Technical Topics > Equipment
Can an antenna work while laying on the ground?
RobRich:
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.
alpard:
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.
ThaDood:
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...
RobRich:
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.
alpard:
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
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