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Messages - ultravista

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General Radio Discussion / QRM Question ~ 15000 KHZ to 50000 KHZ
« on: March 17, 2019, 1535 UTC »
I am in Southern Nevada and finding QRM spikes on my SDR that are also present on other SDRs in area (Southern California, etc). I am can see these noise signatures above 15000 KHZ spaced somewhat evenly all the way through 50000 KHZ.

When tuned in AM, it is like a rushing sound - every one sounds the same. The QRM is always present across multiple antennas and geographically distant SDRs.

I see the same QRM on a California SDR at exactly the same frequency. It appears day and night.

I would like to know the source of this QRM. Perhaps a natural source?

Broad view from my SDR

Close view from my SDR

Close view from Tokens Southern California SDR

so ... does any of that help explain the noise or how to fix it?

I am using an Astron linear PS with a Rig Runner. I could use this to power the antenna too, correct?

Make sure the gain is the same as well as the freq range when testing, reason being if the same conditions do not apply, then you may be overloading the radio with one amp and not the other.

Also some switching mode power supplies use 10kc as a resonating freq and can show up on an antenna as they are transmitting, this is a good reason to endeavor to persevere to use only linear power supplies. Also also, a pc or networking gear may make rfi every 10Kc or so, most pc and networking related gear employs switching mode power supplies due the efficiency, rfi be damned.

I am using an Astron linear PS for my Yeasu. I can say with certainty that the noise is not present with the PA0RDT or any of the random wires I've messed with. The noise is only present with the RA0SMS.

Have you tried to use the RA0SMS with the other wall wart ? Or with a 12V battery ?

Edit :
But the strange thing is that the spikes are right on 10 kHz harmonics. The second idea is some rectifying of strong MW (AM band) signals, inside the RA0SMS or from a bad contact in the downlead line.

I swapped the PS between the two antennas. The noise stays with the RA0SMS regardless. Someone suggested I swap the polarity of the PS by flipping it upside down, or powering it the 'opposite' way. That produced no change either.

What is a downlead line?

I have been using a PA0RDT active mini whip from Roelof Bakker for about a year now. The PA0RDT antenna has served me well. Clean and able to pull in signals that a 260 foot loop and various long wires cannot.

I recently bought a RA0SMS active mini whip from Anton Gavrilov and having major noise issues.

Both the PA0RDT and RA0SMS are powered by a 12v wall wort (same model #), on a non conducting mast @ 20 feet, and fed with 50 ohm coax. The radio is a Yaesu FT-950 with an RSP2 as a panadapter. The 12v power supply is choked with snap-on ferrites.

The RA0SMS produces noise approximately every 10 KHZ - the noise is present from LF all the way through HF. The noise is visible and is rendering the antenna unusable. You can see the noise spikes in the first three photos, and the lack of noise with the second set of three photos.

Below is a comparison on of the two antennas switched through an Alpha Delta 4 position coax switch.



What could be causing the noise across all bands with the RA0SMS? All things are equal with the exception of the antenna and power feed unit. The PA0RDT is clean and rarely overloads, even with Broadcast AM, with the Yaesu FT-950.

General Radio Discussion / Re: KiwiSDR On Sale
« on: January 27, 2019, 0149 UTC »
Looks like the deal expired :(

General Radio Discussion / Re: KiwiSDR On Sale
« on: January 26, 2019, 0407 UTC »
How does the KiwiSDR compare to the SDRPlay RSP2?

HF Mystery Signals / UNID Voice & Sounds @ 3397 or 3400 KHZ
« on: January 16, 2019, 0312 UTC »
Received 01/15 @ 7 PM PT in Las Vegas, NV and also on Tokens KIWI SDR.

I couldn't determine whether it was USB or LSB. The voices were very disjointed, almost digital like and the signals sounded like garbled ALE (to this novices ear).

Very strange. I was not able to receive via the WebSDR in the Netherlands.

Josh, yes, I have a digital multimeter.

I noticed that on 80 and 60 meters, the loop is comparable to the active mini-whip for amateur stations in California, Arizona, and Northern Nevada - I am in Southern Nevada. So 'local' stations are pretty much the same but elsewhere across the bands, the mini-whip outperforms the loop 10 out of 10 times.

SDR - Software Defined Radio / Re: KiwiSDR antenna question
« on: January 15, 2019, 0319 UTC »
p.s. I am going to have some inexpensive fixed value matching transformers for sale shortly, suitable for LoGs and other antennas.

Count me in. How will you announce availability?

I bought a Palomar Engineers MLB-2 Long Wire antenna matcher (9:1) balun (100KHz-30 MHz). I'll use this once it arrives.

The coax is good, brand new in fact, but I'll try another one to test it.

The eaves are wooden, the wire stands off the wood by 1 inch (via ceramic insulator), and runs around the perimeter of the house.

There are some spots where the noise floor is higher while others it is lower.

Signals like WWV @ 5000 khz are strong with the active mini whip and nearly imperceivable with the loop. To me, it is very odd. I didn't expect such signal loss. It is almost like I do not have an antenna attached in HF.

I'd use both wires in the pair as a single conductor, but it'd be fun to see how the loop fared with two turns instead of just one.

I'll give the 'both pairs as a single conductor' a shot this weekend, in addition to a different connection from the coax to the antenna wire. The coax is new but my homebrew connector is about 15 years old. Heck, I should be able to use a clip to connect the conductor and ground to the coax to see what happens.

Not sure about the double run loop. Considering the second run of wire would be running parallel to the first run, wouldn't there be a coupling problem? It would be twice as long electrically but it will share the same stand-offs attached to the wood trip.

The mini whip power supply is in the shack (the dining room table ..) next to the radio and laptop. I have tried ferrites but it didn't seem to help, or at a minimum, had no material effect on the signals visible in the SDR waterfall.

The mast is 10 feet of galvanized steel fence post with a 10 foot section of PVC clamped to it (wooden dowel inside for strength). The active antenna sits at the top of the PVC.

What amazes me is that this little antenna in Las Vegas, NV is capable of receiving NDBs in Montana, Canada, and Oregon in addition to XSG, HLG, HLO, HLF, and HLW Coastal Radio markers when the conditions are favorable. Not bad if you ask me, but as a novice, perhaps something everyone can do.

The active antenna is great, awesome for me in fact, but I would like a working alternative to compare results. I was hoping the loop would be effective; sadly, it is not.

Equipment / Outdoor Under the Eaves Loop vs. Active Mini-Whip Antenna
« on: January 09, 2019, 1802 UTC »
I have been using an active mini-whip antenna (PA0RDT) at approximately 20 feet on a non-conducting mast. From my QTH, the mini-whip has been exceptional for RX.

Over the weekend, I ran a wire around the house under the eaves, approximately 200ft of wire @ 10 feet or more off the ground. As a loop, the coax braid connects to one side and the conductor to the other. It is two conductor alarm wire and I am only using one in the pair. No balun, just a simple PL-259 connector connecting the conductor and braid to the wire.

The mini-whip wholly outperforms the loop antenna. Strong signals present on the mini-whip practically disappear with the loop. On a scale of 1-10 for RX, the loop is a 1 or 2 compared to the mini-whip. Using the loop is like not having an antenna at all.

As a novice, I thought for sure, the long wire around the house would be at least as good if not better due to the electrical length. Not at all.

Can someone help me understand why the mini-whip @ 20 feet is outperforming the 200 foot loop @ 10 feet?

Josh, thanks for the thorough reply.

With my SDR and active mini-whip antenna here the SouthWest, I routinely and consistently can find STANAG and what I call FSK like signals with the 'twin towers' or left and right peaks. On any given day, I can find at least 20-30 similar signals and I would like to at least start somewhere.

With FLDIGI, MultiPSK, or Sorcer, I don't know where to start.

Decoding FAX and ACARS has been easy. The rest, not so much.

If you don't mind my asking ... which software do you use for decoding?

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