Monday, 20 January 2014

Junkbox desk Microphone


Amplified electret desk mic


Not really ever using ssb or other phone modes, this is a strange project for me. When I saw an abandoned, novelty usb desk fan in the bin at work, I could not resist making this little project.
It is basically a electret insert and a single transistor pre-amplifier for which I claim no originality. In fact it is based on a pdf download from Waters and Stanton's website some years ago. A BC182 provides the gain and a few components combined with capacitors for a suitable ssb response, also supplying the voltage for the electret insert, which was bought in a lucky bag at a rally for a pound.
The rest was just a case of squeezing the ugly pcb into the old case and fitting an electret insert onto the boom. This is  a piece of plastic tube (empty till roll) into which the insert was bonded, a piece of foam on the end acts like a pop filter. Underneath the battery case supplies the power and there is access to a pot for gain control. The original button on top is used as a push to talk and on the rear a slider switch has been fitted to switch power off when not in use. The mic when powered will also work with a Vox equipped rig.
The gain control has to be carefully set as not to overdrive the rig.
A nice, simple project using a load of old junk!

  

Transistor pre-amp and gain pot 


Battery case, gain pot access and power switch 

Pop filter!


Original circuit by Bob Boddy G6AKL 

Rockmite40 QRP Kit



Having read and heard much about the Rockmite range of xtal cw transceivers by Dave Benson K1SWL, I was disappointed to find these kits had been discontinued. Then, good news, Rex Harper of QRPme fame, has decided to reproduce the kits with Dave's blessing.
The kit has been revamped slightly with standard 612 mixer instead of surface mount job on previous kit, this make it even easier to build. There are no toroids to wind so quite a possible evening project, though I spent an hour or so over several nights. The kit does not come with an enclosure, most people use an Altoids tin but it is complete with all necessary connectors, wire, plugs etc. It also uses a specially produced version of Hamgadgets Pico keyer which has a two memory keyer and adjustable speed up to 45wpm! and is suitable for straight key use amongst other features.
Having ordered one direct from the US I have since found out the KangaUK are going to distribute this kit in the UK and Europe.
I would happily recommend the Rockmite as a kit for beginners in radio kit construction, the end result is a simple but quite usable rig.

Rockmite40 Qrp
A couple of UK contacts have been made to test the radio which hopefully will be used on a camping trip or two this Summer..

Sunday, 19 January 2014

Alinco DX70TH Multi-Function control problems.

Alinco DX70TH


Although a great rig and normally available at bargain prices second hand, mine had a niggling problem..Used mainly as a back-up HF rig and a driver for transverting to 2m and 4m, also the occasional portable outing.
Since I have owned this rig I have noticed a rather annoying skipping fault on the multi-function control. This has various uses the main one being sequential band changing. A quick turn of the knob would cause a 'random' selection of band but persistence would select the band required.
Researching this problem  most people point to a faulty rotary encoder which I have tried a couple of times to source a replacement without any success.
Reading August 2013's Hints & Kinks in the Arrl's QST magizine, I found reference to a similar problem with an Alinco DR610T's main tuning control. The author , Kirk Ellis (KI4RK) found that adding a couple of 0.1uF capacitors between each output terminal and ground seemed to cure the problem.
Always looking for easy, cheap solutions here so I had a go with my alinco. Please see picture below. Smaller caps would make a neater job..

Caps added between up/down terminals and ground
  Pleased to report this mod seemed to work on my rig and has done for a few months now.


Monday, 23 December 2013

Xmas Greetings



May I take this opportunity to wish everybody a Merry Christmas and a Happy New Year for 2014.
Hoping to melt a little more solder and keep this blog up-to date next year... we'll see.

73 Ian MW0IAN


Present

Tuesday, 15 October 2013

Attic Dipole

My attic dipole is now an inverted V for 20m with separate elements for 10m band.
I have decided to remove the 40m loading coils which, although worked were not really practical in such a small loft space. Noise was quite high and signals down too.
The 20m reception is really quite surprising and being a popular band , there are nearly always signals present.
As a simple test I ran WSPR on rx  for a while.


Wspr RX on 20m

Sunday, 22 September 2013

5Mhz Band

I have recently been issued with an NOV for the 5Mhz (60m) band.
Hope to try out this winter.
Will be using Alinco Dx70 and endfed wire aerial, probably just on cw using 5w qrp.
Link below for UK 5Mhz bandplan.


http://rsgb.org/main/operating/band-plans/hf/5mhz/

Monday, 22 July 2013

Summer

Not posted for a while and I apologise but not much been happening here.
A couple of projects are in the pipeline, probably to be looked at later in the year.

Ultimate 2 QRSS kit build.
Another go at EI9GQ 2m transverter
Compact 2m linear PA using Mitsubishi module.
30m portable rig for camping with matching 1/2 wave endfed aerial.
Maybe try to get a signal out on 160m or improve 80m reception.







HF conditions have been quite poor lately, a bit disappointing for this stage of the solar cycle.


Other news is the weather has been great here for the last couple of weeks, very hot for the UK.