After reading your first post about the converter, I built one myself. It doesn’t look as shiny as yours, but it works very well. Took me about one hour to build and test.
I just used standard moulded inductors for the LPF, I get -3 dB at 400 kHz, -30 dB at 700 kHz, and abt. 1 dB loss in the passband.
Below is my simplest SAQ receiver, just a coupling to the soundcard input (two 1N41489 anti-parallel and a 1k resistor on the antenna input, and a series cap to the soundcard connector). The rest is software … using the SAQrx program.
Strange enough I had better results by using my 20m groundplane than by using a 33m long wire. I have tested a mini whip as well, but also no reception with that one. I do have high noise levels here in my city environment.
73
Luc ON7DQ
The Mini Whip works best when it has as large as possible counterweight area.
Otherwise, it receives the noise via the coaxial cables in urban environment.
It works so well at the SDR in Twente because it is (imho) mounted on a metal roof of a high-rise building.
Yes Chris, I always wondered how it can work so well in Twente.
But I don’t have any big metal surfaces to connect to … I may try to get my car up on the roof and connect the ground there
Luc ON7DQ
The Rx-performance of my K3 in combination with this little converter seems to be at least comparable to that of a sound card + Software.
I’m using a Mini Whip as an antenna with good results despite the urban environment. It’s located on the flat roof, approx. 15m above ground. The braid of the coax is connected to some large steel parts up there.
The weakest station received so far was RSDN-20 on 11.905kHz, 12.649kHz and 14.881kHz after our local sunset. SNR is less than 6 dB.
I was astounded by my mini whip, it seems to pull everything in at strong signal strength. I don’t have anything consisting of a large piece of metal but my shack earth is connected to two 1m ground stakes that I drove in during construction. I guess the earth is fairly mediocre but it is definitely better that nothing. I’ll have to see if connecting the braid of the mini whip coax makes any difference.
There are many different opinions on the web about how the Mini-Whip should be installed. What I did was:
Move the PCB as far as possible away from all QRM-sources (that’s why it ended up on our roof, we don’t have enough space in our tiny garden)
Connect the braid to ground, in my case a tall, grounded steel beam (there are similar recommendations, e.g. here: How DOES the PA0RDT Mini-Whip work)
Install a Common Mode Choke near the Bias-Tee (on the coax to the Mini-Whip).
Connecting the braid of the coax to the shack’s earth is worth trying (depending on which noise sources are already connected to the same earth ). A separate ground stake outside the house could also be an option. Good luck!
I’m a bit gutted as I’ve only just got interested in SAQ. I heard about the Grimeton station several years ago but I didn’t grasp the details, now I’m fascinated by it! I know nobody can really help catching Covid, and I wish the team all the best, but I’ve put so much work in to my receive project! Not for one minute do I think ill of the team, it just feels like a case on bad luck on my part. I arranged my weekend around listening for SAQ transmissions.
In a way, I’m glad that I went to town on building my equipment, it’s all neatly finished and ready to go, so it can be stored neatly in a box until needed.
That is a great pity! After I finished the converter, I became really fascinated by VLF and would have liked to listen to SAQ’s broadcast.
Of course there are other stations in this frequency range, but there is not much you can do with the encrypted MSK and FSK signals, except to see in the waterfall how one goes on or off the air.
Well, let’s hope the SAQ team recovers quickly and look forward to the Alexanderson day broadcast.
Congrats on this great success, Colin!
The Mini-Whip is an amazing antenna. Signal strength here was S7, approx. 12 dB SNR. There was a strong station on 16kHz with a wide signal making reception not too pleasant.
Anyway, it was lots of fun
73, Roman
I heard them abt 539, on my 20m vertical, with H/B upconverter and IC-7300.
My 33m long wire gave a much worse result, but then, it runs North to South.
I haven’t found the time to put up my miniwhip yet … it’s still on my ToDo list.
I had a strong QRM, like a HUM, not sure if this was from the 16 kHz signal that Roman mentioned, or just a local man-made noise.
Still happy with the result, and also watched the YouTube broadcast.
Luc ON7DQ
Tried desperately to hear SAQ but nothing at all heard unfortunatelly in Greystones, Co. Wicklow. My VLF antenna is shielded mag loop 50cm dia. + pre-amp + Behringer 202 Using the setup for SID monitoring and casual LF/MW BCB listening. Normally hear very well all of the closer FSK regulars, including decent reception of few farther away alike NAA, ICV, JXN, NSY, NAU But in case of SAQ haven’t even seen anything on waterfall Something to think about now …
73 de EI4JY
