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Author Topic: Best MWDX antenna?  (Read 48780 times)

Offline ~SIGINT~

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Re: Best MWDX antenna?
« Reply #285 on: April 01, 2024, 1520 UTC »
Quote
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.

By now, most installers are aware of the potential noise that the inverters can create. I seem to recall seeing something on TV, might have been on "Ask This Old House" about solar panel installations. Installers are supposed to mitigate the issue so I would approach them sooner than later to bring it to their attention.

Electrical noise pollution is a big issue.

Offline RobRich

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Re: Best MWDX antenna?
« Reply #286 on: April 02, 2024, 0126 UTC »
My luck it could be a DIY install as there are are not many panels involved. I still need to check it further with a SA or at least a portable receiver, as admittedly, it might not be related given the number of new houses popping up in my neighborhood.

Perhaps 40 acres in a remote Wyoming location would be the better radio listening solution for me. o.0



Dropped my 31' vertical back down to the previous ground mount location. Same ~2.5:1 hybrid dual-core unun at the feedpoint. Just a ground rod without radials for now as it got dark outside. RG-11 back to the house.

The hybrid unun as designed was intended for a wideband end-fed vertical antenna with minimal RF grounding anyway. It seems to be doing okay so I might forget the radial field for awhile.

The noise profile already looks better IMO, though it is nighttime so I suppose the real check will be tomorrow during the day.



Skimmed multiple bands. I have WWV(B) time signals on 60, 2500, 5000, 10000, 15000, 20000, and 25000 at ~1:30z using the 31' vertical. :)



KiwiSDR 2 at default dB calibrations. 31' vertical fed with a dual-core hybrid unun against a ground rod. -10dB shelf filter under 10MHz.

Acopian VA5H3200 5vDC 32A regulated linear power supply. Straight to the plug on each side. No extra mains filtering, ferrites, etc.

Only 15dB SNR during mid-day as I post this message, versus my Kiwi often reporting in the mid-30s at night even on its previous switching power supply. A loop with the HFDY LZ1AQ-based preamp I have on order might improve the daytime number.

I am using an old router running as a station bridge for testing the 5v PSU. It is on a 12v linear regulated power supply, but the router itself could be contributing to a little longwave noise. I did not bother with ferrites on the LAN cable, either.

Mediumwave:


(click to enlarge)


Longwave:


(click to enlarge)


269KHz is GN in Gainesville, Florida.


(click to enlarge)


40.75KHz is Navy NAU in Puerto Rico.


(click to enlarge)


Here is that "wonderful" 15dB SNR during the day. This is with noise blanking and tweaking the waterfall to better hide some of the noise. I have seen much worse, but yeah, it is not great IMHO.


(click to enlarge)


Again I am hoping the situation improves with a loop actually having moderate decent nulls. Also I still need to check RFI near that house with the solar install.

BTW, noise blanking is one area where I find SDRSharp excels with the Airspy HF+D. Really can comes in handy when needed.



Need to find one of my radial plates, but anyway, there are four ~31' ground radials now under the 31' vertical. It is start.



Tossed this small recharable hi-z preamp on the 15' loop in a window currently feeding my Tecsun PL-330.

https://www.ebay.com/sch/i.html?_nkw=High+Impedance+Amplifier+Donut+Antenna

Bought mine on AliExpress for ~$16. eBay was just easier to search on my tablet.

It is designed for impedance matching instead of any appreciable gain. Not sure it helps much on MW in a very quick skim of the band, but seems to be doing decent on HF in my limited testing.

An ETM scan of HF BCB bands returned 93 possible stations at 0139z. Noted an image at 2360, but that could just as well be the portable radio. Otherwise I have been listening to MRI, Wolverine Radio, and even some 75m amateur radio as I type this post. Not bad for a portable and indoor antenna IMHO.

Probably would be a decent addition to a small loop or wire antenna for portable HF listening at the beach, park, etc.



Received the LZ1AQ-based HFDY loop kit as well. Wanted to make sure the preamp board works. Deployed the kit in a window, set it to be a shielded loop, and powered it via a 9v battery. Hooked up to my Tecsun PL-330.

A skim of MW is pointing towards decent potential.

I will need to hookup a SDR to check LW.

At ~0500z....

Various European ops working 40m DX and whatever contest.

An op in the Canary Islands working 80m.

On a lark since the HFDY does not have a lowpass filter, an ETM scan of FM BCB band returned 82 possible stations compared to 67 on the radio's own whip.



Experimenting with a couple of TDK ferrite mixes. Trying a N30 toroid and a T65 toroid in series with 10 turns of RG-174 on each.

https://www.tdk-electronics.tdk.com/download/187204/fd7b13cb06de3e2edca6c617ac9de7da/pdf-n30.pdf
https://www.tdk-electronics.tdk.com/download/528846/1598c89da613db594840e493e0ffb9fe/pdf-t65.pdf

I should test the setup with my NanoVNA, but anyway, a quick waterfall skim of 0-30MHz looks decent for a common-mode choke without galvanic isolation.

Exmaple of lower LF with WWVB. Notebook on battery. Airspy HF+D and 31' vertical.


(click to enlarge)


I figure this choke will end up near the feedpoint of my HFDY loop if/when I get around to deploying it.

I obtained TDK N30 binoc ferrites as well. I suspect they likely will compare well with my usual mix 73 binocs for 0-30MHz galvanic isolation chokes.

^Mutiple posts merged.
« Last Edit: May 09, 2024, 0000 UTC by RobRich »
Tampa, FL USA | US Map Grid EL88
Airspy HF+ Discovery | KiwiSDR 2 | 2x Msi2500 Msi001 | 2x RTL-SDR V3 + NE602 | 2x RTL-SDR V4
148' Loop-on-Ground | 31' Vertical | 18' End-Fed Vertical | 9' NCPL | PA0NHC MiniWhip

Offline RobRich

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Re: Best MWDX antenna?
« Reply #287 on: May 09, 2024, 0058 UTC »
Changed out the hybrid transformer on the 31' vertical for a LDG 1:1 balun. The RG-11 feedline was rerouted and dramatically shortened.

Once again put a KD9SV common-mode choke near the house entrance.

An eBay "SDR protector" and the earlier mentioned TDK N30/T65 series choke are close to the Airspy HF+D, though I need to get around to swapping that choke for a galvanically isolated one to better cleanup LW and lower.

Now to eventually get around to deploying more than the current four on-ground radials. I am thinking about acquiring some long ribbon cables. 10m 10-wire cables can be found for like a dollar or two shipped via welcome deals at AliExpress. Seems like they would be somewhat easier to deploy in greater quantities. Attach then separate as ya' go. On the downside I suppose they might even be CCS wire, but I have used CCS speaker wire for on-ground radials in the past with okay results if sealing the connectors and ends from water intrusion.
Tampa, FL USA | US Map Grid EL88
Airspy HF+ Discovery | KiwiSDR 2 | 2x Msi2500 Msi001 | 2x RTL-SDR V3 + NE602 | 2x RTL-SDR V4
148' Loop-on-Ground | 31' Vertical | 18' End-Fed Vertical | 9' NCPL | PA0NHC MiniWhip

 

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