"Phil Hobbs" wrote in message
...
On 11/30/2015 08:05 PM, Jeff Liebermann wrote:
On Mon, 30 Nov 2015 19:05:02 -0500, Michael Black
wrote:

It seemed like the Tunnel Diode got a lot of press in the sixties
in the hobby magazines, but much of it wsa novelty.

For good reason. Tunnel diodes flew in most of the early satellites
up to about 1990 because it was the only reliable microwave device
available at the time.

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.

I believe you're referring to the HW-10 GDO:
http://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_H-HM/HM-10a/



http://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_H-HM/HM-10a/HM-10A.gif
No pulse counting detector but rather a simple half wave RF rectifier
followed by 3 stages of DC amplification. As I vaguely recall, I had
difficulties getting a clean dip because the tunnel diode was
probably oscillating on multiple frequencies at the same time.

I may have an HW-10 GDO somewhere in my junk pile. I dropped it from
about 60ft up during an antenna raising party. It landed in some
bushes and did not appear to be damaged, but failed to function
afterwards. I also have a few new TEK tunnel diodes.

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.

Tektronix also used tunnel diodes in their oscilloscope trigger
circuitry: http://w140.com/tekwiki/wiki/Tunnel_diodes I use one
testing scope rise time:
https://richardsears.wordpress.com/2013/04/27/tunnel-diode-pulser/
GE Tunnel Diode Manual (1961):
http://w140.com/Ge1961TunnelDiodeManual.pdf Today,
Aeroflex/Cobham/Metelics currently sell tunnel diode detectors and
use them in their instruments:
http://ams.aeroflex.com/metelics/micro-metelics-prods-TD-MTD.cfm
http://ams.aeroflex.com/metelics/micro-metelics-prods-TD-MBD.cfm
Sorry, but tunnel diodes are not quite dead and obsolete.

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

Nope. During the 1960's, the big draw for Heathkit was that kits
were much cheaper than labor intensive assembled products. Heathkit
had to do something to keep the price down on their products. Cheap
was the order of the day and tunnel diodes were CHEEEEEEP.




I've never used one, but I suspect that part of the reason that tunnel
diode dippers are inferior is that you can't run a high-Z tank without
tapping the TD way way down, so that you need an impractically large split
variable capacitor.

Nuvistors are really good for that, over a pretty wide frequency range.

There's a low voltage 8056 Nuvistor in my bits box waiting for a *VERY*
elusive round-tuit.