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G4WIM England flag England

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Hi, here's a few notes and photographs detailing my 'ham radio career' going back over 40 years now.

Main main interest has always been home brew and over the years have designed and built quite a few items - frequently having the design published and occasionally winning an award.

I was first licensed in 1972 (at age 16) as G8GIW while living in St Annes-on-Sea, Lancashire, United Kingdom and was very active on 144MHz SSB using a home brew QRO station. Amazingly I survived despite 'messing around' with 2kV power supplies to run a pair of 4CX250B's !

Pictured below are my home brew amplifiers for 144 and 432MHz based on the K2RIW design using a pair of 4CX250B's in parallel. So much easier these days with solid state devices and not quite so lethal :-)

In 1981 I moved down to Hanslope Park near Milton Keynes to work for   HMGCC and while I was living in Milton Keynes I obtained my Class A callsign of G4WIM in 1984.

In 1994 I resigned from HMGCC and moved into Formula 1 racing at Cosworth where I was electronics manager for a small team  developing some new engine management hardware and software.

In January 1997 I re-located my family (xyl and 9 year old daughter) to San Diego California and in 2000 decided to get a US callsign.

I visited the local VE (volunteer Examination) session and went from not having a US callsign to extra class in just under 2 hours, nearly failed the General Class stage though ! My US call is KT6UK.

I've recently (2013) retired from being the Chief Hardware Architect for a large telecomms company - it was bought by Google - a big thankyou   to Google for enabling my early retirement back to the UK !

While working in the USA I created and hold 33 issued US Patents with a further 3 pending - it's all about the patents these day as Google has learnt.

Over the years my interest has seen peaks and troughs, but always managed to keep some level of activity - even when I've been distracted by other matters / hobbies.


I've always been interested in 'home brew' equipment and have written many technical articles for various publications over the years - most notably for RadCom where I won two awards. One for a 1.8MHz auto tuning vertical antenna and a second award for a processor controlled multi-mode dual band transciever for 50 and 70MHz bands. The 1.8MHz design is published in the RSGB's HF antenna collection and in many ways is the ancestor of todays 'screw driver' antennas.

Below - award for 1.8MHz antenna design

Below - award for my 50/70MHz dual band processor controlled multi-mode radio. Shame they couldn't spell my name correctly :-)

Now I'm back in the UK and have some time on my hands I decided to set up the shack again along with a well equipped work bench ready for my next homebrew project.

In the meantime I have started to repair and restore some of the older amateur equipment which commercial repairs shops prefer not to touch. Here's a video of one such repair, it's in hi-def if needed.

These repairs are strictly for fun and 'not for profit'. E mail me if you have an older rig which needs attention or you no longer need. I maybe able to fix it up and pass it onto a deserving cause.

Despite my interest in 'home brew' I've recently bought a few 'black boxes' namely an Icom IC-7800 primarily for HF and 50MHz, ICOM 910H, IC-9100, IC-7300, IC-7100 and an IC-5100 - yes I do like Icom gear !

All these radios (and my test equipement) are locked to a GPS frequency standard which in theory gives the station a frequency accuracy of better than 1 part in 10 billion or if you prefer better than 1 Hz at 10GHz :-) In real life the accuracy is probably only 1Hz at 1GHz.

I've also assembled a Hermes SDR (Software Defined Radio), designed and produced by OPENSDR, Apache Labs and TAPR groups. It's basically a very fast 16 bit A >D converter running at about 133Msps meaning it has an instaneous bandwidth of about 55MHz. The performance is outstanding and easily compares or even exceeds that of my IC-7800

I've now replaced the Hermes with an ANAN 100D which has dual coherent receivers which can be used to cancel interference.

I also run a number of sdr's which can be found on websdr.org  The recievers cover 40, 6, 4, 2 mtrs and 70cms  - all publically available.

Previous to the SDR I had just completed a mast head pre-amp / 150 watt power amp for 23cms. It helps me 'get out' on 23cms from my location (IO83NS) which is at sea level.

I also run a DSTAR 'hot spot' MB6FCon 144.825MHz - interestingly the NoV only took 18 hours from start to finish to get approved - a big thankyou to all those involved for this record !

Below are some of pictures of my station as it stands at present (always being improved / changed !) along with the 'work bench' equipped with various items of test gear.

The plaques in the background are some of my patents. I hold 33 in total and a couple of awards from the RSGB.

From left to right on the desk Icom IC-7800 plus SP-20's and SM-50 for HF back up with SGC3000 200 watt remote HF tuner.

IC-7300 almost exclusively for 70MHz, PS30M power supply.

IC-7100 for local chit chat

IC-9100 plus Sp23's for 144/432MHz FM / Dstar plus 23cm SSB prime mover for 150W Solid Stae 23cm power amp located directly above.

Apache Anan 100D SDR with home brew 435MHz and 1300MHz DATV tx / rx.

IC-910H for 144 / 432MHz SSB and 23cms FM

Home brew 24cm FM TV tx/rx with DATV Express digital exciter

IC-5100 for ATV talk back

DJ Hercules controller for Apache 100D SDR - makes controlling it very easy.

Aerial stuff.

The rotor controller is a Yaesu G-800DXA used to rotate a 7 ele for 144MHz,  a 19 ele for 432MHz and a 38 ele for 1296MHz.  Luckily the shack is on the top floor so the coax runs are only about 7 mtrs of eco flex 10 per band.

I also have roof mounted colinears for 50, 70, 144 and 432MHz bands

For 160, 80 and 40 mtrs I use a 204 foot doublet at about 40 feet AGL running east West.

For the higher bands I use a 36 foot vertical with remote tuner and an extensive ground mat.

For LF / HF reception I use a couple of switchable 1 mtr diameter magnetic loops at 90 degrees to each other with a low noise balanced pre-amp, this means I have a very quiet receiver which helps immensely on the lower frequency bands.

And yes - I still keep a paper log book !

Below - close up of the IC-9100, Apache Anan 100D and D700 for Dstar hotspot and local 432MHz repeater. Each rx has it's own external speaker, this side of the desk can monitor six freqs at once. The Apache has two phase coherent receivers making diversity reception work really well. The Hercules device is what I use to control the Apache 100D SDR.

Below - close up of IC-7800, two SP-20 speakers (one for each rx in the 7800), SM-50 microphone and Power SDR. You can also see the IC-7100 control head in this picture.

Below - IC-910H for 144/432MHz SSB use along with a vintage TS-700 and Dstar hand held. The SM-50 desk mich is switchable between the IC-7800 and IC-910H. I've recently restored the TS-700 to original factory specs and for an old radio still works surprisingly well !

Again two speakers, one for each rx in the IC-910H.

Below some pictures of my 70cm and 24cm Digital and Analog ATV station.  It can muster 70 watts Digital on 435MHz, 80 watts digital on 1249MHz and 120 watts analog FM on 1249MHz. 

Below -  Note the bandpass filter for 435MHz to make sure the digital signal is as clean as it can be on transmit.


Revised main VHF / UHF station showing digital ATV exciter and camera,  Mag Loop controller, TS-480HX which is coupled to the auto tuning loop and normally sits on 40 mtrs.

ID-5100 local FM and D-star and Kenwood D700 for the local Dstar hotspot (MB6FC)



Below shows the 144 / 432MHz SSB station along with a 144MHz doppler direction finding receiver (an old Trio TR-9000) and display - gives a quick bearing read out of where a signal is coming from.

The Samsung box below is is the 435 /1249MHz digital ATV receiver.


Below - GPS freq reference, Dstar hotspot controller, 23cm 150 watt PA and IC-7100 on upper shelf

Below - Old home brew rigs for 50 / 70MHz and 23cms along with a couple of old Trio's for 144 and 432MHz

Below - frequency generation distribution. This box takes in 10MHz from the GPS reference and generates 32MHz and 30.2MHz for the IC9100 and IC910H. It also passes thru 10MHz for the IC-7800 ensuring frequency accuracy on all bands.

Below - main linear DC power supplies all protected for over voltage and current. The home brew 50 amp PSU is conservatively rated at 50 amps 100% duty cycle.


Over the past 12 months I've been working on an automatic tuning mag loop which covers from 80 mtrs thru to 20mtrs.

It uses a coupler of stepper motors in 1/4 micro stepping mode with controlled acceleration and de-acceleration. One stepper drives a vacuum variable capacitor and another drives the orientation of the input coupling loop.

The micro controller is a Teensy ++ with some custom firmware I've written.

The combined effect is the ability to qsy from 80 to 20mtrs in less than 4 seconds and have a VSWR of typically 1.05 to 1 yes that is 1.05.  It effectively tunes the loop to within a few hundred Hertz of the applied frequency.

Here's a youtube vide of it in operation.

The design is being published by the RSGB.

Below is a picture of loop showng the vaccum vaiable capacitor at the top and the input coupling loop at the bottom.

Below is a close up of the motorized input coupling loop showing the lead screw positioner

Below is a picture of the controller PCB

Below is the front panel showing the controll buttons and typical display after automatic tuning.


Below - On the other side of the shack I have my work bench. Mostly HP / Agilent / Tek test equipment. The Metcal dual soldering station is marvellous for all types and sizesof soldering jobs.

Test gear covers from practically DC up to 6GHz and 18GHz for the power meter. Assorted PSU's, arbituary function generators, DVM, 3GHz frequency counter, Modulation meter, dual channel RF power meter, Sig gen, spec analyzer, 2.5Gbps DSO, 275MHz anolg scop.etc etc.

The work bench is not normally this tidy :-)

Below shows DVM, a couple of arbituary waveform generators, a 275MHz analog scope and modulation analyzer.

Below shows frequency counter, power meter, spectrum analyzer and signal generator etc.

Below shows a collection of PSU's a 2.5G bits/sec digital storage scope.

Below are thumbnail links to a selection of the various home brew projects I've constructed over the years. Click on the photo's for a larger image and to learn more about them ! (Spot the odd one out...)


From Home Brew

Below are a couple of pictures of my HF antenna, a 'Scorpion' SA-680 screwdriver antenna covering 3.5 to 30MHz.


Even though it's a very compact antenna I have been able to work SSB all round the USA and even back into Europe with comparative ease.

This is also the antenna I used for WSPRnet operation while in the US - amazing what a few hundred milliwatts can do in a narrow bandwidth. Check out wsprnet.org for more info. Feel free to qsl if you should see or hear my signal.

Click on the photo for a larger image and more info.

free counters

From KT6UK


7902932 Last modified: 2017-02-15 11:52:59, 27662 bytes

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