[ARC5] A simple receiver improvement

[Kenneth G. Gordon]

On 14 Jan 2014 at 12:15, Ian Wilson wrote:

> A couple of schematics - sorry, didn't have time to check for the R-26
> specifically - show values for C1 of 8.5pF and 11pF. At 3.5MHz, 11pF
> looks like 4.1k of reactance.

Now, this makes me wonder if one couldn't build a 4K:50 ohm balun fairly 
easily, and what improvement that would make.

What would this be? An 80:1 balun? Or a 40:1? I can't remember how that 
works.

It certainly shouldn't be all that difficult to make one for each range, since the 
receivers are relatively narrow banded, covering only one "band".

Perhaps the right kind of toroid and some few turns of small wire?

If I remember correctly, it would be something like 2 turns on the primary and 
40 turns on the secondary...maybe?

I guess I'll go dig out my documentation...

To get some sort of idea about this, I could connect the 300 ohm sides of 4 
of the baluns in series to the receiver input terminals, and use one of the 75 
ohm inputs to connect to my antenna to see if there was any improvement.

That would be an "interesting exercise" at least.

However, last night, even with the 300:75 ohm balun, in many cases (like for 
5.0 MHz WWV) I could not turn the RF gain down far enough to silence the 
receiver. Even with the RF gain as low as it would go, WWV was still 
copyable from the speaker.

Perhaps a 4K:50 ohm balun would be very serious "over-kill".

Ken W7EKB