HFU HF Underground
Technical Topics => Equipment => Topic started by: alpard on March 25, 2023, 1300 UTC
-
https://www.youtube.com/watch?v=wBS-CNtY2Uk
https://www.youtube.com/watch?v=e0WvIxoU0LI
What do you think? Have you tried this type of HF LF MW LW Rxing with the ground lying wire antenna?
What was the result?
-
I use an off-the-shelf (MMD-40) end fed dipole on the ground (D.O.G.) that gives me good results with low noise when used this way.
I have also used the same dipole laid directly on top over 100ft of pvc 22 ga. stranded wire (attached to a RF-Systems MLB) and then using an A/B switch can get some directional differences between the two to avoid QRM/enhance reception.
I'm sure soil conductivity plays a big part in all of this.
-
My former 148' loop-on-ground was a good antenna particularly for regional reception from LW to mid-HF frequencies.
https://www.hfunderground.com/board/index.php/topic,29940.msg114696.html#msg114696
A terminated beverage-on-ground is a popular directional antenna, too.
On-ground antennas are designed typically for signal-to-noise; not gain. Losses can be in the many tens of negative dBs, so a low-noise preamp might be required depending upon various factors.
As Sealord noted, ground conductivity can be a factor. I am over sandy soil with poor conductivity, so my LoG probably would have performed about the same slightly above ground, on the ground, or even buried in the ground several inches. YMMV.
-
Some HAM antenna books have given details on subsurface antennas for hf. One of the more effective setups was simply remove the outer shield from some rg8, waterproof the ends and center connector and bury it about 3 inches below. Another that comes to mind was an antenna laid out in a horizontal mine shaft in the American sw, worked great on the lower bands. The US missile silos have an interesting subsurface vlf antenna array too. Antennas on the surface is like cheating compared to these.
-
There are several links to the subject of loops on the ground (LOG) antennas here in the RadioReference wiki....
https://wiki.radioreference.com/index.php/Loops#Loop_on_the_Ground_.28LOG.29
Mike
-
Yeah - this is an interesting topic for me. I am going to give a try with this antenna configuration for purely RXing MW and HFLF dxing, to see how it compares with Active or just normal long wire high up.
-
I tried 40m wire on the ground in end fed configuration into the ATU. It certainly shows big signal boost on some bands 6 Mhz 11 and 12 Mhz.
But on the other bands such as 4-5 Mhz, noise has increased a lot. And especially on MW, the noise is quite bad.
I had to lay the wire on the concrete slab path in the back garden along the garden shed to make it look inconspicuous. Would it be better if the wire were on the soil or grass, rather than the concrete slab path? No?
I felt that it could do a good balun. How do you choose what type of balun it needs? There are various type of baluns 1:1, 1:9, 1:49, 1:4 etc?
-
http://www.antentop.org/021/files/k3mt_021.pdf
https://www.youtube.com/watch?v=aSioSzSiScc
type " grasswire " into your favorite search , and you'll find all kinds of stuff .
and yes i have broadcast with a grasswire in the past when out camping on motorcycle trips.
-
I've used BOG's for decades for listening on family property out in the sticks. All you need is something along the lines of a chalk line reel to hold the wire, they work great for listening.
I knew a pirate who used wires for transmitting cut to frequency like Outhouse is talking about. He lived in the desert southwest, I never bothered to try one here as we get heavy dew and fog in good weather. He liked to use them for tx'ing laid on wooden fences and block walls.
Outhouse, don't drank too much on those motorcycle trips. Too much lean in a curve could kill you.
-
Try doing a loop-on-ground. A 60' circumference (i.e. a square with 15' sides) is a good starting point for a basic LoG.
I would be more concerned with common-mode choking than impedance matching if using a LoG or unterminated BoG as simple impedance is going to be a moving target depending upon frequency. Pretty much any 1:1 choke designed for MW/HF should suffice. Do not spend any serious money. For example, wind some of your feedline through a Fair-Rite mix 31 or 43 torrid, or even a TDK N30 if desired.
Alternatively, I even use inexpensive mix 73 binocular cores and enamel magnet wire to wind basic chokes for low frequency receiving antennas. Four turns for primary. Four turns for secondary. End result is a little 1:1 isolation choke, at least for up to a few MHz. Fair-Rite 2873000202 is under $1 each.
If doing a true *terminated* BoG with a resistor to ground at the far end, then figure around 200 to 300 ohms simple impedance on MW and lower HF bands. A basic 4:1 current balun at the feedpoint should suffice.
All that said, I actually tried various baluns on my 148' LoG over the years. I ended up tossing them and using feedline straight to the LoG. I did have a few snap-on ferrites of whatever mix(es) on the feedline near the feedpoint, plus a KD9SV common-mode choke back near the receiver, but neither did much for my particular environment. Another YMMV situation.
-
Try doing a loop-on-ground. A 60' circumference (i.e. a square with 15' sides) is a good starting point for a basic LoG.
I would be more concerned with common-mode choking than impedance matching if using a LoG or unterminated BoG as simple impedance is going to be a moving target depending upon frequency. Pretty much any 1:1 choke designed for MW/HF should suffice. Do not spend any serious money. For example, wind some of your feedline through a Fair-Rite mix 31 or 43 torrid, or even a TDK N30 if desired.
Alternatively, I even use inexpensive mix 73 binocular cores and enamel magnet wire to wind basic chokes for low frequency receiving antennas. Four turns for primary. Four turns for secondary. End result is a little 1:1 isolation choke, at least for up to a few MHz. Fair-Rite 2873000202 is under $1 each.
If doing a true *terminated* BoG with a resistor to ground at the far end, then figure around 200 to 300 ohms simple impedance on MW and lower HF bands. A basic 4:1 current balun at the feedpoint should suffice.
All that said, I actually tried various baluns on my 148' LoG over the years. I ended up tossing them and using feedline straight to the LoG. I did have a few snap-on ferrites of whatever mix(es) on the feedline near the feedpoint, plus a KD9SV common-mode choke back near the receiver, but neither did much for my particular environment. Another YMMV situation.
Great info. Thanks. Yeah 1:1 homebrew balun sounds easy and simple enough. The Wire on the ground of about 40m long (I have added more wire), is definitely hearing the stuff on the HF and MW, but also some portion of the bands sound extremely noisy. And it has not heard anything exotic DX yet. Just usual night time stuff on LF and MW is heard with the wire on the ground. Having said that, the whole HF and MW condition is very poor lately. I think there have been some gigantic geo solar activities recently, and it might still affecting the band condition?
Not sure, if there could be better and more efficient DX receiving antenna - preferably homebrew ones. My active miniwhip and longwire and youloop are OK for the run of the mill stuff, but not really exciting for hearing more challenging DX.
And I was hoping that this LoG or WoG receiving antenna could bring some exciting DX, but so far, it has been medium success. Longer and bigger antennas are not necessarily better, I was reflecting. But search and experiment will continue finding the right cheap simple DX antenna.
-
The LoG seems a lot better RX antenna than my MIC Active Miniwhip from side by side testing on MW and the most of HF LF portion of the spectrum.
It definitely needs good ATU. A 1:1 balun would help even more as well.
-
One thing that needs to be said about LOG's and BOG's is they're quiet. You normally have to turn up the gain on your radio up a bit to get the best out of them.
Once you get used to the little tricks of using them, I think you'll really enjoy them. You can literally take them anywhere. I take one about 50 meters long to the beach with a portable and lay it out LOG style. I stay out until the wee hours of the morning waiting for the Cuban MW blasters to go long and the Caribbean and S. American MW's to pop up.
-
One might be able to roll out a directional ground rhombic, orient the antennae so it has a pointy end towards the region of interest, add a variable resistor of a few hundred ohms there, and feed it at the opposite end. A balun of a few hundred ohms to 50 ohms at the feedpoint and tweak the resistor to get the best front to back.
-
One might be able to roll out a directional ground rhombic, orient the antennae so it has a pointy end towards the region of interest, add a variable resistor of a few hundred ohms there, and feed it at the opposite end. A balun of a few hundred ohms to 50 ohms at the feedpoint and tweak the resistor to get the best front to back.
Related - I've read claims of directionality from LOG antennas, depending on where you locate the feedpoint. I experimented with LOGs several years ago, but never delved deep enough to see what sort of directionality I was getting, if any. It could however be an interesting area for experimentation.
-
Supposedly feeding the corner of LoG can impart limited directivity. Conversely I fed my symmetrically square LoG on a side to supposedly be a more omnidirectional.
"Supposedly" is the keyword. I suspect the differences are in the noise except for maybe extremely large LoGs.
Like Josh, I suspect a rhombic-on-ground (RoG?) technically would fare better for F/B gain. Enough to be realistically usable, though?
Anyone have a rhombic model? Ya' could lower the overall elevation to like an inch or few above whatever ground model(s) your software uses.
-
I have been testing RXing HF and MW LW for several days with the Wire On the Ground. It is about 40m long wire, and really it is just thrown onto the ground - concrete path, and the end of the wire comes into the house via the window in the upstairs room. It then goes straight into the ATU like long wire, and from the ATU, 50 ohm coax cable feeds the receiver.
It is pretty good RXing on 4 - 7 Mhz. It is so so on 10 - 13 Mhz, and really poor on 14 - 15 Mhz (cannot hear the DX signals, which can be heard on Kiwi SDR sites with active loops = for example 15476 kHz LRA36).
On MW, I am not still sure - not hearing any exotic new DX signals on MW such as transatlantic AM stations. No sign of them at all.
So, what could be done to improve this Wire On the Ground antenna for RXing?
-
As described, you have more like an end-fed vertical with the feedpoint at the top. The wire section on the ground might act like some type of end loading, though it is swamped by ground losses, so.... ?
Replace the vertical section with coax. Even cheap RG-6 from a big box retailer. Center to your wire on ground. Shield to a ground rod and/or a comparatively short counterpoise wire running opposed or perpendicular to the primary antenna wire.
-
I have been testing RXing HF and MW LW for several days with the Wire On the Ground. It is about 40m long wire, and really it is just thrown onto the ground - concrete path, and the end of the wire comes into the house via the window in the upstairs room. It then goes straight into the ATU like long wire, and from the ATU, 50 ohm coax cable feeds the receiver.
It is pretty good RXing on 4 - 7 Mhz. It is so so on 10 - 13 Mhz, and really poor on 14 - 15 Mhz (cannot hear the DX signals, which can be heard on Kiwi SDR sites with active loops = for example 15476 kHz LRA36).
On MW, I am not still sure - not hearing any exotic new DX signals on MW such as transatlantic AM stations. No sign of them at all.
So, what could be done to improve this Wire On the Ground antenna for RXing?
I would not expect any exotic signals such as transatlantic MW DX with a 40m wire on the ground.
My experience with one-the-ground antennas is that in general they are a compromise, and utilized in cases where traditional (euphemism for lots of wire in the air) antennas are not possible (small yards, etc.) or useful (high local RFI environments). They're not magical silver bullet antennas that will pull in amazing DX.
-
I would not expect any exotic signals such as transatlantic MW DX with a 40m wire on the ground.
My experience with one-the-ground antennas is that in general they are a compromise, and utilized in cases where traditional (euphemism for lots of wire in the air) antennas are not possible (small yards, etc.) or useful (high local RFI environments). They're not magical silver bullet antennas that will pull in amazing DX.
I think you are right. 40m long wire on the ground seems have its limits for DX antenna. But it was very good on the tropical bands hearing 4885 kHz R. Clube do Para from Brazil, and 5025 kHz Cuba.
https://www.youtube.com/watch?v=46s-V12_f8w
For MW DXing, maybe it is a different game. Wire antennas must be at least 100m long and in the Beverage configuration or Active Magnetic Loop?
-
Given space considerations, have you into a stacked tunable ferrite loopstick antennas that you can take with a decent portable radio to a RFI quiet location for MW DXing? It is a popular design and hobby with portable radio enthusiasts.
http://www.thomasn.sverige.net/7_Inch_Affordable_FSL.pdf
https://swling.com/blog/2017/01/a-new-approach-to-fsl-antenna-construction/
Otherwise, again given space considerations, you might start looking at what amateurs are using to optimize 160m-band reception. Examples include flag, pennant, kaz, etc. You might even ask the SULA terminated loop enthusiasts about scaling the design for optimizing MW reception, as the basic design is relatively easy to build.
https://swling.net/viewtopic.php?t=55
Though still no guarantees, especially if MW DXing across the Atlantic is a goal.
Also might as well note that location tends to be a strong consideration. I do not bother much with MW DXing, but further down the spectrum I can often listen to at least one LW broadcaster many nights with my 31' vertical now, and it was pretty much the same with my 148' LoG up until decommissioning it a couple or so years ago. Meanwhile others with *much* better low-frequency antenna solutions in eastern North America rarely ever seem to hear any commercial LW broadcasters. In my particular case, it largely seems to be my particular location.
-
Great info. Many thanks.
Funny you mentioned FSL antenna, because I was on the way building one.
I used a biscuit tin long tube shaped one to wind the enamel wire around it, and it is reading 410 uH with
the ferrite rods inside. Someone said that it should be about 210 uH for MW tuning.
Last night when I tried tuning MW, it wouldn't work at all. It was not tuning for LW either.
I am suspecting the biscuit tin tube is the problem, because it is made of some type of thin metal.
I am suspecting the ferrite antenna doesn't work near metals and especially when the wire is wound around the metal tube?
I need to find a plastic tube and rewind the wire again, and try to make the inductance of around 210 uH.
And I think you are right in saying that location of RXing is also an important factor for DXing LF and MW LW.
Many of these factors are important I feel - the location, height, soil conductivity and good antenna and good receiver.
And not to forget, the band condition, time of day and season.
It is mysterious and complicated phenomenon DXing is, which makes the hobby fascinating I suppose.
-
Last year, after JTA swearing to me to try this, I've decides to make another W.O.G., (Windom On GND.). The feed point is a W2DU 4:1 Current Balun, one W.O.G. 60ft leg runs down hill, into the valley floor, and away from the power lines, and the other 123ft leg is hugging the hill point, then head down hill. I also have a GND tap on the Balun at the outer SO-239. Then, about a 50ft run on leftover RG-8X, (Mini-8.), coax to the Beverage ANT Input of my rig. And??? Have you ever DX'ed and QSO'ed on the VHF / UHF bands, like 144.200MHz, 222.100MHz, or 432.100MHz, in CW / SSB? That's what I get now for a noise floor on MW, 160M, 75M / 80M, 60M, and 40M. I do hear lightning crashes, still, but at a few S-units, and not crashing at S+20/9. A station at S1 sounds like it could be at S9 strength. Reception is more, or less, regional. I do still hear the Euro-big-guns, like those EA1 / EA2 stations, but I can listen to low bands during the warm season, again. YEA!!!! Still, experimenting. Can I TX on this? Well, the match spectrum-wide is anywhere from 1.7:1 to a flat 1.1:1! (Interesting...) Question is, does this W.O.G. radiate, or is it an over bloated dummyload? Oh yeah... The wire is trashed CATV RG-11 coax, where I use the AL shield, coated with that PVC jacket. A bit of a pain to work with, but should last outside for years. Should...
-
Pretty much the same results as my previous 148' LoG. It is about SNR. Many times I would listen to armchair copy of signals well under S1 without a preamp. It was intended mostly for regional reception of 160m-40m amateur bands and pirates, plus occasional LW/MW listening.
"Gain" is reciprocal. More like loss to due to ground losses. Say if your antenna on ground is -20dB on receive, it will be similar on transmit. 100w into -20dB is ~1w radiated. A large beverage might be -15dB to -20dB down. Some of these other on ground antennas we are discussing can be into the tens of dB losses. All of that is before any feedline losses, too. Expect QRPp performance even with a decent amount of transmitting power.
Most horizontally polarized antennas placed on the ground are actually reliant upon vertical polarization, as horizontal polarized signals tend to cancel at ground level. That is one of the reasons they tend to be rather "quiet," as we are factoring both ground losses and potential cross polarization losses. The result tends to lower the noise floor far into or even below the receiver's noise floor. Decent modern receivers have incredible gain, particularly in the AF section, thus why a S1 signal over a low noise floor can be armchair copy.
As such I suspect your dipole-on-ground (DoG?) is probably more or less vertically polarized as well. If it acting as a traveling wave antenna, i assume that would be somewhat directive at the far end of the longest leg, at least where it is longer than say a wavelength or two. YMMV.
-
I tend to run my radios with lowest sensitivity whenever possible. As you pointed out, when sensitivity is set to max, the noise QRN also increase, and it hinders reception. My ICOM R71E is a very old radio, but is equipped with the bells and whistles - Preamp, Attenuator, RF control, PBT and Notch filter. It is excellent in that, it can be all adjusted for best reception in bad QRN and QRMs. With the LOWE HF-225, it is simple attenuator OFF or ON. I usually put the attenuator ON. And there is also attenuator on my ATU. It is really helpful in that way. But with the portables such as XHDATA, there is no RF control or attenuator control, which can be bad. But then it seems coping well up to a point with poor signal reception.
My wire antenna is now in total random structure - I added another few more meters of wire into the existing wire, and for that the wire had to be bent in few places to be fit into the limited space. And some part of the wire touches the roof of the garden wooden shed, and wall. It still seems working OK.
I had to clear the wire on the ground, because it looked a bit messy, and my wife was keep making comments on it. So it is just zig zag random wire I have got about 5m at highest point, 2m high at the lowest from the ground, and am using it for my main SWLing these days. I am still thinking of improving the wire zig zag antenna I have, by adding another 10 - 20 m of wire, and cram into the garden in some random shape.
There are parts of the wire which is horizontal, and parts vertical now being zig zag random shape. With the wire antenna, I have logged a new DX signal last night - Myanmar Radio on 5985 kHz.
You can see the R71E attenuator is getting switched off at 00:47 in the video for more sensitivity. Sometimes when the DX signal is needing more sensitivity, the preamp and more sensitivity definitely seem to help. But for most strong inter continental signals in the busy band such as 49m at night, the attenuator is MUST.
https://www.youtube.com/watch?v=gUlyu7adEwo (https://www.youtube.com/watch?v=gUlyu7adEwo)