If enough people were prepared to use it, this could be a good tool for discovering Sporadic-E openings on the VHF bands. The 30 second transmit cycle seems more appropriate for this type of propagation than WSPR's two minute periods.
Sunday, February 26, 2012
Opera on 6
I haven't used the Opera digital mode on HF for a bit as it seemed that interest had dropped off and there is not much point in beaconing in no-one is receiving. It seems to be one of those modes where there is a resurgence of interest whenever there is something new to try. This weekend the new thing was some fast Opera modes for use on VHF so I fired up the K3 on 6m (50.700MHz) to see if I could receive anything.
As you can see, not only did I receive some other stations but my own Opera signals were received around the UK. No great DX, but I was only using 20W to my attic dipole and would not expect to hear anything on 6m at this time.
If enough people were prepared to use it, this could be a good tool for discovering Sporadic-E openings on the VHF bands. The 30 second transmit cycle seems more appropriate for this type of propagation than WSPR's two minute periods.
If enough people were prepared to use it, this could be a good tool for discovering Sporadic-E openings on the VHF bands. The 30 second transmit cycle seems more appropriate for this type of propagation than WSPR's two minute periods.
Mistaken identity
A couple of weeks ago I came across FreeTrak, a PIC based APRS tracker developed by N0QBH. I have wanted to build a small 'grab-and-go' tracker for a while now. The FoxTrak works fine but is too big and bulky by the time it is paired with an HT. The TH-D72 is too much hassle as I need strong reading glasses to see the LCD screen and inevitably go out with some essential menu option disabled. Consequently these days I rarely bother taking APRS with me when Olga and I go for a walk around town.
I sent off for a couple of PIC 16F628A microcontrollers, thinking that I could program them in my EasyPIC5 development board. But when I tried, I immediately hit a snag.
My PICFlash programmer detects a PIC 12F508 instead of a PIC 16F628A.
I don't think I've been sold a fake MCU. If I remove the 16F628A so there is no micro plugged in at all I still receive the same warning. So I don't know what to do. I've bricked too many PIC chips by programming them with the wrong settings to try crossing my fingers and clicking Yes. So it looks like my FreeTrak project is not going to get off the ground.
I sent off for a couple of PIC 16F628A microcontrollers, thinking that I could program them in my EasyPIC5 development board. But when I tried, I immediately hit a snag.
I don't think I've been sold a fake MCU. If I remove the 16F628A so there is no micro plugged in at all I still receive the same warning. So I don't know what to do. I've bricked too many PIC chips by programming them with the wrong settings to try crossing my fingers and clicking Yes. So it looks like my FreeTrak project is not going to get off the ground.
Saturday, February 25, 2012
Prop drift uncovered
Yesterday I wrote that I was shelving the Propeller beacon project after discovering that the frequency stability is unacceptabe. Eldon WA0UMH persuaded me to try some tests to identify the cause of the drift. My conclusion is that it is a combination of factors.
The major factor causing the drift is the power supply voltage. Whilst developing the beacon using just the Gadget Gangster board I was powering it with a 6V supply - the minimum needed. After adding a PA I needed to increase the supply voltage to 9V. The drift is greater with 9V, regardless of whether the PA is actually connected.
If you look down at the Gadget Gangster Propeller USB board there are two SMT chips to the left of the Propeller and its clock crystal which appear to be voltage regulators. There is a 5V regulator a few millimetres to the left of the 10MHz crystal and a 3.3V regulator below it. The greater the supply voltage, the more heat the 5V regulator has to dissipate. Plugging the LCD UI board on top of the Propeller board traps in more of that heat making the drift even worse. This is not the first time I have discovered that voltage regulators and crystal oscillators don't go well together.
Whilst it is useful to know what is causing the drift, my discovery has not indicated an easy solution. Either I use a temperature compensated 10MHz crystal oscillator as suggested by one of my readers, or I use the Prop to control an outboard and more stable synthesized oscillator. The first option looks the easiest, but the TCXO is not an inexpensive component.
The major factor causing the drift is the power supply voltage. Whilst developing the beacon using just the Gadget Gangster board I was powering it with a 6V supply - the minimum needed. After adding a PA I needed to increase the supply voltage to 9V. The drift is greater with 9V, regardless of whether the PA is actually connected.
 |
| Looking down on the Propeller board |
Whilst it is useful to know what is causing the drift, my discovery has not indicated an easy solution. Either I use a temperature compensated 10MHz crystal oscillator as suggested by one of my readers, or I use the Prop to control an outboard and more stable synthesized oscillator. The first option looks the easiest, but the TCXO is not an inexpensive component.
Friday, February 24, 2012
Disastrous drift
I have decided to shelve the Propeller Beacon project. Actually the project made the decision for itself. Bored with receiving spots for my 250mW WSPR signal on 30m I decided to try 20m where there are almost as many monitors. But after a handful of spots there was nothing. After a while I decided something must be wrong.
I checked that the beacon was still transmitting at the right times and it was. So I switched on the K3, ran the WSPR software and the reason for the lack of spots became clear. My signal was drifting the best part of 10Hz in each two minute cycle!
When I first ran the beacon on the bare Propeller board I had found the signal to be pretty stable after only a few minutes warm-up. After adding the LCD board - which plugs on top of the Propeller board - I noticed that my 30m transmissions were being quite consistently reported with -3Hz drift. The RF amplifier board with its heatsink is separate from the Propeller board and nowhere near its crystal oscillator. I hypothesized that the LCD board is trapping some heat in, enough to make the master clock oscillator drift.
The drift is probably a multiplication factor of the clock frequency so the higher in frequency you go, the worse the drift. Whatever the explanation, the Propeller + LCD combination is not usable as a WSPR beacon as it is.
It seems to me that there are two possible solutions. One would be to make my own Propeller processor board with a temperature controlled crystal clock. The other would be to use the Prop to control a Si570 synthesizer or something like that. Unfortunately I don't think either of those solutions are within my capabilities just at the moment. So I'm afraid the beacon project will be going on the shelf.
I checked that the beacon was still transmitting at the right times and it was. So I switched on the K3, ran the WSPR software and the reason for the lack of spots became clear. My signal was drifting the best part of 10Hz in each two minute cycle!
When I first ran the beacon on the bare Propeller board I had found the signal to be pretty stable after only a few minutes warm-up. After adding the LCD board - which plugs on top of the Propeller board - I noticed that my 30m transmissions were being quite consistently reported with -3Hz drift. The RF amplifier board with its heatsink is separate from the Propeller board and nowhere near its crystal oscillator. I hypothesized that the LCD board is trapping some heat in, enough to make the master clock oscillator drift.
The drift is probably a multiplication factor of the clock frequency so the higher in frequency you go, the worse the drift. Whatever the explanation, the Propeller + LCD combination is not usable as a WSPR beacon as it is.
It seems to me that there are two possible solutions. One would be to make my own Propeller processor board with a temperature controlled crystal clock. The other would be to use the Prop to control a Si570 synthesizer or something like that. Unfortunately I don't think either of those solutions are within my capabilities just at the moment. So I'm afraid the beacon project will be going on the shelf.
Monday, February 20, 2012
On the move
Due to the eventual closure of our website business the server on which my website g4ilo.com runs will be unavailable before long. I am now in the process of moving the site to a standard shared hosting account. It is possible that the site and even my blog may become unreachable or seem to be down during the transition. If this happens, don't worry!
For information, my sites are hosted and g4ilo.com will continue to be hosted by HawkHost which I have found to be an absolutely first class hosting service with support staff who really know what they are doing. If you are looking for high quality hosting for your own website I can wholeheartedly recommend them.
For information, my sites are hosted and g4ilo.com will continue to be hosted by HawkHost which I have found to be an absolutely first class hosting service with support staff who really know what they are doing. If you are looking for high quality hosting for your own website I can wholeheartedly recommend them.
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