Pictures from OH8X WPX SSB 2012

Here are some pictures from the WPX SSB 2012 at Radio Arcala. Enjoy!

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                   CQWW WPX Contest, SSB

Call: OH8X
Operator(s): LB3HC, LA7JO, CU2DX, CU2CE
Station: OH8X

Class: M/S HP
QTH: Arcala
Operating Time (hrs): 48

Summary:
 Band  QSOs
------------
  160:   36
   80:  106
   40:  478
   20: 2259
   15: 1082
   10:  178
------------
Total: 4139  Prefixes = 1379  Total Score = 11,906,286

Club: Contest Club Finland

Comments:

Great to be back operating from Arcala now that the SSN is higher! All
operators: LB3HC, LA7JO, CU2DX, CU2CE had a great time and a lot of fun (as
usual from OH8X - Arcala). 

Thanks to OH2BH, OH8NC and OH6KN for hosting us! Also thanks to the rest of the
Arcala team for making this possible!

This time we also had time to take some HD video and wide angle pictures of the
station.

Plusses:
=========
This time we had relatively good conditions up here at 65 degrees north
latitude in the ice and snow.

No significant technical issues were experienced.

This station station is professionally built by the extremely skilled guys in
the Arcala team. Kudos!

The Arcala antenna park is nothing less than extreme.

It was nice running with the new Yaesu FT DX 5000. Yaesu did it again! 


Minuses:
=========
We were likely affected by aurora at several time periods during the contest
that affected rates. We were unable to achieve runs at 40 and 80 to DX
locations and that resulted in that the DX runs was worked on 20 and 15. That
cost us 6-3=3 points per DX QSO and our average QSO points were below target. 

Our target was to beat OH10X from 2011 and we wkd more mults, but somewhat less
QSOs corrected by the QSOs/36*48 factor due to condx and latitude (claimed
score). In fact 40 meter did not give good DX propagation at all.  OH10X is
approx 500 km to the south. 

We lost power due to a power company outage / spike at night and lost control
over all tower rotators and the voice keyer. It took several hours to correct
this.

Summary:
=========
WOW! What a station and what a team. Contesting has got a new meaning. 
Updated pictures will be posted at http://www.lb3hc.net

On behalf of the team 
LB3HC
Marius

WPX SSB meeting @ 65 degrees north – OH8X – Radio Arcala

Before LA7JO, LB3HC, CU2CE and CU2DX was working the WPX SSB 2012 contest from OH8X, we had  some very good time discussing conditions, radio contesting and amateur radio with the Arcala team and with our new friends from the Azores. On the below image from the left: Juha OH8NC, Marius LB3HC, Martti OH2BH, Jose CU2CE, Veijo OH6KN, Stig LA7JO and Francisco CU2DX.

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This was a very nice meeting at the Arcala Xtreme Station @ 65 degrees northern latitude. The Arcala team has an approach to amateur radio that is both social, technical, and serious. This time in nice weather with spring temperatures around the corner and snow melting. Check in later. More pictures and video from Arcala will be posted. And also check 3830 for contest results!

HD videocamera with flash storage for USD 39

For some time several vendors in Hong Kong has offered HD video cameras for below USD 50. There are several versions of these cameras. Some cameras are good and some are not so good. Over at RCgroups http://www.rcgroups.com/forums/showthread.php?t=1556994 they have done extensive testing of the type 808 #16 camera.

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cmos_sens The inside details and the chassis can be seen in the above pictures. In the left picture, it can be seen that the designer has used a image sensor that has been designed for the cellphone industry. There is a detachable lens (with threads in some of the sensors used) and the lens is attached to the mainboard via a flexiprint and via a controlled impedance and controlled delay connector. The sensor has the type designation OV9712. It can deliver 1280×800 in 30 fps or 720p WXGA HD format. The sensor has gain control, color balance control, and can even correct distortions caused by optics on die. Here is the datasheet of the sensor: http://www.ovt.com/products/sensor.php?id=29   There is a memory chip and a System On Chip (SOC) on the printed circuit board. The SOC has the designation NT96632BG. This SOC appears to me manufactured by the Taiwanese company Novatek . Their website was slow when I visited it, but here is the link http://www.novatek.com.tw/products/SoCSolutions.asp The manufacturer says this about their chip: “Novatek provides DSC/DV SoC solution, which features high image quality, high performance, excellent digital still image capturing and video streaming capabilities at a cost effective base. It is targeted for the application of VGA to 32M pixel DSC/DV resolutions. It can be easily adapted to many CCD and CMOS sensors with on chip programmable interface timing approach. Novatek’s DSC/DV controller provides sophisticated video processing methods with built-in hardware acceleration pipeline. Hardware H.264 video CODEC is embedded with The HDMI 1.3 Tx.“ A significant feature would be analog low latency video out. Then this camera would be ideal for FPV RC flying.

There is a reliable Ebay source for this camera here: eletoponline365

Testing of a HF current transformer with a vector network analyzer

I wanted to check the load that a ferrite core with a secondary winding presents to the common mode current carrying conductor (the outside of a coax) when set up as a current transformer. The coax runs thru center, the secondary winding could be one or several turns loaded by a R+jø load.  (+jø load but the windings of the secondary will give some +jx component).

I did the following three S11 measurements with the VNA (M1, M2, M3):

M1) No secondary winding is present but the single turn is running thru the core

M2) A shorted two turn secondary and an open two turn secondary (winding is pulsed in and out off to be able to better detect a difference). The time domain is captured by the slow scan and sampling rate of the VNA.

M3) Only the primary winding is attached to the calibrated S11 measuring plane. (to measure the self inductance of the single turn in itself. This is an air-core measurements.)

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Above is a similar test setup. The core is an “unknown” Amidon toroid core. The red conductor is the simulated coax common mode current path (a one turn loop). The green conductor is the secondary winding. The load could made by paralleling several resistors in series with the secondary (the blob on the left side, right picture). Note that the measurements below were done with a one turn loop and a short – no resistor. The measurement device is a VNA from DG8SAQ calibrated by O S L  references in the S11 measuring plane (the SMA in the end of the coax from the TX port).  
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The left picture shows measurement 1) The mid picture shows measurement 2) the right picture shows measurement 3)

Edited: What is interesting to see is that the image to the left shows that this core has some resistive loss as can be seen on the blue trace. The Q is quite low. When there is a secondary winding present, the loss is shorted out but the inductancechanges since the inductance of the secondary is reflected into the S11 measurement plane. On the right image it can be seen that there is no resistive loss and a linear inductive reactance caused by the air core inductor (no appreciable drop off or frequency dependent effects, in the measuring frequency range)

What this tells me is that this core setup probably is not too well suited as a high current measuring setup for frequencies above 160m because it will affect the measuring circuit too much. Not in terms of the R element but because of the +jX element. The R is low to the RF current passing thru the core (in the common mode), but the +jX element will present a reactance to the RF current and thereby giving you lower current than should be expected without the core.  My analysis says that another core type should be selected or that a frequency compensation technique should be used. Alternatively that a lower turns ratio should be tried. However looking at the plot to the left, it can be seen that below 30 Mc*s^-1 the +jX component is too high. Perhaps this core has a too large permeability and that a lower permeability core should be used. The primary turn with secondary loading should give a low reactance on the primary. The voltage given over Rt would then be lower but the gain of the detector could be adjusted. (I may be wrong). Please comment if you have comments or suggestions.

Collinear airband antenna design

I wanted to test a simple airband antenna design since I had a roll of balanced feedline laying around in my shack doing nothing useful. First I had to measure the velocity constant of the feedline with my MFJ-259 to be able to come to an estimate of the required length of the matching section. I could also have used my vector network analyzer (VNA) to do that by the way.  To measure without interference from coupling to adjacent objects I did the measurement with the cable hanging out from my balcony as you can see in the left picture. The MFJ-259 was connected in the end and held by hand (that is a benefit of the battery operated MFJ 259 even if the instrument is not of the most accurate on the market). I wanted to make two antenna segments folded over each other. Therefore the top of the feedline is shorted and the currents will be in phase if the antenna is of a proper length. The matching section is a shorted line section that is tapped by the transmission line. The coil on the coax is a choke (I haven’t done any measurements on that choke yet by the way).

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The procedure I used to find the velocity factor of the balanced transmission line was to first measure a length of the feedline with a tape measure. Then I connected the MFJ-259 and found the frequency where the lowest reactance could be measured. (See pic two from left on the upper row above. You can see that the X is very low). This was done in the mode of the MFJ-259 where it is possible to measure both R and X. This is the quarter wave frequency of the line when the wave propagates in the line – not in the free air (“ether”). Then I calculated that frequency back to the wavelength with  y=300/f. I then divided the tape measure length by the calculated length and came to a velocity factor of 0,89. This is the ratio of the wavelength in free air and the wavelength in the transmission line. This is directly related to the propagation speed of the line when it operates in transmission line mode. From that I calculated the required length of the matching transformer and the approximate tapping point on that transformer to reach 50 ohms. Please note that you cannot use the velocity factor of the transmission line to calculate the required length of the antenna (only the matching section), since the RF currents on the two folded legs on the antenna are in phase and therefore the one lead is coupled to the ether and not to the other lead.

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The picture above shows the SWR as measured with my vector network analyzer from DG8SAQ. The markers on the right side shows a 1:2 SWR bandwidth of 118,5 to 128,6 Mc/s which is OK. The reference level is 1:1 SWR. This level is lifted one division for clarity. (I think the Mc/s  is a cool way to express frequency by the way.)

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Here my DG8SAQ1 kc/s to 1,3 Gc/s VNA is shown. It is connected to my PC via USB.

Conclusion: a combination of the MFJ-259, the DG8SAQ vector network analyzer, some balanced line and some coax can be used to make a good collinear airband antenna in less than one our at a cost of a few dollars. The antenna was screwed to a wooden section of my roof by a small screw by the way and can be removed in approx 2 minutes.

PL519 HF linear amps by PA0FRI and EA6AFJ

PA0FRI and EA6AFJ has made some cool low power HF tube amps with the old and thrusty PL519. Here is a picture taken by EA6AFJ.

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This is actually a nice amplifier that should be quite easy to build for the experienced engineer and experimenter. The benefit of using lower anode voltages is that the tank circuit capacitors can be of a low cost variable type. The PSU can also be integrated more easily in the same cabinet as the amplifier circuit. You can check out more information over at PA0FRI’s webpages: http://pa0fri.home.xs4all.nl/Lineairs/Frinear150/fri150eng.htm

SMD resistor lab kit

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Finally Elfa has increased their range of SMD lab kits. It is somewhat difficult to select the kits from their webpage (that detoriated after they started to use SAP). The manufacturer Nova has a website with better information. You can check out the resistor kit pictured above here http://www.nova-elektronik.de/en/compcards/chip0805.php 

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Nova also has capacitor kits. Their SMC-36 kit contains 6030 pcs. SMD ceramic capacitors in size 0603. (6 mil x 3 mil). The range is E6 to 4,7pF with CØG dielectricum. Then they have a 6,6 pF to cover the gap and after that the kits includes the E12 series up to 680 pF. This also CØG dielectricum. Wikipedia has some info about C0G diectricum here: http://en.wikipedia.org/wiki/Ceramic_capacitor You can probably use < pF values up to approx 1400 Mc/s (Megacycles per second = 1/p = Megahertz, p= period) before hitting the self resonant frequency.

By the way the information in Elfas catalog is inaccurate in a lot of areas so make sure to do research before you order from them. For example they stated that the above resistors can dissipate 1W. The manufacturers datasheet says 0,1W. Only a factor of 10 wrong. (Probably due to that incompetent spotty teenagers are making their catalogs these days, instead of engineers?)

Sending hellschreiber from an Arduino –> Helldunio!

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Mark over at www.brainwagon.org has posted some interesting info about sending hellschreiber from an Arduino (see Marks image above). He has used KD1JVs oscillator circuit that was originally used for the wireless morse code thermometer project. Mark has written code for the Atmel Tiny 13A uC for Hellschreiber transmission. You can find code on his website. Below you can study the schematic designed by KD1JV ( you can find more info over at KD1JVs site http://kd1jv.qrpradio.com/temp2morse/temp2morse.htm).

 

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The way this circuit works is that the XTAL oscillator (left) is powered on and off via PB3 output from the Atmel uC. The emitter of the 2N3904 has been tapped with a 6” antenna. Here a DS18B20 Maxim temp chip is used for accurate temp sensing. The temp is sent out via Hellschreiber together with the callsign. The circuit could be expanded with a buffer tapping the signal from the emitter of Q1. That buffer could feed a power amplifier (well filtered of course). Then a Hellschreiber telemetry beacon could be set up. Cool idea!

HF converter for SDR Funcube dongle

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Tony CT1FFU and Diogo CT2IRW has released a converter for the Fun Cube dongle. The design is a based on the old NE602 workhorse. One new approach is to use a wideband MMIC amp in the front end. The unit is powered via a USB connector. Looks like this may be a good add on if you want to do some basic HF monitoring with the Fun Cube. You can find more information here: http://www.ct1ffu.com/site/index.php?option=com_content&view=article&id=178&Itemid=104

Selected photos from OH8X, the megastation in Finland

By popular demand I have posted some pictures from OH8X, Radio Arcala. Enjoy!

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This picture (above) gives a good overview over the antennas at OH8X. You can see the M7 and the M1 towers stand out. Notice how small the M6 rotatable tower looks. The M6 tower in not small in real life its 32m high.

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This is how a real stack should look (above). Notice the icy elements. The orange cables inside the tower is for operating the ice knockers that keeps the elements free from ice and snow. (Snow turns to ice etc). The tower is fully rotatable.

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This is the 5 el yagi on 80, 3 el yagi on 160 and 4 over 4 on 40 (above). The tower is rotatable. It weighs approx. 40 tonnes. The rotor sits in the bottom of the tower and the rotator gearbox is BIG!

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This is the correspondent LB3HC calling in to the shack (via cellphone and not VHF for the occasion) to ask for a rotator turning operation to check proper rotation of the tower before the ARRL CW contest. The tower in my view that is… (behind the camera). The other towers speaks for themselves in the background.

The guys that built this station are extremely skilled. Kudos and congratulations to the Arcala team!
You can find more information here: www.radioarcala.com