It is some time since I built a crystal set, but these are great fun and very easy to build. Remember you are using the TX station for all power. There are no DC supplies in a crystal set.
Most designs are still for Medium Wave reception, but I had most fun with short wave designs based around T50-2 (red) or T50-6 (yellow) toroids which allow small hi-Q coils to be wound. Larger T68 or larger diameters are also suitable.
There are PLENTY of resources on the internet (just Google "crystal set" ) but a typical one is:
http://www.mds975.co.uk/Content/crystalsets2.html . Never assume crystal sets are useless: I have copied stations (not via relays) directly from all over the world including All India Radio, Radio Australia and Cuba. The short wave design used just a handful of parts. Signal levels will be in 500uV to 2mV region. A good crystal set design can detect down to about 400uV or less, but a lot will depend on your earpiece(s) and your ears. One has to ride QSB as some distant stations appear to be co-channel with less distant stations.
It would be fun to build a multi-band (LW, MW, SW and VHF) design some day. There are even designs for Band II FM using slope detection. They should work well on VHF aircraft band which is still AM with local airports and planes. I have never seen an aircraft-band design. You can always add a small audio amp, but this rather defeats the purpose of a crystal set.
See also my own website about crystal sets :https://sites.google.com/site/g3xbmqrp3/hf/crystalset .
30 Jan 2014
73kHz band in the USA
In recent days and nights European LF enthusiasts have been looking, with some success, for the transatlantic transmissions in the 73kHz band from W4DEX and others who have been granted special permits QRSS60 transmissions have been copied well in Germany by Marcus Vester DF6NM and others. See http://dl.dropboxusercontent.
With the right kit (and stability) almost anything appears to be possible.
With the right kit (and stability) almost anything appears to be possible.
WSPRnet database was down
This morning, the WSPRnet on-line database has been out of action, so it is not possible to see who is receiving transmissions. This is a handicap of WSPR: when the database works it is a great asset and help, but when down for any reason, the whole fun of WSPR disappears. At best, WSPR is really a QRP BEACONING system, not really a 2-way communications system. JT65-HF and JT9-1 are ideal for QRP 2-way communications on HF.
As of 1500z, the database was still struggling - but there occasionally.
As of 1500z, the database was still struggling - but there occasionally.
29 Jan 2014
Health Update
I have now been out of hospital for almost a month following my stroke, so thought I'd better update you on progress.
Well the good news is my walking is coming along quite well. Although I still need a stick, the Zimmer frame is now almost unused. My wife and I do a 10 minute walk around the Close daily. A couple of weeks ago I managed a 1 mile walk at Anglesey Abbey (NT). My main issue when walking is giddiness. This is I believe improving. Another issue is feeling sick inside at certain times of the day. I sleep (usually) very well and for a long time at night. Getting around the home, even a stick is more for psychological support. I can get around OK apart from feeling giddy.
The BAD news is Community Stroke Support. I was told 1-2 week visits would be the norm, but I was, this week, told the waiting list is 13 weeks and I was 13th on the list! The CST refuse to leave messages on the phone and had I not chased them up, I would never have known my status! This part of my post hospital recovery is PATHETIC.
My experience is NHS clinical care is usually excellent but simple communications around the NHS is appalling. If this was the private sector and MY company several people would be SACKED without delay. Really, communications in the NHS is APPALLINGLY bad generally. This is my experience, my wife's and my daughter-in-law's. It HAS to improve. The sad thing is so little needs to change to make it good and save money and give patients and families a better experience.
I have written to the DVLA but don't yet know how long they will withdraw my driving licence, but I assume for 12 months. I now have a blue disabled badge which allows easier parking when my wife drives us to the shops and National Trust properties.
Swallow is slowly improving. I eat a Weetabix and banana at breakfast and pureed food lunch and tea. I am also on an 8 hour liquid feed.
Overall, I am making progress steadily on all fronts, still doing my exercises more despite the NHS than thanks to the NHS. My own doctor and local surgery have been excellent. At the current rate I can expect to be back to near normal health in the late summer.
Today, Thursday, I wrote an email of complant to the local NHS ,copied my MP, James Paice MP. I am pleased to report the NHS listened and I got some positive action this afternoon (speech and language lady coming to my home this coming Monday). It should not be necessary to do this to be heard. What if I was 85 and suffering from dementia?
Well the good news is my walking is coming along quite well. Although I still need a stick, the Zimmer frame is now almost unused. My wife and I do a 10 minute walk around the Close daily. A couple of weeks ago I managed a 1 mile walk at Anglesey Abbey (NT). My main issue when walking is giddiness. This is I believe improving. Another issue is feeling sick inside at certain times of the day. I sleep (usually) very well and for a long time at night. Getting around the home, even a stick is more for psychological support. I can get around OK apart from feeling giddy.
The BAD news is Community Stroke Support. I was told 1-2 week visits would be the norm, but I was, this week, told the waiting list is 13 weeks and I was 13th on the list! The CST refuse to leave messages on the phone and had I not chased them up, I would never have known my status! This part of my post hospital recovery is PATHETIC.
My experience is NHS clinical care is usually excellent but simple communications around the NHS is appalling. If this was the private sector and MY company several people would be SACKED without delay. Really, communications in the NHS is APPALLINGLY bad generally. This is my experience, my wife's and my daughter-in-law's. It HAS to improve. The sad thing is so little needs to change to make it good and save money and give patients and families a better experience.
I have written to the DVLA but don't yet know how long they will withdraw my driving licence, but I assume for 12 months. I now have a blue disabled badge which allows easier parking when my wife drives us to the shops and National Trust properties.
Swallow is slowly improving. I eat a Weetabix and banana at breakfast and pureed food lunch and tea. I am also on an 8 hour liquid feed.
Overall, I am making progress steadily on all fronts, still doing my exercises more despite the NHS than thanks to the NHS. My own doctor and local surgery have been excellent. At the current rate I can expect to be back to near normal health in the late summer.
Today, Thursday, I wrote an email of complant to the local NHS ,copied my MP, James Paice MP. I am pleased to report the NHS listened and I got some positive action this afternoon (speech and language lady coming to my home this coming Monday). It should not be necessary to do this to be heard. What if I was 85 and suffering from dementia?
Excellent amateur VLF reception
OK2BVG has been having very good results on 8.270kHz picking up Uwe DJ8WX. Note timescales of the plot are in many hours. The wideband noise blocks are nighttime when reception is more challenging.
 |
| OK2BVG's reception of DJ8WX on 8.270kHz |
Bye 6m, hello 20m
After over a day on 6m with just G8EPA and G4IRZ in the log on 6m, I have QSYed to 20m WSPR. I have not tried 20m for a few weeks. Already transatlantic spots are in the log and best DX spot of me is at 8307km in DM09 square (KI7CI) so far with 2W. Not sure what happens on 20m in the evenings, but plenty of transatlantic traffic still at 2112z, which is hours later than on 10m. Overnight and Thursday were handicapped by WSPRnet being down , or very flaky.
PA1SDB on VLF
PA1ASB has been active recently on VLF and on his site he has a grabber showing what signals he has/is copying around 8.270kHz which is the new favoured spot. This is below 8.3kHz and so falls in the unallocated part of the spectrum as 8.970kHz is now within the spectrum reserved for sferics research. Most amateur VLF TX stations are now operating around 8.270kHz. Here in the UK I believe it is legal for ANYONE to TX below 8.300kHz as long as no harmful interference is caused to allocated services above 8.300kHz. This is my view, not a legal statement. I have asked OFCOM to clarify.
Also of note on these pages are the .SDR configuration files for Spectrum Lab software. It is ESSENTIAL to use Spectrun Lab or very similar software to detect anything at any range. See http://www.qsl.net/pa1sdb/index.htm . I suggest that, if you want to build a VLF amateur RX, to base your configuration files on those given on these pages.
My own experience is that 420uHz or less bandwidth is essential to see any trace of amateur VLF signals integrated over many hours. 42uHz is better. In both cases you have to lock to a VLF MSK signal, Russian Alpha beacons or GPS for excellent stability. This is all sorted out with the .SDR file automatically. You may be surprised how stable a RX you can make very simply.
Also of note on these pages are the .SDR configuration files for Spectrum Lab software. It is ESSENTIAL to use Spectrun Lab or very similar software to detect anything at any range. See http://www.qsl.net/pa1sdb/index.htm . I suggest that, if you want to build a VLF amateur RX, to base your configuration files on those given on these pages.
My own experience is that 420uHz or less bandwidth is essential to see any trace of amateur VLF signals integrated over many hours. 42uHz is better. In both cases you have to lock to a VLF MSK signal, Russian Alpha beacons or GPS for excellent stability. This is all sorted out with the .SDR file automatically. You may be surprised how stable a RX you can make very simply.
28 Jan 2014
Our windmill in action
Right next door is the local museum (excellent) which is open Thursday and Sunday afternoons from Easter until late October and WELL worth a visit.
The windmill appears to wobble because Google removed the video's shakiness -in reality it is very stable.
6m - no good today
After a full day on 6m WSPR not a single entry in the log.Even the spots by G4IKZ,were last evening! Even othersmdid not seem to be doing very well either.
Meanwhile, 10m was in good shape yet again with lots of transatlantic stations copied and worked by G4NUA, a friend in Cambridge.
I'll keep 6m WSPRing for another day, and hope for better solar conditions tomorrow.
Meanwhile, 10m was in good shape yet again with lots of transatlantic stations copied and worked by G4NUA, a friend in Cambridge.
I'll keep 6m WSPRing for another day, and hope for better solar conditions tomorrow.
73kHz UK access?
According to my interpretation of the latest UK frequency allocation table, one can use the old 73kHz band without a license as long as the output is less than 72dBuA/m at 10m under inductive devices rules. Perhaps someone can tell me if I am wrong. A very low ERP is not a handicap as amateur antennas tend to be VERY inefficient.
See http://stakeholders.ofcom.org.uk/binaries/spectrum/spectrum-information/UKFAT_2013.pdf
See http://stakeholders.ofcom.org.uk/binaries/spectrum/spectrum-information/UKFAT_2013.pdf
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