Super simple FM TX - try on 2m?

See http://makezine.com/projects/super-simple-fm-transmitter/ .

This is a super simple TX for Band II FM using readily available parts.  With a smaller coil (1 turn less) and C4 smaller (and made tunable) I think it could be used experimentally on 2m FM, but stability is likely to be poor, so really only of use for short range and short durations.  From here, I'd expect this to be detectable at least 3km away (next village) even if the power is at uW or low mW levels. A few uW go a LONG way if connected to a reasonable antenna like my V2000 or 3el beam. There is no harmonic filtering either: a small low pass filter is advisable really.

With lower modulation levels (adjust) it should be fine with NBFM. The 2N3904 is a ubiquitous transistor available for just a few pence from many sources. The other parts are just pence.

Image at http://makezineblog.files.wordpress.com/2013/10/kogawa_simplest_transmitter.png?w=620&h=354

My thanks to Southgate Amateur Radio News for finding this before me.

Simple Home-Built Radio Projects page

The website of Rick Anderson KE3IJ is one of my favorites as it is filled with simple circuits, mainly simple receivers, that can easily be reproduced and that work well. See http://www.ke3ij.com/radios.htm. What I like is that on many pages there are little extra bits of circuitry that can be used in other projects too.  Lke me, Rick loves the humble 2N3904 transistor which is useful from audio to VHF.  They appear all over the place in his novel circuits.

Reliability of radio gear

Tin Whiskers on an IC contact

When I mentioned the eHam review of the KX3 on the GQRP reflector last night most of the replies focused on the reliability of complex modern electronics equipment. Some people believe that with fewer parts and SMA components reliability is higher today than in earlier times. Others, including me, were more circumspect and feel that, unless production processes are well controlled, the danger of failure is higher. There are also potential issues with leakage in small geometry ICs as well as the dreaded "tin whiskers" issue where metal dendrils can grow over time between IC balls. My own experience in mobile radio design and manufacture may have coloured my views. We got it right in the end i.e. getting production processes well honed, but you cannot take process control for granted, ever. The slightest drift in quality can spell disaster, field failures and a ruined reputation.

One thing many people agreed on was this: if you want to be sure of the reliability of your amateur radio equipment then build your own. A simple QRP transceiver, easy to make from many published designs in QRP books, should last a lifetime and will be easy to fix in the unlikely event of something going wrong. There is also nothing quite as satisfying as making contacts with something you have built. Even a simple crystal controlled TX and direct conversion receiver are likely to give FAR more satisfaction than a rig costing £1000 with all the bells and whistles. I still recall the thrill of my first ever hombrew contact across the Atlantic with 800mW CW on 15m using my little Pipit transceiver with 7 transistors total and a handful of parts. This rig was so effective that it was my main station rig for many months. Every QSO, and there were lots, meant something special.

USB powered direct conversion RX

G1INF has a neat idea on his blog for a simple direct conversion RX that is powered from the USB connection of a PC. His application was for LF reception but it would work equally well as the front end of a simple SDR for any HF band, replacing the loop with a bandpass filter. The audio output from the NE602 is connected to the PC's mic connector. Simples!