December 30, 2012

SRMSAT spurious emission or FCD front-end overload ?

 SRMSAT    Spurious emission or FCD  front-end overload ?

The center frequency was ok with Doppler  .
Spaces between the main frequency and Spurious frequencies was 25 KHz at both side .

Pre-Amp position does not affect the presence of it.
For sure it's most prominent during on position.
Need more  digital  tracking  and dusting off my analogue gear  :)
Have fun with fun-cube.


December 29, 2012

putt putt putt

 Audio amplifier motor-boating sound.

Adding a Pre-Amp in front of the LM386 creating a Motor-boating sound when I increased the audio volume .

Obvious wasn't  due to interaction between audio amplifier circuit and radio frequency circuit .

A good shielding and power supply decoupling may solve this .

See 30 sec motorboating video clip .


December 27, 2012

Recent bookmarked

 Recent bookmarked links


HSMM-MESH™ is a high speed, self discovering, self configuring, fault tolerant, wireless computer network that can run for days from a fully charged car battery, or indefinitely with the addition of a modest solar array or other supplemental power source. The focus is on emergency communications.

 The aim of this project is to provide an open source (and, hopefully, high–quality and well–written) Global Navigation Satellite Systems software defined receiver.



ADSB# – A simple and cheap ADS-B receiver using RTL-SDR



OsmoSDR is a 100% Free Software based small form-factor inexpensive SDR (Software Defined Radio) project.
If you are familiar with existing SDR receivers, then OsmoSDR can be thought of something in between a  FunCube Dongle (only 96kHz bandwidth) and a USRP (much more expensive). For a very cheap (but inaccurate) SDR, you can use the DVB-T USB stick using the RTL2832U chip, as documented in rtl-sdr.

Ancient reduction gear

Reduction gear mechanisms are often used to achieve finer tuning control for variable capacitor .The turning  ratio is 6:1

                                                          External  reduction drive



December 24, 2012

20M DC Rx initial test

Direct Converter receiver  Initial test .

 No shielding or band spread yet ,but the stability and sensitivity was so good for this prototype Rx.


20M Front-end filter

Front-end filter

Bandpass filter for 20M - Tested at Satellite Communication Lab (SCL)
University of Khartoum .by Cube-sat engineers.


December 22, 2012

MC1496 Product Detector

MC1496 Product Detector .
 All components are easy to to find except the old MC1496 . luckily I've got one piece.
Initial tests gave a good result. Injected 14 MHz at 1st input and  RF via  a long wire to 2nd input (without pre-selector ) . Next  I will add pre-selector and 386 IC.

Back ground -Solid State Design by Wes Hayward W7ZOI and Douug DeMaw W1FB .

December 21, 2012

Catch RTL-SDR fire .

DVB-T dongles based on the Realtek RTL2832U can be used as a cheap SDR, since the chip allows transferring the raw I/Q samples to the host, which is officially used for DAB/DAB+/FM demodulation. The possibility of this has been discovered by the V4L/DVB kernel developer  Antti Palosaari.

 From: Antti Palosaari>
Subject: SDR FM demodulation
Date: 2012-02-09 15:01:12 GMT (45 weeks, 9 hours and 10 minutes ago)
I have taken radio sniffs from FM capable Realtek DVB-T device. Looks 
like demodulator ADC samples IF frequency and pass all the sampled data 
to the application. Application is then responsible for decoding that. 
Device supports DVB-T, FM and DAB. I can guess  both FM and DAB are 
demodulated by software.

Could someone help to decode it? I tried GNU Radio, but I failed likely 
because I didn't have enough knowledge... GNU Radio and Octave or Matlab 
are way to go.
I smell very cheap poor man's software radio here :)

 SDR# is probably the best application to start out with.
RTL-SDR and GNU Radio with Realtek

December 14, 2012

FCD stress release connection + EMI chock

RFI / EMI snap-on ferrite suppressor choke core at USB extension cable, and SMA cable with a double ferrite beads. 

December 11, 2012

NOAA-18 with the Funcube Dongle Pro+

NOAA-18 ---- Funcube Dongle Pro+ ---- SDR#---- Audacity(11025 sampling)---- WXtoIMG----Image enhancement

December 10, 2012

NOAA-19 with the Funcube Dongle Pro+

Funcube Dongle Pro+ ---- SDR#---- Audacity(11025 sampling)---- WXtoIMG----Image enhancement

December 4, 2012

Very interesting ITAMSAT documentary

This documentary shows the preparation and launch of the first Italian amateur radio satellite,  September 26, 1993. It was encoded and uploaded from original video master.

IO-26 carried a Mode JD (145 to 435 MHz) Digital Transponder using the 1200 bps AX.25 protocol store-and-forward PACSAT Protocol Suite communications system.

 Thanks Very much AMSAT-UK

December 1, 2012

Satellites in a box – Radio Aurora Explorer video

In this video radio amateur Professor Jamie Cutler KF6RFX highlights the ability of CubeSats to test new technology in space at low cost.

The Radio Aurora Explorer (RAX) mission has proven that scientific information can be gathered from a CubeSat, which is a small satellite encased within a box and attached to a spacecraft to achieve orbit.
The scientific data gathered by RAX has been published in peer-reviewed science journals.

More at