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Author Topic: Best MWDX antenna?  (Read 53632 times)

Offline RobRich

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Re: Best MWDX antenna?
« Reply #210 on: December 13, 2022, 0429 UTC »
Based upon my experience, you will likely do better with the Youloop and a preamp (if needed). At least it is a relatively balanced antenna, versus a miniwhip using the coax as a RF ground, so hopefully better SNR even if lower S levels.

I used to use a Youloop in a window as a backup indoor antenna during storms. Extra gain when needed was usually via a MFJ-1020B or a cheap eBay "+20dB" wideband preamp.



Estimated regional MUF is ~14MHz at 0958z. Numerous stations on the 19m band. Like 4-5 stations on the 16m band. Not too bad.
« Last Edit: December 13, 2022, 1044 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' + 60' Loops-on-Ground | 31' Vertical | 18' End-Fed Vertical | PA0NHC MiniWhip

Offline RobRich

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Re: Best MWDX antenna?
« Reply #211 on: December 17, 2022, 0253 UTC »
Not BCB, but MW related. Winter season activity has arrived on 160m. Multiple frequencies being worked with CW, digital, and SSB at 0252z.



Moving much further down the spectrum, I am listening to Medi 1 on longwave at the moment.

Now on to Radio Algerie International on longwave.
« Last Edit: December 17, 2022, 0311 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' + 60' Loops-on-Ground | 31' Vertical | 18' End-Fed Vertical | PA0NHC MiniWhip

Offline RobRich

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Re: Best MWDX antenna?
« Reply #212 on: December 23, 2022, 0157 UTC »
I can barely solder anymore, but anyway, the eBay dual-ferrite unun is in an enclosure.



Yeah, the SO-239 mounting screws are long. They are what I had available. I have a dremel, but doubt I will bother.
« Last Edit: December 23, 2022, 0202 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' + 60' Loops-on-Ground | 31' Vertical | 18' End-Fed Vertical | PA0NHC MiniWhip

Offline RobRich

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Re: Best MWDX antenna?
« Reply #213 on: December 23, 2022, 0312 UTC »
The dual-ferrite unun installed on the 31' vertical antenna elevated on a 10' mast, grounded back to the mast and metal guy lines. No VNA compensation for the feedline, so it is pretty much what the receiver is seeing. Still running RG-6 for now. Hoping to get my RG-11 deployed in the near future.





As to the nightstand receiver, I recently swapped the temporary 12' vertical on the tripod to an eBay made-in-China active miniwhip on a piece of PVC pipe stuck into the tripod. RF ground is the feedline back to an 1:1 choke near the house. Not a great improvement, and not like I expected much. There is some mediumwave improvement.

I stiil have my masts for active antennas or whatever. I even have a few antenna choices available. I just need to get them deployed.



Speaking of active antennas, I had to fix three of my bias tee injectors, including completely replacing the board in one. IIRC, I kept my old active antennas to check them further, so there might be a slight chance they were actually okay.
« Last Edit: December 23, 2022, 0400 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' + 60' Loops-on-Ground | 31' Vertical | 18' End-Fed Vertical | PA0NHC MiniWhip

Offline ~SIGINT~

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Re: Best MWDX antenna?
« Reply #214 on: December 23, 2022, 0334 UTC »
Oh my, that looks like a very noisy antenna based on the SDR screen, or maybe it is just the way it is displayed.

Here is my Barker & Williamson T2FD antenna with a 30 dB NooElect Flamingo AM Broadcast Band Notch Filter installed at the SDR's input. As expected, one station every 10 kHz. Now that I am 400 miles North of all of those 50 kW Toronto broadcast band transmitters that used to be in my back yard and overloading the front end of my receiver I probably no longer need the notch filter.

« Last Edit: December 23, 2022, 0339 UTC by ~SIGINT~ »

Offline RobRich

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Re: Best MWDX antenna?
« Reply #215 on: December 23, 2022, 0352 UTC »
I had the waterfall rather squished. A little better now? ;)

Quick look at the mediumwave band. External inline attenuator is set to no attenuation.



Alternatively using SDRSharp under Wine.





Skimmed longwave BCB. Just Medi 1 right now, but that is not bad IMO considering current regional thunderstorms.

https://www.hfunderground.com/board/index.php/topic,107149.0.html

Some NDBs between longwave BCB and mediumwave BCB.

A few of the more powerful signals moving further down the spectrum....

60KHz - WWV - S6 - 40dB SNR
40.75KHz - NAU Puerto Rico - S6 - 30dB SNR
25.2KHz - NML North Dakota - S4 - 24dB SNR
24KHz - NAA Maine - S5+ - 25dB SNR
8KHz - ?? - S5 - 32dB SBR

Low frequency seems to be working okay. :)



Both of my decent PA0NHC active miniwhips work! Glad I kept them to check out. The prob was damaged bias tees.

I intend to put them right back on their existing masts along with new feedlines.



Replaced the temporary active miniwhip with a temporary active loop. Copper wire inside a hulahoop feeding a MLA-30 preamp modified with a F connector, all wire tied to a PVC pipe stuck into a tripod. I pointed it vaugely NNW/SSE to favor NA for now. I am not sure SNR is improved much, but gain is improved on at least a couple of bands where the miniwhip was quite low.



The 31' vertical with the new unun is working okay for upper-HF as well. Listening to the European 11m SSB traffic right now.

Been raining otherwise I might have considered fixing the small on-ground radial field on my 18' end-fed vertical this morning. Maybe later or tomorrow if it dries up.... or the ground freezes, which is a possibility this weekend in Florida. o.0



Lowered voltage at the bias tee I was using to feed the MLA-30 preamp down to 4.5v last night. Add some voltage drop due to 75' of RG-6 feedline. Gain barely dropped at lower-HF bands and MW, while SNR likely improved. I still need to check voltage versus gain on upper-HF bands.

Positive supply voltage for the TL592B differential amp is listed at 3v to 8v. That tracks with my results. Gain at 3v (minus line loss) dropped considerably. The preamp at 1.5v dropped out.

12vDC as supplied by the stock USB->12vDC boost regulator in the bundled bias tee is likely overdriving the amp IC and potentially affecting SNR. YMMV, of course.
« Last Edit: December 23, 2022, 1811 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' + 60' Loops-on-Ground | 31' Vertical | 18' End-Fed Vertical | PA0NHC MiniWhip

Offline ~SIGINT~

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Re: Best MWDX antenna?
« Reply #216 on: December 23, 2022, 2111 UTC »
Those screen shots definitely look better. I cannot drop down much further with the B&W T2FD antenna. It has a pretty sharp roll-off below 1.8 MHz. That antenna is not designed for use that low. This is where I used to switch to the vertical, the end-fed or the loop antenna.

Offline RobRich

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Re: Best MWDX antenna?
« Reply #217 on: December 24, 2022, 2148 UTC »
My temporary loop is nearly a short on MW and lower now. I swapped the MLA-30 preamp with an 1:1 balun.

Turned on the Kenwood R-2000 to be greated to horrid broadband RFI. o.O Turning the loop did not help much. There is not much use having a noisy preamp further amplifying RFI noise.

The reciever noise blanker helps, plus I put a MFJ 1030B in line for preselection and a comparatively better preamp. Forget weak signal work, but least I am back in business for casual listening in the bedroom. I did not even bother to check the SDR and 31' vertical this afternoon, though I seriously doubt the situaton is any better with them.

I am hoping the RFI is temporary. The same or very similar RFI sound has happened in the past and went away after a day or two. If not, I get to break out a portable and go searching. Been there, done that, and had to file reports with the power company. Fun stuff.



Found a few degrees of rotation with lower RFI noise floor using a portable tuned to longwave. I turned the loop edgewise perpendicular to the portable. MW seems better. Not enough directivity on HF to matter much. Anyway.
« Last Edit: December 24, 2022, 2241 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' + 60' Loops-on-Ground | 31' Vertical | 18' End-Fed Vertical | PA0NHC MiniWhip

Offline RobRich

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Re: Best MWDX antenna?
« Reply #218 on: December 28, 2022, 2124 UTC »
Significantly elevated noise on 40m today. Sure, I can knock it down with noise blanking and some attentuation, but it is still quite irksome.

HF readings with my TinySA look rather flat near the house. I probably should make a loopstick or some other low frequency antenna for it.

It was a broken pole insulator several years ago, but that was right in front of the house. It was a rather quick fix once the tech came out.

A few years ago it was something neither the power company or I could really pinpoint, though the tech did do a little general pole maintenance in the area while hunting. Thankfully it just went away a few days later.

I used to occasionally notice RFI from something that sounded like maybe a plasma television or similar, but it was low-level enough and rare enough to be more of a mild annoyance than an issue.



Tracked down a small part of the immediately local RFI to tool battery chargers in the garage. Unplugged them for now.

The Samsung washer and dryer control boards are not exactly RF quite, either, but they do not seem to be affecting my SDR in the den and 31' vertical in the backyard.

Guess I get to go for a drive around the neighborhood one day.
« Last Edit: December 28, 2022, 2230 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' + 60' Loops-on-Ground | 31' Vertical | 18' End-Fed Vertical | PA0NHC MiniWhip

Offline ~SIGINT~

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Re: Best MWDX antenna?
« Reply #219 on: December 29, 2022, 0046 UTC »
Rob,

I built a direction finding (DF) loop antenna some time ago based on the design found at QRM Guru and it works very well.

Look under Direction Finding (DF) Loop Antenna Kit and follow the link to the video How to locate the noise source: building a DF Loop.

This is a picture of my finished product. I added a small wooden dowel to retain the form and also provide a handle to hold the loop antenna with while sweeping for signals.

« Last Edit: December 31, 2022, 0012 UTC by ~SIGINT~ »

Offline RobRich

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Re: Best MWDX antenna?
« Reply #220 on: December 30, 2022, 1441 UTC »
A shielded coaxial loop. That is basically how I build my loop-on-ground antennas, though naturally much larger and with the loop "shield" connected to a ground rod.

I could use my existing hula loop as a portable easily enough, though that might look a little odd to the neighbors. ;)
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' + 60' Loops-on-Ground | 31' Vertical | 18' End-Fed Vertical | PA0NHC MiniWhip

Offline ~SIGINT~

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Re: Best MWDX antenna?
« Reply #221 on: December 31, 2022, 0020 UTC »
Don't the neighbours already think things are odd at your place already anyways? LOL

I would have loved to have known what some of my neighbours back at my former location thought of my antenna farm sprouting out from every corner of the house!

I got the Wellbrook loop antenna up again this afternoon. All that is left to do on this antenna now is to run the control cable to the rotator. For now it is in a fixed beam pointing to central USA which also gets me somewhat in the middle of London / Africa on the back side.

Offline RobRich

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Re: Best MWDX antenna?
« Reply #222 on: December 31, 2022, 0045 UTC »
Congrats on getting the loop back up. :) Did it actually get above freezing for awhile today?

Thankfully my neighbors do not say much of anything about my antennas.



I got one PA0NHC miniwhip redeployed today. Went right back to the mast where I removed it awhile back.

I ran the "proper" RF ground wire from the miniwhip PCB to the mast this time. Previously I just used clamps around F barrel connectors along the coax and mast for RF grounding. Anyway.

Feedline is like ~120' of Belden PPC RG-11 to the backyard. Still needs buried, but that is a job for another day.

Four snap chokes at the base of the mast. TDK whatever mix since I already had them in parts box. The chokes are better at VHF+, but I remember the specs still showing some RF choking at HF. I have a bunch of them available.

The bias tee has an integrated choke. I have a KD9SV SV-CMC choke before the Kenwood-2000 as well.

The very bottom of mediumwave and down into longwave has that annoying area RFI that recently popped up, but mid-MW to 10m has a low enough noise floor and decent enough SNR for casual listening in the bedroom. I left my MFJ-1020B inline for added gain and preselection, though it might be removed if not really needed.



Next up might be the 18' "end-fed" vertical. It just needs a few ground radials redeployed and the feedline rerouted.
« Last Edit: December 31, 2022, 0055 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' + 60' Loops-on-Ground | 31' Vertical | 18' End-Fed Vertical | PA0NHC MiniWhip

Offline ~SIGINT~

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Re: Best MWDX antenna?
« Reply #223 on: December 31, 2022, 0239 UTC »
Yup, it has been above freezing for the past several days, raining and 46 deg F today. It should hover around the freezing mark for the next week.

I am very pleased with having the Wellbrook loop back up. It is 13 db quieter than the T2FD and makes a world of difference. I can pick-up signals on the Wellbrook that the T2FD doesn’t even register.

T2FD:


Wellbrook loop:

« Last Edit: December 31, 2022, 0242 UTC by ~SIGINT~ »

Offline RobRich

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Re: Best MWDX antenna?
« Reply #224 on: December 31, 2022, 0347 UTC »
Nice SNR bump on the loop. 8)

BTW, I am having to copy-and-paste your image URLs. Is your personal site perhaps blocking image hotlinking?



I am thinking about having my Kenwood R-2000 recapped and aligned; both of which are likely still factory. Likewise I could imagine the front-end Q1 amp and Q2 follower have taken considerable abuse after several years of Florida thunderstorms. I do not feel like bothering with it myself, plus I have other desktop HF receivers, but it is my favorite.
« Last Edit: December 31, 2022, 0353 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' + 60' Loops-on-Ground | 31' Vertical | 18' End-Fed Vertical | PA0NHC MiniWhip

 

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