30 Jun 2009

SixBox QRP 6m AM rig closer to completion

Today I did a full rebuild of the 6m QRP AM transceiver on a much smaller (dead bug style) board so that it will fit in a small diecast (or aluminium) box. In the course of the rebuild I tried out the RX varicap tuning idea which works, but I was unable to move the frequency more than 1-2MHz before the superregen stopped oscillating. I tried a 1N4007 and the collector-base junction of a 2N3904 as varicaps. In the end I decided to use a low cost polyvaricon tuning cap in series with 22pF and this covered 6m plus a few MHz either side. I also ran the PA stage in class C and this seems to improve the modulation. Here is a picture of the SixBox after rebuilding, but before I started the testing. Because of family commitments I shall not be able to finish this now for a few weeks but I am looking forward to some local "DXing" with this around the Cambridge area. It is funny but working local stations with this is (almost) as much fun as working real DX with a proper radio!

29 Jun 2009

SixBox 6m AM QSO

A solid QSO this evening with G6ALB (2 miles away) on 6m AM using the 50mW SixBox rig with vertical antennas at each end. In the other direction, using the super-regen RX at my end, we did some sensitivity tests with Andrew putting a signal generator on and gradually dropping his AM modulated carrier. I was able to copy his signal when it was reduced to 0.5mW.

I also tried to receive a 7dBm carrier from Andy on 70.26MHz AM using the retuned super-regen RX, but was unable to hear it, although we were both using 6m antennas which were not resonant on 4m.

Currently I am putting a rebuilt SixBox in a real box. Later, I will make a breadboarded DSB version.

More details on the SixBox page of my website.

G3XBM webpages have moved

Today I switched my webspace from NTL to Google Sites. I've been having issues with FTP connection to the NTL webspace for weeks and the Virgin Media "help" has been anything but. I do so HATE having to press button 1 for this, 2 for that etc and in the end getting connected to someone who doesn't have a clue. No problem with the help centre being in India, but I would like to get help in the end. No joy.

So, I decided Google Sites would be a better bet. Google Sites is free, allows 100M of webspace and pages can be edited without HTML. There is also good feedback on site visit statistics using Google Analytics. The downside is the page formatting I can use is less complex, less fancy, but this is no big deal.

If you go to http://www.g3xbm.co.uk you will be directed to the right place.

In praise of the Asus EEE Netbook PC

For over a year I've used a little 7 inch screen Asus PC701 Netbook PC running the preloaded Linux operating system "as is" as my main PC. It has never crashed, always boots up in seconds, does 95% of what I ever need from a PC and is inexpensive. It went with me to New Zealand on holiday (allowing me to do a daily blog from hotel rooms and to video Skype our sons) and fits easily in the hand luggage. Today in the UK the version ships with 8GB of solid state memory (mine just has the 4GB) from around £151 brand new.

If you want simple, low cost and effective computing you'd be hard pressed to beat this little beauty. Of course there is now a lot of choice in netbooks with larger screens, XP etc, but for me the original Asus EEE is hard to fault.

28 Jun 2009

SixBox 6m AM (improvements)

Been doing some more work on the SixBox AM transceiver and have come up with a simpler and better TX lineup. I abandoned the osc/multiplier in one stage and went instead for a 3rd overtone xtal followed by a modulated buffer and PA. The third overtone oscillator values shown ensure the crystal reliably oscillates on its 3rd overtone.

The little PA and buffer work well with just T37-6's as (untuned) chokes in the collectors of the buffer and PA followed by a low pass filter. This arrangement is very stable and simpler than before. Modulation is clean and deep. As it stands it produces 50mW of AM on 6m. A further single stage linear PA would take this to around 1W of AM, but I will leave this to others.

25 Jun 2009

Lenticular (lee wave) clouds

The last few days I've been in the Yorkshire Dales area of the UK and was treated to a sight I'd not seen before - lenticular cloud formations over the tops of the higher hills in the Dales. These are sometimes called flying saucer clouds as this is just what they look like. These were all seen yesterday June 24th in the late morning. I only managed to photograph one (a poor example) as I was being driven and was unable to stop when the very best examples (really like flying saucers with nice sharp edges) were visible. A few hours later these had all disappeared. I expect these are quite common in areas like the Dales, but this was the first time I'd seen them.

For more information see http://en.wikipedia.org/wiki/Lee_waves

22 Jun 2009

A very basic 4m AM transceiver

In the coming days I am planning to modify my SixBox 6m AM QRP breadboard to 4m so that I can have a first 4m QSO using my own callsign. As I don't have suitable crystals I was planning to use (very temporarily) a free running oscillator at half frequency, even though I might have to re-net to 35.13MHz (half 70.26MHz) quite often. Today, someone pointed out that the 14.060 crystals sold by GQRP club multiply x5 to 70.3MHz, which would easily pull down to 70.26MHz. Although a x5 multiplier won't be efficient, it is worth a go don't you think?

If things go to plan, I should have a very basic 30-50mW AM transceiver working on 4m by the weekend. It will be a rats nest on a piece of copper clad board, but it should allow me that first 4m QSO. Whether it gets put into a neat box remains to be seen.

[See later blog post on improvements to the TX lineup]

21 Jun 2009

Cambridge Radio Club is 90

Today, the Cambridge and District Amateur Radio Club held a 90th birthday picnic at the village hall in Foxton, Cambridgeshire. The weather was good and there were plenty people there. The club put up antennas for HF plus 2m and 6m with the aid of the Cam Hams group recently back from Harris in the Hebrides. I managed to get along for a couple of hours in the morning and rejoined the club. It was nice to operate on 6m with a big station (QRO and a big, high yagi) for a change. The band was open to Europe and there were plenty of stations to work. In the afternoon, at home, I worked their special call GB0CAM on 2m FM. A nice friendly day.

The CDARC website is http://www.cdarc.org.uk/
Cam Hams website is http://www.camb-hams.com/

Transatlantic 6m summer super DX - what mode?

The usual assumption for the super-DX across the Atlantic from Europe to the Caribbean and S.America is multi-hop sporadic-E. Certainly the contact to K1TOL that I made a few years ago was by this mode.

But, with the recent questioning of the mode for the Europe to JA path on 6m in summertime, I am wondering if mesospheric cloud reflection is a possiblity for other extremely long paths too? YV and other places on the north of South America is some 8000kms away from here, yet people seem to work such distances every summer on 6m.

I'd welcome your comments and views.

20 Jun 2009

QRP 6m multi-hop Es SSB QSO

Just switched on the FT817 at 0820z and worked EA8CQS (Canary Is) on 6m SSB with 5W to the vertical. DX was 3010kms. He was quite weak so surprised he got me so well.

19 Jun 2009

Noctilucent cloud DX - microwave mega DX mode?

There was a MOST interesting note on the ARRL propagation report tonight:

"Noctilucent Clouds Return - As reported at spaceweather.com on June 1, the first noctilucent clouds (NLC) of the 2009 season were sighted over Russia on May 27. NLCs typically appear about 20 days prior to the summer solstice, increase quickly to a high summer level, and then disappear about 50 days after the summer solstice. These clouds are mostly a high latitude phenomenon, and are believed to be composed of ice crystals. VHF radars see very strong echoes from these clouds, and since they are at mesospheric heights (80 to 90 km), they are also known as polar mesosphere summer echoes (PMSE). These clouds are hypothesized by JE1BMJ and others to be responsible for 6m propagation across high latitudes (for example,
from the East Coast of North America to Japan) during the northern hemisphere summer. This mode of propagation has been dubbed Summer Solstice Short-path Propagation (SSSP). Check out page 34 of the February 2009 issue of WorldRadio Online (available free at
www.cq-amateur-radio.com/wr_back_issues.html) for a general discussion of PMSE and SSSP and for references in the technical literature. To reiterate, SSSP is still just a theory,
but the occurrences of QSOs appear to match the occurrence pattern of PMSE."

Now, there is also evidence (from radar returns) that microwave DX might be possible using the same noctilucent clouds, possibly allowing superb DX possibilities on 10GHz possibly even with low power.

This is a whole area of future ham research just waiting to be exploited. It may be one upside of global warming as these high altitude clouds are now more common than hitherto.

For more on these mesospheric clouds see http://www.chiandh.me.uk/p/Noctilucent_cloud#Results

The SixBox - A Simple 6m AM transceiver

NB There is an updated schematic uploaded June 28th 2009.

Well, I've completed a breadboarded version of the SixBox, an ultra-simple 6m QRP AM transceiver which I've had in my mind for some time. As it stands, without a linear, it produces around 50mW AM (200mW peak) from the 2N3904 series modulated PA. It is not in a box, just a rats nest on a piece of copper clad board, but it works. The receiver is a super-regen using MPF102s with an isolating RF amplifier loosely coupled to the super-regen detector. A varicap diode (to be added) is used to tune across the band. The TX consists of a 25MHz xtal, a x2 multiplier and PA both of which are series modulated. Ubiquitous 2N3904 transistors are used throughout apart from the super-regen stages.

Click on the schematic to see what it consists of. It would readily scale for 4m although the T37-6 toroids would be a bit marginal this high. I was surprised how well they worked at 50MHz.

I should be DELIGHTED if someone wanted to develop this circuit further and maybe produce a small PCB and case.

On reflection, I think the DSB version of this would be a better bet. Much of the TX line-up can be re-used for this but I would use a DC receiver. 200mW pep of DSB (equivalent to 100mW SSB) would be quite a useful power. My next project will be to complete the DSB version, either for 6m or 10m.

17 Jun 2009

6m (4m?) distraction

OK, I'm about 40 years out of date with my technology, so if I live to be 100 you may just find me getting excited by SDRs and the like when the rest of you are busy with thought and matter transfer. Who cares, it keeps me happy and doesn't cost a lot :-)

This last week I have had a spurt of creative (?) energy and have been building. Firstly I started work on the 10m DSB rig. The RX is fully working using the Neophyte as a basis. Next I tried the 14.3MHz ceramic resonator-doubler idea for the LO but was disappointed that I couldn't get it to reliably pull down to a useful part of the 10m SSB band. The plan was to look at a mixer-VFO and then put the whole breadboard together with the DSB TX. But I got distracted....

Instead, I built a simple super-regen AM RX for 6m (or 4m), which works well using T37-6 toroids. All that I need to do is arrange for the RX tuning across the chosen band with a varicap. Next I built a simple series modulator (even simpler than the Fredbox one) and now I've started on a very simple AM TX strip and small linear. The idea is to do a Heathkit Lunchbox "Sixer" AM transceiver replacement but in a very simple solid state and no-IC design. The design is likely to produce around 100mW of AM and can be completed for either 6m or 4m. I haven't decided which yet.

There is not a lot of AM on 6m, but a bit in pockets on 70.26MHz. I know 100mW is not much. But, this is a project I've just wanted to do for years and you'll have to bear with me. When this is done I'll get back to the serious stuff - the proper DSB transceiver that is!

13 Jun 2009

Colpitts VFO parts value calculator

PY2OHH is a very creative ham with an excellent website full of good circuit ideas. I noticed a neat Colpitts VFO calculator there today. You put in the frequency range needed and the variable capacitor range available and out pop all the capacitor values in the tank circuit.

Since including this link the original site has removed the schematic.

10m RX using 14.3MHz ceramic resonator

Tried using a 14.3MHz ceramic resonator (in a x2 oscillator circuit selecting x2 at the collector) with the Neophyte derived 10m RX today. Applied the external oscillator to pin 6 of the NE602 and used the on-chip LO as a buffer.

With a 60pF variable capacitor I could pull the oscillator from 28.563-28.641MHz i.e. about 80kHz shift. Adding some inductance in series with the resonator allowed it to pull lower, but I could not make the circuit work reliably with too much inductance. Conclusion so far is that with a ceramic resonator at a better frequency (e.g. 14.23 or 14.24MHz) this would make a neat 10m SSB RX with the Neophyte. A small amount of series inductance would allow around 100kHz shift around the main SSB part of the band.

Next I'm going to try the mixer-VFO using a 32MHz xtal and a 3.58MHz ceramic resonator. This should cover around 28.40 - 28.46 I think.

12 Jun 2009

10m Neophyte RX

Today I breadboarded a 10m version of the Neophyte direct conversion RX from a 1988 QST. The Neophyte uses an NE602 as the RF amp, LO and mixer and with the output fed differentially into an LM386 audio amp. In my version I used a single toroid 10m tuned circuit and a free running LC oscillator using the oscillator onboard the NE602. As it was a lash-up, frequency stability was a bit average, but it had good sensitivity and allowed plenty of Europeans to be copied on 10m CW and SSB. I used an 8 ohm LS and there was plenty of audio. Overall I was impressed that something this simple worked so well.

Tomorrow I want to try the same circuit but using an external VFO using a VXOed 14.3MHz ceramic resonator in an oscillator/doubler. I am hoping that the resonator will pull well over 100kHz so that it covers a useful part of the 10m SSB band. The same LO will be used for the DSB transmitter assuming it pulls OK and is sufficiently frequency stable.

Ceramic resonator VFOs

David W Searle ZL3DWS sent me a very useful link about the use of ceramic resonators in VFOs. These can be pulled more than crystals but the pulled stability is still better than a VFO. I am trying to use these in a mixer-VFO for my 10m DSB rig. See the webpage by Jack Ponton GM0RWU at the address below. I think taking the output differentially from a tuned circuit across the output pins of the NE602 would be better with a simple link winding down to 50 ohms. http://eweb.chemeng.ed.ac.uk/jack/radio/projects/resnote3.html .

11 Jun 2009

A crystal set transceiver?

JF1OZL has some fascinating ideas on his inspiring website. Typical of his wacky ideas is his 20uW TX for 7MHz powered only by the human voice bellowing into a mic. I wonder if a crystal set transceiver is possible using either the rectified human voice (as per JF1OZL) or rectified received RF to power a micropower TX working alongside the crystal set RX? Even a 0.5uW TX could cover miles on VHF line of sight with a beam and generating this sort of power should be possible through rectification of MW and lower HF broadcast stations.

Japan worked from Europe on 6m

Right on schedule the path across the pole from Europe to Japan has opened up on 6m again this late spring, at least for well equipped high powered 6m operators. The distances are amazing (around 10,000kms) yet this path opens up most (every?) year at this time. Whether or not this is really multi-hop Es is very debatable. Once again it proves there is still much we do not understand about HF/VHF propagation. Amateur radio is continuing to add to scientific knowledge.

Now, wouldn't I like to work JA on 6m with my vertical and a few watts!

10m (and 15m) DSB rig ideas

The GQRP club sell xtals for 24.906MHz for £2 each. They also sell 3.58 and 3.68MHz ceramic resonators at 50p each. Now, mix 24.906 with either 3.58 o 3.68 with an NE/SE602 and you end up with a stable and simple mixer-VFO (when the ceramic resonator is pulled in a VXO) covering two very useful parts of the 10m SSB band or the 15m SSB band. All it needs is a filter on the output to select 10m or 15m injection. I have ordered the xtals and ceramic resonators and will start on the mixer-VFO when the parts come.

My idea is to use the VFO with a simple DSB TX and DC receiver. Such an arrangement will give a simple 10m (or 15m) DSB transceiver covering very useful parts of either band, but with few parts.

9 Jun 2009

Antennas for 6m DXing?

Dave ON8WW sent me an email asking me about what antenna to use for 6m DXing. I replied saying that all I had on the band was a triband vertical colinear (the Diamond V2000) but this has allowed me to work over 50 countries on the band with QRP SSB/CW (best DX >5000kms). It is mounted just above the guttering at about 7m above ground level.

6m is an odd band in that there is not a lot of local SSB traffic (I think) and when the band does open up for either Es or F2 propagation the polarisation probably doesn't matter. Certainly I am able to work (at least) as much DX with the vertical on 6m as I used to work with a rotatable horizontal dipole. The antenna works very well for local (and DX) QSOs on 6m, 2m and 70cms FM of course.

OK, if you want to work marginal propagation modes (e.g. MS using JT6m) or tropo DX then a beam would help. But, if you are prepared to go DX hunting when the band is open, then I think a simple vertical is all you need.

10m/6m Sporadic-E update

It usually happens about now: after the first few weeks of frantic Es activity on 10m and 6m working around Europe (after months of silence), activity starts to drop off. The band is open to somewhere but people are less interested in working you unless you are a new country.

The next excitement is looking for more distant Es openings - into the Middle East, North & South America and the Caribbean. So far this year I've yet to hear a transatlantic opening on either 10m or 6m, but it is still quite early, so I remain hopeful.

7 Jun 2009

Monitoring Monthly - gone

Monitoring Monthly, the UK magazine catering for SWLs and scanner enthusiasts, ceased publication last month with May 09 being the last edition. Their website is still in place for electronic copies to be retrieved.

One wonders, in current market conditions, how well (or not) some of the other ham radio and SWL magazines and ham equipment traders are managing. Anyone know?

LA1TPA - a fellow QRPer

Just got this nice email from a fellow QRPer, Mads LA1TPA, from Norway. Mads, I hope to work you soon on HF or 6m QRP. In this part of the UK there are no mountains to climb with the highest being less than 150m! There are a lot more in the rest of the UK though and I think SOTA is a great idea.

Hello Roger
My name is Mads and I'm a Norwegian QRPer. I'm writing you to tell you that I really enjoy reading your Ham Radio Blog. I got my licence in 2005 and my main interests are Summits On The Air activations and QRP DXCC hunting. I also write a QRP Blog myself: http://la1tpa-qrp.blogspot.com/. I'm a G-QRP member and attended the Rishworth convention last year and also intend to go there this year. Hope to work you 2-way QRP one day.


6 Jun 2009

6m PSK31

Just heard CT1ESJ working an ON station on 6m PSK31. Not thought of using this mode on 6m, but it could be pretty useful for working DX on the band. Certainly the PSK31 area around 50.250 was quite quiet.

Incidentally, I was using Pocket-Digi on my Dell Axim PDA to do the decoding just picking up the signal from the loudspeaker.

7X, EA8 and CT3 on 10m QRP SSB

Sporadic E was good today on 10m allowing QRP SSB QSOs with 7X4AN, EA8CEQ and CT3FQ with the halo antenna. 32 countries worked so far on 10m QRP this year, although there are quite a few "easy" countries still missing, so the total should climb somewhat further before the summer ends. By the autumn the sunspot count should be climbing, so we may get some transatlantic F2 layer propagation this year.

5 Jun 2009

10m very short skip

Just worked EI7JN in Dublin on 10m SSB. He gave me a 59 report. When the skip is this short on 10m it usually suggests the Es MUF is getting very high, so expect 2m to open shortly if not already open for Es DX.

2 Jun 2009

ZB2FK on 10m and 6m

In the course of a week I've managed to work ZB2FK on both 10m and 6m QRP. No great distance, but I don't recall working Gibraltar before, apart from ZB2VHF on 4m when I was at Liverpool University (G3OUL) in the late 1960s when running 4W AM!

1 Jun 2009

DSB transceiver circuits - 10m and 6m

Michele IZ8JJI has just sent me a link to a neat, very simple, DSB transceiver suitable for either 10m or 6m. It is from a Japanese magazine (CQ?). See http://www.cqpub.co.jp/hanbai/books/15/15061/15061_p.180-181.pdf

I am not sure of the power (milliwatts I think) but WHAT a neat circuit!