NOT, then
you'd need some gain ahead of the on the X410 to compensate for the
poor noise figure of a naked ADC.
Any insights, test results, or design pitfalls you can share regarding
HF performance on these two platforms would be highly appreciated.
Best regards
Urban Hakansson
Principal DSP / Communications System Engineer Saltenna Inc.
M: 410-980-4577, E: [email protected] W: www.saltenna.com
image.png
_______________________________________________
USRP-users mailing list [email protected]
To unsubscribe send an email [email protected]
_______________________________________________
USRP-users mailing list -- [email protected]
To unsubscribe send an email to [email protected]
