On Sun, 24 Jan 2016, gareth wrote:

At one time, what set you out on the path of becoming a real radio amateur
was your construction of your Grid Dip Oscillator (or transistorised ones);
the most useful of tools for many applications in the shack.


Has tht worthy insrument noe died-the-death in the face of developments
such as N2PK and VNWA, and antennae analysers from the llikes of MFJ?

They took a hit to some extent when toroids came along, the
self-shielding of those meant a GDO didn't directly work with them.

I suspect the transistion to transistors didn't help either. Because
transistors are low impedance, you get less of a dip from a coil in
circuit with a transistor. But also, while a really simple tube circuit
worked as a GDO, it took time for good solid state GDOs to come along.
Everything was described, and some were better than others, but FET and
MOSFETs probably helped more. Early transistor ones had such a limited
frequency range, because the early transistors had limited frequency
range, and the value of a GDO is that it's wide range, so you can check
for undesired oscillations and such.

When everyone was building something, even just an antenna tuner, a GDO
was cheap and since it provided a number of pieces of test equipment (not
perfectly, but it was cheap), it made sense to have one around. WHen the
seventies rolled around, there were some interesting commercial GDOs, the
Heathkit with the MOSFET and the Millen solid state one come to mind, but
they were higher priced, so there was probably more of a pause before
someone bought one.

Then other things came along, and if someone was only using a GDO for
antennas, for instance, those other devices probably made more sense for
them. And as people were willing to spend more money, the GDO became less
special, and probably later iterations of hams knew less about them.

Of course, there was a wave in the seventies to improve GDOs. Adding a
socket to feed a frequency counter, which was one of those pieces of test
equipment that came along to spend money on instead of a GDO, that was a
good thing. At one point I thought about it, GDOs had been minimal
devices, what happened if you started being more careful, a three terminal
regulator, a buffer to feed that frequency counter (or put a counter right
in), a reduction drive on the frequency knob, things like that. WIth the
price of solid state devices, adding more transistors didn't add much to
the cost, or size of the cabinent.

And over here, the hobby electronic and ham magazines are mostly gone,
certainly the ones that covered construction projects. So in the old
days, a GDO (like a power supply or a "wireless microphone") were steady
features, a "new" one every few months, someone picking and choosing from
a previous article and making do with what they had, so there could be a
new construction article. With those magazines fading or gone, people
have less chance to be aquainted with GDOs, or to see new innovation.

Michael