I have several small measuring instruments in my shack, but I have
always been unable to find plans to build a DIP METER for use in
LF Freqs. I already have a LEADER DM that begins at 1.5 Mhz but I
would like to be able to measure resonant circuits at say 40 Khz
or 470 Khz. Is there a thecnical difficulty I should be aware of ?
Any help or reference appreciated.

Andrew.

Hi,

I have several small measuring instruments in my shack, but I have
always been unable to find plans to build a DIP METER for use in
LF Freqs. I already have a LEADER DM that begins at 1.5 Mhz but I
would like to be able to measure resonant circuits at say 40 Khz
or 470 Khz. Is there a thecnical difficulty I should be aware of ?
Any help or reference appreciated.

Millen used to make a set of LF coils that plugged into one of
their GDOs without any modifications to the unit. It seems then
that you simply need to make an appropriate coil (old wave-wound
IF transformer coils perhaps) and to draw a calibration graph for
it. I was thinking of doing just that but on the other hand,
should anyone have a set of LF coils for sale for the 90652 or any
information on them, I would be most interested.


Cheers - Joe (G3LLV)

No real technical difficulty. Simply use a suitable (large) inductance
and it will probably work.
However, there is a very real practical difficulty. The tuning capacitor
in a Dip meter designed for 1.5Mhz and up, will provide a very small
coverage at LF and the dip may be hard to identify. You will require a
lot of coils to get continuous coverage. This might be OK if you are
working at narrow range of spot frequencies and the circuits under test
are reasonably close to the spot frequency to begin with.

In message , Andreu
writes

I have several small measuring instruments in my shack, but I have
always been unable to find plans to build a DIP METER for use in
LF Freqs. I already have a LEADER DM that begins at 1.5 Mhz but I
would like to be able to measure resonant circuits at say 40 Khz
or 470 Khz. Is there a thecnical difficulty I should be aware of ?
Any help or reference appreciated.

Andrew.



--
Derek R. Smith.

In article , "Andreu"
wrote:

I have several small measuring instruments in my shack, but I have
always been unable to find plans to build a DIP METER for use in
LF Freqs. I already have a LEADER DM that begins at 1.5 Mhz but I
would like to be able to measure resonant circuits at say 40 Khz
or 470 Khz. Is there a thecnical difficulty I should be aware of ?
Any help or reference appreciated.

Andrew-

Do you have an audio oscillator that goes up to 470 KHz? That could be
hooked up to a resonant circuit through a resistor, and a high impedance
AC voltmeter connected to measure voltage across the circuit. You would
look for dips or peaks depending on whether it was series or parallel.

73, Fred, K4DII

On Thu, 19 Jan 2006 16:37:05 +0000, Derek R. Smith wrote:
No real technical difficulty. Simply use a suitable (large) inductance
and it will probably work.
However, there is a very real practical difficulty. The tuning capacitor
in a Dip meter designed for 1.5Mhz and up, will provide a very small
coverage at LF and the dip may be hard to identify. You will require a
lot of coils to get continuous coverage. This might be OK if you are
working at narrow range of spot frequencies and the circuits under test
are reasonably close to the spot frequency to begin with.

In message , Andreu
writes

I have several small measuring instruments in my shack, but I have
always been unable to find plans to build a DIP METER for use in
LF Freqs. I already have a LEADER DM that begins at 1.5 Mhz but I
would like to be able to measure resonant circuits at say 40 Khz
or 470 Khz. Is there a thecnical difficulty I should be aware of ?
Any help or reference appreciated.

I'd think coupling to the DUT would be a problem. Physically small dip
coils would not couple easily to large tuned components, and versy vicey.
Of course, if you build to just _your_ custom requirements....

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
Pueblo, Colorado | @ | Jonesy | OS/2 __
38.24N 104.55W | config.com | DM78rf | SK

Andreu wrote:
I have several small measuring instruments in my shack, but I have
always been unable to find plans to build a DIP METER for use in
LF Freqs. I already have a LEADER DM that begins at 1.5 Mhz but I
would like to be able to measure resonant circuits at say 40 Khz
or 470 Khz. Is there a thecnical difficulty I should be aware of ?
Any help or reference appreciated.

Andrew.


I've built a few dip meters, most with the circuit using a dual
gang variable cap. The Millen dip meter is the same circuit.
The variable caps are usually around 100 to 200pf per section
giving a total tuning range of 50 to 100pf across the coil.

This works well up to about 1mhz tops, below that feedback
drops off as the reactance of the variable cap is too low.
IF the tuned circuit is ac coupled to the tube (plate blocking
cap in place) you can ground the center of the coil to provide
additional feedback. The Millen coils DO have a third pin
for this purpose. (My dipmeters used the 'Heath' method of
an RCA plug for the coil connecter so they lacked the means
of providing the ground).

My coils were wound on 3/8" dia plastic tubing (like Heath)
and I could get down to about 2mhz with a single layer coil
wound with #36 wire. To get down to where you want to go
will require a larger diameter coil form, and a "Pi" winding
(like on rf chokes). Litz wire would also be a good idea.
The tuning range even with a 200pf / section variable cap
will be less than a 2/1 frequency range due to distributed
capacitance across the coil. Coupling should not be a problem,
if you can get the dip coil close enough to the inductor in the
circuit under question. This is where a small dip coil has an
advantage....Try getting those Millen coils close enough to
a modern solid state circuit!

Surf my web site (www.qsl.net/wa2mze) to see my mini gdo built
with a 6cw4 tube.