29 May 2012

My May Objectives - achieved

This month I had two objectives:

   (a) make my 10m halo into a dual band 10m/6m version.
   (b) complete my 481THz optical speech transceiver.

Although a few days late, both objectives have been achieved with decent contacts on 10/6m and a 10.5km 2-way QSO on 481THz AM.

Several things will interrupt any objectives in the next month or so, but my next objectives are:

   (a) Improve the sensitivity of my optical transceiver RX.
   (b) Build a new transverter for the 472-479kHz band due to be released Jan 1st 2013 in the UK (we expect).

The first will allow me to use the dual-optics 481THz transceiver over longer paths. I hope to make some contacts over 20km in the next few months.

The second one (472kHz transverter) only needs to be completed before Christmas, but I'd like to get this moving soon. If possible I'd like to run the PA at around 20W - my earlier 500kHz transverter was just 5W - and to improve the RX sensitivity and selectivity. This new band will be a most interesting allocation and I expect quite a few stations to give it a try.

28 May 2012

Joining the "over 10km" optical club

This morning I got a note from Stuart G8CYW which surprised me:
"Roger,

It has occurred to me that you have joined a "select" group, who have made an optical contact over 10km here in the UK with modulated LEDs. I had a quick count up of the people I know about and I do not think there are 10 yet. (probably more I do not know about though) .....so no small achievement."
So apparently very few of the people experimenting with 481THz red LED optical communications have broken the 10km barrier for 2-way QSOs. This surprised me. At the same time I am even more encouraged to continue this fascinating area of amateur radio as there is so much more I can do. The beauty of this is that test equipment needs are basic, skills needs well within my capabilities, and the results when success comes are extremely satisfying.

27 May 2012

Multi-hop transatlantic Es on 10m

What I think is multi-hop Es propagation on 10m this evening allowed me a QRP contest exchange with NR4M in Virginia USA on CW at a late 2222z.  Big contests show up these openings so it is worth some late evening WSPRing too when there are no contests running.

Despite the usually poor summertime conditions, Es can open up the band in surprising directions.

New LF Yahoo Group

After some debate, the old RSGB LF-reflector is now migrating to a new Yahoo group at http://uk.groups.yahoo.com/group/rsgb_lf_group/ . If you have an interest in the VLF/LF/MF amateur bands such as 8.97kHz, 136kHz, 472kHz and 500kHz then you may want to join. It is sure to become one of the most useful resources on the web for up-to-date information as well as a valuable archive of schematics, photos and ideas.

26 May 2012

My first 481THz 2-way QSO

The 481THz kit at the G3XBM/P end of the path
This evening, thanks to Bernie G4HJW, I managed my first 2-way optical QSO over a path of around 10.5km.  For the AM baseband QSO, Bernie used his Finningley transceiver with 100mm optics and I used my simple AM TX  with my modified KA7OEI receiver with unbiased BPW34 connected directly to the FET gate.  For some reason, the RX in my dual tube transceiver (the one on the larger tripod) was about 3-4dB less sensitive than the separate RX, so in the end I used this to copy Bernie at a solid 58-9 with scintillation.

25 May 2012

481THz transceiver ready for QSOs

The electronics of the 481THz AM transceiver
My first complete optical speech transceiver has been finished and is ready for a line-of-sight test over a few kms. The pictures show the assembly of both the electronics and the optics. All the TX and RX electronics are built "dead bug" style on a piece of copper laminate and housed in a small metal box. There are holes for the BPW34 detector diode and the high brightness LED that line up with the focal point of each 100mm optics tube.
The optics showing the 2-tube construction with sighting scope
A quick "in strong daylight" test down the road over 0.3km was successful one way: my wife could see my TX beam strongly and I could detect my CW beacon OK, so I am hopeful that a proper 2-way amateur QSO with this kit should now be possible. Sensitivity at night is very considerably better.

G4HJW is set up to do a 2-way test, so this is now likely to be attempted in the next few days. if successful I will then try to make a better, more permanent, version.

23 May 2012

144MHz across the Atlantic?

A new beacon, GB3WGI in Ulster, has been approved by OFCOM. When turned on it will radiate at least 100W ERP (possibly much more) in the direction of the USA. It will be monitored in the USA and Canada for possible 144MHz openings across the Atlantic.

For many years people have speculated about the possibility of working across the Atlantic on 144MHz. On very rare occasions, this might be achieved by various propagation modes including multi-hop Es, auroral E, tropo or MS, or more probably a combination of these. There have been tantalising hints that this path has been open before now, but no objectively verifiable proof. With new weak signal modes it surely will happen sometime soon.

481THz optical transceiver progress

My AM baseband optical transceiver build is nearly finished (mechanics and electronics both almost complete), although I have to optimise the sensitivity as it is several dB less sensitive than my stand-alone optical receiver.  I am not quite sure why. All being well I should be ready for a real QSO with fellow local optical enthusiast G4HJW next week.

RSGB member for 50 years

When we got back from seeing our grandchildren in Kent today there was a small package from the RSGB on the doormat. I'd not ordered anything, so was a little puzzled what it might be.

Inside was a very nice letter and a personalised callsign RSGB lapel badge as a thank you for being a continuous RSGB member for 50 years this month. Apparently it was April 1962 when I first joined. It was very gratifying to get this: thank you RSGB!

Things have changed a great deal in the hobby since then, but there is as much, if not more, to enjoy today than back then. Whether I get to reach 60 years of membership remains to be seen but I certainly intend to do all I can to enjoy radio electronics for as long as I possibly can.

The RSGB has had a difficult recent history but it deserves our support so that it can work for UK radio amateurs in the years ahead.

20 May 2012

Finningley Optical Transceiver (G4HJW)

Bernie G4HJW is well known for his innovative microwave designs as well as many other good projects in recent years. This year he has produced another winner for the Finningley Round Table in mid July:  a baseband optical transceiver kit designed with SMA components. For details see http://www.earf.co.uk/nanotrx.htm . I am not sure if Bernie is planning to make kits available more generally. Bernie has tested this design over a 65km line-of-sight path recently.

19 May 2012

Dayton and new QRP transceivers

Not being in the USA, I don't get to visit the big Dayton Hamvention held each May, but I do look out for announcements from the big suppliers about newly released products, especially QRP radios. Elecraft were displaying the new KX3 and Ten-Tec announced a new Argonaut VI due to be released later this year. This is a little larger than the FT817 and has HF only coverage (less 12m) but looks ideal for a high spec, inexpensive QRP radio up to 10W. For more on the Ten-Tec Argonaut VI (was the Ten-Tec 539) see this link.

But, yet again Yaesu has NOT released, as far as I am aware, a successor to the FT817.

One of the best places to look for news of Dayton is http://qrper.com/ which has reports and photos of new products.

16 May 2012

Sonicencoders.msi - where can I get it?

My 7 year old Dell Inspiron 630m WinXP laptop has been restored to "as factory settings" to properly clean it out of files detritus that had accumulated over the period despite numerous defrags, ccleaner clean-ups and deletion of unwanted files. I've loaded Windows service packs, McAfee etc and all seems to be well ....apart from one small annoying issue: I keep getting a pop up box  telling me I need a file called sonicencoders.msi to install some software which I think is to do with some Sonic software for DVD burning. This never goes away and it tells me the file is on a D/ drive which I don't have access to. This is a partition allowing full and partial restores on a Dell machine.

Searching the internet it appears this is a very common issue yet no-one seems to be able to tell me where to find this file which I appear to need to even delete the files that are causing the problem. Ccleaner doesn't allow me to delete it, neither does the usual Windows add/remove programs.

When I first had the PC, from my son about 5 years ago, I seem to vaguely recall having the same issue and I managed to fix it but I haven't a clue what I did back then.

Anyone know how to get this file or how to stop the annoying pop-up message? I am not a PC expert at all by the way, so keep it very simple. Ideally someone please email me the file and put me out of my misery.

15 May 2012

136kHz grabbers and a DC receiver for the band

A list of all the known LF grabbers (on-line to the internet LF receivers) in the world is available at http://icas.to/argo/grabbers-list.htm . A receiver to use with a 136kHz grabber is available as a kit or ready built from http://icas.to/e/ . This is a simple, but effective, direct conversion design which is already in use at several grabbers around the world.

Germany- Venezuela on 136kHz

DK7FC has been helping YV7MAE set up a grabber for 136kHz and over the last month they have been improving the system day by day. Last night Stefan's DFCW signal was copied quite well for the first time over a distance of 7818km. This is the first time a European station has been copied in South America I believe on this band. The grabber can be seen at http://dl.dropbox.com/u/74746618/LF/YV7MAE_LF_Grabber.html .

13 May 2012

Universal QRP Projects Box?

This is really a follow-on from the previous post. As a "mechanically challenged" QRPer I really do hate the stage of putting a completed project into a tidy box. Some people love drilling holes but many do not, so I wonder if there is a market for a "universal" QRP projects box with pre-drilled holes at the front and back? Perhaps a variation of the GQRP Limerick project box could be made available for wider project use?

Most QRP transceivers need a power connector, a coax socket and a key on the back. They need a VFO(or VXO) control knob, a gain control and a socket for phones. Maybe another control and a couple of front panel switches.

So, I wonder why no-one (as far as I know) produces a pre-drilled box that could be used for a range of projects. Surely there is a market for this. A set of water transfer control legends could also be supplied with the box (remember the Radio Constructor sets?).

Just my thoughts having spent an afternoon engineering a 481THz transceiver mechanics and drilling an aluminium box.

How I hate drilling boxes

This afternoon I have been "engineering" my dual lens optical transceiver mechanics. This consists of 2 34cm long 110mm drain pipes (with 100mm lenses at one end) fixed together on a tripod mount with a sighting scope attached to one tube and an end piece at the focal points which will support the aluminum box housing the detector, the TX LED and the electronics. I had to work out how to support the two tubes in close alignment and how to fix these and the electronics to the tripod mount. This has involved a fair bit of mechanical engineering, which is the part of the hobby I absolutely detest. By this evening I think everything is ready and fixed together OK. The electronics box has all the holes drilled for switches and sockets. Now all that remains is to build tidy versions of my sensitive detector and AM transmitter.

When everything is finished - the end is in sight now - I will ask Bernie G4HJW for a sked over a fairly short (2-3km) line-of-sight path to check alignment and that everything is OK. Assuming this goes well then it will be time to try a 481THz QSO over a reasonably DX path.

12 May 2012

Light beam RX improvements

This afternoon I played around with my light beam RX trying to squeeze a few more dB of sensitivity from it. Well I think I have managed it by further optimisation of the electronics and by optimising the focal length. Now, in the dark, a barely lit LED in the ceiling of my lab is detectable on the bench without optics. With the 100mm lens I can detect a 1kHz subcarrier on the 481THz optical signal when there is no sign at all of the LED being illuminated. Some tests using an LED as a detector were less successful, so my plan is to make a dual optics AM transceiver with 2 drainpipes and 2 100mm lenses. With this I should be able to work the local nanowave stations over line-of-sight paths.

JT6m 6m QSO

This evening was a slightly historic occasion: my first ever QSO using JT6m mode on 50.230MHz. I have used JT65HF on HF but this was the first time with JT6m. Now you may be expecting me to say I worked some exotic DX by MS but this first contact was with M1BXF who was only about 20km away! Listening (more accurately looking) on 50.230MHz has resulted in seeing European DX on 6m under flat band conditions using JT6m. It can be quite entertaining to just leave the RX and PC running to see what DX turns up. You'd be surprised.

11 May 2012

QRP Auto-ATUs

For some years now I have owned an Elecraft T1 auto-ATU which works very well with the FT817, especially with the FT817 interface cable which automatically retunes the ATU when changing bands on the rig if the settings have previously been used. Just recently I started to have problems with this ATU when sometimes it simply refused to work. I contacted Elecraft for help and they replied to my email overnight, which was pretty good customer service. In the end it looks like the problem is just battery contact pressure: I managed to snap the plastic that ensures good pressure on the battery contacts and, by chance this evening, I found that pressing the battery hard brought the unit back to life. I may replace the 9v battery contacts with a snap connector. 

On the subject of QRP auto-ATUs, has anyone experience of the LDG Z-817? This is a bit bigger than the diminutive T1 but in some ways is a better arrangement for home use. This has to be retuned every time bands are changed but the method of interfacing to the FT817 control (to change mode and power during tuning and then switching back automatically when done) is good. The memories also store previous tunes so retuning when changing bands takes just a second or two I believe. I also like the way the Z-817 sits on top of the FT817. The T1 is fine for portable use but I never quite know where to put it when used on the desk at home!

Now, of course, if the FT817 replacement ever happens (Dayton in a few weeks maybe?) we will expect to see an ATU inside the rig, as for the Elecraft KX3.

10 May 2012

Radio Nederland and shortwave broadcasts

One of my favorite shortwave broadcast stations back in the 1960s was Radio Netherlands . I still have my QSL card from them somewhere. When testing my shortwave crystal set today I noticed a strong transmission of the Dutch language service today in the 31m band. Little did I realise (until tonight) that this is the very last day ever of transmissions in their worldwide Dutch language service.

The HF broadcast scene is quite a lot different from when I last seriously listened some years ago: there are far fewer English language services to be heard. I guess these days people who want to find out about different countries listen to broadcasts on the internet.

Also, the CW maritime services, which could be perfectly copied sometimes on a crystal set as a result of cross-modulation (the CW sounded like a raspy hiss keyed) are long gone. One of my interests some years ago was seeing how many HF marine coast radio stations I could positively ID on a simple crystal set: the answer was quite a few around western Europe.

In fact SWLing on HF is rather a dying scene I think, although devotees will no doubt disagree.

9 May 2012

Crystal set sensitivity experiments

This afternoon I had a little play with a simple crystal set to see what sort of minimum discernible signal (MDS) was possible. My previous experiments with single germanium detectors had yielded an MDS of around -55 to -57dBm in the 5-30MHz range with a high impedance crystal earpiece.

Today I tried the same test with both germanium diodes and a hot carrier diode (HP2835) with and without some bias applied to the diode(s). Best results were with the HP2835 and with about 0.11V forward bias applied. Only a few uA are needed so battery drain is next to nothing. MDS was around -62dBm for a well modulated AM signal. For the tuned circuit I used a T50-6 toroid with around 20 turns with an antenna link winding adjusted for best sensitivity/selectivity and a 365pF variable capacitor .

Incidentally, forward bias for the diode could be obtained by rectifying other signals available on the antenna such as MW/LW broadcasters using a separate tuned circuit, rectifier and reservoir capacitor. I must give this a try sometime. Several hundreds of mV DC should be possible.

Then I tried switching the diode with a second signal generator at a power of between 1-10mW to see what sort of sensitivity could be obtained on a CW signal. MDS improved by around 25dB to around -86dBm i.e. I could just hear down to around 10uV. This would be a just usable level as a basic HF SSB/CW receiver.

I also tried the same tests with a pair of high sensitivity ST-3 headphones that Michael AA1TJ kindly managed to find for me. These are much lower impedance than the crystal earpiece so I experimented with antenna match and the match of the diode to the tuned circuit, expecting a better performance at the best settings. Disappointingly, the results were several dB worse than with the crystal earpiece.

Now, the results with the crystal earpiece are very close to those (without bias) that I obtained some years ago, so I don't think my hearing (at 63 years old) has changed much for the worse. So, Michael must have incredibly sensitive ears as there is no way I was able to hear down to the levels he could with his passive receivers.

At the moment I am playing with the AM crystal set with -62dBm sensitivity listening to shortwave broadcasters. Fun.

Six continents on 10m WSPR

This afternoon I exchanged WSPR reports with RI1ANF in the South Shetland Is in Antarctica on 10m. This now means I've had reports this year from every continent on the 10m band using 5W or less with the wire halo antenna.

PA1B's power attenuator calculator (see link below)
As this is all getting rather too easy (!) maybe I need to follow Bert PA1B's advice and build a switchable attenuator so I can repeat the challenge with much lower powers. See his power attenuator design page for details of how to make suitable RF attenuators to reduce QRP rig output powers to milliwatts.

8 May 2012

50MHz, 432MHz and 481THz this evening

Well, this was an interesting evening. Just after teatime I noticed 50MHz was open with some strong Es signals from Europe. A few stations were worked on QRP SSB using the newly erected halo antenna (S52NR, S53OQ and OE5FIN). Heard, but not worked, on 50MHz were CT8/K0RUI in HM68 (Azores Is) and 4X4DK in KM72. Both DX stations were good solid signals on the halo.

Stations worked on 432MHz this evening (5W/4el)
Later I went out portable with my FT817 (5W) and my small "coat hanger" 4 element yagi for the RSGB 432MHz activity contest and worked 14 stations in just over an hour before closing as it was dark and I could not see the logbook very well. Best DX 155km although I did hear, but not work, F8BRK in IN99.

Finally, for the very first time, I have detected GB3CAM on 481THz (red light beacon) at a distance of 32km from the Nine Mile Hill site where I was active in the UHF contest. Signal was weak with lots of scintillation, no doubt caused by the rain that started up just as I began listening with my 100mm optical receiver (KA7OEI/K3PGP hybrid). If I can find another 6dB sensitivity I think the signal will be solid in low haze/clear conditions over this LOS path. GB3CAM is a very low power light source, so copying it is a big challenge.


7 May 2012

Monday nights at 8pm on 144.575MHz FM

Every Monday evening a number of East Cambridgeshire locals get together on 144.575MHz FM for an hour between 8-9pm clock time. The usual stations on the net are G6ALB, G3KKD, G4NUA, M3YPZ and G3XBM.

Originally this started as a regular session between G6ALB and G3XBM on 144.55MHz AM. We managed to engage in some sort of QRP related experiment most weeks. We've worked each other on all bands from 1.8-432MHz with extreme QRP and had 1-way contacts on 8.97kHz, 136kHz and 500kHz QRP too. We are 3km apart, which is an ideal distance to try all sorts of things from listening to each other on crystal sets to trying to see how weak a signal can be copied on each band: you may be surprised how little signal can be copied at this range: it is no wonder we suffer from so much interference on HF these days as nanowatts go a long way.

These days the net conversations cover all manner of subjects but, sadly, Andrew G6ALB and I don't get to do experiments so often: this is a drawback of a larger net. At some point I think Andrew and I will find another spot to do experiments on another evening whilst letting the Monday net continue as it is. It is fun to simply chat.

Let me share a pearl from this evening:  Alex M3YPZ, who has a truly fascinating background going back to working on radar in WW2 and research in Cambridge University, mentioned he had a book on how to improve his memory.  He lent it to someone   ....but could not remember who.  The joys of getting a bit older!

If you are the area feel free to call in to the net.

10m across the pond

Late this afternoon I was very surprised when my 5W to the halo was spotted on 10m WSPR by K9AN 6505km west of me. It is unusual, I think, to get 10m transatlantic propagation at this time of the year by F2, so wonder if this was Es propagation? There were quite strong PY stations coming through earlier, so it could be F2 back-scatter. Incidentally, 4X1RF and I seem to have a pipe between us on 10m: we WSPR spot each other most days and I often copy him when his beacon is running 50mW.

Further to my earlier post, WSPR allows one to do "gentleman's DXing": you can see how far your signal is reaching whilst running QRP and a simple antenna and still do other things in the shack at the same time. Perfect.



DX Chasing (no thanks)

Chasing DX is just not my thing any more. For example, on 10m CW this afternoon there was one heck of a pileup of stations trying to work 7O6T in Yemen. This is a rare country but those who get through tend to be the stations with the BIG beams, high power and who call and call. Occasionally, a QRP station with good skills can manage it. On rare occasions I have found DX before the pileups or the DX cluster shows it's there and then a QSO is possible.

But basically I am past this stage in the hobby now. I prefer to explore new things, experiment and have fun. I know that if I had 400W+  and a big beam up high I could work the world if I was patient, but having amassed well over 100 countries worked with 5W SSB/CW it matters not to me that I don't work that rare DX.

On VHF and UHF it can still be fun though, and counting squares is still my answer to train spotting, HI.

6 May 2012

AM lightbeaming down the street

With my wife manning the TX this afternoon and pointing it out of the landing window we managed a daylight speech test today with 100mm optics at both ends at 0.3km using the v.simple AM lightbeam TX described in the previous post. The LED was run with an 80mA standing current. Biggest problem was aligning the TX beam and the lack of talkback, but I managed to get 59+ copy of my wife saying, "I'm bored with this. Come home and have some tea" when I was aligned on the TX beam.

There is no doubt the simple circuit can be refined to improve audio quality when clipping, but it works. The RX is far more sensitive at night too.  I am now finding a way of replacing the XYL for these tests by using another source of speech such as a radio receiver or MP3 player. She is good at cooking and other things, but not at doing optical tests!

Later this week I'll begin experiments with a simple single LED AM 481THz transceiver.

481THz AM transmitter

This morning I took a step further towards making a complete 481THz lightbeam transceiver by breadboarding and testing a simple AM transmitter for use with a high brightness red LED. The circuit could hardly be simpler but works very well. The bias on TR2 is adjusted to give around mid-rail so the LED has a standing bias before audio is applied. Listening (without optics) on my modified KA7OEI receiver head and looking on a scope, the modulation looks good with around 150mA current into the LED.

4 May 2012

Dual band 10m/6m halo erected

10m and 6m nested wire halos on the mast
The Homebase-10 halo is now a Homebase-10/6 with a second dipole within the first covering the lower part of 50MHz. After just minor adjustment both bands have a near unity VSWR over the parts of the bands where there is CW/DATA/SSB activity.

Since making the changes I have exchanged 5W WSPR reports with FR1GZ  on 10m, and got -19dB S/N on 10m WSPR from CX2ABP (11127km), so that is still working as before. I have yet to work something on 6m to be able to judge the omni-directivity of the 6m halo.

Dimensions for the inner 6m dipole were simply scaled down from the values at 10m: the outer sections are 564mm long and the folded dipole inner section 873mm long (these are the dimensions each side of the feed point). A single 50 ohm RG58 coax feeds both 10m and 6m sections.

Details of the original Homebase-10 were in my Practical Wireless article a few years ago and also on my webpage at https://sites.google.com/site/g3xbmqrp/Home/homebase10 .

3 May 2012

Optical DXing and refraction

Although my own experiments at 481THz have so far been limited to around 9km non line-of-sight, the amateur experts around the world have been achieving remarkable ranges both line-of-sight (LOS) and over the horizon (NLOS). In the UK several groups are looking for longer line-of-sight paths up to around 147km.

Some interesting information is coming to light (no pun intended) about the refractive index of the lower atmosphere at optical frequencies. At radio frequencies the refractive index (K) is around 1.33 and I had always assumed that for lightwaves it was just over 1. But tests suggest this is NOT the case at lower levels such as over the near line-of-sight paths now being attempted. A recent paper by Barry Chambers G8ACN on the UKNanowaves Yahoo group suggests a much higher figure may be more appropriate for a lot of the time meaning that what may appear to be a non line-of-sight path actually is one. He cites some observations by G8CYW and others of distant factory chimneys and cooling towers that should not be visible over the distant horizon but frequently are clearly visible.

Many are familiar with optical mirages, but the fact that the optical refractive index is frequently in the 1.1-1.33 range surprises me. It suggests many more distant optical paths may be workable with suitable equipment than was previously thought possible without having to resort to clear air scattering or cloudbounce. With 481THz cloudbounce and clear air scattering the additional path loss (compared with a LOS path) can be in the 30-50dB range, so equipment for NLOS paths is much more demanding than for a quasi line-of-sight path.

May Projects

All being well I have a window of a few weeks before visiting grandchildren and the like, so I have a couple of new aims:

(1) Convert the 10m halo to a dual band 10m/6m halo
This should be a fairly easy task as I already have dimensions for the 6m halo and I've air tested it in the loft. All that should be necessary is to take down the 10m halo and change the feed and support arrangements so both the 10m and 6m halos are fed from the same coax. The pair of halos well clear in the air should prove an effective QRP antenna system for my 2 favourite bands.

(2) Complete my first optical speech transceiver
Strange though this is, I have made several quite sensitive optical receivers and a couple of reasonable power QRSS3 and CW optical beacons, but I've still not got around to making a complete optical speech transceiver. Locals hereabouts use baseband audio for TX, so this is what I should do if I want to work people like Bernie G4HJW. It would be good to get a few line-of-sight short range (up to around 10-15km) 481THz QSOs in the log-book soon. Based on my optical work so far this is not a difficult task, just one I need to crack on with.

Target for both projects is within 2 weeks i.e. by May 17th. We'll see.

New Granddaughter

Our granddaughter - just a few hours old
Not much amateur radio here these last few days as we've been to stay in Kent welcoming our newest grandchild into the world: Lucinda was born on May 1st. She is our fourth grandchild. Mother and baby doing well. Not sure if I'll manage to get her interested in our hobby, but her brother is very keen on batteries and screwdrivers at the age of 3, so there is some hope there.