ERP calculation on 472kHz

In an attempt to establish my ERP on 472kHz, I have crunched some numbers. I think it is error free, but no doubt someone will soon tell me!

With a 1:46 step up toroid, I am measuring the DC volts rectified across a 470 ohm secondary load resistor using a small 50uA meter in series with 240k ohms (120k twice) and a series silicon diode. This circuit is straight out of the "LF Today" book available from the RSGB bookshop.

DC current = 30uA
DC voltage across 470ohm secondary load  = 0.6 + (240 x 10E3 x 30 x 10E-6)  = 7.8V
DC voltage (rms) across 470 ohm = 7.8/1.414 = 5.52Vrms
I secondary = 5.52 * 10E3/470 = 11.7mA
I primary =  46 * Is = 46 * 11.7mA = 0.54A

Rrad = 160 * pi^2 * Heff^^2/lambda^^2 = 160 * 3.14 * 3.14 * 2 *2/(630 * 630) =0.0159 ohms

P(erp) = I^2 * R = 0.54* 0.54 * 0.0159 W = 4.6mW

My original guesstimate of 5mW ERP is not far out!

Clearly getting the antenna much higher would help enormously as ERP is proportional to Heff^^2. All one can really be sure of is the order of magnitude. I am running low milliwatts.

Sunspots

Sunspot count today is 68 and 20-30MHz propagation "normal", so 10m F2 propagation is possible N-S although I've seen no evidence here on WSPR yet. There seems little doubt now that we are on the slide down to the next minimum now. See http://www.solen.info/solar/ . This will takes years. The slide downwards tends to be slower than the climb up.

I do hope people stick with the higher HF bands during the whole cycle: we'll learn a lot if people do.

More 472kHz disappointment overnight

Yet again, a disappointing evening and night on 472kHz. The same stations are spotting me and I am spotting them. Reports are quite decent and I would have expected to have spotted, and been spotted by, far more stations by now. Just like 6m , the problem is too few active WSPR stations on the band. Such a shame as 472kHz is a fascinating band and WSPR a superb mode for weak signals.

As long as the storms abate, I shall be back on 472kHz again this evening, ever hopeful. I'd like to be spotted by at least 3 times the number of stations.

10m Es - good (until storms stopped play)

There was plentiful 10m Es about this morning, until I had to disconnect everything at 1205z because of very close storms. Spotting me were OZ7IT and CT1JTQ and I was spotting EA6GF and EA5CYA. Es has been present since (at least)  0850z when I first turned 10m WSPR on.

At the moment (1215z) the storms are only a few miles away - hence going QRT (for now).

UPDATE 1450z:  Storms have move on now.  EA6GF (1428km) is being spotted many times here at decent strengths this afternoon on 10m WSPR.

UPDATE 1511z:  EA5CYA (1376km) now being spotted on 10m WSPR. Thunder is still being heard, but distantly. I shall have to keep checking how close any nasty storms come.

UPDATE 1540z:  Thunder and lightning again very local, so all systems disconnected again for safety.

472kHz WSPR - from 2054z

I have now QSYed down to 472kHz WSPR for the night. In the first transmission there were 3 spots, but sadly all from stations that have spotted me before. I am still hopeful of spotting new stations this season or being spotted by new stations myself.

WSPR spots 472kHz - 13 August to 2120z

10m - teatime Es

It is teatime and 10m is open to Portugal and Germany.  Funny how often Es peaks at lunchtimes and teatimes. I shall stick with 10m until dusk, then switch to 472kHz WSPR.  No DX outside Europe seen here as yet on 10m.

UPDATE 1905z:  German stations and Portugal still coming through on 10m WSPR at 1900z.

More Es and MS on 10m

CT1JTQ  is spotting me again by 10m Es at 1250z.

There is more evidence (short, strong non-decoding bursts on his frequency) that the PD0OHW reports are by MS bursts and probably not Es. The Perseid meteor shower is peaking around now in Europe and this will result in lots of long bursts.

Lawn cut - totally exhausted!

Just cut the rear lawn, well 90% of it, and I am totally exhausted. This is a result of my brain bleed. I still get very exhausted doing any physical activity. A year ago it was all so different.

Please may I get back to health again soon. Amateur radio building/field work is all but impossible at the moment as I am still so clumsy with my hands. I hate depending on others as much as I do.

Back on 10m WSPR

After an overnight session on 472kHz - no new spots or spotters seen, just the usual ones - it was back to 10m this morning with 3 early Es spots by CT1JTQ (1843km). I am suspicious of the spots by PD0OHW (459km).   These may be tropo or even MS as there are lots of short, strong bursts on his frequency this morning. For Es, the skip would have to be very short and tropo/aircraft/MS might be more probable over this sort of range. I see I have just spotted him at 0924z.

Sunspot count today is 80 and 20-30MHz propagation "normal".  F2 has been reported in Portugal, but no evidence here as yet. Conditions on 10m are likely to be "interesting". Basically, it is anyone's guess. There is always the chance of F2 linking with  Es, in which case some real DX is possible.

472kHz WSPR

472kHz unique WSPR spots to 2100z.

At the same time as entering the 70cm UKAC,  I was operating on 472kHz WSPR. No new stations spotting me or being spotted as I write. For my very first transmission I forgot to change my ERP: it should have been 5mW and not 2W which was the ERP on 10m.

UPDATE 2200z:  Still just 10 unique reports received on 472kHz so far this summer. Will leave WSPR running 472kHz overnight in case I spot new stations or new stations spot me. You never know!