[Hammarlund] National NC-173

[Bob Camp]

Hi,

Back in the good old days three wire plugs were not a common thing. The 
world was wired with two wire sockets. Since there was no easy way to 
check the polarity you had about a 50/50 chance of getting the neutral 
on one side of the plug.

With a long wire antenna a ground is a nice thing to have at the end of 
the antenna. The bypass caps are a fairly simple way to ground the 
chassis to the power line neutral line. The assumption was that it was 
a better ground than no ground at all in this case.

The second thing they served to do was to try to cut down line induced 
interference when the chassis was properly grounded.

If you think about the two ideas above and get a bit confused then you 
caught the point. They basically contradict each other. In one case the 
AC line is so quiet that you can use it as a ground. In the other case 
it's so noisy you have to do something about it.

Another version of this that you can run into on guitar amps is a 
switch that lets you pick which side of the line the bypass cap hooks 
to. It's a cute idea, but i have never seen it on a radio.

	Enjoy!

		Bob Camp
		KB8TQ



On May 5, 2004, at 4:14 PM, Ross Stenberg wrote:

> Just curious George, but what purpose did the original bypass caps 
> serve?
>
> Thanks, and 73 Ross K9COX
>
>
>>> Dan,
>
> I'd suggest putting the 0.01 uF bypass caps back in, but use 1600 VDC 
> or 630
> VAC caps.  Not urgent, but they do serve  several purposes, and should 
> go
> back in when it can be done easily.  73.
>
> George
>
>
>
>
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