30 Jun

HBØ/SMØW – Liechtenstein holiday style DXpedition

On the other side of the move.. I have not been very busy on the blog lately. Me and my fiancee just moved to a new house 5 weeks ago and alot of time have been spent unpacking all boxes etc.. that needs to be done =) But still decided to do a very relaxed DXpedition to Liechtenstein just before the hamconvention in Freidrichshafen Germany. I wanted to try a new DXpedition holiday concept antenna. Criteria for the antenna would be,

1. Small,
2. Very lightweight (Whole antenna + 100m of transmission line + tuner + glassfibrepole <10 kg of weight)
3. Very low loss

So the week before our trip I made a vertical dipole out of 300 ohm twinlead for 28 MHz. At the ends of the antenna i mounted cableshoes that fits into cableshoe joints. For 28 MHz there is just a small short circuit plug and then I made extensions for the other bands. In this way I got optimal monoband vertical dipoles for all bands 10, 12, 15, 17, 20 and 30m. The vertical dipole is just taped to a 10m long glass fibre rod that fits neatly into the travelling bag.

The folded monoband vertical dipole at resonance is very close to 300 ohms, which means that I fed the antenna directly with 300 ohm twinlead! Twinlead as all balanced lines has very low loss. This means you can have several hundred meters of transmission line and barely loose anything.

This is the basic sketch of the antenna:
  Basic sketch of folded vertical dipole antenna with tuner

At the shack end the balanced 300 ohms needs to get down to 50 ohms unbalanced, so a simple "lumped element L-network tuner" was built. Basically just a small variable capacitor capable of taking the power you are running that sits in between the leads of the twinline. After that a short piece of twinlead (different for each band) is inserted as a lumped L. The two components in the L-network bring the impedance down to 50 ohms balanced at very low loss. Then I wound 10 turns of small lightweight teflon coax on a 43 material ferrite bead. This will make the balanced to unbalanced part of the tuner and also make sure nothing spurious escape from the shack to the antenna.

Here are some more pics, enjoy!

3 May

RXADS progress #3

Was quite some time since i posted anything to the blog. Life's been busy. We're just in the process of moving into a house so most of the time has been spent on that. But I have still had some time to do some ham radio stuff in between everything =) I have mostly been working on the RX Antenna Distribution System (RXADS). It's nearly finished now, two band pass filter units are missing and when they are done I need to do more exstensive measurements of everything, but at the moment insertionloss through the system is well below 1dB which is really good! The most inserionloss occours in the band pass filter units of course!

This is how the 1RU box looks like!


And on the inside like this:


The card closest to the camera is the combiner card, the the openASC driver module that will connect the unit to the rest of the antenna switching at the station. After that the interface card that collects and filters all low level signals between the driver card, arduino micro controller, band pass filters and the switchingcards that will be in the forest. In the middle the blue card which is the bought Arduino programmable microprocessor that works as the logic in the system and to the far right the band pass filters. You can see two is still missing, they actually take some time to make, I will post more on them later.

It was really fun to start learning the Arduino and I got the source code ready and working after many hours of pulling hair, but I think I got the hang of it now ;)

I also finished the Switchbox for the WARC bands this weekend, so tomorrow I will go up to the station and hook it up in the rest of the system. Some pics here:


11 Mar

RXADS progress #2

Last week my RX antenna switching cards finally came in the mail from the PCB maker. Had to solder them up right away last week. =) The design came out just the way I wanted. There are 7 antenna inputs per card and possibility to extend to another card with additional 7 antenna inputs, so in total it will be possible to switch any of 14 RX antennas to any of 3 receievers. Theese cards will be in the forest about 150m away from the house/shack in a plastic box as described in an earlier post.

The relay matrix for each receiver is controlled by a 4-bit binary code, where the last bit is used only for switching to the extended card. All of the inputs are protected by RC low-pass filters and MOVs. The antenna inputs and outputs are protected by 90V gas discharge tubes. I added the possibility to connect preamps in the future with relays for that as well. Here are some pics of the finished cards.

3 Mar

WARC band switch box

This weekend I built the WARC band switch box for the antenna switching system at the station. This was the last box to be finished so the only remaining thing to do now before the new switch system will be taken into use is to get the 12 & 17m yagis up the tower as "multiband" antennas are banned in the new switchsystem. I used power splitter cards from SJ2W but have omitted the transformers so it will only be possible to use one antenna on each WARC band. But It's possible to add transformers later if there would be use for power splitting but I doubt that on WARC.

24 Feb

12m, 5el monobander from Hy-Gain scrap

As described in the previous post I have been working on a 12m 5 element monobander that I designed from old Hy-Gain scrap we had lying around at the station. Last sunday I picked up Thomas SMØCXU/PY2ZXU and Hans SMØBYD who also took theese pictures. Myself and Thomas made the Beta match feed arrangement for the beam. The calculated Beta match length was 15 cm but it became rater 30 when we hoisted the antenna up for tuning. Driven element tips had to be shortened by 2 cm on each side and that gave a perfect resonance in the middle of the 12m band with a flat 1:1.1 SWR over the whole band. Now I will build a similar 5 element design for 17m and after that both antennas will get a new home in a WARC band tower.

Here's the design measurements for the SMØW 5 element 12m yagi.

  Boom 5,08 cm – Place T1 – 2,225cm T2 – 1,113cm Total
Ref 0 2,134 1,072 3,206
Driv 1,036 1,829 1,094 2,923
D1 2,073 1,829 1,115 2,944
D2 3,859 1,829 1,066 2,895
D3 6,607 1,829 0,923 2,752

All measurements are in meters if not otherwise noted. All tube diameters are hy-gain standard diameters, I recalculated "inch" into cm for the design.


13 Feb

Old Hy-Gain “scrap” gets new life!

Last summer we organized all aluminum scrap at the station. I found several Hy-gain antennas in really bad shape. Still I did not want to get rid of the stuff rather reuse them for some project. Last fall I was reading some stuff in the ARRL Antennabook and found remodeled versions of popular Hy-gain monobanders for 20, 15 and 10m. So I started thinking and got the idea to build 5 element monobanders with high performance on 12m and 17m. So I remodeled the ARRL versions yet again, firstly re-scaling the ARRL design down to 17m and 12m, then making additional tweaking to get just the right performance. I knew I had a big bunch of Hy-gain 2" booms, and lots of element parts and clamps so I could design pretty freely.

Last fall I took the bull at it's horns and took all rusty and corroded parts into pieces with the angle grinder and gave them a good cleaning, and assembeled the new elements and clamps with new hardware. Last sunday myself with the help of Thomas SM0CXU assembled the 5 element 12m yagi. Boomlength is nearly 7m. Now I will have to prepare the feed details for the beta match and then get it up the tower after final tuning.

28 Jan

CQWW 160m Contest 2014

Last weekend myself and Thomas SMØCXU/PY2ZXU decided to participate in the CQWW 160 contest. Knowing we had several RX antennas broken we decided to do it "semi-deadly-serious" only and just for the pure fun of working DX's on "topband". Propagation was excellent on friday evening before the contest but never picked up quite to the same level during the contest. On saturday the magnetic field was also disturbed by the sun which gave the impression that somebody had disconnected the antenna from the transceiver. Here's a summary…


Contest         : CQ World Wide 160-meter Contest
Callsign        : SM0W
Mode            : CW
Category        : Multi Operator - Single Transmitter (MS)
Overlay         : ---
Band(s)         : Single band (SB) 160 m
Class           : High Power (HP)
Zone/State/...  : 14
Locator         : JO99BM
Operating time  : 30h43

  160  1086  26  70  14    5833  5.37 
TOTAL  1086  26  70  14    5833  5.37 
        TOTAL SCORE : 489 972

Dupes are not included in QSO counts neither avg calculations

Operators       : SM0W, SM0CXU
Soapbox         : 


24 Jan

it’s up!

Finally after months of work the 3 element 3,5 MHz yagi (80m) is up again! Around noon with the snow slowly falling down from the skies and -7 deg C it was there again on top of the tower. The real hero, with all hats off goes to Dag SMØKDG who climbed the tower and stayed up there for some hours in the cold!

The rest of the ground crew on the ground was SMØW Teemu, SMØSHG Adde, SMØDZB Tor, SMØCXU/PY2ZXU Thomas and crane man Lasse who did a superb job manouvering the "monster" around.

Theres still stuff to be done, the coax and control cabled for the rotator and antenna relay boxes has to be hoisted back up the tower again.. to be continued.. here are some pics from yesterday!

21 Jan

RXADS progress #1

Last week I started building the new RX Antenna Distribution System. I don't own a good accurate inductance meter so I built a small probe with two alligator clips and a capacitor of known value that I hooked up to my Vector Network Analyzer. Placing a coil in between the alligator clips creates a LC parallel cirquit that displays it's resonant frequency in the VNA. Using the formula f=1/2*pi*sqrt(LC) it's easy to calculate the L (inductance) value of the coil. Played around abit with that and started assembling and tuning the bandpass filter cards. Will probably give you the finished filter cuves in the next post.

I also started assembling the Combiner card and Patch card of the system, now I ran out of components so I made an order of the remaining ones so hopefully next weekend I can continue the build.

Here are som pics.

11 Jan

RX Antenna Distribution System

During last year I have been thinking alot about how to distribute RX antennas to different operating positions at the station. Like the rest of the antenna switching the scope is different, allowing contest operations in different configurations like SO2R, M/S, MM. Working regular DX and also good remote switching capability. All ideas and possibilities was cooked down to an RX Antenna Distribution System.

Main parameters that I had to do was:

1. System should be able to be controlled by the openASC system.
2. As little electronics as possible at the beverage switching hubs in the forrest 150m away from the house.
3. Three operating positions should be able to use any of 14 possible RX antennas, even simultaneously!
4. Few feed cables into the forrest
5. Few control cables to the forrest.
6. Low loss even when several RX'es use the same antenna.
7. Possibility to switch on preamp.
8. Good filtering not to blow RX'es if several transmitters are at use simultaneously.

The RX antennas (beverages) are fed into two hubs which are about 150m away from the shack/house in the forrest. From there I will run three 150m long 1/2" hardlines to the house. The two hubs 50m apart are also connected by three RG-58/RG-213 feedlines. There will be a 2x10pair control cable from the house down to the forrest as well.

RX_Antenna_SystemThis is a basic scetch of the whole system. Two relay switching cards (antenna hubs) in the forrest are connected to the 150m long feedlines going up to the house. In the house I will build an 1RU box containing the following cards:

1. RX Antenna Combiner Card
2. RX Antenna Patch Card
3. openASC Driver Card
4. Arduino Microcontroller
5. 3×3 Band Bandpassfilter Cards (160,80 & 40m)


Here is a layout of the current Beverage antenna park. 10pcs of ~500m long beverages.

The relay cards in the forrest (RX Antenna Selector Cards) are controlled by the 2×10 pair cable run down from the in-house unit. There are about 60 relays in the RX Antenna Selector Cards that needs to be individually controlled so I decided to multiplex the control signals from the house down to the forrest and de-multiplex the signals there so with just 4 bits per "RX-Line" (total of 3) = 12 bits = 12 control lines I can control all 60 relays. It will also be very easy to control antenna selecton this way through the openASC system since I can assign several driver outputs for each antenna in the system.  Each of the three "RX-lines" has the possibility to use any of 14 RX antennas.


RX Antenna Selector card. Schematic here. RX_Antenna_Selector

So when any of the 3 operating positions that will have RX antenna capability selects an antenna in the openASC system the RF signal from that antenna is routed up to the house and into the RX Antenna Combiner Card. This card assures at all times that in and out impedances are correct. If two RX'es use the same antenna one of the incoming feedlines from the forrest is disconnected at both ends by relays and if the RX'es are on different bands the signals just pass on to the Bandpassfilter cards. If the RX'es are on the same band there will be 0 degree hybrid combiners connected to always assure the right impedances are used before the signal is passed on to the Bandpassfilters. If the RX'es use the same antenna on different bands the Bandpassfilters work like passive splitters only introducing the low passband loss of about 0,5-2 dB (frequency depandant) between the antenna and each RX since the filters only filter out the incoming energy of the actual tuned frequency and blocks all other signals with the high impedance input outside the passband.


RX Antenna Combiner card. Schematic here. RX_Antenna_Combiner

The Box contains three independent Bandpassfilter Cards originally designed by OH2U for 160, 80 and 40m. Mike SJ2W made PCB designs for the filters that I will be using in the box.

bpfThe Bandpassfilter cards are used as passive splitters and also as "pure" bandpass filters to protect RX frontends when there are several transmitters at work simultaneously.

The selection of the correct filter is also done with the openASC system. openASC detects the band that the RX/TX is on and activates an output in the driver card. To minimize the amount of outputs used in the driver card I have also decided to multiplex the signal by 2-bit encoding. The multiplexing between the openASC driver card and BPF cards are done on the RX Antenna Patch Card that also distributes and filters signals to and from the driver card and forrest. Filtering includes lowpass filters on all control lines and varistors. The RX Antenna patch card also distributes the 4 bit antenna selection data and 2 bit band selection data to an Arduino microcontroller that I will program to control the Combiner card depending on all different scenarios of:

1. Different antennas/different bands
2. Different antennas/same bands
3. Same antennas/different bands
4. Same antennas/same bands


Picture of the RX Antenna Patch Card. Schematic here.RX_patch_card

This project will be continued! =)


OJØR Market Reef

OJØR Market Reef

OJØR is my callsign during visits to the barren rock of Market Reef in the middle of the Baltic sea. [&hellip

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