Hi Michael, depends on the rig you are working with.
If the power supply is sufficiently low-rated, means that as the rig draws
more current, the louder the hum from the laminations. Thus, out of tune,
the more hum you get, the rig beginns dancing around on the table, screws in
the case begin to resonate, and smoke starts curling out of the system,
until you correct the situation.
When the current is at a reasonable level, the hum is generally almost gone.
But, it depends on the rig. Those old Globechiefs, and some of the others
used as little as they could get away with, and so, just a bit out of
resonence made a loud hum.
This was one of these unforeseeable accidents that could never have been
predicted, or even implemented by an engineer.
The noise bridge you have could be used as a tuner-tuner.
But, you'd need to preset the thing to a known resonance *I.E. a known
resonent antenna, or 50 ohms.
Then, don't touch the controls, use an atu, and tune for minimal noise.
If you start trying to use the bridge to determine where the antenna is
resonent, and moving the controls, its value will be lost. Unless you can be
sure where the true setting is for the correct resonence.
Essentially, what I am trying to do is show you how to build a tuner-tuner.
I wish I had thought of this, when I had my original Palomar noise bridge
many years ago. I could never get any real use out of it, because of the
fact that I never set it to a known value, and worked from there.
That would have been a lot smarter. But, Palomar jumped ahead of my
thinking, and created the tuner-tuner.
Now, the best situation would be a noise bridge with detents at a tested 50
ohms, then you could preset the bridge by feeling the detent in the control,
and working from there. The best of both worlds. Even a bit of nail pollish
could help, but I tried this, and didn't like the inaccuracy of it.
----- Original Message -----
From: "Michael Ryan" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, November 21, 2002 7:17 PM
Subject: tuning up an antenna


> Can   a noise bridge which was once used on an old heath kit
> HW-12 be used in conjunction with an antenna tuner for reading SWR?
> I will try and describe it.
> It has a switch on the lower front which slides back and forth to the left
> or right for turning on or off and a flat roguery knob next to the
> switch.  The connectors for antenna and so on are on the top.  It also has
> a round raised speaker.
> I would also like to know what to look for, when it comes to the power
> supply hum, when the rig is loaded up for maximum out put.
>
> Thanks all:
> Michael