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    Antenna advice

    Posted in: Technology

    • Visitor
      Anonymous on January 21, 2015 at 19:21#11404

      Hello,
      I would need advice on building an antenna, or what kind of antenna. I found a large number of antennas but I don't have much time for experimenting due to work, so I would like to build something that would work, ideally on the first try.
      The antenna should be at 80m. It can be multi-band but it will mainly be used on 80m. And it would be best if it were something vertical. The antenna will be at the cottage with an A-frame roof. I was also thinking about building a vertical on the ground but again there is the problem of making radials since I don't have such land. Plus building an antenna before each transmission... 🙄 I had a wire antenna suspended but there is again the problem with the length. I had it over foreign land... well, not great. Within my land, one can consider a length of about 20m with the condition that the antenna would have to be powered at the end. Do youhave any advice for me?

      Reply
      Visitor
      Anonymous on January 21, 2015 at 10:41 PM#14104

      Hello

      Well, if it should be mainly on 80m, the best solution in terms of simplicity, undemanding, good performance and price is clearly a dipole or inv. vee (the same, only bent 🙂
      It is better and more reasonable to agree with the neighbors and pull a piece of wire over their land (if they don't mind) – that's how I also have to build a structurally demanding vertical with a dimensional earth radial system and adaptation (if you want it to work - I don't mean some substitute so-called antennas). If you mount it high enough above the ground above the roof, you just run the coax into the ham shack and that's it. You pull the arms away - best at a mutual angle of about 120 degrees - at least in my case, the impedance at the input approached this to 50 ohms and slanted to the ground.I have a feed point (center of the antenna) about 12m above the ground, one end about 3 and the other around 7 meters.
      The price of the execution is about 30 euros (including symmetry) and it works like a charm 🙂

      I don't know, but in my opinion, it's the most feasible, simplest, and cheapest solution that still works 🙂

      Best regards, Peter OM4ASI

      Reply
      Participant
      om1aeg on January 22, 2015 at 7:57#14105

      http://www.iw5edi.com/technical-articles/morgain-antenna-4080

      http://www.QSL.net/pa3hbb/ll.htm

      http://www.QSL.net/dl7jv/e.hf2v.htm

      http://www.g7fek.co.uk/blogus/newsshow.php?page=80m_Antenna_for_small_gar_49493

      http://www.n on stopsystems.com/radio/frank_radio_antenna_80m_vertical.htm

      Any vertical that is less than 10m will be quite narrowband on 80m, I built a vertical for 10m laminate for 80m and also 15m, it worked, but only about 80kHz below PSV 1:2 on 80m and the reports were not very dazzling 🙂 It was also very sensitive to changes in the ground, so for the 80m I use a regular dipole, often as an inverted V and it performs better within the possibilities and with less influence from the ground and surrounding objects. Om4ASI advises you well, if you can fit a full-size INV V, if you can't fit, then shortened, while if you choose the location appropriatelyof extension coils or traps, you will get a multiband antenna, again at the cost of a narrower band on 80m (below 100kHz).
      A good solution for a small plot is a Morgan antenna, with arms of 2 x 10m it has the largest BW of shortened types of antennas (slightly smaller than a dipole) and works on 40m.
      At first, I had an inverted V dipole 2 x 12m extended with coils so that it would work on 40/80m and on 80m it had a BW of about 70kHz, also thanks to nearby metal objects. For comparison, the current delta loop inspired by SP7LA has a BW of 240kHz on 80m under 1:2 and is usable on 40/20/18/15 and parts of 10m without a tuner. Of course, it works well on 80-20m, but I can't launch it if I also depend on a higher band 🙂.

      Reply
      Visitor
      Anonymous on January 22, 2015 at 10:50#14106

      @brto wrote:

      Hello,
      I would need advice on building an antenna, or what kind of antenna. I found a large number of antennas but I don't have much time for experimenting due to work, so I would like to build something that would work, ideally on the first try.
      The antenna should be for 80m. It can also be multiband but it will mainly be used on 80m. And it would be best if it were something vertical. The antenna will be at a cottage with an A-shaped roof. I also thought about building a vertical on the ground, but then there is the problem of making radials since I don't have such a plot. And besides, building an antenna before each transmission… 🙄 I had a wire antenna suspended, but here the problem is with the length. I had it over foreign plots… not great. Within my plot, I can consider a length of about 20m with the antenna needing to be powered at the
      end. Can you advise me on something?


      You will do best if you build two antennas right away, a vertical and a dipole. You will find out for yourself, based on reports from stations, which antenna is most suitable for which connections, whether a vertical or dipole antenna.
      Read about building a DIPOLE antenna for multiple bands, the construction of which
      was solved by German radio amateurs. The antenna has minimal requirements for placement and dimensions:

      http://otc.CQ.sk/index.php?option=com_content&task=view&id=459&Itemid=45

      Reply
      Participant
      om3cvv on January 22, 2015 at 11:10#14107

      Hi Brťo, I don't know why you are ashamed of your callsign. It should be mentioned along with your QTH. There will always be an amateur nearby who can advise you. Regarding the antenna, you should specify whether you want it for DX or local communication. If for local communication, then a vertical is unnecessary for you. I would recommend a horizontal quad. You mentioned 20 meters. 4 * 20 is 80m and you have it tuned as well. Or try this:
      Shortened antenna INV-V

      I was considering a new antenna for my favorite band 80 m, but due to the considerable length of the half-wave dipole that won't fit on my roof, I had to think about how to shorten the antenna. I started thinking like this: what if I wound a piece of the antenna onto a roller, that would shorten the overall length! So, let's go for it!

      You can see how it turned out in the picture. I hung the center of the antenna on a small mast from a former shared TV antenna, secured the ends to the edges of the roof – and hooray! It works!

      As for the extension coil, that is also very simple:

      And the results? In conjunction with the transceiver according to the next picture, with an output power of about 3 W, I reliably 'work' all of Europe. Over time, I will also connect a balun between the coaxial lead and the center of the antenna, next week I will head to the waste dumps to look for some sources from computers from which I could harvest suitable toroids.

      And that's it!

      Transceiver SELIA for the 80 m band, the dimensions of the front panel are 3 x 7 cm, depth 7 cm plus another 7 cm box with batteries mounted from the back. The red and blue wire at the top is the output to the antenna and grounding, or to the coaxial cable to the above-described antenna. On the right is the key, on the left the headphones from the Korespondent tape recorder from the sixties.

      Write to me at OM3CVV(at)omradio.sk and I will send it to you along with the picture

      Reply
      Participant
      om3cvv on January 22, 2015 at 10:29 PM#14108

      I have an old program on my computer, so it refuses to forward images. The shortened antenna is described here:

      http://ok1ike.c-a-v.com/files/dipol80m.htm

      Reply
      Visitor
      Anonymous on January 24, 2015 at 11:52 AM#14109

      Gentlemen, thanks for the responses. Of the proposed options, this one seems the most feasible to me at first glance:

      http://www.g7fek.co.uk/blogus/newsshow.php?page=80m_Antenna_for_small_gar_49493

      http://www.iw5edi.com/technical-articles/morgain-antenna-4080

      As for the second option, I just mind that it is powered in the center and the coax would hang into the middle of the garden. For a better idea, the mentioned plot is a rectangle about 20x15m where at one end is a cottage and at the other end is a neighbor's tree that I was approved to use 😀 The advantage is that the cottage is relatively high so the antenna will be about 12m above the ground from the roof. However, for example, I cannot set up the Inv V there due to the angle of the arms, I wouldn't have anywhere to attach one arm (not even at the neighbors).

      Here I dealt with the problem in the case of a vertical how to make ground radials. If I wanted to keep at least lambda/4, the radials would only go in one direction.

      Also, when it was mentioned whether I want local or DX. At the moment, I would be happy if it works at all, but in the long term, I would prefer DX.

      But that shortened inv.V… I have to run to the cottage and take a look there, with an arm length of 8m, maybe something could be thought of there.

      I still have a question that might not be very wise: purely theoretically, if I build, for example, a quarter-wave vertical on the roof of the cottage (so the base would be on the roof, 12m above the ground) and I would bury the radials in the ground, connect them at one end and pull one wire to the radiator (with the total length being lambda/4). It would actually look like one radial that branches out after 12 meters. Would something like that work, or would it make any sense to 'branch out'?

      Reply
      Participant
      om3cvv on January 24, 2015 at 19:29#14110

      The dipole does not have to be inverted, you can make it slanted or straight, or even bent. You can also make a shortened version of the windom antenna, but the problem is with the setup. Look online for companies that sell antennas, there are plenty of verticals that don't have such terrible radials. Those radials do not have to be buried in the ground in every case. Look at the dipole and try to stretch 10 m 2 x four wires and see where it resonates and adjust the rest with a coil. And I will return to the beginning, you need to state the brand and QTH. I firmly believe that within 20 km there will definitely be someamateur who has already gone through these things.

      Reply
      Participant
      OK1FTJ on January 25, 2015 at 19:09#14111

      There are also verticals that seemingly have no radials.. I use the vertical antenna MFJ-1798 about 7 m above the ground and I somehow don't miss radials.

      Reply
      Participant
      om1ci on January 26, 2015 at 6:42#14112

      @OK1FTJ wrote:

      There are also verticals that seemingly have no radials.. I use the vertical antenna MFJ-1798 about 7 m above the ground and I somehow don't miss radials.

      CLEARLY it has no radials, because it is a dipole set up vertically, fed in the middle.

      Reply
      Participant
      ok2pdn on January 26, 2015 at 11:42#14113

      „... I still have a probably not very wise question: purely theoretically if I build, for example, a quarter-wave vertical on the roof of the cottage (meaning the base would be on the roof, 12m above the ground) and I would bury the radials in the ground, connecting one end and bringing it with one wire to the radiator ...“

      In this case, it might be possible to pull the radials from the base of the vertical along the roof and then suitably down and into the ground / along the ground ...

      Another option would be to build the vertical in the middle of the garden and bury a fan of radials from its base (so that they do not interfere with the use of the garden – the more, the better and if they are buried, it doesn't matter much how long they are – they increase the conductivity of the ground ...

      Something about shortened verticals can be found, for example, in the Radio Amateur's newsletter from 1972 – no. 5 (and about a year later also in AR in a series of articles by Jarda Erben OK1AYY).
      In the mentioned year of the newsletter, more articles about shortened antennas were published – especially for the lower bands ....

      Reply
      Participant
      om3cvv on January 27, 2015 at 11:35#14114

      A bomb idea, if it manages to maintain the impedance and radiation angle, it will be a great thing, but it probably won't be a vertical anymore.
      In Žilina, in Púchov, and in Dubnica, there are a lot of amateurs. You need to arrange a date, and one three-hour consultation will give you more than this writing on the internet.

      Reply
      Visitor
      Anonymous on January 27, 2015 at 1:32 PM#14115

      OK2PDN, regarding the radials and their length. If I understood correctly, when they are in the ground (let's say about 20cm) their length is not that critical? If I have, for example, a 20m vertical, then in free space the radials should ideally be 20m (if I'm not mistaken), but if I set it on the ground and bury the radials, it wouldn't matter if they are, for example, 5m long?
      In any case, I will look into that Guide.

      Regarding the dipole and inverted V - I will have to go to the cottage and measure the distances of possible anchoring points precisely, as this estimate is incorrect.

      My QTH is Púchov, the brand should already be in the signature 🙂

      Reply
      Participant
      ok2pdn on January 27, 2015 at 2:29 PM#14116

      yes - that's right.
      When the radials are in free space (elevated above the ground), it is good to have them resonant - a quarter wavelength.
      When you bury them, they are in a more or less conductive environment, and their number determines the transition resistance to the ground - the more there are (up to several dozen - as desired), the lower the transition resistance to the ground and thus lower losses in the ground.
      Those 20 cm are sufficient from an electrical point of view (perhaps in winter, when the ground freezes to a depth, the properties of the antenna deteriorate), the question is whether it will be enough if you run the wire over a flower bed ...
      As a material, galvanized iron wire (3.5mm) for fences works well - it is easy to handle and sufficiently resistant to corrosion. It must especially resist corrosion above ground at the point of mutual connection at the base of the antenna - connection to some plate of the same material - screw joints, or weld - according to taste - and treated with some suitable coating.

      Reply
      Visitor
      Anonymous on January 27, 2015 at 14:33#14117

      ….. I bring to your attention 8m vertical for all bands: http://g8jnj.webs.com/cometcha250b.htm
      … for the balun, like toroids, I use snap-on ferrites on the cable….

      Reply
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