The workshop clean up was delayed, I just had to get the VFO working. When I built the kit a few months back I did not solder one of the headers! Found that this afternoon, soldered it and all was well.
First job was to setup the IF at signal frequency + 9Mhz. Then a quick run through to see if all the functions were working as they should.
I like the minimal display. It would be even better to be able to go back to using one the old Eddystone slow motion drives like this one on a G2DAF RX from 1963. No water falls, flashing lights, bleeps, tones or warning messages on screen. Don’t get me wrong there is a place for all of that but sometimes I just want a radio that is simple and easy to operate without the need for an A4 ring binder full of instructions.
At the end of the afternoon this is what I had; a VFO covering all bands from 160M – 10M with the IF set to 9Mhz and giving about 80mV P-P of sine wave ready to go straight into the mixer.
Over the years I have built a lot of gear from simple test equipment to an eight band CW transceiver using reclaimed parts. Technology moves on and I now have three commercial SDR rigs. The performance of modern transceivers is amazing but I feel something has been lost; it’s all done in software which feels a bit cold, clinical even.
A few years back I followed a series of articles in RadCom written by Eamon Skelton, EI9GQ, where he described how he built a transceiver mainly from discrete components. I bought the book a couple of years ago and now feel I want to make my version of his project.
Why now? It is mainly the availability of cheap test equipment like spectrum analysers, VNAs, GPS locked frequency meters and wide band noise sources which work well with SDR receivers like the RSP1A.
Not long ago all we had were grid dip oscillators, drifting sig gens and frequency counters with dubious accuracy.
I have made a start and almost fallen at the first hurdle! Instead of making a 9Mhz, 2.4Khz wide SSB filter I have bought one from Spectrum Communications. That will save buying lots of 9Mhz crystals and spending hours matching them to get a good shape.
I have already built a VFO based on a synthesiser chip. There are some things it is not worth trying to replicate and a drifting VFO is top of the list. I did build a free running 8 Mhz VFO in the early 1970s that was multiplied by 18 to drive an old Pye valve TX on 2M. It took hours to sort out the drift but eventually it was rock solid. The key was an Oxley Tempatrimmer. The fixed vanes of the capacitor were fixed to a bimetalic strip so as as the temperature varied the capacitance changed. They are impossible to find these days.
Watch this space as I will post progress reports as each stage is completed. The first thing to do is tidy up the workshop, I may be some time…
Although I still make stuff it is getting harder especially with small components. Last year I was told that I have rare form of cataracts. That makes working on circuits boards difficult. When the current pandemic is over maybe they will be able to replace to duff components and restore the circuit to its original condition.
This is all leading up the to be the excuse for buying an IC-705! It’s an exceptional radio with amazing performance which is hard to believe for an old timer brought up on HF receivers that occupied a full 19 inch rack.
Above left – Marconi HR11 telegraphy receivers with the boss pretending to tune one and above right, Plessey PVR800s telephony receivers. The first transistorised professional RX for the HF point-to-point service. Pics from around 1968 at PO radio station Bearley.
The IC-705 which I can hold in one hand!
So now the work is on perfecting the HF /P antenna. I have gone back to an end fed half wave made from a homebrew system that breaks down into 1m long sections. The aim is to cover 40m-10m with different lengths of wire wound on a reel, after removing the washing line. See Steve Nichols, G0KYA, post on his blog here.
I also have a couple of light weight fibreglass poles and a drive over support just to make everything more flexible. That will allow me to operate from the car/micro camper.
Had this kits for a while. Built it but at the first attempt it did not work. Tried again a couple of weeks back and got it going! Must admit to getting the biggest kick from making something and then having a QSO.
Had a bit of trouble with the faulty, cheap, trimmer caps and idiotic SOIC to pin converters for the NE612s but after going back the the DIL versions all was OK. It still needs tweaking and putting in a box.
Could not resist trying on an antenna, heard a MM station, gave him a call and he came straight back!
10 July 20
It’s in a box, just needs wiring up.
The Morse tutor is complete. I chose a plastic box that was only just big enough, I like a challenge and this certainly was one! It all worked out OK in the end but was a real fiddle to get the measurements right.
What I learned apart from home construction is fun:
1. A nice bezel hides a lot of mistakes!
2. Covering a plastic box in masking tape prevents it being scratched when drilling and filing.
3. Removing the glue after covering a box in masking tape is not easy.
4. Red is always the positive wire on battery connectors!
Next project – Arduino based VNA, 1 – 60Mhz for around $50!
Just ordered all the parts from ebay and the PCB is on its way.