Sunday, 22 January 2017

Friday, 23 December 2016

Successful EME contacts

Massive EME array?  8 element DK7ZB
 Success

After several weeks of trying I finally got lucky and had two QSOs via EME.  Below are several screen shots from the contacts. The only thing that was different this time was the antenna. I used my 8 element DK7ZB instead of the thirty year old 9 element Tonna.  The Tonna is showing signs of it's age and I'm wondering if the corrosion is affecting it's gain.

Equipment

Modified Kenwood TM255E (SI570 LO, IF tap)
Homebrew SDR tuned to TM255E IF
Homebrew 300 Watt amp (Freescale MRFE6VP6300 mosfet)
8 element DK7ZB  (gain 12 dBd)
Software;
WSJT-X v1.7.0-rc2
PowerSDR-IQ


So I'm pretty happy with that and looking forward to more contacts.

Transmitting RO
Completed QSO
The second contact was an answer to my CQ, pretty suprised I can say
Second contact
And a card

Saturday, 5 November 2016

EME, to the Moon and back

 Inspiration

It's the ultimate challenge of amateur radio, Earth-Moon-Earth also known as moon bounce but is it possible with a small station like mine? Until recently I would have said no but after using MAP65 from K1JT I'm starting to think that maybe it is possible.
I've been using SDRs for some time now on VHF, so I already had available the IQ output needed to use MAP65.  This allows the decoding of all JT65B signals within a 90kHz bandwidth.  I've used the software to monitor beacons on Two with good success, at times being able to decode four beacons at the same time, GB3WGI, GB3NGI, GB3VHF and F5ZRB. But it never occurred to me to try and hear anything off the Moon. That was until one evening while watching an art programme an item appeared about artist Katie Patterson's Earth- Moon - Earth.




Katie used EME to record Beethoven's Moonlight sonata complete with gaps due to fading and then replayed it on a modern player piano. This romantic idea of radio waves going to the Moon and back was an inspiration so I started reading all about EME. I soon discovered that with JT65B, on Two, small stations were having success with single yagis and no elevation.

 Help needed


Ground gain or in this case sea gain


Apparently, EME is possible with 100 Watts and a single Yagi using JT65B.  It is often achieved at Moonrise or as the Moon is setting when ground gain is available.  I took this photo of the Moon over the sea a while ago and if I've got this right it should help to illustrate the principle.  Light from the Moon is taking two paths to the viewer, direct and that reflected from the surface of the sea. The reflected light adds to the overall illumination. In radio that can add as much as 6db to the signal at 144 MHz.  There's much more about ground gain online as a search will reveal but it's just like having four Yagis, not just one. Of course, it's only available when to Moon is at low angles as in the photo. ↗

 First monitoring


So with this in mind, I started to monitor off the Moon. Pointing my small 9 element beam towards Moonrise I left MAP65 running overnight.  Moonrise would occur in the early hours so I wouldn't know if anything had been received until the following morning. Come morning there was just one line in the band map, "73", time, signal strength, etc.  So to see if anything else had been received I opened up the text file Map65-rx found inside the MAP65 folder.  It contained all decoded data received through the night and to my amazement several stations had been received, two Russians and an Italian. Pretty encouraging but I had in the past, while monitoring beacons, seen false decodes so to be sure I turned off the Deep Search and renamed the CALL_3 file to be sure that I was indeed hearing off the Moon.
Once again I pointed the beam towards Moonrise, left MAP65 running and waited to see what might be decoded with the Deep Search disabled.   Once again there were several stations decoded and this time they could not be false decodes.


 More monitoring

 

 Over the following weeks, I continued to monitor and I soon started to realize that signals could be heard from Moon elevations of just 1 degree to as high as 25.  Outside this range decodes are few and far between but they did occur even 1 degree below the horizon on one occasion and at 60 degrees above.

Next.......

 I've improved receive performance by building a new preamp.  I'm looking very carefully at the transmitted signal as getting audio harmonics to a low level seems important to me. I need to familiarize myself with the operation of WSJT JT65B. Just monitoring is easy but TXing is going to be more demanding. I need to test my amp at the high duty cycle of JT65B........etc...etc....... but hopefully I'll soon be ready for that first contact.  I'll post here if I make it.

Cheers & beers

Dave G8TTI

UPDATE
15/12/2016
Well, I keep trying but not had much luck so far.  Was spotted on Livecq by a Dutch station but can't help wonder if that was tropo.  Also had a QRZ, well I think it was for me.  I'll just have to keep trying. Amp works fine and I have a 12dBd antenna to try, hopefully, that will help.
73


Saturday, 24 September 2016

G3VRE Mini Rally

Rally was a great success and will return in 2017

NOTE POST CODE SHOULD BE SN15 5NJ

Friday, 16 September 2016

Some success with 1296MHz WSPR

Had some success with 23cms WSPR but found that transmit with my old transverter will not work as there is far to much drift even tough I've ovenized the LO.  Needs more work on the oven.



Monday, 29 August 2016

Removal of WSPR VHF spot frequencies in IARU Region 1

 At the beginning of June 2016 the WSPR VHF spot frequencies in IARU Region 1  where removed from the band plans.

At the time I wrote this response but have only now decided to publish it.

 

I'm new to VHF WSPR and am really enjoying it. I've been on Two for over 30 years and if you'd ask me before I started using WSPR if I could put a signal into JO23 (600Km) with 5 Watts under flat band conditions I would have said noway but with WSPR I can! I'm impressed and would like to find out what more can be done. So I'm not going away yet but I do believe we should take the olive branch offered by the RSGB VHF Manager and on Two, which is where the problem seems to be, all just QSY to DIAL 144.490500MHz.


We should also ask the VHF Managers to re-read their handbook paying particular attention to these passages;



The basic philosophy behind bandplanning should be:

to assign frequencies for certain activities in such a way that all current users can practice

the various modes of amateur radio with a minimum of mutual interference, provided they

are using state-of-the-art equipment and communication techniques”.



Technical investigations by amateurs, be it in the classical field of propagation research or on

modern digital communication techniques etc. are a laudable and legitimate aspect of amateur activity”.



The definition of the Amateur Service implies that bandplanning should take into account all

aspects of amateur radio – self-training, intercommunication and technical investigations.

Consequently, for any band the bandplan should aim to accommodate for the maximum

number of amateur activities (modes, techniques), both now and in the future.

Clearly there are impossible situations: CCIR ATV cannot be carried out in the 144 MHz

allocation etc”.

WSPR, JT65 and other screen shots

Here are some screen shots that should be largely self explanatory but I'll add more if I think necessary.

1296.500MHz WSPR 



The 220km path on 23cms
WSPR & JT65 at he same time on 30 metres
The relocated GB3USK beacon on 23cms not to strong with me
200 mW heard in Antarctica

A good day on 70MHz