IK1ZYW Labs

CD-R and time

2012-02-01T13:03:00.000+01:00

I had to burn a CD-R last night. I rarely do it, maybe twice a year. I located the old 50 pieces tower, which was sitting in a shady shelf inside the flat, cover still there to keep dust away from the content.


Left: not working. Right: ok.

The first CD I picked was not recognised by the laptop CD-ROM reader/writer (made in 2004). It looked empty, but it was late and I moved forward to the CD sitting in the second place from the top. First thing I noticed was they had a different color: the topmost Sony 700 MB silver CD-R made in Malesia in 2003 was looking gold-ish (oxydated?), while all other positions retained the expected color.

Needless to say, the normal-looking-color CD-R was recognized, written and verified correctly. A second copy (3rd topmost position in the tower) was equally successfull.

Most of my recorded CD's at home come from the same tower so I will inspect them, compare colors and read the data.

So far I can conclude that a 9 years old virgin CD-R is still good for storing new data.

Feedthrough capacitors in XXI century

2012-01-27T17:51:00.000+01:00

Since I am planning to go QRO with my 4m CW TX (5W RF out), I thought it would be a good precautional idea to shield the main oscillator. So, if it is going to be boxed, I need a way to let allowed electrons in and out:

power supply
RF out (more a square than a sine wave)
frequency control (capacitor or varicap)

Remembering projects seen in the past two decades, I imagined feedthrough capacitors would be ideal interfaces for my signals. But, which values amongst those that I could easily locate? 1000pF, 150pF, 22pF.

The DC line does not mind being decoupled to ground with 1nF, so that one would do. As an alternative, I have been suggested to simply drill a hole through the shield and decouple +V to ground with 100nF. Plain simple and equally effective.

The RF out would be totally shorted to ground by a 22pF. And 1000pF imposes an unacceptably high capacitive load to my oscillator. Alternatives are:

use a passthrough RF connector, like SMA
use a small piece of RG174 coax with the braid soldered to the shield/ground
make the 22 or 150pF part of an output filter

Given that my circuit needs a square wave signal rather than a sine wave, I will probably use the short piece of coax.

Last but not least, the frequency control. Not sure whether this will be a variable capacitor or a varicap. In the former case I could install the capacitor inside the shield and let out only the component shaft. The varicap control voltage instead is DC, so the same rule as DC line applies (standard decoupling).

(My) Conclusion. Feedthrough capacitors are a useful tool that is becoming harder and harder to source. Practical alternatives are available to the hobbyst with a little imagination (or guidance from The Wise Ones), so don't give up!

Calibrated signal generator at harmonics

2012-01-22T23:06:00.000+01:00

Even the XG2 manual mentions that the circuit produces useful harmonics at predefined levels. Using the 14.000 MHz XTAL and the IC706MKiiG as a test instrument I recorded the following:

14 MHz: S9
28 MHz: S8
42 MHz: S6
56 MHz: S3
70 MHz: no signal, barely audible

I cross-checked 2nd and 3rd harmonic readings with FT-817 too.

Single frequency calibrated signal generator

2012-01-17T12:41:00.000+01:00

This piece of lab instrument was built after the curiosity to measure (... estimate ...) the sensitivity of an homebrew receiver. As described in a previous post about measuing RX sensitivity with simple tools, I tried to reproduce the Elecraft XG2.

The local shop did not have the 1.22V zener diode and a couple of 1% resistors were not available, but in the end I could get it working with a LM317T regulator at minimum voltage, giving about 1.268V. Having an higher supply voltage means that the generated signal is slightly more powerful than advertised (according to my calculations the difference lies within 1dB).

I used a single 14.000 MHz XTAL which resonates steadily at about 14.0045 MHz.

The completed circuit on a piece of recycled copper-clad board was powered with two exhausted CR2032 button cells (theoretically 3+3 = 6V). Current drain from the battery measured 4.98mA load independent, which is 20x higher than XG2's 250microA but still acceptable for portable use (just in case).

When feeding my commercial receivers with the generator output I could read the S9 signal, a bit on the high side, FT817 indicating S+ few times. Is that caused by the 48mV higher supply voltage, some "hand" effect increasing the output coupling or a calibration error on the receiver's meter?

I took only one test at S1 level and my FT817 went down to S0: need to cross check the result with other receivers.

Another measurement done was to check the signal level on 14 MHz harmonics, which I will publish in a future post. With the 14 MHz XTAL the S9 signal is readable up to the 4th harmonic at 56 MHz

NB: FT-817 conditions were IPO ON (no antenna preamplifier), ATTenuator OFF and NARrow filter OFF.

New frequency formatting for I.F.R. - dial-in 100 Hz

2012-01-11T12:59:00.002+01:00

An update to yesterday's post. I fixed the frequency visualization when the operator is supposed to type the 100 Hz value too (it is a user configuration option).

"Small" 0's are the "locked" digits, all other can be typed in.

I feel a new I.F.R. demo video is needed.

New frequency formatting for I.F.R. - dial in

2012-01-10T19:15:00.000+01:00

After fixing the frequency display with dots and right-alignment on the Interactive Frequency Reader, it was time to improve frequency dial too.

The picture below shows how it looks like when typing 145'550 kHz, with the trailing zero still awaiting for key pressure. Last three zero's are shown slightly differently since they cannot be modified.

I am also working on a meaningful way to show the frequency being typed when the 100 Hz digit is also required (a configuration parameter allows to enable/disable 100 Hz dial in).

Measuring RX sensitivity with simple tools

2012-01-04T19:59:00.012+01:00

Yesterday I had the 'scope ON and it occurred to me that I could visualize the output of a simple 20m CW RTX I had designed and built back in 2005.

While it measured 100mA at 12V input key down, I could see a relatively well shaped sinewave of 7,4Vpp, which should equate to ~140mW on 50 ohm (ouch! That's 11% overall efficiency!).

Later on, I wondered if and how I could measure the receiver sensitivity, which I remember sounding good in my ears. I did some internet searches and I would need a 14 MHz source in the ballpark of -100dBm. My lowest power generator is FT-817's 500mW, +27dBm: 130dB is too much attenuation to be implemented! Even commercial fixed attenuators don't go beyond 30dB (source JFW catalogue). Should I build a Colpitts oscillator and compute its output power with the oscilloscope? Are there other techniques to generate really low power signals? I have the advantage that I need a single frequency...

Fellows over at GQRP reflector suggested three already tested circuits/products:

Elecraft's XG2 (-107 and -73dBm)
Norcal's S9 (-107 and -73dBm)
a test generator published on SSDftRA book

Both commercial kits documentation include schematic and parts list. They are also quite similar, so I will go with either circuit, depending on parts I can locate. I will tend to use 1% precision parts whenever available.

To complete the test, on the other side of the receiver I would probably use a computer software doing audio spectral analysis and look for a 20dB S+N/N signal. Or a DVM.

More ideas came up around the little RTX too...

So, your expensive piece of technology had a bath?

2011-12-23T13:33:00.000+01:00

Picture by Patrick Hoesly.

It happens. Sometimes technology packed expensive electronic equipment (decide to) get in touch with liquid substances. As many online sources will tell, hope is not lost the very moment the two incompatible objects get in touch. I will not reveal any new method, just what I have done.

Let us consider the case of a smartphone (Galaxy S) being dipped in clean drinkable water.

First of all: read the picture on the right.

As soon as the bath is over take the device apart (battery, main body, back cover, memory card, SIM card) and dry it wth towel/napkin. Don't shake it, but turn it around to get the water out of holes such as the earphone and USB sockets. Then let it dry for at least 48 hours. Be patient: you aim to recover your data from the device, don't you? This should be your first target. If your device works afterwards then it is luck or well designed technology. Or a combination of both.
I dried mine in a bowl filled with (uncooked!) rice close to a heat radiator. Temperature should have peaked to more than 40°C, but heat is not a must: leave it longer.

When you are ready plug the battery and keep your fingers crossed. If the device powers up be prepared to extract your data using the standard method.

Additional notes.
Some online resources mention water-sensitive labels all around these expensive mobile devices. I haven't been able to spot them on the external body of the i9000. Anyway do not lie to the customer service if you are going to return it.
If your device allows to use an external memory card, it is probably wise to save your mobile-authored data on it, or take periodic backups. It is more unlikely that a self-contained hole-less memory card becomes damaged with water (anyway let it equally dry).

UV-3R data cable (homemade)

2011-12-19T18:08:00.000+01:00

I had ordered an USB-to-UART TTL adapter to debug the rotary encoder on the Frequency Reader. While it was on the way to my lab, I solved the encoder problem, so the adapter had to be tested somehow.

Around the shack I had found a cable terminated in a 4-way 3.5mm jack, probably from an old digital camera. That is the connector of UV-3R data cable (and external ear/microphone too), so I gave it a chance. Steps were:

identify which cable goes to which connector ring
draw a map of pin matches between the cable and the adapter
test the whole thing (as shown in the picture)

My ugly UV-3R data cable (not for permanent use)

At first there was no communication with the radio. Then I swapped RXD and TXD connections: UV-3R software downloaded radio parameters. Cool. Note that the UV-3R says nothing on the display about the data cable being inserted or ongoing computer communication. If data is uploaded to the radio it will automatically power cycle.

The adapter is based on the CP2102 chip and costs 3 USD (2.3 EUR) shipped from Hong Kong. Both WinXP and Vista 64bit recognized the device (XP grabbed the driver from an online source).

The same adapter can be used to build a data cable for the FT817, or other transceivers that expose a serial port with TTL logic levels instead of RS-232 voltages (ICOMs, ...).

New frequency formatting for I.F.R.

2011-12-18T00:20:00.000+01:00

My development board with the new display

... and new display too.

On the I.F.R. firmware I have modified the way the frequency is displayed when there is no transverter connected or configured. Information on the first line is right aligned, "Hz" symbol expanded and decimal separator dot added to make the frequency value look nicer.

On the picture you can also see a new display I received: orange on black. For operations in a dark environment it is less bright than the white on blue LCD. Last but not least it matches 817's amber display color (not too closely, I know).

TX-only transverter for 4m - with mixer

2011-12-05T13:08:00.000+01:00

The picture shows my TX-only transverter with the diode ring mixer (SBL-1 or ADE-1) component added. The circuit has not grown a lot, but it does indeed work.

The canned oscillator is now terminated in a 1kohm trimmer and feeds the IF port of the mixer. RF from the HF transmitter goes to the LO port. Trimmers will most probably be replaced with fixed resistors.

As a signal generator I used the FT-817 at 24.9 MHz. Listening on a panoramic receiver I could clearly hear LO-HF (20 MHz) and LO+HF (69.8 MHz). The frequency counter on the mixer output picked up the LO-HF difference, which was expected since there is no bandpass filtering afterwards.

I tried swapping HF and LO signals but the result was the same. Signal output decreases if the HF trimmer reduces the mixer drive.

Next step is to build a resonating termination followed by an amplifying buffer. G3XBM circuit calls for a BF199, which is already sitting on the workbench, committed to take part into this project.

TX-only transverter for 4m

2011-12-01T20:26:00.008+01:00

While I have no news about a possible 4m allocation for Italy in the next months, I have started working on my TX-only transverter - a "txverter"? - for HF-to-70 MHz.

The idea behind this project is that the IC706MKiiG receives on 4m, so there is no need for a full transverter, provided the operator accepts to operate split. It is a KISSAL principle: Keep It Short Simple And Lazy :-)

I decided to replicate G3XBM's simple transverter, TX chain only. I will build it manhattan/dead-bug style using an ADE-1 passive DBM mixer.

The picture shows first components placed on the copper clad board:

5V voltage regulator
canned oscillator @44.900 MHz
HF input attenuator of about 30dB (50, 680, 100 ohms)

Current drain at 12V is about 18mA, all for the voltage regulator and the canned oscillator.

The output of the latter is not a sine wave on a 100 MHz scope&probe, but it swings 0-5V if left floating.

I plan to blog how the circuit grows and how it performs.

UV-3R VHF second harmonic

2011-11-29T02:31:00.036+01:00

Definition: a second harmonic is a spurious emission of a transmitter located at twice the fundamental frequency (or first harmonic or "dial"). In most cases the second harmonic is not produced on purpose.

UV-3R, especially the single-line display, exhibits too little suppression of the second harmonic of the VHF transmitter. This occurs when the RTX is used on the VHF HAM band (144-146/148 MHz). Suppression gets better and within required limits when the VHF transmitter is used above 150 MHz.

This means un-modified UV-3R is not certified for VHF amateur radio operations. Transmitting, say, at 145.500 MHz, will result in a parallel transmission on 291.000 MHz, which is probably allocated to a Defence Ministry. In the Files area of the Yahoo! group some LPF modifications have been measured and described in detail. Unfortunately they are not for everyone.

So, what options do I have?

use unmodified UV-3R on VHF only if strictly needed, being aware you might be disturbing communications around 290 MHz. On UHF the little "R" is spurious emissions compliant.
insert a VHF band/low-pass filter between UV-3R and the antenna
have someone apply the LPF modification

Why is it so? No one has figured out why the VHF signal is so dirty. It might be a driver/final wrong bias current. UV-3R Mark II is apparently performing better, but still above the required suppression level.

Back up pictures during long trips

2011-11-28T19:10:00.021+01:00

I have had an interesting chat about methods for preserving your digital pictures (movies) while being out on an important and long trip. In other words, how to make sure you precious shots come back home with you.

Assumption: you have a way to read memory cards through a computer (not necessarily yours) or use a stand-alone card copier.

Memory cards are pretty cheap. So, why not bringing along an additional extra set, making a copy of a full card and sending it to your home address? You may even prepare addressed envelopes with a thin cardboard reinforce inside. Stamp can be bought as if you were shopping for postcards and you don’t even need a trip to a post office unless you want a Registered letter. Better to send one card per envelope. Once you have safely backed up your picutres (at home), extra cards can be reused for the following adventure.

If you know a trustworthy local, leave her/him your backup copies, either an external HDD or extra memory cards. This will minimize the risk of loss/damage on the journey back home too. If nothing bad happens to your "originals", she/he will keep the hardware afterwards as a reward for the service offered.

Online storage populated overnight is another option, if your hotel has a fast and cheap Internet connection. (If you carry your own laptop consider using Dropbox through my referral link.) But if you shoot a lot (and in RAW ), it might not be practical.

Worried about someone stealing your shots? Either the postman or your local contact person? Encrypt the backup card content with a tool like TrueCrypt. Format the card/disk to resume full, unencrypted, functionality.

Fast knob rotation solved

2011-11-21T02:41:00.014+01:00

Good news: I have solved the puzzle of missing steps with fast rotary encoder rotations. It was a piece of inefficient code, which has now been rearranged using AVR's Pin Change INTerrupts ("PCINT").

The 96 states / 24 cycles per rotation encoder is now read properly: it doesn't miss a step.

Now the FR/IFR firmware has to be adapted to a new form of interaction...

Hey! Isn't that a knob?

2011-11-09T18:26:00.002+01:00

It is a knob indeed. I have started tests of a quadrature rotary encoder connected to my (Interactive) Frequency Reader development board. This extension will allow to tune the FT817 as if we were rotating the main knob on the front panel.

The firmware is able to read the rotation direction and increase (decrease) the VFO frequency accordingly. I am having troubles with fast rotations, something that should be mitigated with the use of a larger knob or a less sensitive encoder. I would like to avoid the addition of a binary divider between the encoder and MCU.

Broken AF on Canon 18-55 IS lens, what about IS? - part 2

2011-11-03T20:16:00.001+01:00

Previous blog post ended with a question: "if the AF is lost, how about the IS? How to find out?"

Many people say that you can hear the Image Stabilyzer in action as soon as the shutter button is half-pressed. Honestly, on the 18-55 IS lens, I didn't feel/hear anything. Other references online tend to confirm that the lens is "quiet" and you can't tell the IS is in action.

Another test is to shoot two pictures, with and without IS, freehand, and look at the difference. You need the proper subject and light too, and perhaps more than just a couple of shots (and maybe 10 coffees...).

Then it occurred to me once that if I hold the camera lens against my ear (grab the camera with the right hand, so the bottom side of the lens touches the right ear) and half-press the shutter button ... I can hear a faint ringing, like a few small bells at the other end of a tunnel. When the IS switch is turned off, no ringing can be heard.

What does this mean?

Well, in my case it means that probably the IS is still working despite the AF being out of order. If you have doubts, listen closely to your lens whispers.

Broken AF on Canon 18-55 IS lens, what about IS?

2011-10-11T18:09:00.001+01:00

With no previous signs of failure, the autofocus of a Canon 18-55 IS lens stopped working (this is the lens being offered in kit with low-end cameras, like the 1000D, 450D, 1100D).

Few searches online suggested that a flat cable has gone bad inside the lens. The cable brings commands from the camera body to the lens front, where the autofocus motor is located.

This failure occurred after about 7000 shots taken through the lens, with a lot of zoom in/zoom out. A new lens costs 95-100, the repair service has been quoted at 60-70 (€uro). The flat cable itself is about 12 €uro.

I could keep the lens without autofocus, but it also has another electrically controlled feature: the Image Stabilyzer. If the AF is lost, how about the IS? How to find out?

The answer will be in another post.

Calibrating AVR RC clock using a frequency counter (idea)

2011-09-30T19:08:00.002+01:00

Not that I want to calibrate all my AVRs' internal RC clocks, but I want to test this non-automated procedure. These microcontrollers can be programmed to output a buffered version of the master clock (+ prescaler, if enabled) to the CKOUT pin. So, why not measure the output with a frequency counter?

Also, section 8.12.1 of ATmega168 manual describes the OSCCAL register, which should allow to change RC frequency during program execution.

So, why not build a simple firmware that sweeps through the OSCCAL value? Then with a big red button the operator interrupts the sweep when the frequency counter reads the desired value. Last but not least, either use an LCD to display the result or store the value in the onboard EEPROM for future reading.

UV-3R has a FAQ

2011-09-15T01:14:00.005+01:00

With a fast collaborative approach, in less than 24 hours a FAQ for UV-3R has been compiled and published in the UV-3R Yahoo! Groups files area. With 11 pages packed of information, the FAQ already looks like an UV-3R Bible ;-) And it is still incomplete.

UV-3R received carrier on 156 MHz

2011-09-11T18:01:00.008+01:00

If you let the "R" scan through the entire VHF band, it will stop on 156.000 MHz, whatever antenna you try, change location, ... S9 signal.

The "R" has an internal oscillator at 26 MHz. Since it is an SDR, it runs the receiver with square waves, so you're hearing the 6th harmonic of 26 MHz. There might be one or two on UHF too (the proof is left as an exercise for the reader).

By the way, the diagram published on the Yahoo! Group mentions a 13 MHz oscillator, while I'm holding right now a UV-3R board with 26000 (kHz) oscillator right next to the RDA chip. I've also found a difference on VHF and UHF mosfets, to be documented in another post.

Wrong 1wirecount result

2011-09-10T14:41:00.000+01:00

If the 1wirecount function returns a wrong (higher) number of devices, try decreasing the pull-up resistor between Vcc and the data line.

Just tested on my DS18B20 network :-) Going from 4k7 to 2x4k7 in parallel solved the device enumeration error.

Failing button cell batteries

2011-09-06T20:08:00.006+01:00

I had seen a leaking button cell battery, but never found a jumping one. The AG10 cell on the left (picture) was found 20cm away from its cousin, that's where it was put to rest after removal from a toy pen.

It felt fat and round, and still gave some energy to power my Joule Thief, but then overnight it probably exploded:

There is no leak of any substance and the process has apparently stopped by now. Other two specimen removed from the same toy do now show the same failure signs.

FT-8x7 CAT Emulator - power budget

2011-09-02T22:07:00.003+01:00

One of the adavantages of not relying on the real FT-817 for testing an I.F.R. is the fact that it is easier to measure current consumption. I plugged a milliAmp meter in series with the 12Vdc line before the Emulator and measured:

FT-8x7 CAT Emulator + IFR: 50 mA @12V
FT-8x7 CAT Emulator alone: 17 mA @12V

So the I.F.R. with a white/blue LCD and my choice of resistor values (for backlight intensity) drains 50-17 = 33 mA.

It's not much (could be lower?), the whole equipment could be powered off a 9V rechargeable battery or a 7.4V Li-ion cell.

FT8x7 CAT Emulator: success

2011-09-01T12:00:00.000+01:00

As announced few days ago, I have developed a simple and cheap hardware that emulates the CAT interface of ACC port of a FT-817/FT-857/FT-897 transceiver.

This is useful for testing devices without having a real FT-8x7 at hand. A short circuit on the accessory will not damage radio internals. A software bug will not keep your radio on hold or ruin its settings while you are busy developing or testing your solution.

The FT-8x7 CAT Emulator is based on a Atmel ATtiny2313 microcontroller (the same of my FT-817 keypad) and it accepts all standard documented CAT commands at 9600 baud. Feed it with 12V and the Emulator will power your accessory too, as if it were a real FT-8x7 transceiver.

A LED blinks when a 5-byte sequence is received at the emulator side.

Schematic diagram for IK1ZYW FT-8x7 CAT Emulator

The emulator handles two VFOs with frequency and mode and the get RX/TX status commands. Other Yaesu officially documented commands have been implemented but do not return data to the CAT accessory, so their usefulness is currently limited.

At powerup the Emulator initializes its internal VFO representations on 14200 USB and on 145500 FM. You may QSY using your accessory (keypad, FR, IFR, computer control software, ...) and the new value will be kept until power off. Since this is a tool meant for testing devices, it always powers up in a known VFO state (14200 USB and 145500 FM).

RX and TX status are returned with a static string, just to give some valid data to the CAT accessory to play with.

Conclusion. This is a blind emulator of the FT-8x7 standard CAT protocol. It feels like hiding your transceiver in a black box and controlling it with an external accessory. But it is indeed useful for testing all sort of CAT devices without having an FT-8x7 at hand. Firmware for ATtiny2313 will be available through my pages soon (the impatient can send me an email request).