Akademisk Radioklubb

LA1K / LA1ARK / LA1UKA

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Special Callsign, LM100UKA

 

In September and October, we will be running the special callsign LM100UKA to celebrate the 100-year aniversary of the UKA-festival.

The UKA festival is a festival that has been arranged by students at the Student Society of Trondheim once every second autumn since 1917 (except for the war years of 1941 and 1943). The festival originally grew out of a student revue at the student society, in the early days lasting a week hence the name (“uka” translates to “the week”). The revue is still an integral part of the festival to this day, but the festival has grown to last for three weeks and now includes multiple concerts and various social arrangements.

This year, artists who will be performing at the festival includes Highasakite and Cashmere Cat. To get more information about the festival, please check out https://uka.no/ (Norwegian).

 

Updates on the SSTV project

After a long break, Henrik LB5DH and I decided to start working on the SSTV project again.

This time we wanted to look on how we wanted to mount and secure the antenna up on the roof.

Handmade foot

We found an old foot on the loft, which seems to work well for our installation.
We later found that we could rest the antenna on the roof without it, but in the finished installation we will be sure to make use of it.

The antenna after taking it down

The mounting solution

For mounting the guy wires we drilled two holes through the pipe on the opposite sides of each other.
This way we got four points for securing the mast. Luckily we already had structures on the roof to secure it to.

Temporary length of wire added

The issues came when trying to tune the antenna. Even though the antenna tuned fine inside, it gave us different results with the best SWR around 100Mhz when we took it outside.

This drop was the closest to 1:1 ratio we could find.
We tried adding more spools, extending the wire etc with not too good results. We did have a drop at about 3-4 in SWR around 10-11Mhz, so we seem to be close.
It does seem like the antenna isn’t reading it’s full length, so we’ll have to do some more calculations before proceeding with mounting the antenna.

We’d also like to mention that the SDR dongle has arrived, and initial testing has showed us that the direct sampling technique will work adequately for us.
More info about this and the antenna is coming soon!

-LB0VG

An update on the 1 to 10 GHz project

ARK is making an open source ground station that is compatible with GENSO and SatNOGS. We want to focus on documentation, making it easy for others to adopt.

We are attempting to approach this problem from a radio system perspective. We want to give a guideline to set up a modular distributed network node. The node should support common ham activities in the bands covered, such as EME and satellite work.

The ground station will cover 1 to 10 GHz and be RX and TX capable.

Block schematic of the project

The reference ground station will support up- and downlink covering 1 to 10 GHz using a cross-polarised dish feed. A dual channel software defined radio is used as the central transceiver, allowing for a wide range of applications to be programmed on the fly.
By using two radio channels and two polarisations we want to control polarisation schemes dynamically in software. This will allow for optimization of a large range of satellites. Using this setup we aim for access to linear vertical and horizontal, right and left handed circular as well as some elliptical polarisations.
This ground station (and network) could be interesting for amateur radio groups, CubeSat initiatives and research projects.

The Antenna(s)

We are going to use a parabolic dish antenna with around 30 to 45 dBi gain, increasing with frequency. The parabolic dish will be a 3 m kit by rfhamdesign. In the long run we might attempt a custom parabole design that aims to lower costs even further, utilizing machined or 3D-printed parts and metallic mesh.

At the core of the project at this stage is the choice of feed antenna for the dish. We want a feed that has the following attributes:

Continuous coverage over 1 to 10 GHz, S11 < -10 dB: Covering the ham bands from 23 cm to 3 cm. There are also a lot of interesting satellites in these frequencies.

Stable phase center over the frequency range: The phase center is the apparent center of radiation, for a feed antenna this is particularly important as it decides where the antenna should be placed in relation to the dish. If the phase center shifts with frequency the main lobe of the antenna will also change with frequency, making calibration and gain optimization hard.

Constant antenna pattern over the frequency range: Similarly to the previous requirement it is desireable to have a stable main lobe. Distance to the dish, as well as a backwards ground plane will have to be considered.

100 W power handling: In Norway this is the legal limit output power for the bands 23 cm to 3 cm.

Dual linear or dual circular polarisation:  By having either of these combinations it is possible to combine the remaining polarisations as well as a set of elliptical polarisations.

We are looking into several antenna topologies. Luckily there’s a lot of research available for ultra wideband (UWB) dish feeds, as they are very common in radio astronomy. Our design differs a bit from these however, since we also intend to use the antenna for transmit applications. The main difference is the power handling, as radio astronomy applications usually are RX only.

So far we have found two promising designs, and are running simulations to get the exact dimensions.

Dual linear spiral antenna

The first of the two is the dual linear spiral antenna. This is a planar antenna that is realizable on printed circuit boards. For additional power handling machining the elements may be a better choice. For high frequencies the antenna has to be scaled in a way that leads to lots of tight gaps between metallic elements, for high power levels this will cause spark-gaps, and the antenna will not function as intended.

Dual linear spiral antenna

Dual ridge vivaldi antenna, alternately called quad ridge horn antenna:

The more promising of the two designs is the horn antenna, as several commercial designs that fit our specification already exist. One such design by Schwarzbeck Mess-Elekronik is shown in a picture below. This antenna covers 0.4 to 10.5 GHz with an efficiency of 90% or better. It also handles 200 W.

We are looking forward to learn more about the design as we progress with our own.

A dual polarised horn by Schwarzbeck Mess-Elektronik

Getting funding

The other thing that we have been working with at this stage is getting funding for development. Transistor costs alone are so high that we couldn’t do this on our own.

We would like to give a big thanks to NTNU IES, KSAT, Marlink, Sit, Radionor, Jotron and Kongsberg for making this happen!

What’s next?

We have prepared a  lamp post mast that will serve as an attachment point for a tiltable mast, which LA2USA is designing. The lamp post previously housed ARKs 5.5m spoil in the early 90s, seen in the photo below.

The story of the old spoil ended with a winter storm, which is why we’re making some changes to the mast. Hopefully by tilting it down during windy periods it will catch less of the harsh winds. This also comes with the benefit of easier maintenance since the feed will be more accessible.

We have also ordered a rotor and 3 m mesh parabole kit from rfhamdesign. Building will commence when parabole kit and the LA2USA mast arrive here mid June.

As the design on LNA, PA, antennas and software continues there will be more updates.

CQ WPX SSB 2017

This weekend we participated in the CQ WPX SSB contest. The conditions were rough, but we had a lot of fun in the multi-two category.

Øyvind LA3WUA (left) & Henrik LB5DH (right)

This was our first serious entry with the new Flex 6500 in parallel with the old IC-756 Pro III. The panadapter on the flex allowed us to find open frequencies swiftly and easily.  When operating multi-two previously, we have had a lot of trouble with self-interference. To amend the problem, we recently purchased bandpass filters. The 4O3A bandpass filters for 40 to 10 meters were used for this to great effect. This allowed us to transmit and receive simultaneously, as long as we remembered to stay away from the direct harmonics. 🙂

The conditions were difficult, with no real openings on 15m or 10m, and subsequently no QSOs on these bands. We had no serious runs towards North America, and were only able to obtain some  S&P contacts. We did obtain an Alaska contact on the 40m greyline, however, which was fun.

There were lots of different operators on our side this time, thanks to everyone who showed up and thanks for the QSOs!

Harsh conditions resulted in low rates.

Call: LA1K
Operators: LA2QUA, LA3WUA, LB0HG, LB1HH, LB2NH, LB4ZH, LB5DH, LB5QG, LB6RH, LB7JG
Club: AKADEMISK RADIOKLUBB 
Category : MULTI-OP TWO ASSISTED ALL HIGH
Operating Time: ~46 hrs
Band QSOs Pts WPX Pt/Q
3,5 130 298 76 2.3
7 580 1 275 257 2.2
14 673 849 311 1.3
Total 1 383 2 422 644 1.8
Score 1 559 768

New hams

After the test last Wednesday there are 11 new amateur radio operators. We are proud to announce:

Martin Hergot Festøy: LB7AH
Ken Are Meisler: LB7CH
Ole Christian Tvedt: LB7DH
Håkon Eide: LB7EH
Haavard Knibe Fiskaa: LB7FH
Anders Liland: LB7GH
Anders Selfjord Eriksen: LB7HH
Dennis Skulbru Eriksen:  LB7IH
Einar Uvsløkk: LB7JH
Svein Ove Undal: LB7KH
Ragni Helene Halvorsen:  LB7RH

You will recieve a letter from NKOM with the final details.

Congratulations, we look forward to hearing you on the air.

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