Eddy EC10 Recycled

[Wendymott]

Hi Peeps... After 6 months of intermittent work..its up and running... just a couple of minor tweeks to do but ostensibly its finished...
It started as a "bog standard" EC10... but I decided two or three years ago to make it Amateur band only....However due to the construction of the Local oscillator assy it was not very stable and very microphonic.
As I had finished another project, I was looking for the next thing..which turned out to be this...
I decided on 5 local oscillators, each tuned by varicap diodes, the reason being they were easier to keep stable and tune remotely.
The I.F was chosen at 4.433 Mhz, as I had a number of crystals, 4 pole for the filter and 2 for the BFO.
I used the trusty MC1496 as the first mixer, a SL610 as the front end RF amp and another SL612 as the I.F amp. No AGC, as I prefer to control. with an RF gain / Atten pot.
I double ganged the tuning pot 100K lin, so if one track was noisy the other should help, but as its new it shouldnt be a problem
The tuning pot has only a 180 degree travel, due to the original gearing, so I adjusted the lower end to give about 1 volt on the slider. Each VFO has a trim pot to set the upper end and the L/C tune the start point LF end
The VFO frequencies, as seen in the photo, were chosen to give IF + 80m then the others were IF- to minimise drift.
The audio output stage is preceeded with a Baxendall tone control preset circuit so I can trim the response if required. I have not built the CW Filter yet, as I am not a CW Fan, but I had a spare switch on the front panel, so it may come in useful.
Really its not an EC10 anymore.. only the case and the dial drive are original, even the knobs are replaced.
If anyone is interested I can post the schematics later.

[Wendymott]

Here are another few photo's.. The last photo shows the bare bones before construction, The chassis is two pieces of copper coated some sort of plastic back to back so I could tap the mounting pillars with no need for nuts,

[Terry_VK5TM]

Nice job Wendy, how does it sound?

[Andrew2]

That's a nice job, Wendy. I bet it works better than the original design - I had one a few years ago and despite my efforts to do it up it remained drifty and a pain to tune. SSB performance was poor and it felt generally a bit cruddy, although better than most of the late 60's cheap imported sets.

[Wendymott]

Hi peeps... It sounds ok for a communication receiver...The BFO consists of two crystals tweeked for LSB and USB.... The VFO's are of the CLAPP design with small thermal latency.
Heres the schematics....

Maybe of use to some of you.....

[G6Tanuki]

That's neat! I particularly like the pragmatic commoning of the tuning-pots.

(something similar I've used in the past is to have one going low-to-high and the other going high-to-low as it's turned - the wipers then feed independent A/D converters with the values compared-for-sanity in software).

Thinking of your "EC10 Mk.3" I might do something similar with an old Heath "Mohican" that's spent 20 years sitting in an outside shed and now has a bit of mouse-related trouble. Shouldn't be too hard to make it into a nice 80/60/40M receiver.

[Wendymott]

Hi Tanuki..... At one point I added a 10 K resistor to the bottom end to the wiper to make a pseudo Log pot, but the dial spacing was all wrong.. so I decided to leave it....
There are some areas with massive band spread as in the LF end of 40 M..But in each VFO different varicaps are used to get me the coverage.....
Like the 10 m band I parallel two diodes in one package, but it works for me so its good

[IanG3XYV]

Wendy,

Excellent to see good use being made of the venerable Plessey SL6xx series. I recall using the 610 and 612 in an SSB transceiver based on a Plessey design. It also included the 640 mixer and 621 audio derived agc IC. That was back in the 1970s and 80s. It all worked well if good attention was paid to layout and earth returns.

Ian

[G6Tanuki]

Originally Posted by Wendymott

Hi Tanuki..... At one point I added a 10 K resistor to the bottom end to the wiper to make a pseudo Log pot, but the dial spacing was all wrong.. so I decided to leave it....
There are some areas with massive band spread as in the LF end of 40 M..But in each VFO different varicaps are used to get me the coverage.....
Like the 10 m band I parallel two diodes in one package, but it works for me so its good

Pragmatism is often better than over-analysing these things! If it works, it works.

I've got a couple of 100K linear 10-turn pots here, which would probably be the basis for my "FrankenVFO" - feeding the output into an A/D converter to drive a synth. A bit of software can then do things like automatic acceleration (as in mouse-pointers). One thing I saw a while back on a radio which impressed me was the ability to manually VFO-tune to one frequency, press a button, tune to another frequency, press the button again, and it would then automatically scan between the 2 frequencies at the same speed as when you tuned between them.

Somewhere I've got a couple of the old MD108-style balanced mixers, too.

[Wendymott]

Thankfully there are still a "few" constructors and inventors left...what will happen in 20 years time when most of us have "shuffled off".... these university bods wont have a clue.
Tanuki.. looks like you have your work cut out on that one

[Aub]

Lovely work Wendy. I hope you have lots of fun with it.

Cheers

Aub, G4KQL

[Radio Wrangler]

Originally Posted by G6Tanuki

A bit of software can then do things like automatic acceleration (as in mouse-pointers).

You might not enjoy it.

I find that accelerating controls give a non intuitive feel to a control. You expect that if you turn a knob, change your mind, and rotate it back, you should be where you started. But your speed profile won't be the same in the two directions and you'll have travelled different amounts at different acceleration factors.

I once bought a bag of RAY-3 mixers from John Birkett who was selling them for less than his price for SBL1/MD108 because everyone wanted SBL1 or MD108 and weren't aware what RAY-3s were. I did explain what they were and what they were worth, but he said he was still making a profit.

David

[Wendymott]

Thanks for your nice comments peeps.... but I bet you may not have noticed the schematic error of the Detector / BFO section.. I didnt show the supply switching to the BFO correctly... smacked legs and no supper LOL