This little top band AM transmitter and a companion receiver were first published in the GQRP club SPRAT magazine. This TX version was built by M0DAD. Where the noise floor allows, 160m AM is quite popular for local nets. There is something nice about "rolling your own" builds and getting satisfying results without spending a fortune. For daytime local use 160m AM is a great mode and rigs are simple. I am still surprised that more is not made of AM on 10m at night for local nets here in the UK.
See http://www.delboyonline.co.uk/m0dad/construcion/poppet_top_band_am_transmitter.htm.
26 Jan 2015
QRP 5W CW transmitter from SM0VPO
Many years ago Harry SM0VPO worked at Pye Telecom. I had no idea back then that he was such a prolific and good designer. This is his design for a simple HF 5W CW transmitter. His website has loads of great ideas.
See http://www.qsl.net/qrp/tx/5wtx.htm .
See http://www.qsl.net/qrp/tx/5wtx.htm .
472kHz WSPR overnight
G0MGM (101km) has spotted my 472kHz WSPR (5mW ERP or less) several times. I think he is a new reporter and very welcome too. Tonight I may go back on the HF and 6m wire antennas (with loading coil) to see how results compare with the earth-electrode "antenna" currently in use.
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G8HUH (250km) always seems to copy me. He has a good system on RX. He even copied me on 136kHz WSPR from the old QTH, before I had my cerebellum bleed. I have yet to try 136kHz WSPR from this QTH.
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G8HUH (250km) always seems to copy me. He has a good system on RX. He even copied me on 136kHz WSPR from the old QTH, before I had my cerebellum bleed. I have yet to try 136kHz WSPR from this QTH.
Sunspots and 10m - Jan 26th 2015
Sunspot number has climbed a little to 65 and 10m propagation is forecast to be "fair" again today.
UPDATE 0925z: 4X1RF (3519km) has already spotted my 10m 500mW WSPR beacon 4 times,which is a hopeful sign on 10m.
UPDATE 0925z: 4X1RF (3519km) has already spotted my 10m 500mW WSPR beacon 4 times,which is a hopeful sign on 10m.
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.
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.
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.
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.
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.
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