On Mon, 30 Nov 2015, Ian Field wrote:



"mike" wrote in message
...
On 11/29/2015 6:03 PM, Michael Black wrote:
On Mon, 30 Nov 2015, Cursitor Doom wrote:

On Sun, 29 Nov 2015 16:16:27 -0800, Jeff Liebermann wrote:

Sorry, no recommendations as all my stuff is ancient.

So's a lot of my stuff. But there's nothing wrong with old gear IMO it's
the quality of it and whether it's in calibration that counts. The only
issues with GDOs IME are that they're not too bad for the lower frequency
RF stuff, but hopeless for anything higher.


Huh? VHF and UHF is where they really worked well, because at lower
frequencies, a lot of the coils were shielded. There were GDOs that
worked well at VHF and UHF.

Michael

Best one I ever used was the tube version of the Millen.
I switched to the solid state version and regretted it.
Much less sensitive and more fiddly than the tube version.
Tunnel dipper was the worst for sensitivity.

A while back I acquired a small Tektronix component envelope containing very
tiny "top hat" style diodes that there's a faint possibility they could be
TDs.

Copying the Heathkit TD dipper had crossed my mind - now I probably won't.

It seemed like the Tunnel Diode got a lot of press in the sixties in the
hobby magazines, but much of it wsa novelty. I can't remember anything
where some other device couldn't be used. I suppose when the Heathkit GDO
came out, the Tunnel Diode might have had better bandwidth, though I don't
remember that GDO has having great VHF and UHF coverage. But while neat
things were shown, that tunnel diode FM broadcast receiver was more unique
becuase of the low IF and pulse counting detector than that it used a
tunnel diode as a mixer/oscillator down to that low IF.

There were uses for tunnel diodes that hobbyists generally didn't see, and
those at least took advantage of the device at the time, but the time
passed pretty fast before other things didn't do most of what a tunnel
diode could do.

So I think the Heathkit tunnel diode dipper was mostly for novelty sake.

Michael