Saturday, March 31, 2012

More Propeller Projects

I plan to attempt to use the Propeller for both LO and BFO for a small receiver. Jeff put me onto a neat little receiver which is just begging for experimentation. The Propeller can produce multiple RF signals simultaneously, just as needed for the receiver. More information can be found on this single conversion superhetrodyne receiver kit from N3ZI

But, I am diverted to yet another project, to build an even more accurate Frequency Source for the Propeller Master Clock. The TCVCXO that I built using the Homebrew circuit board has been doing very well in all experiments. It occurred to me that if it was connected to a GPS one second tick, it could be steered to even more accuracy.

So far, only initial plans are in place, with some circuit diagrams and example code.

The strategy is to implement a Huff-n-Puff circuit and support Propeller SPIN code to "drive" the Voltage Control Pin with corrections - Results: A GPS Disciplined Frequency Master Clock.

Google: Huff-n-Puff Oscillators

Actually, this is all experimental, and I do not really know what to expect. But, this is what I have at present.

The following is a code snippet from my current GPS ISR Object (has not been tested).

PRI Huff_n_Puff | C, PrevC
  PrevC := 0
  Trend := 0

  dira[GPSPin]~              ' Set for Input, and Float high via Pullup 10K Resistors

    Trend #>=  10
    Trend <#= -10
    pause(80 * ||Trend)    'Pause should be less than ~900ms
    dira[HnPPin]~          'Set Tri-state Mode

    waitpeq(0, 1<<GPSPin, 0) 'waiting for CPS SEC Pin to be LOW
    waitpne(0, 1<<GPSPin, 0) 'waiting for CPS SEC Pin to go HIGH

    C := cnt
    CountError := C - PrevC - CLKFREQ
    PrevC := C          'Save for next iteration

    if(CountError > DEAD_BAND)
        Trend #>= 0
        IF( HnPEnabled)
            outa[HnPPin]~     'Huff - Make Pin LOW
            dira[HnPPin]~~    'Output Mode

    elseif(CountError < -DEAD_BAND)
         Trend <#= 0
         IF( HnPEnabled)
             outa[HnPPin]~~    'Puff - Make Pin HIGH
             dira[HnPPin]~~    'Output Mode

         Trend := 0

The intent is to "drive" the Voltage Control Oscillator (TCVCXO) to match the GPS. The RC time constant of the Huff-n-Puff circuit above, along with the Program logic should only gently correct the output Frequency.

What I expect for output is a square wave (at HnPPin), varying duty cycle depending on correction needed.

Obviously, more development and testing is needed.

Please comment, if you have experience with this sort of thing.

I found the following interesting page:


Wednesday, March 21, 2012

My 30m QRSS Grabber is Back Online

Finally, my 30m QRSS Grabber is back online. It has been off for about three years, lacking the bits and pieces that make it all work easily (and maybe my lack of trying :-(

My QRSS Grabber URL is at:

A link to the Grabber is provided on the right of my blog.

If you do not know what QRSS is all about, check out:


Several things all had to come together for me to attempt to re-establish my Web 30m QRSS Grabber.
  • I recently learned; for a donation QSL.NET is providing web space to Amateurs for Ham Radio related topics (this may be old news to some, but not to me).
  • A new ARGO program is being beta tested and copies available for use. A new capability included an FTP client for capture transfer to a server.  A beta copy can be downloaded from here.
Establishing an online QRSS Grabber has never been easier.
  1. Establish an QSL.NET Web and FTP account (takes a few days)
  2. Build a few simple web pages
  3. Run ARGO, schedule a grab and transfer to your QSL.NET account
  4. Publish your web page, Let the QRSS Compendium Owner know your URL, GRID and capt file name.
  5. Set back and watch the fun
Note: I understand that with a little more difficulty, a Grabber can be established using the Spectrum Lab Program ( I just have not yet found all of the needed magic).

So, now anytime I am not activity Transmitting, I will be providing a Northwest QRSS Capture Service for the MEPT QRSS Knights.

Join the QRSS Knights, and have some fun, if you have spare receiver time available.

( Hopefully, this time my grabber will be up more, than down ;-)

Jeff - KO7M took up the challenge, and has put up his own KO7M Grabber, the more the better.


Due to the new Beta ARGO getting lost while attempting to transfer grabs to QSL.NET my QRSS Grabber is DOWN, again! More investigations is needed to proceed. While testing, the Grabber will be up, but mostly down.


Proposed OS Freq Standard

I have an idea for an Open Source Project, but first some background, . .


Dave Jones of EEVblog fame, is designing and building a very neat Open Source Power Supply, if you are not familiar with his project check it out at his Blog. His other blog enteries describe some of his design, process, and trade-offs. It is a very interesting project and I for one, will be ordering at least two when they are available.

If you are a reader of the blog, you will know that I have been experimenting with the Parallel Propeller Micro Processor (Prop) for use as a Amateur Radio Multi-Mode Beacon. The Propeller has within is the ability to generate RF square waves that I use to drive my Beacon. This Frequency can be set to any frequency from 500Hz to 120MHz. But there is a bit of a problem with the "stock" Propeller frequency synthesizer; it is not very stable or accurate. In my quest to solve this problem; Jeff - KO7M and I ( and with some help from some of my readers) hit upon the idea of using a TCVCXO for the system clock. Initial experiment suggest the Beacon frequency can be made to be very stable and accurate.

Last night at Jack - WA7KMR's Homebrew Meeting; we discussed Frequency Standards and the relative size, resolution and stability of some of the equipment that Jack had collected over the years. We also discussed feedback loops to increase accuracy and stability.

After getting home late, and after turning off the lights, my brain tuned on.

Most readers of this blog can always use more test equipment - right?. Therefore, . . .

My Proposal

An Inexpensive Open Source Variable Frequency Standard, based on the hardware design of Dave Jones's Power Supply; using the same case, battery pack, input voltage regulators, LCD display and push button layout. And using the TCVCXO and Propeller Micro Processor for control and function of the Frequency Standard.

  • Use the TCVCXO for the master clock of a Variable Frequency Standard
  • The Prop could select the source for the output, either a straight divide by N circuit, or an output from the Prop synthesizer.
  • The display could indicate the frequency and source.
  • A GPS input could be used to phase lock and adjust the already +/-2 ppm TCVCXO to much-much tighter tolerances. The Prop has these functions built-in.
  • The Prop would detect and display the TCVCXO and GPS phase error.
  • Feedback from the Prop to the TCVCXO (via filters filters) would adjust as TCVCXO as necessary.
  • The device would be small, battery powered and portable.
  • Multiple Frequencies can be produced simultaneously, on different output connectors.
  • And, relative inexpensive.

Jeff's and my initial work with the TCVCXO was with his Frequency Standard, but it only had a few decade switch selectable frequencies available, I think the Prop can provide much more flexibility.

I know there are many High Accuracy Time Standard hobbiest, and this would not qualify in that category. The expected Stability and Accuracy that can be expected is still debatable and untested, but I think the idea is worth pursuit for a bench source.

Dave Jones has done some great work; his generic input power supply and charging circuit, the case selection and layout, display and controls, are just begging for additional creative devices. I suspect his Open Source equipment form factor and layout will become a Standard, and it will become known as; The Platypus.

My Proposed Variable Frequency Standard would be an Open Source Project based on The Platypus.

Note: there are other similar projects on the web: Google, Open Source Frequency Generator

I am looking for feedback.

What say you?


Sunday, March 18, 2012


I think my 250mW 30m Propeller Beacon has covered North America, except a few stations around Seattle. My Beacon has NOT been received by Jeff - KO7M, about 35 miles away. I guess, there is just not enough ground wave. The stations as shown in the screen print, reported within the previous 3 hours.

WSPR Reporting Station - Previous 3 Hours


Friday, March 16, 2012

Measured Success

After installing the Homebrew PCB with the 10MHz TCVCXO Frequency Standard Clock on the Propeller, I finally got it connected to an Antenna as a WSPR, QRSS and OPERA 200mW Beacon.

The results are amazing, the Frequency is measure as very Stable and the Frequency is measured to be as set.  The reporting site, and measurement that I trust the most is W1BW (Operated from ARRL HQ);  they report Zero Hertz Drift and at the desired frequency of 10.140210MHz - exactly as I have programmed the Beacon.

Note: Not only does the TCVCXO provide for a stable and accurate RF frequency, but it also provide accurate scheduling for the Beacons. WSPR requires scheduled transmittion on two minute boundaries, starting the actual beacon two seconds (+/-1) past the minute. This Propeller Beacon is on-time, every time :-).

Also, the three beacons run in quick succession, that is: WSPR starts on a two minute boundry (runs for 2 min), followed by QRSS on the top of the next minute (runs for about 3 min), followed by OPERA on the next minute (runs for about 2.2 min). Then all repeats 10 minutes later. The 10 minute schedule allows the QRSS beacon to be displayed at the same place within the 10 minute remote Grabber captures.

I am receiving many reports (spots) from around the US, no DX yet, but the night is young.
My WSPR on the Map
Note: the W1BW report (at 3939 km) in the following list (click to view).
My WSPR Spots - as Reported by
Also, the following was reported by the KK7CC Grabber, note the frequency scale, which is out side of the normal QRSS Subband, I had to pick a frequency to allow my signal to show up on his Grabber. I picked 10.139930MHz, KK7CC reports the same !

My signal is the lower trace with Propeller graphic and my Call in slash code.

My QRSS on KK7CC Grabber - Las Vegas

I am a Very Happy Camper !!   :-)

New DX report at 7049km with only 200mW:

 2012-03-17 03:54  WA0UWH  10.140204  -24  -1  CN88xc  0.2  WA2YUN  RK39hh  7049  270

And, Two more:

2012-03-17 10:04  WA0UWH  10.140208  -14  0  CN88xc  0.2  VKFRG  QF44np  12766  244 
 2012-03-17 10:04  WA0UWH  10.140199  -26  0  CN88xc  0.2  VK4TMH  QG56fj  11758  252


Thursday, March 15, 2012

TCVCXO Boards Are On Order

After a few slight modification, I just placed an order with DorkbotPDX for the 10MHz TCVCXO circuit boards. This is the board that will be used for the Propeller Clock (see previous posts). They should be in my hands in two weeks plus a few days.

Gerber File

Note: The boards will not be Green, DorkbotPDX boards are a very nice Purple !


Wednesday, March 14, 2012


I have been watching/testing the 10MHz TCVCXO that I installed to replace the master clock on the Propeller (see previous posts). The stability is better than I had hoped, but the installation was NOT as good. I just soldered the TCVCXO onto the Propeller Protoboard where pads were available, but spacing was not optimal as solder bridges where necessary to make it fit. It was a jury-rig just to do some initial test.

Now that I had time to think about how it should be mounted, I decided to build a small PCB to hold the the parts; TCVCXO, by-pass cap, two fixed resistors, a variable tuning resistor, and a output cap.

Schematic on CircuitLab
Keeping with my on-going project goal, I wanted it to be as small as my ability allow. The results was a PCB that is 0.453 inches by 0.492 inches. The circuit will stand on three legs/pins which insert into mating sockets. I installed the sockets on the Prop Protoboard using existing holes, which provide 3.3v, ground and the clock input.

If the TCVCXO can not to be used, or if I want to use the original crystal, it can be re-inserted. Only the three pin-sockets were necessary and they can be abandoned.

DipTrace Layup
I will have the board made by a commercial PCB vendor, but for a quick test, I resorted to my tried-and-true Toner Transfer Method.
Circuit at Different Stages of Toner Transfer
I made more than one copy, Just in case Murphy was Watching

Components Loaded and Ready to Install
Some things just looks Ugly, when you get TOO close.
Two Fixed Resistors and Pot in Foreground
10MHz TCVCXO Center
Two Cap's in at the Far Edge
Using the board, is just a matter of changing the clock parameters and plugging the TCVCXO in.
TCVCXO Installed on the Prop Protoboard
It Sets Just Below the Edge of the LCD
I was easy to do, and it works GREAT!


Sunday, March 11, 2012

Stable Frequency for the Prop

More testing is needed, but it looks like the use of a 10MHz TCXO is going to work very well with the Propeller Software and Beacons. See previous posts, where the plans were made.

When I first installed the TXCO I could see that it was going work, as it did not produce the Hash (or fuzz) on the transmitted signal that was shown on previous blogs.

From turn-on the Frequency was very stable, after a few minutes no change could be detected. The output was NOT exactly on frequency, as I had not bothered to hook up the "frequency voltage control" line, I wanted to see the behavior without, and the single page manual does not provide much details of it's use.

The Frequency was low by about 1.4ppm as indicated on a previously calibrated Spectran. Within the Spin program I was able to correct the frequency and ran several more tests. All tests worked as expected (or hopped).

To complete the installation I hooked up a simple resister divider to drive the Frequency Control line; a 1K ohm fixed up to 3.3v, 2K ohm variable to Freq Control, and a 1K ohm fixed down to ground. Then I removed the previous Spin Freq Corrections and re-compiled the program.

The RF output frequency was within a few Hz of spot on, a quick twist of the variable Freq Control Pot put it on frequency. The pot is a little touchy for small adjustments; I will replace the two 1K ohm fixed resistors for maybe 2K ohms each.
Beacon Stability with TCXO
WSPR Above, QRSS Below 
as Seen by my Local (overloaded) Receiver
If you look very-very close, you my detect about a 1Hz drift between the two WSPR signals, but I am not sure that I can trust my receiver, or any part of my test configuration for that fine of resolution. Normally I check with and other external sites for conformation of details, but wsprnet was down when I checked.

More tests are needed, but I think this is a excellent fix for the RF Frequency Stability Problem for the Propeller Beacons.

I will add an installation photo here, later.


Mike and Key Swap Meet - 2012

Yesterday, we spent the day at the Mike & Key Swap Meet. As usual there was a large crowd on the two floors of the Puyallup Fairgrounds facility. I got to chat with many friends and enjoyed reminiscing of old projects and now outdated gear of previous desires.
Mike and Key 2012
As always, I enjoy the collection of tuning coils and capacitors.

Coils for my QRP Rig?

Caps and Coils

Older hand crafted projects still, starts me thinking. Here is a very well crafted Crystal Radio Set. I am not sure it was actually hand crafted, but it is very well done.
Crystal Radio Set
The Beauty of the Coil is Stunning
The Cat Whisker and Mount are of  Boyhood Desires
A nice displayed collections of anything, always catches my eye, in this case a large collection of coax switches.
Coax Switch Collection
This year, my only purchase was, . . .  a box of Girl Scout Cookies, but who can pass them up !?

When I got home, a new postal package had arived, and that will be the topic of the next post.


Thursday, March 8, 2012

A New Master Clock - Cont'd 4

Last night, Jeff - KO7M and I did some Propeller Stability experiments while on the phone. The necessary hardware was at his QTH and I was at home. My disadvantage was that; if there was going to be Smoke and Fire, I would not get to see it :-)

From Jeff's Frequency Standard, we injected a 10MHz signal into the Propeller at the XIN pin via a DC blocking capacitor, and set the Prop clock configuration to:


  _XINFREQ = 10_000_000

Note: 10MHz is above the suggested 4 to 8MHz for clock input, but TCXO's do not seem to be available for those frequencies. We were just experimenting with 10MHz.

It worked, The results looked very-very good. Jeff displayed the receive signal without Jitter or Frequency Drift.

The Prop PLL circuit runs at 16 times the injected frequency, or 160MHz, and then the PLL8X config provides the standard 80MHz for the rest of Prop.

Jeff's Freq Standard contains an inexpensive and readily available 20MHz TCXO. His Freq Standard provides a switch to divide by 2, which was used for our tests.

The 20MHz TCXO used for this test is available from Mouser, a similar 10MHz part CVT32-10.000 is also available for $8.00.

We plan to use the following circuit.

Propeller - TCXO Circuit
We now have 10MHz TCXO parts on order, more tests to follow.


Wednesday, March 7, 2012

A New Master Clock - Cont'd 3

To establish that the vendor supplied Crystal and Propeller Internal Oscillator is being effected by the temperature of the processor and it's work load activity. I have built a Homebrew external oscillator using the vendor supplied 5MHz Crystal.
5MHz Homebrew Oscillator

Because my intentions is to use it as an external oscillator if it proves to be effective at eliminating the Beacon drift, I have made it as small as my abilities (and keeping with my overall goal of building very small projects).

Oscillator Schematic via CircuitLab

The selected circuit is much like the 9volt battery oscillator that I use for Marker Oscillators (see many of my previous posts), except even smaller.

Oscillator on Six Pin Header
The new oscillator was built "Ugly Style" without a circuit board on a six pin header. The header provides a place to plug the crystal, and mount the few 0805 components and the SOT 2n3904. Wires attached to the pins will be connected to the Prop, it will hover above the circuit board, mounted a little distance from the processor (or at least that the plan).

Initial tests indicate my HB oscillator has little or no "hash", which is much less than that of the attempted use of the Master Clock (see previous post).

Mast Clock signal on left (with it's Hash)
My Homebrew Oscillator on the Right
The signal displayed on the left was from the Master Clock Oscillator, the signal on the right was the same data, but sent with my HB oscillator. Note: there is a little start up drift with both, and both stabilize after about 4 minutes.

Currently my oscillator is "hanging out" in the air on wire legs, and subjected to air currents and local temperature change that effect frequency (as with most crystals).

I inserted a 60 second delay between test transmissions, similar to a normal Beacon schedules.

Stability After an Hour
After an hour or so, the HB oscillator is stable and does not show signs of short term (2 minutes) stability between Beacon transmission, as seen before.

For this test the room temperature is 72.6F, the HB oscillator is 78.2F, and the Propeller Processor is 81.6F.

Future tests with WSPR will verify short term stability.


I think this proves that the short term stability of the Propeller Beacon during transmit; is due to heating of the internal oscillator from within the Propeller chip.

A low noise external oscillator should provide a stable RF Frequency for use with low band-width Beacons.

I need to find an commercially available Temperature Compensated Oscillator (TCXO). Or, a cheap Oven-Controlled Oscillator (OCXO). Or, package my Homebrew Oscillator for my permanent use with the Propeller.


A New Master Clock - Cont'd2

To make sure that my previous casual observation was correct, I re-installed the 100MHz Master Clock Chip in the Propeller (see previous posts). This time I included a 0.1uF By-Pass Cap at the terminals of the Oscillator for good measure. The results were as I had remembered - BAD.

The 100MHz Master Clock produce terrible Hash on the RF output, as recorded and seen at the receiver.

Vendor Supplied 5MHz Crystal
100MHz Master Clock XO

The left half of the screen grab, shows the signal from the vendor supplied 5MHz Crystal (clean), and the right half is the signal from the 100MHz Master Clock (hash).

I paused the Display to capture the two signals, so they appear side-by-side.

Ignore the apparent frequency ramp on the right, after about 4 minutes, the Master Clock stabilized rock solid on the expected frequency (without a correction applied). I should have waited a few minutes before recording the results. If you look inside the hash, you can see the data is the same for both oscillators.

Note: a -320Hz correction was applied to the vendor supplied 5MHz (x 16) clock, just to bring the signal on sub-band, that is about -32ppm error (well within crystal spec's, but I want better, with much less thermal drift).

See; Jeff -KO7M's efforts with his Propeller Frequency Stability, at his blog.


The 100MHz Master Clock is much more accurate then the open air vendor supplied 5MHz Crystal, but it produces MUCH more phase noisy (jitter).

Note: the problem I am trying to solve is not apparent in the above capture, because the test Beacon code does not provide a rest period (cooling as the cpu is inactive) between transmitted Beacon signals.

So, the quest goes on, I am still looking for a stable, low noise, solution.

I put a 22pF DC blocking cap between the Oscillator and Prop, thinking that maybe DC bias was pulling the Oscillator - No change, still Hash.


Tuesday, March 6, 2012

A New Master Clock - Cont'd

Well, that didn't work as expected !

In an effort to thermally stabilize the output RF Frequency of the Propeller that I use for WSPR, QRSS, and OPERA Beacons, I attached a external 100MHz +/-50ppm/C Master Clock Chip in place of the vendor supplied 5MHz Crystal, see previous post.

The Propeller has options to multiply the supplied source as necessary to obtain the desired operating clock frequency. The supplied 5MHz crystal x 16 = 80MHz, for normal use. My external 100MHz oscillator is not multiplied and over-clocks the processor by 25%. It works and it is fast, but . . .

The 100MHz Clock is accurate for average Frequency, but it produces a lot of jitter. The jitter shows up in the output RF Frequency as noise. For a Beacon, which typically uses a band width of only a few Hertz, the jitter is unacceptable. The jitter appears as fuzz on the received signal.

Another Approach is Necessary

Another type of oscillator is the;  Temperature Compensated Crystal Oscillator (TCXO). The spec's on the TCXO's look very good. A high precision TCXO is typically +/-1ppm/C, with some parts rated as low as +/-0.5ppm/C. These parts are typically $5 to $10. But only a few limited frequencies are available, from 10MHz to 52MHz. They would work with Propeller but the internal PLL could not be configured to multiply the frequency. That is, the Prop internal PLL (1x, 2x, 4x, 8x, or 16x) could not be used, because the Prop PLL has an input limit of 4 to 8MHz.

So, I am looking for a low cost, high precision ~1ppm/C oscillator

  • 4 to 8MHz TCXO (to be used with Prop internal PLL)
  • Or, a 80MHz to 100MHz TCXO used un-multiplied in direct connection

Another type of oscillator is the; Oven Controlled Crystal Oscillators (OCXO), they are available with much better spec's (e.g, +/-0.005ppm), but they are very expensive (and large), > $150.

So far, a suitable part has NOT been found, . . . the search goes on :-)

Note: The included links are for Mouser, other vendors have a similar parts selection.


Sunday, March 4, 2012

A New Master Clock

One aspect of using the Propeller for a WSPR, QRSS, or OPERA Beacon (see previous posts) is that while transmitting, the Frequency drifts (a little), maybe as much as 10Hz. The drift is believed to be due to the rise in temperature within the processor itself. The processor clock/oscillator is within the processor and core activity warms the oscillator and the Frequency drifts low. During the non-transmit period of the Beacon schedule the drift recovers. With normal Amateur Radio use, a 10Hz drift is almost undetectable, but with a Beacon it is NOT acceptable as the band width of most signals is less than 6Hz.

With only limited success, I have attempted to isolate and insulate the Propeller Board to alleviate the problem.

My latest attempt to solve the drift problem is to source the master clock from an external device, which hopefully will not be affected by Propeller Processor temperature change. I purchased a 100MHz Master Oscillator Chip.
Clock Chip

After ordering the Clock Chip I noticed that I ordered "the small one". The original intention was to order a chip about 5x3.5mm which is small, but I felt I could mount it on to the Propeller USB Protoboard without a problem.

WRONG, what I actually ordered was a very small SiT8103 Master Clock Chip, which is 2x2.5mm in size, or a 2025 SMT size part.

The Clock Chip with Wires Attached
For my use, three wire had to be soldered to the four terminals, the wires would then be soldered to the Prop protoboard. Soldering three wires onto this chip was like trying to glue baseball bats to a domino.

The wire attachment task took about an hour to complete.

After wires were attached and it was setting on top up the Propeller Protoboard, I decided to clean some old rosin from the intended attachment area of the board. I normally wash/desolve rosin with spray cleaner into the trash can. Just as I sprayed the cleaner, I saw my newly created part; jump off of the board and disappear into a jumble of trash in the can. It was lost! :-(

It is a good thing I purchased several chips. The wiring of the second chip only took about 30 minutes ( I am getting better at this :-)

The Clock Chip Installed on the Propeller
The Master Clock Chip installation replaces the vendor supplied crystal, and will "hover" slightly above the board on wire legs to the left of the processor.

The vacated crystal socket can be seen, the new Master Clock Chip can be seen center.

The original 5MHz crystal (when internally multiplied by 16), ran the Propeller at 80MHz. The new Master Clock Chip will over-clock the processor by 25%, that is, it will run at 100MHz.

Note: the crystal and the new Clock Chip are both rated about the same stability; that is +/-50ppm. The only real goal with this modification is to; avoid the heating effect of the processor. It is interesting, that the Real Time Clock peripheral that I installed on the Propeller has much better stability spec, at only +/-5ppm. But, there is no way to take advantage of it for a processor master clock.

Currently the new 100MHz Master Clock and Propeller are running my previous applications, just fine. Hopefully the only result will be the Propeller Frequency will NOT drift as before. Only additional tests will tell.

My Propeller Programs needed to be modified a bit to use the new Master Clock, but it is an easy configuration modification.

Old 5MHz Crystal Spin Config:

  _XINFREQ = 5_000_000

New External 100MHz Master Clock Spin Config (Corrected as per feedback in comments):

  _XINFREQ = 100_000_000

This was a good attempt, but it produced too much Hash on the RF Frequency, see follow-on posts of our attempts to solve the Oscillator's Thermal Stability problem.


Saturday, March 3, 2012

CircuitLab Software

I have been playing with the "CircuitLab" on-line circuit simulation software, which is very easy and fun to use.

Here is the circuit for the 30m LowPass filter that I am using with the Propeller Beacon, as documented in previous posts.

Click here to play with the Filter on-line. Note: Because it is on-line, that version my not appear exactly the same as shown here, I am editing it while still playing.

The Circuit
The Simulation Results

I like the software, but it indicates that I may need to work on the circuit. a little :-(