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 Return to top of page · Post #: 1 · Written at 10:02:49 PM on 11 July 2016.
Sue's avatar
 Sue
 Location: Daylesford, VIC
 Member since 13 January 2011
 Member #: 809
 Postcount: 311

This regenerative TRF project, published in the April 1970 issue of Electronics Australia, was my first successful home-made radio. In fact it was the only EA project radio I built that actually worked, even though it was roughly made and I didn't understand the need for an earthed metal front panel; I had to tune it with pair of long nosed pliers. Anyway, feeling nostagic, I bought a kit version of it around 1980, and it sat in bits in a box until this year. One of the reasons for the delay was tracking down all the old parts needed to make it look something like the radio in the magazine. The Aegis MV3/F knobs for example, which turned up in hard rubbish in Melbourne, a proper photo-printed dial, and those unreliable but distinctive "redcaps" typical of the era. Anyway, it's finished and it works. For anyone else who wants to try it, there's a couple of bloopers in the article: the RF board is missing an earth link, and you'll need to add a series 470pF capacitor to the 415pF variable and remove a few turns from the coils to get the tuning to match the dial. This is a fiddly task even though I'm not a "beginner" anymore!


 
 Return to top of page · Post #: 2 · Written at 10:22:43 PM on 11 July 2016.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5263

Photos?


 
 Return to top of page · Post #: 3 · Written at 6:18:46 PM on 13 July 2016.
Sue's avatar
 Sue
 Location: Daylesford, VIC
 Member since 13 January 2011
 Member #: 809
 Postcount: 311

Tomorrow hopefully. I'm just restuffing an old Eveready Nine Lives battery to run it from.


 
 Return to top of page · Post #: 4 · Written at 7:29:17 PM on 14 July 2016.
Sue's avatar
 Sue
 Location: Daylesford, VIC
 Member since 13 January 2011
 Member #: 809
 Postcount: 311

Here are some photos. I've tried to keep the radio close to the original design in the magazine, including the choice of components, but I've made a couple of changes for neatness and practicality. Rather than make a folded metal chassis, something I'm not set up to do, I built a strong wooden frame with two flat panels of thick aluminium bolted in place. I also made the speaker grille round rather than square, and used a toggle power switch for a more visually pleasing control arrangement.

The slow motion dial and the reaction capacitor are made by JB, the tuning capacitor is a Roblan 10-415pF as specified, and the six-pin plug in coil formers are Sato. You wind a set of four coils to cover 550KHz to 30MHz. (Sato Parts are still around, but I don't know about JB or Roblan.) The rest of the electronic parts are also 1970s vintage. As I mentioned, to match the dial supplied by E.A. you need to add 470pF in series with the 415pF tuning capacitor. And there you are. It makes some hair-raising farts and squawks when you're tuning it, but that's all part of the fun.

RBM Long Sydney
RBM Long Sydney
RBM Long Sydney
RBM Long Sydney


 
 Return to top of page · Post #: 5 · Written at 4:10:51 PM on 17 July 2016.
Sue's avatar
 Sue
 Location: Daylesford, VIC
 Member since 13 January 2011
 Member #: 809
 Postcount: 311

Roblan, the Sydney company that made the RMG series of tuning capacitors, is still around, but these days they produce mostly moulded plastic items and metal tools. JB (Johnson Brothers) UK may still be making parts for radio constructors, but I haven't been able to confirm this. Another question is, did Jabel merely import JB radio components, or did they make their own copies of JB items? The slow motion dials from both companies are very similar.


 
 Return to top of page · Post #: 6 · Written at 4:28:47 PM on 17 July 2016.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1074

Impressive.

How is it for sensitivity and selectivity?

How do you select band A,B,C,D ? Is it done by plugging in another coil unit?


 
 Return to top of page · Post #: 7 · Written at 4:43:33 PM on 17 July 2016.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5263

Now that I see the photos, I remember that one. I was considering building it myself back in the day.

Interesting to see the period components. Nice job!


 
 Return to top of page · Post #: 8 · Written at 11:53:15 AM on 18 July 2016.
Sue's avatar
 Sue
 Location: Daylesford, VIC
 Member since 13 January 2011
 Member #: 809
 Postcount: 311

Selectivity I'd rate as good enough for listening to those shortwave broadcasts that are actually aimed at Australia, but it isn't very sensitive, so you need a long aerial and a proper earth. The bands are selected by plugging in one of the four coils. At the moment I've only finished the "B" coil which covers 6 - 15MHz. The 15 - 30MHz "A" coil was troublesome; I've had to halve the number of tuning turns and add a 22pF inside the former to get it to match the dial scale, and now I've got to rewind the reaction turns. Perhaps the blokes at E.A. slapped the dial from another set on to this without bothering to check if it matched? There's often something awry with their radio projects, but nowadays I look at them and think, "This would be fun to build, a bit of a challenge, what would I have to change to get it to work properly?" Like the 1970 EA160 Receiver, which had double conversion, but awful uncalibrated manual RF tuning that couldn't distinguish between the correct frequency and and an image!


 
 Return to top of page · Post #: 9 · Written at 11:57:32 AM on 18 July 2016.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1074

Yes, the projects presented in EA looked appealing, but it was always a good idea to wait a few months for the inevitable corrections in the back pages. Most of their projects suffered from mistakes of one kind or another.


 
 Return to top of page · Post #: 10 · Written at 11:15:19 AM on 7 August 2016.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 574

Hi Sue, what a good piece of work! I never care much about what type of recreation I am looking at whether it be a car or a boat or radio or little or big. It is the amount of care put into it that counts. That set is so good looking with each part on top looking so important and with a job to do.
I think its not so crucial to be exactly like the original but look "right" whether it be a humble 1 fet or a 8 valve radio.
Your little set is so good it deserves a bit of criticism about something that puts the icing on the cake and so simple to do. I had this drummed into me as a apprentice building electro mechanical control equipment; LINE UP THE SLOTS IN THE SCREW HEADS!
I used to sweat on every screw and juggle nuts back and forth to get the magic slots lined up and on a front panel with lots of screws it makes a real difference. If I can do it I still do it.
We were also taught to lace all our wires together in a loom and/or put right angle corners in change of direction and some of my control panels over the years were a picture to behold. Did they work any better? NO. But that was back when pride was taken in work just a tad before mass production and the stop watch took over!
The next time you might also experiment with wire brushing the alluminium sheet to mask over the store bought scratches and provide a more uniform surface. I used to brush all my guitar amp front panels and apply decals, then spray on a coat of clear laquer .
Again, a lovely little recreation and far better than I would do.
Cheers, Fred.


 
 Return to top of page · Post #: 11 · Written at 10:28:59 AM on 21 August 2016.
Sue's avatar
 Sue
 Location: Daylesford, VIC
 Member since 13 January 2011
 Member #: 809
 Postcount: 311

Thanks for the comments, Fred. To tell you the truth, I used to line up screw slots when I put something back together, but decided in the end that it didn't look "natural"! I'd considered brushing the front panel, but thought it wouldn't look right unless the brushing was completely parallel. Is there a way to get that with hand brushing?


 
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