80M Antenna experiments..

As the prognosis for the higher bands looks quite sad now when the eleven year cycle is heading for a low, I decided last summer to try to build an antenna for the 80M band and eventually also 160M. These bands have not been that much activated in my home QTH yet and why not get more active? 🙂

As a general rule, I prefer to have dipole antennas, mainly to keep a balance in my antenna system but with a rather small garden and the fact that a dipole for 80M is rather long I had to leave my principles and look for alternative solutions, balanced or not.

I started my experiment in July with trying to fit a full length dipole, in some way, in the backyard. Since I knew from the beginning it wouldn’t be an easy task as the whole garden itself is far from enough space to put it up in a conventional way, I started to look at alternative ways to get it up. My final solution, far from the most effective one, was to elevate the feedpoint of the dipole and leaving one leg a about 3m above ground and the other straight vertical down to ground level, using the leg more as a counterpoise. A half dipole so to speak. 🙂 The result, well I did get it to resonate but the effectiveness is probably not that good and radiation diagram should be more or less high angles. I managed to work some European stations with the antenna in the SOP-activity and after that as well. The coverage seemed to be mainly Europe and no DX-stations either heard or worked so i guessed the antenna could use more elevation.

The only way to elevate the antenna about 1/4 wavelength at my QTH is to use the house to mount the center of a full length dipole in a Inverted-V configuration. The backside is that only one leg of the antenna would be able to go the full stretch without needing a “bend”. The conclusion was to look for other alternatives.

I wanted to reduce the length of the antenna itself to make it possible to fit, both in the garden and possibly mounted on the house. I stumbled upon an antenna construction consisting of a 80m dipole made shorter with inductances which made the total length only about 17m. I decided to give it try!

The antenna is made up of four segments of FK1,5mm2 wire and two 30uH coils, spooled with the same type of wire. The antenna is feed through a 1:1 balun, which I disregarded for the time being. The segment are two 3000mm and two 5600mm wires connected as shown below. The final length of the outer wires was not consistent with the drawing as it depends on where in the 80m band you will tune it to as well on other factors.

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80m shorted dipole

The coils are made of the same wire as used for the antenna segments. For my part using 40mm diameter pipes, it took about 55 turns to achieve the correct values. The inductances was winded up on the PVC-pipes and, with the help of my Rigexpert AA30, carefully adjusted to about 30uH. I also had a small home brew center isolator with a fitted 50ohm cable which was used for the antenna. The build itself took about 8h, including the purchase of 40mm PVC-pipes on the local hardware store. To get the wires I needed I used parts of an old 3×1,5mm2 cable I have laying around looking for suitable project. After the build, it was ready to be tested.

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One of the antennas coils

I erected the antenna in a inverted-V position using my 5m fishing rod in the garden and measured the antenna. The end wires needed some extensions since the antenna was to short. A quick fix with some spare wire and the soldering iron solved the problem extending the antenna about 1m on each end. Since it is a shorted antenna, the bandwidth is no more than 20-30 kHz why it not suitable for use in the complete 80m band. I focused mainly on tuning the antenna to the lower segment of the band, aiming for 3576 kHz primarily (JT65/JT9). After some tuning in the rain and +2C (cold day) I was satisfied with the result and went in to the warm shack to do some on the air testing. After a few hours I decided to mount it more properly and moved the antenna to the back garden, removing the fishing rod. It is now mounted about 3m above ground as a conventional dipole with one end from the house and the other end in a tree, just at the edge of the garden.

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The 80m shorted dipole in the garden

When moving the antenna, the tuning made earlier of course changed why it need some more fine tuning, however the change was acceptable and I left it as it was. Further testing during the evening showed that, although mounted quite low, it still seemed to have a more favourable radiation diagram than my first experimental antenna. I actually got more heard stations outside Europe than ever before. Even a few VK-stations (VK6 and VK5) was decoded with acceptable levels. Since it’s now colder outside, I´ll leave the antenna as it is for more evaluation. Iplan to look for a mounting point on the roof of the house when the weather gets a bit warmer. 🙂

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The home brew center insulator and feeding point.

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The 80m short dipole viewed from the side with the coils to the left and right.

73 de SM7VRZ

 

 

SJ7SOP/6

The activity for SJ7SOP in the SM6 area is slowly coming to it’s end as me and the family are leaving the summer QTH tomorrow. So far I’ve managed to get about 50 worked stations during my stay. I’t could have been more but the family activities comes first. However I’m satisfied with my activity and especially as I’m working QRP.

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Station setup with FT-817ND, Signalink USB and Acer Aspire One notebook

I’ve mostly activated 40m and 20m PSK31/63 as I didn’t realy find out a good way to work JT65/9 with the /6 suffix in WSJTX. When calling CQ in WSJTX with the /6, the locator is missing in my transmission. This problem will not be an issue back home why i’ll wait activating the JT modes until I get home again.

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The portable antenna, linked dipole for 20m and 40m setup in the garden.

The antenna setup is the same as my portable kit, the linked 20 and 40m dipole. In the garden, next to the house I’ve set it up in a inverted V configuration with good results. I could have set it up in the surrounding trees but I figured that it would be a perfect field testing for the antenna kit so I put it up as it was intended for.

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The house in Tösse, JO68HX.

I’m glad to see that some of the stations I worked are qualified for the SOP award. Hopefully I will manage to get a diploma this year myself, not only helping others to earn theirs 😉

 

73 de SM7VRZ / SJ7SOP/6

 

 

 

Portable kit, last piece of the puzzle..

As some may remember I’ve been looking for a stable, lightweight bracket for suspending the fishing rod for the antenna. After some searching I finally found what I was looking for!

The bracket is originally made for holding parasols during the lazy days outside but it turned out to be able to be used for antennas as well. 🙂

Another advantage is that it’s lightweight and not hard to pack along with the other equipment needed.

With this my kit is complete and just in time for the beginning of the three-week summer vacation. In addition I managed to get my hands on a 24Ah 12V battery for free. This means that, If I can manage the additional weight, I have a whole day worth of energy for my kit.

Now, where should I go first to try out my kit? 😀

73 de SM7VRZ

Family adventures and QRP kit progress…

Yesterday me and my better half, Ulrika, took the kids on a small adventure to a near by nature reserve, Kjugekull.  The site is locally famous for it’s large boulders and beautiful views and nature. In addition to this it´s also said to be the largest and best site in Sweden for an activity called “Bouldering“, a form of rock climbing.  Rock climbing was not on the schedule for my family though. We did just fine navigating the footpaths with sometimes narrow passages between the big boulders and enjoying the nature and the view from the small hill. The hill, which is 66m ASL, is some kind of ancient monument, probably a old fortification. It offers a stunning view of the surrounding landscape in this otherwise flat area.

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View from the top of the hill towards Kristianstad.

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The footpath in the forest among the big boulders.

The adventure got me started thinking about the SMFF activity, Swedish Flora and Fauna Diploma, that is quite popular here in Sweden. When I checked If the reserve ever had been activated for the Diploma, I found that It had not.  This maybe a good testing ground for my QRP kit?

When we finally got home I got some inspiration to start working with the antenna for the QRP kit. I figured that if i wanted to activate the site in the SMFF i needed an antenna for at least 40M band working nationwide stations. However, I wanted the possibility to work European stations aswell so I decided to make it a dual band antenna covering the 20M band in addition.

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Testing under way with the Rigexpert AA30

I went down in the basement to search for a 40M dipole that i knew I had hidden somewhere in the junkboxes and of course found it rather quick for a change. 🙂  The dipole was set up with a fishing rod in a Inverted V configuration and testing began. After some tweaking I got the SWR just right in the passband.

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Spot on with the antenna. 

Instead of making it a “four legged beast” with separate legs for the 20M band, I decided to make it a linked dipole. So I started to measuring exactly where to make the link according to my calculations, cut the dipole, mounted the links and the strain reliefs and made a second measurement on 40M band. Now the SWR curve had moved up in frequency but with some adjustment to the wire connecting to the isolators i managed to nearly the same result as before the modification. On 20M the result was that the dip in SWR was a bit higher than expected but still under 1:1,5. I decided that this was acceptable and relocated the antenna closer to the shack so that I could sneak the 11m RG-58 cable through the window next to the radio counter inside.

The antenna was tested mainly on 40M throughout the evening with some acceptable results. The conditions was not that great which was verified with the stationary 40M dipole in the garden.  So, now I have almost all the things I need for the kit. The only thing missing is a good way for suspending the fishing rod to the ground. Lightweight and inexpensive, any ideas? 🙂

73 de SM7VRZ

Project digimode QRP portable, the first steps…

Today it’s saturday and I have actually nothing planned this weekend. Therefore I decided to startup one of this years projects, my QRP Portable digimode project. The goal with this project is to have a working solution for working digimodes (JT65/9 and PSK31/63) portable with my FT-817ND.  I’ve been giving this project some thought earlier and the other day I got some more inspiration when I got a new follower on the blog. VK1NAM, Andrew is a Australian Ham with an interest in SOTA, Summit on the air, which I think is something that I also would enjoy doing.  Not only is the project a reason to utilize my FT-817, it´s also a good excuse for getting out more! 🙂

Do check out Andrews blog here on WordPress with interesting posts and beautiful photos from his SOTA activations. I do hope to visit “down under” some day as both me and my fianceé would like to explore Australia. 🙂

So, back to the project. I started to collect some useful gear from the hidings in the basement. Through the years I’ve collected some stuff that may come in handy one day. When the search was over I got the following idea on how my “portable kit” could look like:

  • Portable HF antenna for 30m or 40m, 20m and maybe 10m. Andrews portable gear have given me some inspiration for a linked dipole construction.
  • An MFJ-901B manual tuner, if necessary.
  • The FT-817ND (naturally)
  • An old Acer Aspire One, lite notebook computer which I’ve been using before with my “traveling kit” setup. This computer already have the necessary software installed but is maybe a little slow for JT65/9 with WSJTX. The upside is that it´s small and light.
  • The Signalink USB interface for use with the computer and transceiver.
  • A small 12V 7,2Ah lead battery which should supply enough power to the FT-817ND and the computer ( both the transceivers and the notebooks internal batteries is depleted). The power solution should give at least some hours of operation.

That seems like a good starting point for creating a kit!

Now it´s time to build it all together and try it out!  🙂

73

de SM7VRZ

2015 Projects

As it is the beginning of the new year I’ve started to think about future projects and activities. During the autumn of 2014 I.ve collected both som ideas and material to start som inteteresting builds and projects. My goals for this year is:

  • Renovate and improve my Inverted-V multiband antenna.Some renovation is required on the wire connection to the center isolator as i ignored to solder the wire to the cable shoes and weather protect them.DSC_0379
  • Try to find a better place for the GP-1500 vertical, which is now located to close to the kids swing set in the garden. You don’t want them to go to near it when the antenna is in use. Also, it have to be “masked” as much as possible due to demands from the mrs.
  • Move the UHF/VHF antenna to the top of the roof. Well, now it´s located on my balcony and have the house screening the signals from the east. Also, I would like to have the three element yagi for 2m plus a rotator up. That´s a later story.
  • Find a battery and case for QRP portable work with my FT-817. This have been on my mind for a while as I would like to work more QRP portable with my FT-817ND. The antenna part is already worked out with dipole antennas for selected bands. It´s more of a question of finding a battery pack and a carrying case with suitable space for antennas, radio and battery.wpid-IMAG1392-picsay.jpg
  • Try to activate the SJ7SOP signal on more modes and bands during July. I will try to make a third attempt to break the number of QSO made the first year with this call.

Now, that´s what´s planned. Lets see what will actually get done? 🙂

73 de SM7VRZ

Antenna addition..

As I wrote in my last post I’ve started using a new exciting mode on HF, but that’s not the only thing that’s new. A friend of mine,  also a hamradio operator, was getting rid of one of his vertical antennas. As I’ve mode some experiments with a homebuilt quarterwave vertical before and was a bit curious of the construction of wideband verticals, I decided to buy it and make some tests.

The antenna is a Wimo GPM-1500 and is marketed as a wideband antenna covering 1.8 to 30MHz requiring a tuner for matching. Looks like a quite good antenna does it? Well, I as a bit doubtful that it would really be as wide banded as stated, partly from my own experience with building and measuring antennas and also from the theoretic point of view. I decided to make some measurements on the new antenna to see how wide banded it is observing the the SWR value.

For the SWR measurements I used my newly purchased antenna analyzer, the Rigexpert AA-30, measuring 0-30 MHz and a RG-58 cable for connecting to the antenna.

So I started setting up the antenna, mounting it on ground level about 50 cm of the ground on a steel pipe with no ground radials. The antenna is said to require ground radials to operate efficiently but can be operated without.DSC_0585

 

GPM-1500 @ groundlevel, no radials

The output from the AA30 showed the following values:

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First measurement, no radials, steelpipe mounting

As shown the SWR never dips down under 1,5. Although the SWR stays mainly about 4 and under most of the HF band. A built in tuner may be able to handle this and it seems like it may be usable on high frequencies over 30m band but on the lower bands it´s a nightmare.

I now tried to raise the antenna a few meters, because of the risk of touching the feedpoint and the antenna itself when mounted in the garden. I found a wooden pole with a length of about 2m. I mounted the antenna and it is now “free floating” without any ground connection.

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Second measurement, wooden pole 2m, no radials

Now the curve have become about the same as before but with a dip somewhere in the 20 m band area. Still not good in the lower bands and the higher is still around 4 with a dip in the 10 m band.  The next step is to reconnect the antenna to the ground by using a braided copper band and a 1 m copper piece driven to the ground.  This may not be a perfect ground but it is useful just to see how it affects the properties of the antenna.

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Antenna mounted on a wooden pole, connected to the ground with copper band.

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Third measurement with ground connection, no radials

This time the curve shows that the dip in the 20 m band is gone but is now widened with a value under 2 wich can be handled by a built in tuner. Lower frequencies are still bad and higher is still the same with a reduced dip in the 10 m band.

As I wanted to reduce the SWR value in the lower bands I now tried to connect a radial roughly in the 40 m band area, hoping that it may effect the curve. I also disconnected the grounding with the copper band as it had no effect on the lower bands.

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Copper braid disconnected and radial connected.

I decided to lay the radial on the ground as it is impractical with elevated radials with this length in my garden.

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Forth measurement, 40 m radial

The curves show no real improvement on the lower frequencies. More radials with the same length was connected later on but it showed no improvement as well.

I decided to stop my experiment at concluded that the antenna, as it is in my garden, is useful for 30 m band and up. Lower bands is to hard to match. I had a number of radials used for my old 20 m experimental vertical that i connected to the new antenna. They were mounted as elevated radials at roughly 45 degrees angle down to the ground. I also bought some steel tubes pushing the feedpoint of the antenna to a height of 3 m. The combination of 20 m radials and the ground connection of the steel tubing resulted in a deep dip in the 20m band with a SWR value of 1.1 and leaving the higher frequencies  between 4 and 2. The lower bands are still bad.

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The final result of steel tube mounting and radial system for 20 m band.

In it´s current configuration the antenna is useful as a listening antenna for the HF bands and a transmitting antenna for 20 m band.  Even though it is useful in transmitting from 30-10 m I´m choosing to use my more efficient Inverted V antenna for transmitting. I am planning to continue with grounding and radial experiments to try to make the antenna useful in the lower bands, at least down to 40 m.

My conclusion about this antenna is that, as expected, it is a typical wide band antenna that is a compromise to make it work at as many bands as possible. The compromise is in the matching, meaning that it is more or less good matched depending on the frequency but is tunable with a riggs internal tuner. As with other verticals, the risk of RF feedback is high when the matching is not good.

In my complete station configuration it´s a good compliment, despite it´s downsides. The use of a different type of antenna located at a number of wavelengths from the main antenna makes it a good reference antenna with somewhat antenna diversity feature for incoming signals.

73

//Anders