I used to basically assume 120v 15A drops as well, but IIRC, the 120v drops in this house are 20A. Built around 2004.
Anyway, yeah, filtering a whole branch is tempting. I have even considered an isolation transformer on a specific branch for certain equipment.
My most immediate annoyance is a moderate increase in the local noise floor, and sadly, there is not much I can do about it. My community continues to grow with many new home constructions in my immediate neighborhood. Suppose I should be thankful most of the homes are concrete block with stucco over wire, with the house electrical ground typically being the rebar in the concrete foundations, so there is some EMI/RFI dampening already present in the construction designs.
I was able to find a deep null in the noise floor playing around with a passive loop outside awhile back. I am thinking about feeding the KiwiSDR 2 with such a passive small loop for now. Kind of directional and admittedly "gain" well into a few dozen negative dBs, so it is going to "miss" some weak signals, but I would rather it have the low noise floor especially if eventually putting a couple of the channels online.
Update. Forget the active miniwhip. Here is the KiwiSDR 2 and 31' vertical. Skimming upper HF at the moment.
(click to enlarge)Stats are showing 23dB SNR overall at the moment, which is about average for the KiwiSDR network. Area storms, local daytime RFI, and the USB wall wart are not helping.
I am running a RF shelf filter with -20dB rolloff under 10MHz. I still need to tweak the waterfall and meter calibrations a little more.
(click to enlarge)The horizontal lines are static crashes from area storms. No noise blanking enabled right now. Anyway.
There is a slight dip in the tropical bands, but at least 0-30MHz does not look quite like a roller coaster. ;)
I so "enjoy" when that wideband signal pops up. I set the waterfall to somewhat better highlight it.
It is from approximately 6825 to 6975 in the screenshot. It is now about 75KHz higher.
(click to enlarge)
My KiwiSDR 2 is reporting 34dB SNR tonight. That is more like it. That said, it is still on the 31' vertical, plus the dishwasher is running right now. o.0 Anyway.
APC LineR ---> cord --> Schaffner FN9222-3-06 --> Schaffner FN2090-3-06 --> Semiconductor Circuits ES5S300 5vDC 3A bybrid PSU --> ferrite choke --> cord --> ferrite choke --> KiwiSDR 2
The power supply, Schaffner filter, fuses, etc. are in an old ATX PSU case. Even wired up the couple of cooling fans at 5vDC FWIW, and they are quiet for both sound and RFI.
I tried both a Schaffner FN2090-3-06 and a homebrew filter on the DC side. Either delivered 5vDC to the Kiwi, but it would not boot. Hmmm. That is why the ferrites are there for now.
The Kiwi has been reporting an overall SNR around the low to middle 30s range. It is still on my 31' vertical. Any further SNR improvements are likely going to be on the antenna side.
VLF and LF look decent IMO. No noise blanking needed (at the moment?).
Approximately 9' mobius loop active antenna. it is on a tripod in the den right now. It is not even near a window, and I did not bother much with even trying to null noise.
The loop is RG-11. The upper mobius crossover was salvaged from a Youloop, repaired, and potted.
The amp is packaged in a larger enclosure with SO-239 connections. The amplifier is from a MLA-30. ;p It can be changed out later for something better if desired.
on the active loop
I have a 10dB attenuator before the Airspy HF+D at the moment as the amp has plenty of gain at lower frequencies. I will work on tweaking that later.
(click to enlarge)
(click to enlarge)[
(click to enlarge)
(click to enlarge)[/urlg
The active loop is outside now. Around 8' off the ground. RG-11 feedline.
I simply turned it to get a general null one of the usual more noisy parts of the HF spectrum here.
Nulls are vaguely somewhere around WNW/ESE to NW/SE. I did not check a compass.
Gain is not uniform, but I expected that. Longwave is likely a huge YMMV. Both are aspects of the MLA-30 amp board.
A mix 73 isolation transformer between the bias tee and SDR helped clean up noise on lower MW and much of longwave, though actual LW signal reception remains a question mark.
The ~$30 HFDY loop kit at Aliexpress and similar could be of potential interest. It is based upon a simplified LZ1AQ-based amp design. Appears to use a 2SC3357, or perhaps a clone. No regulator. No lowpass filter. YMMV.
More details including measurements:
https://groups.io/g/loopantennas/topic/hfdy_chinese_loop_and_loop/103801226Clone or real, the results look (much) better than the inexpensive video amp typically used in the MLA-30 and related designs.
FWIW, I have WWV on 2500, 5000, 10000, 15000, 20000, and 25000 at ~0140z on the active loop.
No 60Hz on the active loop. As suspected not much happening on longwave and lower with the MLA-30 amp board. Anyway.
Seems I picked the wrong noise source(s) when tweaking the loop direction. The nulls are now more ENE/WSW.
The current daytime noise floor difference on the 40m band is about 2-3dB with SDRSharp noise blanking enabled.
The NNW peak should favor more of North America. Works for me regarding that particular antenna.
The other noise source is towards 8MHz, along with intermittent and variable in strength. Noise blanking largely knocks it out, so I will try to just disregard it for now.
I might have an idea of what one of the noise sources is. I need to verify, so perhaps more to follow.
Suppose my days of HF radio are about done unless I can find the current area noise source(s), It is does not appear to be local to my house.
S5+ noise on 40m even on my LoG, which is in tens of dBs loss by design.
Replaced the preamp with a mix 73 1:1 isolation transformer for the 9' mobius loop. Not much different than the LoG.
Overall SNR on my 31' vertical is down to 19dB with noise.
Even have some EMI/RFI at ~28MHz on my 18' end-fed vertical.
I can still listen to lots of signals, but weak signal reception is trashed. That pretty much takes the fun out of HF listening for me.
Moved location and dropped the now passive 9' mobius loop down to maybe a foot or so off the ground. I am trying to use ground losses to cancel out some of the noise. It helped on several bands.
The noise source dropped out. I am hoping it is not an area solar power install.
My Kiwi with 31' vertical is reporting 34dB SNR.
As for the loop, the 9' NCPL is now about 18" off the ground. Current 7MHz noise floor is floating around S2 with my Airspy HF+D. SDRSharp noise blanking does not effect it.
I probably will have to realign the loop if/when the noise comes back. There was not much else to null tonight, so I just put the peaks back to roughly NNE/SSE.
At approximately 0145z to 0200z tonight with some static crashing from storms in the gulf.
1110KHz | -134dB noise floor | WBT 38dB SNR
5MHz | -116dB noise floor | WWV 41dB SNR
10MHz | -122dB noise floor | WWV 57dB SNR
20MHz | -138dB noise floor | WWV 54dB SNR
Noted at least couple of longwave BCB carriers. Also WWVB.
60KHz | -131dB noise floor | WWVB 22dB SNR | notebook on mains
60KHz | -139dB noise floor | WWVB 20dB SNR | notebook on battery
The NCPL feedpoint is using a mix 73 1:1 isolation transformer, plus there are a few snap ferrites on the RG-11 feedline. Also a few snap ferrites on the feedline near the SDR.
It was dark outside, so I called the antenna project for the night.
Static crashing is horrid tonight, but otherwise the noise situation seems perhaps a little better.
The 9' NCPL needs more feedline decoupling at the loop feedpoint. Suspected it might as I used only a single mix 73 binoc. It probably needs two or more cascaded. Something to poke at later.
I already knew the 148' LoG needed more choking when it was deployed. I replaced the LDG 1:1 (of whatever mix) with a Noolec 9:1 v2. The ratio is little high, but anyway, it further cleaned up mediumwave and lower for now.
Also I reconfigured some inside chokes and filters. I am back to having WWVB 60KHz and area longwave beacons during daytime on my elevated 31' vertical.
It is getting to the point of wanting more directivity than just a small bidirectional loop. I am thinking about building a SULA and deploying it on a rotator.
https://swling.com/blog/tag/sula/https://swling.net/viewtopic.php?t=55
BTW, I am done playing with 5v power supplies for awhile. I just ordered a new (open box) Acopian VA5H3200. That is an A5H3200 with overvoltage protection.
https://www.acopian.com/store/productdetail.aspx?q=i284https://www.acopian.com/inc/streamFile.asp?loc=info&id=AcopianCatGoldBoxLinear.pdf/Current at 40°C: 32 amps
Load Regulation: 0.005+/- % or 2mv
Line Regulation" 0.005+/- % or 2mv
Ripple: 0.25mV RMS
BTW, I suppose the hybrids were not bad for the price, but they were still not quite what I wanted.
Today I noted a new solar panel installation on the next street. The direction appears to correlate with one of the annoying daytime noise sources, and the 20KHz spacing lends further support to a potentially noisy inverter.
The 9' passive loop is back to elevated. Maybe 7' or so. Added more feedline choking.
I have other mixes of toroids on order to potentially further modify the feedpoint transformer.
I might also experiment with changing it to a shielded loop. All I have to do is swap the mobious crossover at the top for a short coax jumper with a shield break.
Ordered an HFDY loop. I pretty much simply want the amp board, but anyway. ~$30 for an assembled LZ1AQ-based loop is decent IMO.
As noted earlier, the HFDY loop amp lacks a low-pass input filter, has no onboard voltage regulator, and has lower OIP2/OIP3 performance than more expensive LZ1AQ designs.
1. A 30MHz low-pass filter between the loop and amp is not difficult to implement, but I doubt it will be needed at my QTH. I have tested rather large antennas and cheap high-gain preamps without noticed FM overload here.
2. A voltage regular on the amp board is not really required if using a decent power supply. I can do that so whatever IMO.
3. The OIP2/OIP3 is still okay enough for my intended mostly HF purposes. At any rate the OIP3 as measured appears to be around 9dB better than the first-gen NE592-based MLA-30 amp board.
On a tangent related to the MLA-30, I ordered a couple of inexpensive NE592 preamp boards as a starting point for some further experimentation. Basically this in the through-hole version but without the bias tee components:
https://www.pcbway.com/project/shareproject/Antenna_Magnetic_loop_on_video_amplifier_NE592_DIP_version_10ff2fb5.htmlThey might prove useful enough for later projects after a little work on the input and output sides.
^Multiple posts merged.
