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.

Southern Brazil PU3RRW 10m WSPR

PU3RRW (10652km) was spotted 3 times (so far) this evening. This station in GF38tf  is about as far south as one can get in Brazil and was a massive +9dB S/N for 5W on WSPR at times.

I wonder if TEP  propagation was helping to give signals this strong on 10m.

More transatlantic 10m

Atlantic

10m is still (mainly) open to the USA and Canada from just before lunchtime, local time. The sunspot number continues to decline, but 10m propagation remains in great shape. Even 6m should be good for TEP from southern latitudes. The MUF near Brazil was 47MHz yesterday, so only a bit short of that needed for 6m TEP.   

PY2RN (9550km) has been spotted on 10m WSPR several times already today. Southern Brazil is a long way from the UK but it is mostly a sea path.

10m oddity

10m WSPR early morning April 11th 2014

WA2YUN has just been spotted by lots of us in Europe, including me, at around 0908z. His reported locator is RK39hh which is near Wake Is in the Pacific. I suppose this is JUST possible at 11946km (especially early mornings) but it is more probable he is reporting the wrong locator. It is too early for transatlantic propagation - very odd.

KH9/WA2YUN is shown as Wake Is, so this is probably genuine.
See: http://www.dxcoffee.com/eng/2012/03/07/kh9wa2yun-wake-island/ 

WA2YUN/KH9 QSL card