25 Jan 2015

Not amateur radio.

This weekend was the Big Garden Birdwatch. People in the UK were asked to observe a garden, park etc. for 1 hour and record the highest number of each species seen, then submit results online to the RSPB. It has become an annual event now. I did a record yesterday in our back garden and, just for fun, I did another 1 hour today at the same time but overlooking the local museum and windmill at the front of our bungalow.

More species were seen yesterday but far more starlings were seen today as they roost on the sails of our windmill next door.

I am still active on 630m and 10m, but will be going QRT on 10m quite shortly.

Interest in AM

I note that my most popular blog posts recently relate to Amplitude Modulation (AM). Who said this was a dying mode? Clearly it is not judging by the interest levels shown. RSGB and ARRL please take note.

USA 10m WSPR spots today

The first USA station to copy my 500mW 10m WSPR beacon today was WG2Z (5600km) at 1312z. Most of the morning 4X1RF (3519km) has been copying me.

UPDATE 1924z:  CX2ABP/D (11080km) has been copying me several times this afternoon. The last USA station to spot my 500mW WSPR beacon was K1OF (5500km) at 1718z. This indeed proved to be the last spot of me from the USA.

Sunspots and 10m - Sun Jan 25th 2015

Sunspot number today is 57 and 10m propagation expected to be "fair". I definitely think solar activity is starting to fall away (on average).

24 Jan 2015

Micro 40 - 40m DSB transceiver

See http://home.alphalink.com.au/~parkerp/projects/projmicro40.htm .

Also: https://aa7ee.wordpress.com/2013/10/19/the-vk3ye-micro-40-dsb-transceiver/ .

Well designed DSB transceivers are much simpler than SSB rigs as no SSB filters and mixing to final frequency is needed. They must not be over-driven to avoid a spreading signal. The PA needs to be linear too. These issues being carefully considered, you end up with a rig that has the same bandwidth as an AM rig but with a suppressed carrier. DSB transmitters are usually received as an SSB signal. The downside is that if a simple direct-conversion receiver is used then there is no rejection of stations sitting on the other sideband. So, they are best on quieter bands, rather than busy HF bands. Bands like 10m, 6m and 4m are probably good candidates.

Although not impossible, it is quite difficult to demodulate a DSB signal on a simple direct-conversion receiver. DSB rigs are ideal as simple transceivers to communicate with SSB rigs.

10m USA WSPR spots of my 500mW beacon today

WG2Z (5600km) was the first USA station to spot my 500mW 10m WSPR beacon today at 1302z. I see that FR1GZ (9724km) on Reunion Is, South Indian Ocean, has already spotted me a couple of times already on 10m WSPR today!

UPDATE 1728z:    KU4QI (6406km) was the last to spot my 500mW 10m WSPR-AXE-CW WSPR beacon at 1708z. There is still a chance others will spot me later.

UPDATE 2110z:   The last USA station to spot me was K9AN (6505km) over an hour later at 1838z. It all depends who stays around and who is active! I was surprised.

UPDATE 2140z:  I went QRT on 10m WSPR at 2112z.  I have now QSYed to MF for the night.

G8HUH - multiple spots of my 5mW ERP on 472kHz WSPR

G8HUH (250km) in IO81 square has spotted me on 472kHz WSPR 16 times so far today since the middle of the night.


Sunspot number is up to 70 today and 10m propagation forecast to be "fair".

UPDATE 1346z:  So far, the 10m band is behaving predictably.

23 Jan 2015

70cms AM

As you may recall, I am quite a fan of super-regen receivers. Nothing as simple is able to match their AM sensitivity, but they tend to have poor selectivity.

With the availability of very low cost 433MHz modules (TX and super-regen RX) designed for AM data, these modules could be ripe for conversion to ultra-simple 70cm AM voice transceivers. One local friend, Andrew G6ALB, is currently carrying out experiments to see if this is feasible. I hope to work him on 70cm AM using such a rig in the months ahead. Sadly, I am still too clumsy to do any building work - very frustrating.

I am wondering if anyone else has tried these modules in such a circuit? With a simple MMIC PA (50 ohms in and out) the power output could be lifted to around 25mW carrier or more. With V2000 verticals this should be good for local ranges. Even at the low milliwatt level from these QRPp modules several km range should be possible with co-linear antennas.

UPDATE 2310z:   I wonder what sort of power the TX modules typically produce with linear (speech) modulation rather than 5V square wave data modulation? Presumably much less than their rated power, so an add-on PA may be essential?

South Indian Ocean on 10m WSPR

Best DX today on 10m, despite the "poor" forecast was FR1GZ (9724km) on Reunion Is who has spotted my 500mW 10m WSPR beacon 17 times this afternoon so far.  Quite a few times recently I have had very good reports on 10m from distant stations when the forecast has been "sub-optimum". It goes to prove that 10m and 6m are fickle bands: don't take propagation expectations as gospel.