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 The 1946 TRF Radio Part 3, Construction and circuit tweaking.
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 Return to top of page · Post #: 1 · Written at 10:48:59 AM on 7 March 2017.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 917

Hullo all, here is the next installment of this project where I bolt all the parts together and then find out the design does not work very well. Who would have thought that could happen!

As usual with any project I then measure and test learning as I go and improve the sections that don't work well until they work as best they can.

This third part covers the assembly of the chassis to the point of working but not the cabinet.
The design of a cabinet is the next step both to hold the receiver and to enclose some speakers.
I'm thinking of an "art deco" style of cabinet probably as a column with the set at the top with some chrome and mirrors and the speakers underneath, not sure yet. I think its going to be pre-plastic looking so will probably be black gloss in colour.

Somewhere in all of this there has to be disc player for 78rpm mono and the new fangled micro groove discs at 33rpm.

The speaker enclosure will take some thought as it needs a frequency response to offset the short comings of the radio response.

All of that is up in the air but here is the solid stuff, the TRF tuner and ultra linear 10 watt amplifier.
I will send a PDF with the article to Brad as usual, hope you all enjoy the saga!

Cheers, Fred.

TRF HiFi Radio Part 3

 Return to top of page · Post #: 2 · Written at 10:27:48 PM on 8 March 2017.
Brad's avatar
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6533

Document uploaded.

A valve a day keeps the transistor away...

 Return to top of page · Post #: 3 · Written at 4:55:31 AM on 15 March 2017.
Wa2ise's avatar
 Location: Oradell, US
 Member since 2 April 2010
 Member #: 643
 Postcount: 772

When you're trying to build a lot of gain at one frequency, stray feedback will cause tons of problems. One benefit of a superhetrodyne radio is that you can have lots of gain in the IF strip and if some leaks back to the front end, it's the wrong frequency and would be ignored. (though you can get birdies at 910kHz and 1365kHz 2nd and 3rd harmonic of the IF freq). It's also easier to build an IF that operates on just one frequency (with some bandwidth) than one with variable frequency.

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