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Topics - Zazzle

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First: yeah... I'm still alive. I just agreed to some RL commitments (more than I could handle due to complications) and that basically killed all my free time in the first half of 2018. Not to myself: be more egoistical...

Seconds:Common and Precious 3 got father and gave birth to... okay... I stop being ridiculous.

The urge to build this beacon came kinda out of nowhere. I always felt for building a entirely solar operated beacon. The urge suddenly hit me hard. Those who follow my projects from the first day might remember that it was an idea that came up every now and then on the way). Anyway. The recent years gave me an good idea about the level of vandalim to expect. Another point is that I now have a source for cheap second hand and/or partly damaged PV module. So a loss doesn't hurt that much.

The frequency close to 'Common and Precious 3' was choosen on purpose. Even with the difference in RF power level (25W VS 2W) it allows a good comparison of the two setups.

It might also happen that I'll loose the location for my beacons during the next months. The city hall published ideas and plans about tearing the areal down, building homes on it.

A documentation with more details/pictures can be found on the Wiki here. (Proof reading/editing anyone? :) )

Open issues...
Opsie #1, I forgot to tune the frequency back to 6.399,500kHz. It's running at 6.399.000 right now. Lucky me that I've build the TX unit with connectors so it's easy to take it home again.

Opsie #2: I've started redoing my Morse-2-Text routines and it took longer than expected. But I wanted to install the beacon on the scheduled weekend. So it's currently sending only 1Hz dashes.

Also... I might change the PV-Module. Chances are I can get my hands on a 170W type for a crate of beer. This provides more resources for operation during winter.

Overall: I'm very happy with this project. It's a good mix of proper engineering and not overdoing it. It also looks beautiful on the roof. Might sounds silly but those who know the beauty of such project might understand. :)

Circuits are about to follow as well.

(Side node: Eww! Whe wiki does a hard re-compression of attachments (pictures), eh? My poor beautiful and crisp pictures.)


The RF Workbench / µC based Class E RTTY with Crystal pulling
« on: April 10, 2018, 1323 UTC »

I prefer to keep it simple, especially with the kind projects I do (which might be busted, stolen or vandalised). Therefore I was looking for a simple (regarding hardware and also software) way to run RTTY. Here's a funny thing I tried and which works like a charm. Let’s share that!

Most modern Microcontrollers (AVR, PIC, STM, etc.) come with multiple hardware functions. UART, I²C, USB – you name it. Also PWM! The awesome things about those hardware functions are, that they run CPU independent and don't consume computing time.
We play with the PWM unit here. Many controllers also provide clock multiplication. This means that a PWM frequency higher than the CPU (master) clock can be archieved. Some fancy controllers even support adjustable PWM and uneven frequencies, which allows to generate a lot of handy frequencies from a fixed source.

Here's where it gets interesting. Since the divider or multiplication is set to a fixed value, the PWM frequency follows the master clock frequency. If the master clock frequency changes, so will the PWM frequency. Hmm! Let's abuse this!

Crystals can be pulled by adding a variable capacitor into its path. Which means it's frequency can be adjusted up to a few kHz. That's done with a mechanical variable capacitor. But it can also be done with electrical variable capacitors (diodes, a VARIAC).

For RTTY we need a frequency shift of a few Hz, i.e. 170. That's doable with a small change of the capacity. The idea is to manipulate the master clock frequency in the pattern of a RTTY-Signal. Software on the controller generates the proper timing for RTTY (Baud speed) by turning an I/O-Pin on and off. The +5V from the I/O-Pin is feed to a VARIAC (Variable Capacitor Diode) which in return pulls the master crystal (frequency). A hardware PWM output generates the carrier frequency. Since the PWM frequency depends on the master frequency, it chances along with it. In respect to the ratio between master- and PWM frequency.

For example:
  • Require PWM duty cycle: 50%
  • An Attiny25 needs at least 4 clock cycles to make the PWM unit run 50% dt in CTC-Mode.
  • We want 4MHz for our beacon.
  • Therefore, we need a 16MHz crystal. That provides us with 4MHz PWM.
  • At 4MHz we need an offset of 170Hz for RTTY. Since the radio is 4 (16MHz Master Clock / 4MHz PWM), we need to adjust the manipulation loop in a way it grants a frequency shift of 4 x 170Hz = 680Hz.

First of all: which oscillator pin should be used for this trick depends on the Microcontroller used. Also, whether the frequency (when key'ed) should go up or down. Have some workbench-testing to get known to your controller. Also, don't overdo the pulling. When introducing too much bypass capacity to the internal oscillator it might stop and freeze. Imagine you climbed all up the Kilimandscharo on your Africa vacation - all wasted from carrying also a 100W solar module and Battery - only to learn that you overdid it and your baby stopped working as soon as you're back home. ;p
  • 1) XTAL may 2-8 times larger than desired frequency. Depends on the used Microcontroller. Read about it's H/W PWM unit and features.
  • 2) Is usually the same as C1 (see data sheet of the Microcontroller). It is required to provide minimal capacitive load to the oscillator circuit. Can also be replaced with a mechanical cap to obtain the desired target frequency on one end.
  • 3) Can be either a classical VARIAC or maybe also some standard diode. All diodes have a VARIAC behavior. Which diode can be used depends on the junction capacity and how far it can be adjusted. Tuning voltage is also a factor. Tinker a bit with it and gain some practial experience. It’s also possible to  parallel Diodes.

Also: it's important that all rails (+5V logic and others that are used for tuning) are high stable and decoupled properly.

Kind greetings,

Software / RTTY protocol help
« on: September 29, 2017, 1034 UTC »

Gonna write a RTTY Encoder in Perl. I read some documentation but like to ask for some checks and advice whether I understood the stuff properly.

RTTY uses CCITT-2, yes?

It's 5 Bits but for practial use it's 8 bits, yes? (2x Startbit, 5x Code-Bits, 1x Stopbit)

Start- and Stopbit always  red "1", yes?

So, sending "A" is "11 00011 1"?

Switch between the NUMBER and ALPHABET blocks is done by it's own command (and not combined with space)? So I send <^letters> <flag or block switch> <bumbers> <Flag or block switch> <letters> (...)

Is there something like a Frame marker, a head/endblock or something?

Some advice on timing between blocks/transmissions?

Could someone provide me with an example? :)

Kind greetings,

The RF Workbench / About Vpp, Vp, Vrms and P(R) [solved]
« on: September 25, 2017, 2252 UTC »

I need a slap onto the back of my head so the bits fall into place. Also, yeah, asking this is kinda embarrassing. I feel stupid. Google doesn't really help here. It all says that my instruments are wrong.

The Oszilloscope (actually five) says Vpp=30V. The Wattmeters says ~8W. I say 'eh?'

If I'm not stupid, then "calculating P on 50R from VPP" works like this:

Code: [Select]
Vpp / 2 = Vp
Vp / SQRT(2) = Vrms
Vrms²/R = P

Which is:

Code: [Select]
30Vpp / 2 = 15Vp
15Vp / SRQT(2) =~ 10,6Vrms
10,6Vrms² = 112,3 / 50R = 2,24W

That's theory. But all five power meters say "approx 8W".
The circuit draws ~1A @ 12V. So 8W out divided by 12W in is n= 67%, which sounds resonable. Also, power loss (heat) feels normal. So it checks.

What is it that I'm missing here?

Some small voice in the back of my head says "theory only looks at the positive swing. But the negative also contains energy, which makes it twice" (double the voltage = 4 times the power. Which would check. I could also run this through Fourier, which also requires to ignore the negative swing but uses two times the positive swing).

Code: [Select]
30Vpp / SRQT(2) =~ 21,3Vrms
10,6Vrms² = 453,7 / 50R = 9W

So, gimme a slap please.

Edit: read values from an CB Radio with Po=4W. Powermeter says: ~4W. Oszilloscope says: Vpp = 20V. Checks with my theory. But I'm none wiser.


The RF Workbench / Project #4 - RTTY Beacon
« on: January 06, 2017, 1016 UTC »

Argh! There's this idea. It's stuck in my head. Since weeks. And it wants out. Okay. Here we go.

I'm running three CW Beacons by now. I wanna do something with RTTY because it's fun and allows "high" Data rates. It's also easy to build. I can use a PI-Zero, which makes it easy to collect data and send it. So, what to send?

First, I wanted to send such like temperature, humity and - if solar powered - Battery status.

But that one disasterous evening, a friend started to annoy me with 'yer mom'-jokes and I got the idea to store a biiig collection of those jokes on the PI, having it sending them in a loop.

The other idea would involve a GPRS-Modem. I could have the PI fetch E-Mails once a day and send it's text content. The Address would be public and anyone could send greetings and whatever. This sounds pretty much fun. But I need to think about the problem with the SIM card. Thanks to our politicians going nuts about Terrorism it isn't any longer possible to get an "anonymous SIM". Buying a prepaid card now requires to register it in the shop with your ID. Sucks. So I've to check the situation in countries around my own. Means that I've to pay roaming fees. I've to think about.

I'd like to have your feedback on that. :)

Kind greetings,

The RF Workbench / Common and Precious IV - Construction phase
« on: October 21, 2016, 1702 UTC »

so, this is the board of the Beacon that I took with me on vacation during Autumn 2015. It Outputs approx 10W+ @ 13V. I wanted to play a bit with push-pull PAs. It's simple: oscillator, keyed buffer, driver and PA. PA (final) and oscillator/driver are feed seperately. Which allows me to feed the PA with higher voltages seperately.

Since I have no use for this as a Beacon any longer (got replaced by the 30W Class D CW Beacon) I'm planning to turn this one into a small AM transmitter for experimenting and having some fun.

The big AM Transmitter project (300W+) already goes by the name "Dirty Phoenix". So I call this one "Dirty Phoenix Jr."

Next todo: mounting it to a chassis with proper heatsink and cleaning up the inductor mess.

Kind Greetings,

The RF Workbench / DIY OpAmp AM Modulator
« on: October 12, 2016, 1051 UTC »

I'd like to share this. It's an AM Modulation Driver. So far it's just a simulation. I've to re-calculate some values to minimise component stress and power loss. I tested the simulation from 8-48V. All it needs it to adapt R6 (voltage feedback to full swing). I think I'll build a H/W version in November.

Just some words on the Bakckground: I have this 10W CW-Beacon that I took on a vacation last year in the shelf. The PA exists of a push-pull configuration. I thought about modulating the PA feed with Audio, turning the Beacon into an AM Transmitter. First I thought about using a TDA2030 with transistorfollower (more current). But, eh, the voltage swing isn't that nice. And I also only need a positive swing. An yeeeeess. I could use an rail2rail OpAmp and give it some transistorfollower to get the current I want. But buying isn't as much fun as building. And, you can build this thing here with simple components you have in your junkbox. ;)

Kind greetings,


Dunno where to start. Just let's say I discovered E-Class amplifiers by "accident" and now  I wanna play with it. But since Class-E is only fun when it comes to "more power" [Tim Taylor] I'm going to build a second "Common and Precious" CW Beacon on 40M with *gsssssp* 25W. Some may render me a bit too bold for doing that. But hey, hey, no risk no fun. And 25W sounds a lot of fun to me. :)

I was doing some engineering work with a resonant SMPS circuit when I started to wonder why it shouldn't be possible to use a pulse driven stage to generate clean HF with a proper resonant circuit on the output. Well, after checking some things with Google I stumbled upon Class-E amplifiers. Oh-yes, baby. Which basically ruined my whooole weekend 'cuz I got absorbed in technical papers and formulas.

Since it's going to be pirate equipment and may be prone to get damaged or busted, I settled with a simple setup. I left more space on the PCB for the output stage because that's what I want to tinker with.

  • The transmitter generates the operating frequency with a simple TTL-based crystal oscillator (which can be pulled a bit).
  • The last TTL-Gate is keyed by an Attiny25 which holds the morse code / identifier that's to be broadcasted.
  • The TTL Block is followed by a high-current FET-Driver.
  • The rest is obvious. A resonant circuit and just to stay clean (which is important to me) a 7-pole Low-Pass.

The whole thing end up in an small aluminium box with an external (15V/3A Notebook) PSU.

I learned from my last setup that having the transmitter high on a pole sucks rocks because I have to tear down the whole setup each time I need to work on it. This time I go with a transmitter that's hidden under the roof. 25W allow me to lose 2-3W on a long RG-58 cable so I can run the cable in a way that makes it impossible to follow easily and to a place where I can hide the transmitter without any risk of it being found by accident.

So far I got myself all the parts needes. Electronis components, wires for the antenna and poles, paint, wood slants and so on.

I think I make this happen around the easter holidays. Hope the weather works in my favor :)

Question: any reasons against f=6.553,5kHz? I wanna keep it simple and a 6.553,6kHz crystal is chep.

Kind regards,

HF Beacons / 40M QSL Contest (2-4. October 2015)
« on: September 24, 2015, 1253 UTC »
Hey everyone! :)

If nothing f***s up my schedule, this is gonna happen! (Feel free to move this post if it doesn't fit here.)

I'm heading to the other side of the Country at the beginning of October. Small vacation, you know.  The other side, that means: lots of high mountains with no people around for miles. I'll take a 10W 40m Beacon with me. And 100Ah Car Battery (oh, the pain. My back is screaming already. But no pain, no 'gain' - Bad pun intended ;p))

So! Here's the deal: try to tune in and if you succeed: send me a REPORT VIA PM on this board. As usual, you'll be rewarded with a special edition high quality QSL card for free. :)

X-Tra points for providing an audio record.

  • Start: 2. of October, 12:00 UTC
  • End: 4. of October, 12:00 UTC
  • Frequency: To be announced (somewhat between 6.950kHz and 6.990kHz
  • RIG used: 10W CW + half have Dipole.
  • Key to get a QSL-Card: the Name and Locator of the Beacon.

(Please; if you post your report public on the board: forsee from adding Name/Locator. You can do yo after the contest is over.)


HF Beacons / Beacons readable in North Europe
« on: August 14, 2015, 2333 UTC »

I decided to follow Teotwaki and listen to several frequencies more frequently. Of course chances are rare that I may hear one of the famous Beacons from the US. But maybe one day, when fortuna is on my side...

What I'm curious about: are there other people in the EU trying to copy the US Beacons?

So far for this evening, 23:30 UTC

  7509.00 kHz "S"
10871.67 kHz "D"
10872.05 kHz "X"

Good show. That was fun. Thanks.

Strong Signal, S9+. Standig out against the noise floor just just a few distortions. Not much fading, just every 10 minutes for a moment  each time. The signal was strong until it faded out with a minute and never returned.

Lots of good stuff, like:

- Phil Collins - Easy Lover
- Simple Minds - Don't You (Forget About Me)
- And other goodies.

(Gone by now)

Strong Signal, S9+. Good Audio quality, only  a few distortion.
Could hear moderation. Unknown tongue. Sounds arabic, but managed to say "dankeschön" in the german tongue quite well! Made me laugh.
Odd music. Sounded like Bavarian "Oktoberfest" Music

Comes in with S7, but with heavy fading and distortions. Some Soft Rock Songs.
Could hear moderation. But nothing distinguishable. Sounded like "Radio wow".

Lovely quality. Almost no distortions. Just a bit of fading. S9+10 - S9+20

Songs know to me:
- Les Humphries Singers - Mexico
- Archies - sugar sugar (currently playing)

Heavily distorted signal. S4 but on a heavy noise floor. Lots of moderation. Can't make out what it is. No english, french, dutch, italian or german).

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