481THz RX issue - now fixed

As mentioned in an earlier post, my sensitive non line-of-sight NLOS optical (red LED at about 481THz) RX packed up when I clumsily dropped it yesterday when out in the field at the test site. An investigation this morning revealed a wire had dropped off the battery feed and this was easily fixed. The  RX now works as before.
 
I shall have to try the NLOS test again when my wife can drive me out there. I shall have to do it soon as tree leaves will soon obscure the path at the home QTH end. Just wish I was not so clumsy still following the stroke last year. In the field I feel so much less able than last year. I feel really disabled and hate being so useless and clumsy.

UPDATE 2050z: for now, all my tests will be shack-based because of my poor health, so no immediate plans to repeat NLOS tests until I feel a lot less wobbly.

10m - mixed fortunes

Today was an odd day on 10m WSPR - some good propagation N-S but very marginal indeed transatlantic.  The band did open up but hardly any transatlantic spots.

I think we are now moving towards summertime conditions and are gradually starting the slide down towards the next minimum. We will have a very long journey downwards and some days conditions will be excellent. On many days, the band will be closed. On some days propagation will be mainly N-S only.

With luck, Es will help to liven up the band in summertime. Just occasionally, mutli-hop Es will support transatlantic 10m and 6m propagation as well as propagation into the Middle East. Also, sometimes the first hop is Es then linking up with F layer propagation further to the south.  Even in the quiet years, 10m has surprises.

At 2142z NA4U (6533km) was spotting my 2W still. Surprise!

Aborted 481THz NLOS test

I am beginning to think that ALL tests outside the house should stop until I am a lot better (stroke). The best description is I feel, all the time when on my feet, as if I have drunk 8 pints of beer and am very drunk and clumsy.

This evening, my wife drove me out to an NLOS test site where I managed to drop the RX head hard on the ground. The head immediately stopped working even before I started hunting for my signal! I could hear no hiss at all. There was no sign of the very visible moon noise in the RX.

The test would have been marginal anyway, especially with a bright full moon, but to be unable to carry out the test at all was a great shame.  It is just that everything is SO hard for me at present and setting up optical kit is stretching the limits of my current abilities. Feeling clumsy nearly all the time is tiring too.

Even getting my VHF/UHF beam up at home will require help. Andrew G6ALB has kindly offered to erect it for me. This should be an easy task for me - normally it would be - but not at present. At least, when erected, VHF and UHF activity should be straightforward at home in UKAC sessions on Tuesday evenings. Sitting down my balance is fine. I just hope this soon improves. Walking is getting better but balance/giddiness are still big issues.

Simple audio filter designs

The PY2OHH pages contain a useful link to a TI paper on active filters. In my experience, virtually any audio or RF transistor (e.g. 2N3904 NPN) can replace the op-amps with little effect. Some prefer "perfect" op-amps whereas I find transistors easier to work with and place. The performance difference is very very small.

2N3906 is a ubiquitous PNP equivalent.  The 2N3904 and 2N3906 devices are available from a range of suppliers for just a few pence each only. A few 2N3904s in parallel with small emitter resistors make a good HF/LF QRP PA replacement for a 2N3866 too. My recommendation is buy 100 of each (2N3904 and 2N3906) and stock your junk-box. Less than £10 and it will be a long time before you run short! Think of all those projects.
 
See http://py2ohh.w2c.com.br/trx/filtroativo/filter%20design%20in%20thirty%20seconds.pdf for the active AF filter paper.

Good start on 10m this morning

EA8/LA3JJ has already spotted my 2W WSPR 3 times and it is only just after 0800z. Sunspot count is 95 and the forecast is for "stable/normal" HF conditions. Perhaps this will be a good day on 10m?

10m WSPR spots with 2W to 1130z today (basically N-S)

PY2OHH's Pititico 10 parts transceiver for 40m

Andy Cutland has sent me this link. It is from, Miguel,  PY2OHH's excellent site which is full of ideas for QRP and QRPp enthusiasts. I can thoroughly recommend it for ideas.  I would expect this RX to hear signals, but be quite deaf as there is no audio gain apart from that in Q1.

Apparently the headphones were around 500 ohms impedance. I guess a crystal earpiece might work as audio is derived across R2. Maybe then C5 could be deleted?

Q1 must act as a (crystal controlled) regenerative detector on RX with the level of oscillation set by R2. Not sure of RX-TX shift as this will depend on RX and TX current. There is no low pass filter either, as shown. This means harmonics will also be detected and emitted. Still, this is meant to be VERY simple. I must try it.

http://4.bp.blogspot.com/-TlNqb0N-7V0/U0SFVljBTjI/AAAAAAAAUkY/xbyhirCu7AU/s1600/pititico.gif

VHF/UHF antenna ordered

Just ordered  a 5 ele for 70cms and 3 el for 2m which are fed with a single feeder coax and form a single antenna from Moonraker.  This antenna is reduced in price by 30% this weekend.

I intend to mount this dual band antenna on my 50mm diameter pole and hand rotate it by turning the pole out of a window next to the shack. It should mean a couple of S-points extra on 2m (compared with a halo fed with RG58 coax) and on 70cms I have no horizontal antenna.

UKAC sessions on a Tuesday night , GDX and beacon hunting should be a great deal more fun.

Simple 3 transistor DSB transceiver for 28MHz

Stephen Walters G7VFY has reminded me of a simple 28MHz DSB transceiver from Japan . I think I have mentioned this before, but it is so simple and elegant that a second outing is called for.

3 transistor DSB transceiver

See: http://www.cqpub.co.jp/hanbai/books/15/15061/15061_p.180-181.pdf .

Windows Updates and (late start) 10m WSPR

This morning , I assumed I was on 10m WSPR but instead I discovered the (new Windows 8.1) PC was doing a Windows update and was quietly waiting for me to restart the computer! This I did at around 1300z after which I was back on 10m WSPR.  Sunspot count is down to 83 with "disturbed conditions" today so I would expect 10m conditions at 2W to be more difficult.

PY2RN 10m WSPR spots early afternoon today

My first spot today at 1318z is of PY2RN (9550km) running 5W.  Excellent reports both given and received.

Interesting that even at 1822z, not a single spot exchanged with North America, well here at least. All 10m propagation, for me, is in the N-S direction so far today. More like quieter years. Others with better low angle antennas may have done better.

Non line-of-sight (NLOS) 481THz paths from home QTH

Before venturing out, I have been trying to plot possible NLOS paths with the optical TX at home (inside) and the RX at a convenient roadside spot at a moderate (local) distance. One possible path is VERY remote down very uneven fenland roads which would have to be navigated in the dark with my wife driving the car. I am thinking about her driving the car. I am not allowed to drive as a result of my stroke.  Many of the NLOS paths are blocked by nearby houses and trees. It is a surprisingly hard task.

 Back to Google Earth to see where might be worth trying. From previous tests it is necessary to aim very carefully.