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, so it begins..

Today is the first day in the month of July and it’s time to activate the SJ7SOP call. Yesterday evening was spent configuring the logbook and software settings in the station computer to be ready to work some stations tonight. Sadly I didn’t manage to get my vacation during the complete month but I’ll do the best I can working as many stations as possible.

I’ve also made some experiments with a 80m sloped antenna during the week and I’m planning to make this a bit more permanent in the antenna farm. Although it has to go through the democratic YL-approval before it will be definitely permanent.. 😉 I will leave it up during July for testing and evaluation/trimming and will hopefully work some SOP-contacts with it.

For those interesting in working the SJ7SOP call, visit the callsigns QRZ.com page where the hrdlog.net online status can be seen. There will also be possible to see the latest worked stations as well as to search the station online logbook.

73 de SM7VRZ / SJ7SOP

Föredrag, Bockebodaträffen 2016

Till årets Bockebodaträff 2016 har jag blivit tillfrågad om jag har möjlighet att hålla ett föredrag om digitala trafiksätt på HF-banden. Det är med stor glädje jag har accepterat detta och arbetet med att färdigställa presentationsmaterialet samt själva föredraget är i full gång. En kort presentation om föredragets innehåll finns att ladda ner här.

Väl mött på Bockebodaträffen 2016! 🙂

73 de SM7VRZ

The design is finished..

The QSL card design for this years SJ7SOP activity has now been decided, ordered and hopefully delivered in a few days. As mentioned before, Tony from LZ1JZ Print have as usual done a great job with the design! Also a BIG THANKS´s to my friend and HAM-radio colleague Patrik, SM7URN, for letting me use one of his wonderful photos as the front side. How it looks? Here it is folks! 🙂

 

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Sölvesborg MW Broadcast transmitter antennas. Photo by SM7URN, Patrik Nilsson.

The front side is a photo combining a wonderful view of the Baltic sea outside Sölvesborg and some local radio history. The antennas in the background belongs to the Medium Wave broadcast transmitter located at Björkenabben in Sölvesborg community, county of Blekinge in Sweden. The transmitter was commissioned in 1985 by the Swedish National Telecommunication Authority and was used by the Swedish public service radio, SR, for national and international broadcasting. Sadly the station was shut down in 2010 after serving the Swedish public and listeners abroad for nearly 25 years. Today, the transmitter itself is long gone and now the only thing remaining is the station house and the two antennas. Their fate is yet to be decided but enthusiasts, which some are members of the local HAM-radio club SK7JC (VBSA), are doing their best to save the buildings and antennas as a historic building.

The QSL cards will be distributed, hopefully, in November to those who requested it. The policy this year is only to send QSL when requested. If you wish to receive a card, please mark your QSL card to receive it or contact me.

The next couple of days will be a time of waiting as I’m expecting a nice surprise in the mail. What it is? Well, keep watching and you will find out what it is! 🙂

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