Noob question - All band antenna!? - Page 1
Forum section: electronics / rf-microwave

author: FriedMule
author_rank: Frequent Contributor
timestamp: December 02, 2020, 05:49:31 pm
content: I have for many years thought about listening to everything from lightning, earthquakes and things like that, but also to UHF or even higher frequencies. I have just always thought of it as an insane and impossible idea that would demand 50 antennas and a 1 mile^2 of space, but then did I stumble upon antennas that should be from DC to 6GHz and was the size of an LP or something like that. In about 3-6 month do I get an antenna pole installed on my roof to my GPS controlled frequency standard and thought, why not get an all band antenna or a couple. It's only the price of $1499+ that keeps me from doing it without asking.Is it possible to construct something yourself or to save money by chose a different option than that "on in all antenna"?

author: geggi1
author_rank: Frequent Contributor
timestamp: December 02, 2020, 06:34:11 pm
content: Wide band antennas are generally not very efficient. You can get away with using log-periodic antenna to get a wider band on an antenna. But if you want DC to multiple Ghz several antennas and splitters is the solution. Tehre will be 3 dB loss each time the signal i splitted.If you want a dc to multiple Ghz the only option is a leaky dummy load is the only option. Not wary efficient on either TX or RX.

author: fourfathom
author_rank: Super Contributor
timestamp: December 02, 2020, 06:52:47 pm
content: Look at biconical and discone antennas. These often have a 10:1 frequency range, and when vertically oriented have an omnidirectional pattern.

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: December 02, 2020, 07:49:07 pm
content: Receiving, especially HF, is relatively easy. Transmitting, not so much.With receiving the main game is signal to noise ratio. The strength of the signal matters less than its strength relative to noise pick up. If the signal coming in is substantially stronger than the internal noise generated by the receiver then you're all good. If your receiver is fairly sensitive then you don't need to worry too much about impedance matching and all that stuff (unless your antenna is very narrow bandwidth and you're trying to use it away from its design frequency).Transmitting relies on efficient power transfer and this does need more care. On HF an antenna coupler can allow a bit of wire (that's not too short) to work OK on multiple bands. But antenna couplers are much less seen on VHF and UHF. A discone or log periodic, as mentioned before, can do OK.As for a resistor and a wire tail? Yes that can work but is lossy. Video shows my attempt at using one. I got results but they would have been better with a 'proper' antenna.

author: bob91343
author_rank: Super Contributor
timestamp: December 02, 2020, 08:29:07 pm
content: Of all the components of a receiving system, the antenna is arguably the most important. The question arises why you want to do this. If it's just curiosity to see what's out there, a spectrum analyzer and a piece of wire will often do the job.If you plan to do some serious listening, it is wise to decide on a frequency range of interest and create a specialized antenna for that alone. You can spend years just tuning around the HF spectrum with readily available gear. VHF and UHF not so much, as propagation is poor in all directions except straight up. Add to that the wide spectrum combined with so many modulation schemes and it gets daunting rather quickly.Back in the day, a long wire and an SX-28 receiver would afford much joy with foreign broadcast and ham and WWV reception. Foreign broadcast is not much any more and ham radio has shrunk to mostly weekend contest operation.Then came VHF with 2 meters and 440 MHz but about all you can easily hear are repeaters, which have largely been supplanted by cellphones. Even television has been reduced. The once coveted spectrum has been largely abandoned below about 2 GHz unless you listen for garage door openers.I was pleased to have HF transceivers that are general coverage but realized I haven't listened outside the ham bands in a long time, other than WWV. I was delighted to receive a QSL from an SWL in France from my 40m operations so there are a few lurkers out there.

author: FriedMule
author_rank: Frequent Contributor
timestamp: December 02, 2020, 08:45:57 pm
content: This is only listening of pure curiosity but Denmark is a bad place to be if you want to listen to very much, there are mountains almost all the way around in Norway, Germany, Russia and to the west, nothing at all. Also, Denmark is so far north that 95% of the planet is south.To be honest do I not care for the usual radio or chit-chat on walkies. It's more nature, satellites and what's else out there.Yes I could start by getting something like a copper wire but now when I am getting up the antenna on the roof, why not get something mounted on that? :-) It's a hassle I have to pay for if I later want to mount something on the antenna mount.

author: David Hess
author_rank: Super Contributor
timestamp: December 02, 2020, 09:56:20 pm
content: Usually the place to start at VHF and above is a discone antenna:https://en.wikipedia.org/wiki/Discone_antennaFor not too much you can buy one which covers 10 meters to 1.2 GHz.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: December 02, 2020, 10:18:28 pm
content: like already said LF/MF/HF is quite easy to cover with just one antenna; the choice can be an active loop or a mini/midi Whip, where the latter can be used upto the lower half VHF; I'd recommend to lookup DL4ZAOs works on Whips, they are easy to build, cheap and do a real good jobcannot say much about discones for VHF/UHF; I guess my choice would be a log periodic

author: David Hess
author_rank: Super Contributor
timestamp: December 02, 2020, 10:53:35 pm
content: I have an old Icom discone which has performed well for both transmit and receive. It lacks the gain of a typical end fed dipole but it is difficult to do better for wideband operation.

author: Circlotron
author_rank: Super Contributor
timestamp: December 02, 2020, 11:07:11 pm
content: Quote from: FriedMule on December 02, 2020, 05:49:31 pmWhen a rain storm is approaching, when I'm working I like listening at the lower end of the AM broadcast band to lightning static. Not the really big crashes, just the spits and sputters here and there. Just another facet of nature to me.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 03, 2020, 11:17:07 am
content: From my experience of DX RXing, there is no antenna under the Sun, which is excellent for the whole spectrum.Even MLA30 active loop has good parts and poor parts in the freq. coverage.And because the propagation changes time to time and day to day, some antennas will be just hearing noise when other antennas can receive the signals you are after.And after a few hours or even minutes, the deaf antennas will hear the signals and the noise clears, and the working antenna becomes deaf. That is the LF, MF and HF bands.Therefore I am trying to have as many different antennas possible for LW, MW and HF.On VHF UHF, it will be different stories although they have unpredictable openings to DX signals time to time, things will be rather stable and very predictable. I have no serious interest on these bands, but a discone or active wide band scanning vertical as high and clear will do the job for me for quick scanning through what is going on the bands locally.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 04, 2020, 08:36:51 pm
content: Anyone familiar with this sort of wideband antenna??Not cheap however. Wonder if you could homebrew onehttps://advancedhfsolutions.com/

author: vinlove
author_rank: Frequent Contributor
timestamp: December 04, 2020, 09:15:01 pm
content: hek $7kMy MLA30 was 25 Euros including delivery from ChinaMy longwire antenna was $ 0.00 made from scrap wire found in the garden shed.

author: tkamiya
author_rank: Super Contributor
timestamp: December 08, 2020, 05:14:09 am
content: Yup, I had one.I've put a light bulb on a stick with coax directly soldered to the bulb. Center conductor also had a short piece of wire. In middle of Japan, I actually made contact all over the city. On HF, T2FD antenna is something similar. This is basically a folded dipole terminated with a dummy load. Not very efficient but wide band and has a long history behind it. One will cover HF bands. As mentioned, discone will cover VHF and UHF. Another discone will cover lower higher UHF into SHF.I'm in US now. I have a long wire/random wire for HF. Discone in attic for VHF/UHF. A separate active antenna for GPS. I think this is the best you can do for all-in-one concept. Certainly not effecient but works well.

author: SM3VLC
author_rank: Newbie
timestamp: December 08, 2020, 09:01:20 pm
content: Quote from: FriedMule on December 02, 2020, 08:45:57 pmAny mountain further away than 100km doesn't matter in most cases.On lower frequencies (<30 MHz) the signals isn't received via line of sight, they bounce all over with the help of ionized layers in the atmosphere.Though yes, those frequencies do propagate differently but they are not affected by mountians as far away as outside of Denmark.On higher frequencies the signal will probably be too weak for the type of antennas you wish for if the transmitting station if too far away.

author: cgroen
author_rank: Unknown
timestamp: December 09, 2020, 12:27:29 pm
content: Quote from: FriedMule on December 02, 2020, 08:45:57 pmAbsolutely not true (and I know from very much personal experience)

author: geggi1
author_rank: Frequent Contributor
timestamp: January 30, 2021, 09:13:47 pm
content: It looks like a fat dipole antenna with som kind of matching network.Most likely decent on transmitt but pretty deaf on RX like all reduced size antennas.

author: coppercone2
author_rank: Super Contributor
timestamp: January 30, 2021, 10:21:40 pm
content: If you do the bicone, keep this in mind1) the calculations someone did in an old thread are wrong (the number result), I believe this is the confusion:flare angleis defined as 1/2 of the angle of the cone interior, i.e. you draw a line in the middle then measure the angle to the sideThey got me on this because I made an antenna that used the full angle as the flare angle, meaning my impedance was 200 instead of 50. To me when someone says 'angle' relating to a cone, I assume you measure the entire thing, however for whatever reason the formulas all use 1/2 of this angle.So if you make a bicone, it looks pretty flat, like Vietnamese traditional hats, not wizard hats. You need a decent amount of fairly expensive copper to make one. If it looks tall (hourglass), you need to deal with a balun. You want to think of rice paddies, not merlins castle, to get good results at 50 ohm impedance.For low frequencies the best wide band antennas are active antennas. Not sure what range they stop working. Cheapest, least sensitive, lightest. Might want to stick to this unless you have a radio license, unless you are die hard, because you are buying 1/2 of the capabilities by paying for a badass antenna that you can only receive with.. put your money in test equipment instead unless you absolutely need the better performance or get great deals.The structures are also kinda hard to make if you want to use lighter metals because you will be fighting deformation when you work, i.e. the tooling they have is often expensive to make the antennas that are seemingly cheap (like a english wheel for rolling metal).

author: fourfathom
author_rank: Super Contributor
timestamp: January 30, 2021, 10:27:16 pm
content: Quote from: geggi1 on January 30, 2021, 09:13:47 pmI've heard this about reduced-size antennas, but I don't believe it. An antenna has gain (or loss), and a directional pattern. The reciprocity principle tells us that this gain and pattern will be the same for both transmit and receive.It's certainly possible to build a reduced-size antenna that will provide an excellent impedance match, but this will be at the cost of reduced bandwidth and/or loss in the matching network. If there is excess loss, your transmitter may be happy but the signal strength at your receiver will be diminished. And, your Effective Radiated Power will be diminished by an identical amount.

author: coppercone2
author_rank: Super Contributor
timestamp: January 31, 2021, 09:02:02 am
content: this relates to my VLF thread but as a reminder, if you use active input circuits.. the match does not really matter because the impedance of the amplifier is humongous, or close to 0, depending on antenna type.

author: A.Z.
author_rank: Super Contributor
timestamp: January 31, 2021, 10:38:20 am
content: Quote from: FriedMule on December 02, 2020, 05:49:31 pmwell, you may start with a relatively simple and probably affordable approach, at least for SW and V/UHF, you may use a wire antenna or a loop for SW/MW and a discone one for V/UHF, that could give you a good start, then going far up/down in frequency will require some more complex and dedicated setup, but the above may be a good startjust my 2 cents

author: ConKbot
author_rank: Super Contributor
timestamp: February 01, 2021, 07:00:52 am
content: Quote from: Wallace Gasiewicz on December 04, 2020, 08:36:51 pmWhile the antenna looks fine, there is a truckload of red flags on that page. "Speherical" polarization? Isotropic, when it's clearly a dipole? Maybe if there was some twist on the elements I could see it being linear on edge, and circular on end, like a helical stuck at a compromise between normal mode and axial mode patterns. All this talk about 1000miles with 1W, sure but not with a 0dbi antenna. Lots of meaningless words, no patterns, no plots.BS meter is off the charts. Maybe it's a perfectly serviceable compact wideband dipole, but they sure don't sell it like that.

author: Bud
author_rank: Super Contributor
timestamp: February 01, 2021, 07:34:45 am
content: HAMs routinely make long distance QRP contacts using 1W or less power on HF. When bands are open you can literally radiate using a light bulb as an antenna and make contacts. I agree this gizmo is a pile of BS. Being broadband and low noise are two mutually exclusive properties to start with.

author: fourfathom
author_rank: Super Contributor
timestamp: February 01, 2021, 04:39:28 pm
content: Quote from: ConKbot on February 01, 2021, 07:00:52 amI agree that the "Advanced HF Solutions" antenna website is full of crap, but it's certainly possible to get 1000 miles with 1W into a 0dbi antenna.Example: as an experiment, I transmitted a 14MHz WSPR signal at -10dBm (100 uW) to a friend 1100 kM distant. We were using half-wave dipoles. That works out to 11,000,000 kilometers per watt. And there was signal/noise margin, enough that had we switched to 0dBi antennas we would still have gotten through.Much of this S/N was due to the low-speed and efficient modulation being used, I seriously doubt that we could have made an SSB contact under the same circumstances. But 1000 miles on a Watt for SSB? It's being done all the time, just not reliably.

author: cgroen
author_rank: Unknown
timestamp: February 01, 2021, 04:43:19 pm
content: 1Watt on 1296 MHz reflected at the moons surface can be picked up on earth using a decent antennaThats 760000 KM (with a path loss pretty big)

author: ConKbot
author_rank: Super Contributor
timestamp: February 02, 2021, 12:26:48 am
content: Quote from: fourfathom on February 01, 2021, 04:39:28 pmHam, obviously isn't my thing,I'm more used to higher bit rate stuff, where i have to beat into the software guys that "no we cant more than double the bit rate and have it work the same. Then watch them get mad when a proposed 10W TX to meet their needs eclipses the power budget for everything else.Wasn't considering narrow band modes/digital with processing gain, or even CW for that matter, was thinking voice when I said that. But yeah, standing corrected, especially since the modes with processing gain make it more than feasible enough to claim it, though them presenting it without qualification certainly is just swapping one red flag for another.