Monday, 31 December 2012

Monday, 24 December 2012

Christmas Greetings

Merry Christmas and a Happy New Year to one and all.
Best 73.

Monday, 17 December 2012

Soundcard Interface and PSK31

After a few simple receiving experiments over the years , I have taken the plunge and built a soundcard interface to use with my HF rig.
This is nothing special just a standard interface for which circuit details can be found on the web.
It is however fully isolated grounds between the PC and the HF rig, so to prevent ground loops.
Isolation is implemented by audio transformers in the RX TX audio lines and an opto-isolator chip in the PTT connection.
I'm also using a cheapo usb headphone sound 'card' instead of the main inboard soundcard, thus freeing it up for normal used. The usb card also has a nice low output which needs little attenuation.
Software at the moment is Fldigi (linux) which features a bewildering array of modes and features.I think my Morse keying is faster than my typing though :)

Soundcard Interface

Sunday, 16 December 2012

QRO on 2 Metres

As an addition to my 2M transverter project I have purchased this Microset RV45 Linear amp which will suit the 5 watt output of my transverter (hopefully), this should give around 25 watts when required.
It also has a receive pre-amp but I don't think that will be used much.
There was no circuit diagram or handbook supplied and searching the net has proved fruitless up to yet.

Microset Linear Amp

Tuesday, 4 December 2012

Finished Project : Single Coil Z-Match

On a bit of a roll here putting up pictures and brief descriptions of recently(ish) completed projects.
Pictured below is my Single Coil Toroidal Z-Match which follows a design by Lloyd Butler VK5BR .
This uses a T200-2 toroidal core and a couple of receiver type variable capacitors which allow a max input power of about 50 watts CW . This depends on the aerial in use i.e. short doublets may cause problems on lower bands but I used a 50ft doublet on 80m with no problems.
The clear lid is due to the capacitor vanes not clearing the box lid :-) looks quite nice...
Vernier drives are cool but hard to get at the right price these days. Got these at Maplins years ago.

Single coil toroidal Z-match (QRP)

Monday, 3 December 2012

Finished Project : PIC Morse Keyer

Nice little project pictured , a PIC morse keyer from a design by DL4YHF .
Very compact , self contained and easy to build - even with point - point wiring.
The keyer has 2 message memories and speed is adjustable 4-60 WPM , also has advanced features like Beacon mode and Iambic modes A & B.


Bit of a rats nest :-)

Sunday, 2 December 2012

MX294 (2m) MX296 (70cms) PIC conversions G8UJS

Just a quick photo of two ex pmr sets running in the shack.
The 2m set is a MX294 and the 70cm set is a MX296 by Pye.
These are rather old sets manufactured in the 1980's and can be picked up at rallies for around £5- £15.
If you have the Tedx front as pictured they can be converted with the addition of a PIC micro controller conversion by Alan , G8UJS.
This adds frequency display, CTCSS encode and channel scanning.
Both sets running around 5 watts via a Duplexer into a dual band co-linear in the attic.

2m & 70cm MX290's

G8UJS PIC conversion module ©G8UJS

Stealthy 80m/40m wire Aerial for small garden.

Nothing original here, but works reasonably well for me in this very compact location.
Basically it's half a 80/40m trapped dipole fed at rain gutter level outside the shack window (1st floor)
This stretches out to the far corner of the garden to a fishing pole behind a Christmas tree which is only about 3-4 metres high. At the 40m 7.0 Mhz point of the aerial is a coax trap, after this is the 80m element.The whole thing is about 17 metres long  though the end dog legs down about a metre at the far end.
The 40m counterpoise goes along the house and down the plastic drainpipe. The 80m counterpoise goes straight down the wall and along and around the garden fence. Both are cut slightly longer than a 1/4 wave long and trimmed to find the lowest swr. On 40m the SWR is reasonable ( 1:1- 1:1.7)across most of the band though on 80m it has a 2:1 swr of about 200 Khz, quite usable.
I have a 2ltr coke bottle in the attic space with about 10 turns of RG174 as a choke for good measure.
All together good for inter G and near Europe, only using QRP here but should be good for a couple of hundred watts QRO !!
Cheap and easy to build, reasonably quiet and stealthy too.

coaxial 40m trap

coax feedpoint. 40m counterpoise left, 80m counterpoise to the right.

80m counterpoise with electric fence insulator

Saturday, 1 December 2012

EI9GQ Radcom 2M converter. Pt 2

Just finished building the preamplifier and receiver mixer/ down converter circuit.
Now running well into HF receiver listening on 28Mhz.
I'm really surprised how sensitive it is on 145Mhz, much better than any 2m receiver I have used before.
Very low noise too. Just needs boxing up ready for transmit stages.

MK2 2M converter