Akademisk Radioklubb

LA1K / LA1ARK / LA1UKA

Month: February 2017 (page 1 of 2)

Shipment from Rohde & Schwarz

We were recently in touch with Bjørn Sveum at Rohde & Schwarz Norway asking if they would be interested in helping us out with some measurement equipment. I was astounded by the generosity Bjørn showed, and today the package arrived!

The hardware enthusiast in me got really excited seeing the packing tape labeled Rohde & Schwarz, an even more impressive sight when we realized that they had sent an entire pallet.

The centerpiece is a FSH 3 handheld spectrum analyzer with tracking generator and preamp. A tracking generator allows the spectrum analyzer to perform scalar network analyzer measurements, allowing for filter and simple antenna measurements. This will be very helpful when working with projects both on the lab bench and when debugging in the field, such as working on the beacons at Vassfjellet.

We also got four NGPE 40/40 power supplies. Using two of these in series will allow us to power most FETs up to 50 V (LDMOS and GaN are usually max 50 V drain voltage), this will be very useful in developing amplifiers up to the legal limit for amateur radio – 1000 W (given that they have reasonable efficiency).

The two other supplies will be part of the 1-10 GHz ground station project. More on this in a separate blogpost.

Finally here’s a glamour shot of all the equipment and some of the goodies Bjørn included.

 

CQWPX RTTY 2017

Just a short non-serious entry to check how the station performs and how the newly installed band pass filters interact with the rest of the setup. 20m was closing quite early on Sunday and the US appeared to be shadowed behind the auroral oval. Thanks for the QSOs.

73s de Jens, LB6RH

CallSign Used : LA1K
Operator(s) : LA1BFA, LA7VRA, LB5QG, LB6RH, LB7JG
Operating time : ~11 hrs

Operator Category : MULTI-OP ASSISTED ALL HIGH
Band QSOs Pts WPX Pt/Q
3,5 63 252 37 4.0
7 136 554 84 4.1
14 101 213 86 2.1
Total 300 1019 207 3.4
Score 210 933

SSTV decoder project

Henrik (LB5DH) and myself (LB0VG) are building a “fully” automatic SSTV decoder to be put up permanently in our club. The biggest part of this project is building an antenna from scratch.

The goal of the project is to have a SSTV decoder that in theory can be online 24/7 for displaying decoded pictures in realtime. In addition, it is also a rough way to display propagation for the 20m band. This will hopefully drive more attention to SSTV so that our club can become more active on digital modes.

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Beacons

ARK develops and maintains some radio beacons from JP53EG at the top of  Vassfjellet, a local mountain. The beacons can be heard on the following frequencies.

LA2VHF/4m 70.063 MHz
LA2VHF 144.463 MHz
LA2UHF 432.463 MHz

If you hear any of the beacons we would love to hear about it at la2vhf or la2uhf@la1k.no.

 

Back in 2012 Jon Petter, LA3JPA, designed a 35-4400 MHz CW exciter board (seen in the left picture below) that is the main building block used in the LA2VHF/4m beacon. The CW beacon project is made open source and can be found on this github page.

The cabin that houses our beacons is placed near the foot of a 196 m tall telecommunications tower. When icicles fall from this height they have a tendency to pierce the roof on our cabin, therefore we reinforced the roof with steel plates (building progress seen to the right above) in the summer of 2016.
We also got a working 5.8 GHz data link between the cabin and our main shack at Samfundet. As soon as the snow melts and we have access to the mountain top again we will work on improving the stability of this link.

Upcoming changes

We also have some other exciting changes to the beacon setup. In the recent years we’ve become particularly interested in the 6m band, dubbed the magic band for the way it suddenly opens and closes. To get an indication of when conditions are good we are hoping to expand our lineup with a 6m addition to LA2VHF in the summer of 2017.
Actually we’re well underway, we’re just missing power amplifier (PA), band allocation and final integration at this point. On the PA side Jotron donated some power transistors and matching 28 V supplies, speeding up the process immensely. Another blog on the design of this PA will pop up in the months to come.

On 70 cm we’re changing the antenna from a 10 element yagi to a big wheel antenna. This is because the main mode of propagation is likely to be via tropospheric ducting, where the antenna gain at each side is not the limiting factor. The big wheel antenna is an in-phase stack of three horisontal loops, yielding an omnidirectional horisontal pattern, with improved gain compared to a single loop. This we believe will improve the chances of this beacon being heard out there as the improved tropospheric volume coverage by going from narrow beam to omnidirectional is considerable.

The big wheel is also a prime candidate for the 6m and 4m beacons, this is primarily because most operators on these bands use horisontally polarised antennas. For 2m the main mode of propagation is aurora scatter, where the antenna gain does matter. So we will stick with a yagi for this band.

January Update

The semester is off the grounds, and we’ve got some news!

Projects

In January, Julian (LB5QG) started a project of building a 40M radio-kit he bought off the internet. Despite some technical difficulties in the beginning of the project, it has been coming along nicely and is almost working as a fully functional radio right now.

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