A local amateur, OZ5AR has started taking the challenge of low power seriously. I should do the same.
He started building a simple circuit, yes, it is just an attenuator. The output (and therefore the attenuation has not yet been measured, and he did not tell me the value of the series resistor part, so I do not yet know how low his power was. Calibration needed.
The signal went from about S5 down to an easily readable CW signal with practically no S-meter output.
We have both tested the lowest power output of our standard rigs, the IC-7300 and the IC-7600, and measured it to be between 700 and 1500mW. A more precise measurement is needed.
The distance between us is almost exactly 2km. My challenge is to see the minimum power necessary to make a contact, and preferably go below 1mW. A contact like this would actually qualify for an award: The 1000 miles per Watt Award. Just for the fun of it.
The initial test is on 28.322MHz, a frequency to which a "standard" crystal oscillator is available. The frequency (+/- the tolerance of the oscillators) is also used by Italian stations for very low power QRSS transmissions.I do have attenuators available to reduce the power from 1.25W to approximately 1mW. More when I have had the time to find everything. The next few days are quite busy with going on and receiving visits.
Yes, we will test as many bands as we can, but the experiments will have to finish some time next year. For some bands, like 472kHz a transmitter needs to be built.
I would like to do the experiments with home brew transmitters (and, over time, receivers), just for the fun of it
Yes, yes, never running out of ideas ...
2019-12-27
2019-12-25
Idea Box: QRSS With Simple Home Made Equipment.
Some years ago, while living in the Netherlands, I made a few experiments in receiving QRSS (very slow morse) with a receiver and a computer running the SpectrumLab software under Wine in Linux.
Despite living in an apartment I had some success, but when I moved everything was dismantled.
I have still been following the developments in the QRSS activity, and I should like to get going again. Running a so-called Grabber (QRSS receiver does not take too much time out for other activities, because the spectrograms are simply up-loaded to a website for all to see.
QRSS provides a quite good weak signal performance, so it is usable for propagation monitoring, provided that there are some QRSS transmitters active.
Last time I was running a QRSS Grabber was before the time of the low cost Raspberry Pi single board computer, but these days it is an excellent candidate for running grabber software.
Now, what about receivers ? I was thinking of running a very simple, low cost receiver to begin with, e.g. a modifies Pixie kit.
The Pixie is an extremely simple 40m single frequency CW transceiver, mostly supplied with a 7023kHz crystal. On 40m it just might be capable of running a grabber on 7040kHz. The "IF" will be 17kHz, that should be within the capabilities of spectrum analysis programs for the Raspberry Pi. Alternatively, a different crystal, say 7030, 7035 or even 7038kHz crystal could be used, substantially bringing the "IF" down. If the missing image selectivity becomes a problem, a simple, single crystal filter with a 7040kHz crystal filter could be used.
To be fair, the Pixie is very low cost, a kit can be had for less than $5, so it is an excellent candidate for experiments. The design, however, is probably quite reliable, but certainly not high performance.
In the coming year I hope to have room for some experiments with QRSS, but a higher priority is getting a signal through the QO100 satellite.
Despite living in an apartment I had some success, but when I moved everything was dismantled.
I have still been following the developments in the QRSS activity, and I should like to get going again. Running a so-called Grabber (QRSS receiver does not take too much time out for other activities, because the spectrograms are simply up-loaded to a website for all to see.
QRSS provides a quite good weak signal performance, so it is usable for propagation monitoring, provided that there are some QRSS transmitters active.
Last time I was running a QRSS Grabber was before the time of the low cost Raspberry Pi single board computer, but these days it is an excellent candidate for running grabber software.
Now, what about receivers ? I was thinking of running a very simple, low cost receiver to begin with, e.g. a modifies Pixie kit.
The Pixie is an extremely simple 40m single frequency CW transceiver, mostly supplied with a 7023kHz crystal. On 40m it just might be capable of running a grabber on 7040kHz. The "IF" will be 17kHz, that should be within the capabilities of spectrum analysis programs for the Raspberry Pi. Alternatively, a different crystal, say 7030, 7035 or even 7038kHz crystal could be used, substantially bringing the "IF" down. If the missing image selectivity becomes a problem, a simple, single crystal filter with a 7040kHz crystal filter could be used.
To be fair, the Pixie is very low cost, a kit can be had for less than $5, so it is an excellent candidate for experiments. The design, however, is probably quite reliable, but certainly not high performance.
In the coming year I hope to have room for some experiments with QRSS, but a higher priority is getting a signal through the QO100 satellite.
2019-12-24
More Solar Cycle 25 Sunspots.
More sunspots from the new solar cycle 25 have appeared on the sun.
Today Spaceweather.com announced that two spots from cycle 25 have appeared showing in the solar disk.
This is the first time this cycle, and suggests that the Maunder minimum sometimes predicted in solar activity is not imminent. The Maunder Minimum was a period of decades without sunspots occurred in the 17th century.
This quickening appears to show a normal cycle 25, with a predicted maximum in mid-2025. The current minimum is, however, considered a "deep minimum", usually occurring once a century.
I am very much looking forward to more sunspots and therefore bettewr propagation on the higher bands.
Christmas present from the sun ? ;)
Today Spaceweather.com announced that two spots from cycle 25 have appeared showing in the solar disk.
This is the first time this cycle, and suggests that the Maunder minimum sometimes predicted in solar activity is not imminent. The Maunder Minimum was a period of decades without sunspots occurred in the 17th century.
This quickening appears to show a normal cycle 25, with a predicted maximum in mid-2025. The current minimum is, however, considered a "deep minimum", usually occurring once a century.
I am very much looking forward to more sunspots and therefore bettewr propagation on the higher bands.
Christmas present from the sun ? ;)
2019-12-23
Construction Style For Home Made Radio Equipment.
We are approaching the Winter Solstice holiday season, and I do not expect to be blogging much in that period.
Therefore, I will take the opportunity to wish you all Happy holidays, Merry Christmas. Happy Hanukkah, or whichever holidays you may want to celebrate at this time of the year.
Now for a little bit of radio:
I was watching some Youtube videos on home made TRXs, by ZL2CTM. He has a very neat style of home building using modules built on strip boards, then mounting on the copper clad side of a un-etched PCB (single or double sided). This should make for some quite good RF construction practice, at least on the HF bands, maybe on the lower VHF bands.
He uses old fashioned non-SMD style components, but actually surface mounted on the strip board. There is no reason that it could not be adapted for SMD style components, too, if space is at a premium, or for higher frequencies.
I have a good amount of strip boards ("Vero Boards"), some "island" boards, and some blank PCBs, so it is possible to start.
I also have some "island" experimental boards with a ground plane on the other side, this could potentially be used for higher VHF, and maybe, just maybe for some 432MHz experiments. This should prove an interesting experiment. Some RF shielding would be in order, though.
So what should happen here in the holiday season and next year ?
Now, I need to finish some projects and get my stock of components and PCB modules in better order. This process has started, but it needs to continue.
Then, I should probably start this by use the construction style mentioned above for the QO100 control boxes, outdoors and indoors. Will need a shielded box or two, too, though. After all, some of the frequencies of the system are in the 100s of MHz range.
Therefore, I will take the opportunity to wish you all Happy holidays, Merry Christmas. Happy Hanukkah, or whichever holidays you may want to celebrate at this time of the year.
Now for a little bit of radio:
I was watching some Youtube videos on home made TRXs, by ZL2CTM. He has a very neat style of home building using modules built on strip boards, then mounting on the copper clad side of a un-etched PCB (single or double sided). This should make for some quite good RF construction practice, at least on the HF bands, maybe on the lower VHF bands.
He uses old fashioned non-SMD style components, but actually surface mounted on the strip board. There is no reason that it could not be adapted for SMD style components, too, if space is at a premium, or for higher frequencies.
I have a good amount of strip boards ("Vero Boards"), some "island" boards, and some blank PCBs, so it is possible to start.
I also have some "island" experimental boards with a ground plane on the other side, this could potentially be used for higher VHF, and maybe, just maybe for some 432MHz experiments. This should prove an interesting experiment. Some RF shielding would be in order, though.
So what should happen here in the holiday season and next year ?
Now, I need to finish some projects and get my stock of components and PCB modules in better order. This process has started, but it needs to continue.
Then, I should probably start this by use the construction style mentioned above for the QO100 control boxes, outdoors and indoors. Will need a shielded box or two, too, though. After all, some of the frequencies of the system are in the 100s of MHz range.
How soon will I finis the next project ? We shall see.
2019-12-21
Idea Box: QSOs With Very Simple Home Made Equipment ?
Making QSOs with modern manufactured equipment is fun, but what about doing it with home made equipment? (maybe not making your on components, such as capacitors, but using existing available components, and maybe sometimes modules. More fun ? I think so.
I have made my own direct conversion receiver for 80m, and later a simple VXO-transmitter for 40m. Making a few QSOs with that TX was absolutely fun. But what about making QSOs with fully home mad transmitter/receivers. Even more fun.
I have got the idea of trying to make at least one QSO on as many bands as possible, with homemade or at least modified surplus modules or equipment, as simple as possible.
On a few bands there are excellent simple options:
With ceramic resonators (CR) it should be possible to build relatively simple transmitters with the resonators "pulled" like it is done with crystals in VXOs, and then keying the buffers/amplifiers.
Many people have done this. As someone once said "a transmitter is 'just' an amplifier". Yes, but one of the stages is unstable, and oscillates ;)
But what about receivers ?
Direct conversion reception is often done with simple CW transmitter/receivers, but could it be even more simple ?
Today I was watching a video by VK3YE. He demonstrated a QSO made with a CR controlled transmitter on 40m (80m easily done, too, with CRs available). and here is the trick: He was using a simple regenerative receiver, set just above the point of oscillation. That makes it possible to listen to CW/SSB signals with a 3-transistor receiver (using an earphone). This is quite well known as well, but the regenerative receiver can be very critical and is considered a "two-hand" receiver. One hand on the tuning, the other on the regeneration control potmeter.
I consider this type of receiver as a direct conversion receiver with a self-oscillating mixer, although it is not classically considered as such.
VK3YE's trick was using a CR for controlling the frequency of the regen-receiver. The result is a far less critical regeneration control, and a far better frequency stability. How about a receiver with no coils to wind? Here it is.
On one of his videos he demonstrated a DX QSO with a CR controlled 30W TX and the above mentioned RX.
Doing this does mean that it is necessary to go "back in time" and use separate frequency tuning for the TX and RX, and having a "spot" function, so the TX frequency (just the oscillator) can be heard in the receiver.
No, I would **not** build such a set with vacuum tubes, though I know that it is quite possible. I do not like high voltages.
So many ideas, so little time, but it is a tempting project to try out after a few other things I would like to finish. Beginning projects is a lot easier than finishing ;)
I have made my own direct conversion receiver for 80m, and later a simple VXO-transmitter for 40m. Making a few QSOs with that TX was absolutely fun. But what about making QSOs with fully home mad transmitter/receivers. Even more fun.
I have got the idea of trying to make at least one QSO on as many bands as possible, with homemade or at least modified surplus modules or equipment, as simple as possible.
On a few bands there are excellent simple options:
With ceramic resonators (CR) it should be possible to build relatively simple transmitters with the resonators "pulled" like it is done with crystals in VXOs, and then keying the buffers/amplifiers.
Many people have done this. As someone once said "a transmitter is 'just' an amplifier". Yes, but one of the stages is unstable, and oscillates ;)
But what about receivers ?
Direct conversion reception is often done with simple CW transmitter/receivers, but could it be even more simple ?
Today I was watching a video by VK3YE. He demonstrated a QSO made with a CR controlled transmitter on 40m (80m easily done, too, with CRs available). and here is the trick: He was using a simple regenerative receiver, set just above the point of oscillation. That makes it possible to listen to CW/SSB signals with a 3-transistor receiver (using an earphone). This is quite well known as well, but the regenerative receiver can be very critical and is considered a "two-hand" receiver. One hand on the tuning, the other on the regeneration control potmeter.
I consider this type of receiver as a direct conversion receiver with a self-oscillating mixer, although it is not classically considered as such.
VK3YE's trick was using a CR for controlling the frequency of the regen-receiver. The result is a far less critical regeneration control, and a far better frequency stability. How about a receiver with no coils to wind? Here it is.
On one of his videos he demonstrated a DX QSO with a CR controlled 30W TX and the above mentioned RX.
Doing this does mean that it is necessary to go "back in time" and use separate frequency tuning for the TX and RX, and having a "spot" function, so the TX frequency (just the oscillator) can be heard in the receiver.
No, I would **not** build such a set with vacuum tubes, though I know that it is quite possible. I do not like high voltages.
So many ideas, so little time, but it is a tempting project to try out after a few other things I would like to finish. Beginning projects is a lot easier than finishing ;)
2019-12-20
Idea Box: Simplest Possible Transmitter Construction.
Here are some thoughts on the simplest possible transmitter designs.
How well (or not) they work will have to be tested some time. Simple designs are sometimes too simple.
Designed for CW only, single frequency.
A single canned crystal oscillator generally available for some amateur radio bands. Examples:
3.579MHz
3.686MHz
1.843MHz
14.318MHz
28.322MHz
I also have some on 14.296, 14.300MHz and 21.175MHz, but I am not sure those are easy to find. The first 5 are, sometimes found in old computer boards.
I have another one on 28.321, not sure where that one came from.
In a surplus shop in The Hague I found one on 28.339MHz.
The absolutley simplest design consists of simply connecting the canned oscillator output to 2 wires, acting as an antenna, and see if any range at all can be seen. The CW keying is simply done by keying the (5V) DC voltage of the oscillator.
Especially on the higher frequencies I would the resulting signal to have chirp, and maybe clicks, when keying this way, but maybe, just maybe the lower (1843 and 3579 kHz) will not have an excessive amount of chirp.
This is a simple enough experiment to make.
The output impedance of this type of oscillator is probably not correct for a 50 ohm antenna, but a simple impedance transformer made with a toroid core could be made, when used for testing it should have a fair amount of taps in the winding, but then, a 2 component transmitter could be fun, just trying to make a QSO.
The other part is the waveform from the oscillator. If it is a computer part, I would expect to see square waves, so harmonics should be filtered out. With the extremely low power, a quick experiment could probably be done, if a local station is available, but if more experiments are done, a simple low pass filter will have to be made. Also, I expect a decoupling capacitor for the power supply will be advantageous.
I have been talking to a local ham (distance 3km/2mi), about making some tests with extreme low power, so this could be one way to try this out.
I suspect that for a decent sounding signal a bit more effort has to be made, but maybe, just maybe, the component count can be kept down to 10.
Anyone out there having tried this ? If so, what is your simplest transmitter tested for a QSO?
How well (or not) they work will have to be tested some time. Simple designs are sometimes too simple.
Designed for CW only, single frequency.
A single canned crystal oscillator generally available for some amateur radio bands. Examples:
3.579MHz
3.686MHz
1.843MHz
14.318MHz
28.322MHz
I also have some on 14.296, 14.300MHz and 21.175MHz, but I am not sure those are easy to find. The first 5 are, sometimes found in old computer boards.
I have another one on 28.321, not sure where that one came from.
In a surplus shop in The Hague I found one on 28.339MHz.
The absolutley simplest design consists of simply connecting the canned oscillator output to 2 wires, acting as an antenna, and see if any range at all can be seen. The CW keying is simply done by keying the (5V) DC voltage of the oscillator.
Especially on the higher frequencies I would the resulting signal to have chirp, and maybe clicks, when keying this way, but maybe, just maybe the lower (1843 and 3579 kHz) will not have an excessive amount of chirp.
This is a simple enough experiment to make.
The output impedance of this type of oscillator is probably not correct for a 50 ohm antenna, but a simple impedance transformer made with a toroid core could be made, when used for testing it should have a fair amount of taps in the winding, but then, a 2 component transmitter could be fun, just trying to make a QSO.
The other part is the waveform from the oscillator. If it is a computer part, I would expect to see square waves, so harmonics should be filtered out. With the extremely low power, a quick experiment could probably be done, if a local station is available, but if more experiments are done, a simple low pass filter will have to be made. Also, I expect a decoupling capacitor for the power supply will be advantageous.
I have been talking to a local ham (distance 3km/2mi), about making some tests with extreme low power, so this could be one way to try this out.
I suspect that for a decent sounding signal a bit more effort has to be made, but maybe, just maybe, the component count can be kept down to 10.
Anyone out there having tried this ? If so, what is your simplest transmitter tested for a QSO?
2019-12-16
QO100 Reception Report.
Today was mostly listening to QO100 with the new set-up with the IC-R7000 receiver.
Compared to the previously used AR-8600 this is a pleasure to use. I now have the inclination to tune the band to listen for signals.
The S-meter readings of the IC-R7000 is much more conservative than the AR-8600, and probably much more accurate. Signals have a good quality audio, and in spite of the 100Hz tuning steps all signals are sufficiently well readable.
Today became a test of the receiver sensitivity:
OE7DBH was running QSOs on the satellite, running just 50mW, and the signal was not strong, but fully readable. During a few QSOs I heard him reduce power further, down to approximately 5mW, as he said, to test the receiver side. His 5mW signal was just audible, with a few words just readable in the noise.
Running my simple system with the reference input modified LNB and the back-end receiver, with a 60cm offset dish, I consider my receiving system adequate. I do have a larger dish, but I would probably use that for the transmit side, as I expect to have just 2W from a BU-500 transmit converter. It will be possible to increase that to about 3.5W with a Chinese "8W" amplifier, and then place the transmit converter indoors.
The second LNB, in the mast, without dish, is now connected , supply voltage ("Bias-Tee") and all, to the AR-8600 receiver, so I can listen simultaneously to the satellite and the simple set-up for local beacon and rain scatter monitoring in the narrow band segment of the 10GHz band. As usual, the local beacon about 36km from here is always audible.
Update: I just added receiver #2 for QO-100. From the signal splitter there is one more output available. This is intended to be used with a RTL-SDR receiver, so the band spectrum as such can be monitored visually. Yes, it is possible to add a speaker to the computer. Is it is necessary? That remains to be seen, I might want to use one of the wideband receivers tied up by the system, for other bands.
I continue my slow progress in the microwave bands. Only drawback is the cold and rainy weather, not fun for outdoor work. Better for indoor work, and there is more than enough to do.
Compared to the previously used AR-8600 this is a pleasure to use. I now have the inclination to tune the band to listen for signals.
The S-meter readings of the IC-R7000 is much more conservative than the AR-8600, and probably much more accurate. Signals have a good quality audio, and in spite of the 100Hz tuning steps all signals are sufficiently well readable.
Today became a test of the receiver sensitivity:
OE7DBH was running QSOs on the satellite, running just 50mW, and the signal was not strong, but fully readable. During a few QSOs I heard him reduce power further, down to approximately 5mW, as he said, to test the receiver side. His 5mW signal was just audible, with a few words just readable in the noise.
Running my simple system with the reference input modified LNB and the back-end receiver, with a 60cm offset dish, I consider my receiving system adequate. I do have a larger dish, but I would probably use that for the transmit side, as I expect to have just 2W from a BU-500 transmit converter. It will be possible to increase that to about 3.5W with a Chinese "8W" amplifier, and then place the transmit converter indoors.
The second LNB, in the mast, without dish, is now connected , supply voltage ("Bias-Tee") and all, to the AR-8600 receiver, so I can listen simultaneously to the satellite and the simple set-up for local beacon and rain scatter monitoring in the narrow band segment of the 10GHz band. As usual, the local beacon about 36km from here is always audible.
Update: I just added receiver #2 for QO-100. From the signal splitter there is one more output available. This is intended to be used with a RTL-SDR receiver, so the band spectrum as such can be monitored visually. Yes, it is possible to add a speaker to the computer. Is it is necessary? That remains to be seen, I might want to use one of the wideband receivers tied up by the system, for other bands.
I continue my slow progress in the microwave bands. Only drawback is the cold and rainy weather, not fun for outdoor work. Better for indoor work, and there is more than enough to do.
Subscribe to:
Posts (Atom)