233RC/MC06

13/07/2012

Considering my last SOTA activation in 11m was well recieved, I decided to activate another peak in the Carpathian Mountains; this time it’s the Omu peak, code YO/MC-006 in the SOTA watchlist, 2508m high, rated 10 points, KN25RK locator. The “Omu” peak (transl. = “The Man”) is the highest point in the Bucegi Massif and the 11th in the country, at the very top there is a 7 meter tall rock with a hut built right next to it and nearby is the Omu Weather Station, the highest permanently inhabited point in Romania.

 

I will use the same K-PO DX 5000 transciever with 15W output in SSB, a quad loop antenna and a 12V/7.2Ah rechargable batery wich should provide about 4 hours of continuous operation. Main frequency will be 27,515 MHz, secondary 27,655 MHz (both USB), and the callsign will be 233RC/MC06. I will be up in the montains from the 17th until the 22nd of July, but this activation will take place most probably on 19 or 20 around 9:00 – 14:00 UTC; also I will try to activate another peak if possible, as well as be active in the evenings under 233RC103/QRP.


233RC/MC015 activation finished

10/06/2012

And I have finished and I’m back home. 233RC/MC015 SOTA activation is done, 38 contacts in the log, a new division for me (115), a S2S contact (14CRX/FPO084), tired and a bit sunburned. Also alot of things learned from this new experience for me, wich will be really useful next time. First of all, some pictures I ahve managed to take on the way. Here’s how the Caraiman peak looks from Busteni, the closest city:

And here’s how I got up there: the aerial tramway that got me from about 850m to 2200m of altitude, it truly looks like the way to the sky.

A view from the Babele plateau at 2200m:

And finally the antenna installed on the Caraiman peak at 2384m height (actually a few meters less, because i wasn’t on the very top):

When the clouds cleared, you could see the Caraiman Cross:

The transciever used was the K-PO DX 5000, wich I found out not to be the best for SOTA as it is rather bulky and takes up space in the bag. Other than that it was great, the integrated SWR meter and supply voltage monitoring are very useful tools for portable operation, and the adjustable power output up to over 15W in SSB was a decent tradeoff. Sometimes i wished for a 100W transciever, but looking back at the 4 hours of activation-style operation (almost 50/50 tx/rx cycle) available from the 7.2Ah battery I think it was worth it to lose a few contacts in order to gain much more operation time.

The antenna was a quad loop built from 2 fishing sticks, one was 6.8m and the other 2.8m; I have used double 0.5mm wire from UTP cable for the loop, wich was strong enough not to break in the wind (even if the antenna was turned by the wind, wich was a real problem I didn’t foresee). At first I have tested with vertical polarisation (fed on one side corner) and the noise was at S3 even on the mountain top and I had SWR 2.5 (normal for a vertical polarised loop), then I switched to horizontal polarisation (fed the antenna at the bottom corner), the noise went away and SWR was down to 1.1, plus the gain is higher and the lobes are better for DX.

Log for the activation: 233RC-MC015-log


233RC/MC015

07/06/2012

This weekend (08 – 10.06.2012) I will try to activate the Caraiman Peak in Carpathian mountains: 2384 meters high, KN25RK locator, code YO/MC-015 and rated 10 points in the SOTA list. It is famous for the “Caraiman Cross”  – a huge illuminated monument built after World War I visible from very far, as well as for the weird-looking rock formations called “Babele” (The Old Ladies) and “Sfinxul” (The Sphynx).

Equipment used will be K-PO DX 5000 transciever at 20W output, quad loop antenna (also known as “Bamby”) and 12V / 7.2Ah rechargeable battery; main working frequency will be 27.515 MHz and secondary will be 27.655 MHz, both in USB. Callsign for this activation is 233RC/MC015, activated and managed by me 233RC103 – George; for info pls email [my_callsign]@gmail.com.


Flex-6000, new generation of SDR transcievers

19/05/2012

Flex Radio Systems introduced yesterday at the Dayton 2012 Hamvention the all new Flex-6000 series of transcievers, called “Signature Series”. These are the first comercially available SDR products intended for HF amateur use that employ Direct Digital Conversion, sampling RF directly thanks to the high-performance Analog Devices AD9467 ADC without the need for mixers such as the Tayloe detector that was the heart of the previous generations of SDR equipments.

But this is not the only thing the FLEX-6000 series brings: it’s purpose seems to change a bit towards better integration into the modern digital world as a shared resource. If until now a transciever was a piece of equipment one operator would use at a time, the FLEX-6000 series is a computer network equipment anyone can use (either on LAN or via Internet), allowing up to 8 virtual 384KHz bandwidth recievers in the 0.03-77 MHz range to be created and operated simultaneously. Ideal for club stations or conditions that require remote operation (Radio Arcala comes to mind), even though the transmission is limited to one user at a time.

Other hardware key points are the pair of Mitsubishi RD100HHF1 finals conservatively pushing out 100W at 13.8V, a rather unusual choice considering the other top manufacturers start moving towards 100V operated final stages wich offer better IMD figures and are easier to work with. Also, the main CPU is a Texas instruments ARM Cortex A8 1.2-1.4 GHz CPU with NEON coprocessor and 1.0-1.2GHz DSP processor. There will be 3 models available, the top dog FLEX6700 transciever, the FLEX-6700R reciever and the FLEX-6500 transciever, with rumored prices os US$7000, US$6000 and US$4000.

More details in the FLEX-6000 series presentation sheet.


Over-the-horizon radar operating in 27MHz

08/05/2012

OTH radars are strategic military equipments that basically allow the operator to “see” beyond the horizon trough the means of ionospheric reflexion that allows HF signals to propagate all over the globe. Regular radars use signals in the GHz regions (better for detection of smaller objects) and are only good for direct visibility, that is why sometimes OTH radars were replaced by more expensive “flying radars” more commonly known as AWACS, but as the Cold War has ended armies are folding back to the cheaper technology and the OTH radard operating in HF are spotted more and more oftenly by amateurs. More details on the OTH Wikipedia page, if you are courious.

Such a signal could be recieved today in Bucharest between 27.480500 MHz and 27.499500 MHz at a S9 level, with a type of pattern I haven’t seen before.  Feel free to check out the video and to see how it looks on my SDR transciever.


233RC103/8SM – RC 8th Spanish Meeting contest

05/05/2012

I’ll try to enter the 8th Spanish Meeting RC Contest that takes place in the first two weekends of May 2012 with the special callsign 233RC103/8SM; i will be my first contest and the purpose is just to gain some experience in these types of traffic conditions.. See you on the air !


Antennas side by side: Ground Plane versus Delta Loop

03/05/2012

At the moment I am using two antennas for 27MHz operation: a 1/4 wave Ground Plane and a Delta Loop, and I had the chance to do a little comparison between them. For who’s not familiar with how these two antennas look, with my inexistent Windows paint skills I have quickly illustrated how mine look and how they’re placed:

The one on the left is the Ground Plane and has 5 elements of 268cm each: the vertical one is connected to the central wire of the 50 ohm coaxial feeder cable, the rest (“radials”) are connected to the outer shield of the cable. Typical impedance of a 1/4 wave Ground Plane antenna depends very much on on the angle between the vertical element and the radials, it’s around 25 ohm for 90 degrees and at 180 degrees should be around 70 ohm; i have used around 130-140 degrees wich should bring the impedance to aproximately 50 ohm, but it didn’t as we’ll see later. It is a omnidirectional antenna, has vertical radiation polarisation and it’s takeoff angle is around 20 degrees.

The Delta Loop on the right is basically a full wave loop in a triangle shape, and fed on the right corner as I did makes it’s polarisation inbetween vertical and horizontal, wich shouldn’t matter too much for DX but it will either be better or worse for line of sight contacts depending on what type  of polarisation your partner is using. To obtain vertical polarisation the feedpoint should be at a level where a line parallel to the ground trough that point would split the antenna in two equal perimeters; for horizontal polarisation, a vertical imaginary line trough the feedpoint should split the antenna in 2 equal perimeters as well. The impedance is around 100 ohm for a triangle with equal sides so it shouldn’t adapt perfectly to 50 ohm feedline, but closing one of the angles like I have done should bring it close to 50 ohm; if instead of a triangle we would make a square from the same perimeter, it would have 50 ohm feed impedance. Because it’s balanced it will need a 1:1 BalUn to work correctly with coaxial (unbalanced) cable, and it can be done either by winding a bifilar wire on a properly chosen toroid (i have used Amidon T80-6, enough for about 100W RF power), or by winding 15-20 laps of 50 ohm RG-58U coaxial cable on a PVC 10cm diameter pipe (enough for much more power). Length of the loop should be a full wave loop, but experiments proved that it properly tunes with a loop slightly longer than full wave: in my case, almost 10% more, 11.7 meters. This really depends on the type of wire used to build it, the height above ground level and what other objects are nearby. The takeoff angle is around 25 degrees but it has about 2dB gain over the Ground Plane so in some situations it might perform better; also the closed loop should offer protection against static noise and improve reception in some cases. It is also slightly directional, favoring the direction perpendicular on the triangle’s plane by 3dB.

Enough theory, now to the real life testing on the next page.