The death of the GDO
 

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?

The death of the GDO
 

On Sun, 24 Jan 2016 12:01:42 -0000, "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?


Yes..when one can get a Sark100 for less than £60

http://www.ebay.co.uk/itm/Mini-ANT-S...AOSwPhdVHCW ~

The death of the GDO
 

Rambo wrote:
On Sun, 24 Jan 2016 12:01:42 -0000, "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?


Yes..when one can get a Sark100 for less than £60

http://www.ebay.co.uk/itm/Mini-ANT-S...AOSwPhdVHCW ~

That is a good price. Is this bit of kit worth it though, Rich, or is it
knock off tat? You used one of these before?

--
STC // M0TEY // twitter.com/ukradioamateur

The death of the GDO
 

On 24/01/16 12:47, Stephen Thomas Cole wrote:
Rambo wrote:


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?


Yes..when one can get a Sark100 for less than £60

http://www.ebay.co.uk/itm/Mini-ANT-S...AOSwPhdVHCW ~

That is a good price. Is this bit of kit worth it though, Rich, or is it
knock off tat? You used one of these before?


Looking at the block diagram, in theory it should be a capable bit of
kit- it has all the right HW to do the job. Assuming they've married
this with appropriate SW, it should be fine. At worst you may need to do
some calibration, which shouldn't be too difficult.

As a general rule, the 'knock offs' (we used to say Chinese copies but
they are nearly all made in China these days ;-) ), tend to fall down
when it comes to the user interface and sometimes build quality.

It has a USB port which seems to be limited to configuration and SW
updates (assuming these are forthcoming). It is a pity it isn't also
able to support graph plotting etc.

Also, that model only goes to 60MHz, of course there may be one which
covers 2m and 70cm.


I have a miniPro VNA which plugs into a PC (MacOS, Linux and Windows)
via USB or Bluetooth. I'm not sure if the model I have is still made but
others are. It lacks a local display and is in a different price bracket
(I can't recall the price but in the £100s), however, it is plots a
range of graphs etc. and can be used in a variety of other ways.
The newer models are even more capable and more cost effective.

A GDO is worth having, especially if you've never used one. You can
knock one up quick easily. While it is more limited, you can do a lot
with it.

There is no shortage of designs for GDOs, the old valve based ones take
some beating in some ways. Of the solid state ones, the G3WPO design is
one of the best in my view.

I no longer use, or even have, a GDO, but I've had a number over the
years. Not because they aren't useful, I can simply do everything with
other kit.

The death of the GDO
 

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

The death of the GDO
 

Brian Reay wrote:
On 24/01/16 12:47, Stephen Thomas Cole wrote:
Rambo wrote:


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?


Yes..when one can get a Sark100 for less than £60

http://www.ebay.co.uk/itm/Mini-ANT-S...AOSwPhdVHCW ~

That is a good price. Is this bit of kit worth it though, Rich, or is it
knock off tat? You used one of these before?


Looking at the block diagram, in theory it should be a capable bit of
kit- it has all the right HW to do the job. Assuming they've married this
with appropriate SW, it should be fine. At worst you may need to do some
calibration, which shouldn't be too difficult.

As a general rule, the 'knock offs' (we used to say Chinese copies but
they are nearly all made in China these days ;-) ), tend to fall down
when it comes to the user interface and sometimes build quality.

It has a USB port which seems to be limited to configuration and SW
updates (assuming these are forthcoming). It is a pity it isn't also able
to support graph plotting etc.

Also, that model only goes to 60MHz, of course there may be one which covers 2m and 70cm.


Cheers. It has the "Make Offer" option so I've put in a low-ball offer,
let's see if they bite!


--
STC // M0TEY // twitter.com/ukradioamateur