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Messages - ultravista

Pages: [1] 2 3 ... 5
1
Equipment / Re: Loop or Longwire?
« on: April 04, 2020, 1342 UTC »
f you can get it to match at 15 ft. you're into Wayne Green of "'73 Mag's" Lazy Loop territory. It's a single loop of wire that works from the upper part of the commercial AM radio band  to the top of 20 meters.

Have a link, I searched but didn't find 'Wayne Green Lazy Loop' results.

2
Equipment / Re: Loop or Longwire?
« on: April 04, 2020, 1328 UTC »
The antenna is for receive only and I tune from below broadcast AM to about 20,000 KHZ - there doesn't seem to be anything above 20 K. The long wire I use is also deaf on LW, although when the conditions are good, 160 meters is pretty hot.

If I do a skyloop, what is the best way to connect coax, something similar to a dipole?

What is the theory of a terminated long wire? How does it eliminate directivity and reduce noise? How do you terminate it?

As far as a beverage, I do have pretty big backyard with a lot of trees and space. I could easily trench and bury wire. Would the beverage be a loop, specific length of wire, or as long as I can go? How do you connect the coax and do you need anything else, an amp, or?

3
Equipment / Loop or Longwire?
« on: April 03, 2020, 0123 UTC »
Will a loop out perform a long wire of similar length?

I have two spools of black 14 gauge wire and enough backyard & tall trees to string up at least 500-700 feet.

A 600 foot loop or longwire?

4
Equipment / Re: MLA-30 Loop antenna
« on: February 26, 2020, 0120 UTC »
Have you replaced the SMA connecter on the antenna box and added a longer wire loop?

5
Equipment / Re: Pixel Pro-1B Mag Loop vs. PA0RDT Mini Whip
« on: February 21, 2020, 0112 UTC »
Right now I am tuning Israel 4XZ @ 2680 CW. The PA0RDT is faint, but audible. I can clearly hear the morse code and it is visible on the waterfall.

The pixel doesn't pick it up, not audibly and not on the waterfall. Turning the loop makes no difference.

6
Equipment / Re: Pixel Pro-1B Mag Loop vs. PA0RDT Mini Whip
« on: February 21, 2020, 0045 UTC »
There's power to the pre-amp. Signals drop-off completely when powered-off.

It picks up plenty of signals, but compared to the PA0RDT active mini whip, it is far inferior. Trying to figure out why.

Would elevation make that much of a difference?

Canadian Weather @ 2749 KHZ with the PA0RDT is easily heard and understood, strong signal. On the Pixel, I can barely hear it or see it on the waterfall.

AGC is turn off, HDSDR settings remain the same between the two antennas.

7
Equipment / Re: Pixel Pro-1B Mag Loop vs. PA0RDT Mini Whip
« on: February 21, 2020, 0015 UTC »
The antenna works, it's sort of 'deaf' compared to an active mini whip. I expected the Pixel to blow me away, quiet, and a signal grabber.

This is in near-new condition, I doubt it has been outside. The aluminum element is clean and not oxidized in any way.

Is there a secret to map loops, height, or something?

8
Equipment / Pixel Pro-1B Mag Loop vs. PA0RDT Mini Whip
« on: February 20, 2020, 2017 UTC »
I bought a 2nd-hand Pixel RF-PRO-1B antenna and unimpressed thus far when comparing it to a PA0RDT (Roelf Baker made) active mini whip.

The Pixel is ~5 feet off the ground, mounted to a tripod, isolated properly (per instructions), sitting on a cement patio, about 5 feet from the house. 50 feet of 75 ohm coax connects the antenna to RSP2 SDR w/HDSR software.

The PA0RDT is ~20 feet off the ground, mounted to a PVC pipe, no grounding, sitting on a wooden deck, about 5 feet from the house. 50 feet of 75 ohm coax connects the antenna to RSP2 SDR w/HDSR software.

While tuning through the HF dial last night, all signals were significantly stronger with the PA0RDT. Changing the orientation of the loop made no difference.

Shannon Volmet was easily understood with the PA0RDT; with the Pixel, it barely produced a signal in the waterfall. Greece beacon "SVO" likewise was strong and very audible w/the PA0RDT; the Pixel was non-existent. STANAG signals were very pronounced and strong w/the PA0RDT while the Pixel was pulling in the signal, it was much weaker and very evident in the waterfall display.

Why would the PA0RDT mini whip outperform the Pixel mag loop? The PA0RDT should be grounded to improve signal and lower noise. Mine is not grounded; it is not performing as efficiently as it could yet it runs circles around the Pixel mag loop.

Does height above ground affect the Pixel?

Am I incorrect to assume that the Pixel mag loop should outperform the PA0RDT?

9
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
https://imgur.com/RYCFVpK

Close view from my SDR
https://imgur.com/J6Cqezs

Close view from Tokens Southern California SDR
https://imgur.com/rJeESnw

10
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?

11
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.

12
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?

13
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.

RA0SMS







PA0RDT







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.

14
General Radio Discussion / Re: KiwiSDR On Sale
« on: January 27, 2019, 0149 UTC »
Looks like the deal expired :(

15
General Radio Discussion / Re: KiwiSDR On Sale
« on: January 26, 2019, 0407 UTC »
How does the KiwiSDR compare to the SDRPlay RSP2?

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