Clublog

Wednesday, 28 September 2011

SR63ng build

Well I am building and I came across this site.

http://www.vk2zbb.com/index.php/sr63ng

It doesn't go through the build stages as per Robby's instructions and is a sequence of placements of every component on the PCB but I'd recommend anyone building to take a look at it.

Saturday, 24 September 2011

SDR homebrew project that covers VHF/UHF/SHF frequencies?

As I push solder around a board that could be used at 70cm I thought... I wonder if there any interest in an SDR homebrew project that covers VHF/UHF/SHF frequencies?

I mean 70MHz up so 70MHz, 144MHz, 432MHz and 1.2GHz (maybe even 2.4GHz).

Frequency agile, meaning not single LO frequency.
Using Silicon Labs Si570 (e.g.http://www.silabs.com/Support%20Documents/TechnicalDocs/si570.pdf), might need modification to the circuits to obtain the quadrature LO required at SHF (An LO at 4 times 1.2GHz or 2.4GHz will be beyond the Si570). Maybe look at Analogue Devices DDS?

Display and Control (PC software aside) by
4x20 LCD or 128x64 GLCD (or better)
Rotary and push button front panel controls
PC and non-PC options (i.e DSP processing)
JTAG/ISCP programming options, probably AVR rather than PIC
Stereo CODEC (via USB so no sound card interface if PC involved)
Modes as per usual SDR capabilities including FM.

Might be interesting to see comments.

Building SDR again

In advance of the RSGB conference in October I am putting together a new SDR setup and I have just been sent two of the SMT versions of Tony Parks excellent SR V6.3 from Yoyodyneconsulting

http://www.yoyodyneconsulting.ca/pages/SR63ng%20Information.html

It is called the SR63ng and it is a near clone of Tony Parks' retired SR63 RXTX board where the board has the same physical dimensions and connector registration as the original. This mans it will be a direct plug in replacement for the original. One noticable thing is it differs from the original in the use of surface mount components (SMT) rather than axial leaded resistors/caps, which make the build cleaner. 

Why am I building these: To provide the RF 'deck' to use the American term for the MOBO-4.3 system as I am building another pair of them (I sent one out and it went missing) and I have managed to obtain a couple of PCB for it as well. This time I will use with the SDR Widget, that was still in Alpha last time, so this will mean no audio output to a PC sound card will be required and will use a single USB connection only. Should have a at least 48/96kHz bandwidth and be frequency agile as it is based on the Si570 DDS but the MOBO will contain a limited number of band pass filters ( up to 9) in the amateur bands.

I am hoping to also have this built side by side with the SDR-Cube shortly.

Sunday, 11 September 2011

PIC-A-Star meeting

Today I attended a meeting for PIC-a-Star builders:




>>The Pic-A-Star event will take place next Sunday 11th September between
>>11am and 4pm at the Milton Keynes museum England.
>>
>>Pic-A-Star constructors (whether completed or not) are invited to come
>>along and are also invited to bring their Stars as well; for those who
>>would like any assistance with their build we will have test equipment
>>including spectrum analyser / power attenuator and a calibrated signal
>>generator.
>>
>>I have updated the web page at
>>http://www.radio-kits.co.uk/pic_a_star/event.htm to show where we will
>>be in the museum.
>>
>>See you there,
>>Steve G6ALU - Calvin M1EPM

Thursday, 8 September 2011

PTO

Back in January 2010 I built and blogged a PTO http://m1kta-qrp.blogspot.com/2010/01/pto-vfo.html I threw together using either a Starbucks or a MacDonalds straw as the former and a small brass plug and M5 Nylon bolt that generated a fair bit of interest. It appears Rev George Dobbs from GQRP club referenced it in an October 2011 Practical Wireless article. Anyway after a brief email exchange with George I am going to see if I can create a 'kit' of sorts for the GQRP convention 2011 at Rishworth of all the mechanical parts and the electronics. I'll update the blog with progress. If anyone has ideas then glad to hear them.

The ideal is 100kHz swing preferably not needing more than 3 full revolutions of a tuning knob.
If I have time will be usable for both a direct conversion setup so will be 80m or 40m or will be usable in a superhet type vfo+IF option. (11.0592MHz maybe??)

Slow motion would be nice but I know this is easier (read cheaper) to obtain by using fine threads OR A BIG TUNING CONTROL.
I found using a blass slug not an iron one was easier so that way you work from a maximum inductance and it drops as you insert the brass slug (made the tuning the 'right way' on the tuning knob too!).

Will be either colpitts or vacker type vfo as stable, I am sort of familiar with them and part counts are low.
Active device will be a FET J310, 2N3819 or similar depends what I have a few of.
Caps will be black spot NPO ceramics.
I'll try and see if I can include a voltage stability at 6V or 8V but will wait and see.

There are two main options
1.The PTO assembly sit 'proud' of the main board (pretty much as my original bodge did, and as per George design) or
2. An on board design a bit like the MMR-40 from KD1JV.
Go to qrpkits.com and you'll find docs for it or there was an ARRL article (I might update these with real links)

The assembly needs to turn a rotation into a horizontal motion. There are probably as many ways to do this as there are resistors in a E24 series but in short you move either the coil over the slug or vice versa, the later is easier. George has already whimiscally shown one option using a used up old lipstick for this.

Anyway more later off to work at the salt mines....