Re: PHSNA & Measurement Receiver


Another good option for a Poor Ham Spectrum Analyzer is using a SDR receiver. You have many choices, for example if you want V-UHF, there is the RTL Digital TV dongle that is being sold for $10 and it is supported by the most popular free software. The spectrum display con resolve 1 Hz so you can see the modulation sidebands fairly well; the amplitude absolute calibration is not easy to do, but the relative is good so you can measure sideband to carrier ratios, sideband asymmetry and suppression and splatter. Using the waterfall display you see off the air how bad some "linear amplifiers" are. Even I have seen a professional CW station whose key clicks invaded an aeronautical station.

If you want HF coverage the hardware is more expensive, but not too much. I successfully installed one of these TV dongles as a panadapter in a HF transceiver. This doubles as an HF spectrum analyzer with its limitations, but is adequate to check modulations, carrier hum and so.

I even sent several receiving reports to a big HF station, informing them of power supply hum without obtaining an acknowledge. Later I realized that it was not just hum, they were sending 100 Hz encrypted data on their carrier.

73 de Ignacio EB4APL

El 27/05/2020 a las 4:20, wb6ogd escribió:
Hi Nick,
They might be the ones working on the tinySA, they have a prototype tinySA that looks
just like a nanoVNA, screen included.  I stopped working on my PCB version since I can wait
to just buy theirs  ;-)
I don't think the tinySA has enough RBW to look at the sidebands but don't know for sure.
I have used it to look at harmonics and search for spurs.  It displays in real time on the PC
screen or you can add a small display.

On 5/26/2020 6:12 PM, Nick Kennedy wrote:
That’s very interesting, Gary.  I’ll check it out.

Some of the brains behind nanoVNA are supposed to be working on an
inexpensive SA. That sounds interesting. And then there are people using
those DSP wideband dongles to do SA as well. I just wonder how well they
work and if their resolution allows you do look at different side bands and
so on.

Yes, the Measurement Receiver does function as a kind of simple SA. I’d
used it before to look at harmonics coming out of some of my boat anchors
and homebrew QRP transmitters. It did well for that. This application of
comparing the amplitudes of sideband and carrier is nice to have, but
there’s no fast sweep type functionality.


Nick, WA5BDU

On Tue, May 26, 2020 at 6:27 PM wb6ogd <garywinblad@...> wrote:

If you guys haven't built your receiver yet...
The main purpose of the receiver is just to be a simple spectrum
analyzer, if I am not mistaken.
You may want to join the HBTE HomeBrewTestEquipment group.
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Erik, PD0EK, has a great simple design for a 0-200MHz spectrum analyzer,
built with ebay modules
for about $35.  Mine is still in the proto stage but works amazingly
well.  Goes right there along
with my PHSNA as most used test equipment.
His project is called tinySA.  It uses an Arduino(or similar) to control
two Si4432 modules.

On 5/26/2020 3:10 PM, William R Maxwell wrote:
I agree with ted, please keep working on this. My receiver is still
awaiting assembly but it is on the task list.

Bill, VK7MX

On 27/5/20 6:56 am, Ted KX4OM wrote:

Keep it up! I think those of us who have built the measurement
receiver are starved for working ideas to play with. When I built it,
I assumed the initial use would to inject an LO to a mixer such as an
SBL-1 to move an RF signal down to the measurement receiver for
analysis. Sort of like the idea from old QSTs to mix an RF frequency
down to a limited bandwidth scope. I would think that the IF crystal
filtering in the measurement receiver would do a pretty good job for
something like that, and we would be able to see the frequencies like
you have done with your experiment. I need a bit more of the concepts
to work with, but I am interested in what you are doing.

Ted, KX4OM

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