Millen 90651 grid dipper calibration
 

Is there anyone left who is familiar with calibration of a Millen 90651 grid
dip meter? I recently acquired a nice one, but the dial scale is a bit
compressed and I need to discuss with someone the possibility of adjusting
C3 and C4.

--
73, Floyd - K8AC

Floyd Sense wrote:
Is there anyone left who is familiar with calibration of a Millen
90651 grid
dip meter? I recently acquired a nice one, but the dial scale is a
bit
compressed and I need to discuss with someone the possibility of
adjusting
C3 and C4.

--
73, Floyd - K8AC

The Millen grid dipper was never a calibrated ,or accurate device, to
get an accurate reading ,tune a receiver to the desired frequency and
set the dipper to the receiver ,You will be anble to get "in the ball
park" Good Luck W4PQW

On 17 Jan 2005 09:47:43 -0800, wrote:

The Millen grid dipper was never a calibrated ,or accurate device, to
get an accurate reading ,tune a receiver to the desired frequency and
set the dipper to the receiver ,You will be anble to get "in the ball
park"

If you need accuracy an alternative is to install a small cap (~10 pf
or less) connected to the plate of the tube and connected through,
say, a piece of RG-174 to a BNC jack. That will let you connect a freq
counter for accurate determination of the 90651 frequency.

Dale H. Cook, Chief Engineer, WWWR Roanoke VA, WCQV Moneta VA, WKBA
WZZI Vinton VA, WKPA WLNI WZZU Lynchburg VA, WMNA/WMNA-FM Gretna VA,
WOWZ Appomattox VA
http://members.cox.net/dalehcook/starcity.shtml

Hi Dale. Great idea. I was thinking that I no longer have a portable freq
counter - only a lab model - then remembered that my MFJ-259B has a freq
counter mode. I just set up the Millen next to the MFJ with a 1' whip and
was able to read the Millen frequency all the way up to 300 MHz just by
getting within a couple of inches of the Millen coil. Your idea would give
me a bit more flexibility and there's already a small hole in the side of
the Millen cabinet (factory hole) that could be used for the cable exit.

There's really no reason why the Millen analog scale couldn't be made to
read out at 1% or better accuracy. I'm going to remove the dial scale and
scan it and then relocate the index marks to be accurate. The corrected
scale will then be transferred to a new dial sheet and installed in place of
the old one. Sounds time consuming, but bound to be faster than screwing
around with those immovable trimmer caps and more accurate in the end.

Thanks for the idea.

73, Floyd - K8AC


"Dale H. Cook" wrote in message
...
On 17 Jan 2005 09:47:43 -0800, wrote:

The Millen grid dipper was never a calibrated ,or accurate device, to
get an accurate reading ,tune a receiver to the desired frequency and
set the dipper to the receiver ,You will be anble to get "in the ball
park"

If you need accuracy an alternative is to install a small cap (~10 pf
or less) connected to the plate of the tube and connected through,
say, a piece of RG-174 to a BNC jack. That will let you connect a freq
counter for accurate determination of the 90651 frequency.

Dale H. Cook, Chief Engineer, WWWR Roanoke VA, WCQV Moneta VA, WKBA
WZZI Vinton VA, WKPA WLNI WZZU Lynchburg VA, WMNA/WMNA-FM Gretna VA,
WOWZ Appomattox VA
http://members.cox.net/dalehcook/starcity.shtml

Hello Floyd:

Years ago, I decided to convert one of my Millen tube jobs to a solid state
one, using the article in QST. It was an exercise more to see if I could do
it than any other reason.

When I got done, the 2 highest bands were off calibration. Sounds just
about like yours. After looking at the options, I decided to simply make
new scales for those bands. I did it by hand and the result looks quite
good, although the paper is whiter than the original background.

This is what ham radio is all about. Now, I suppose I will get death
threats for converting a perfectly good Millen dip meter to solid state.
The tube version is more sensitive, but I do not need an extension cord for
the solid state version.

73, Colin K7FM


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"COLIN LAMB" wrote in message
k.net...
Hello Floyd:

Years ago, I decided to convert one of my Millen tube jobs to a solid
state
one, using the article in QST. It was an exercise more to see if I could
do
it than any other reason.

When I got done, the 2 highest bands were off calibration. Sounds just
about like yours. After looking at the options, I decided to simply make
new scales for those bands. I did it by hand and the result looks quite
good, although the paper is whiter than the original background.

This is what ham radio is all about. Now, I suppose I will get death
threats for converting a perfectly good Millen dip meter to solid state.

Personally, I think the 90651 in its original condition is one of the least
practical grid dip meters around. It's big, heavy, and you need two hands to
use it. On top of that, it is not that sensitive, and the sensitivity is not
adjustable! If you want a real instrument, get a Boonton/Measurements Model
59.

Unless yours serves as a shelf queen, I think any modification is an
improvement! Go for it!

I don't recall ever seeing that QST article - perhaps you could tell me when
that was. Creating a new scale occurred to me as well and that may be what
I end up doing. I can remove the current scale, scan it into the PC, and
relocate the index marks with a graphics program. Then reprint it on film
or whatever and no one would know the difference. On my highest coil range
(up to 300 MHz,) which I would likely never use, the scale is on the button
over most of the range, with readout that's accurate at 1% at 300 MHz.

73, K8AC

"COLIN LAMB" wrote in message
k.net...
Hello Floyd:

Years ago, I decided to convert one of my Millen tube jobs to a solid
state
one, using the article in QST. It was an exercise more to see if I could
do
it than any other reason.

When I got done, the 2 highest bands were off calibration. Sounds just
about like yours. After looking at the options, I decided to simply make
new scales for those bands. I did it by hand and the result looks quite
good, although the paper is whiter than the original background.

This is what ham radio is all about. Now, I suppose I will get death
threats for converting a perfectly good Millen dip meter to solid state.
The tube version is more sensitive, but I do not need an extension cord
for
the solid state version.

73, Colin K7FM

On Tue, 18 Jan 2005 06:08:14 GMT, "COLIN LAMB"
wrote:

Years ago, I decided to convert one of my Millen tube jobs to a solid state
one

When I got done, the 2 highest bands were off calibration.

That's because the inter-electrode capacitance of the tube is part of
the tuned circuit.

Dale H. Cook, Chief Engineer, WWWR Roanoke VA, WCQV Moneta VA, WKBA
WZZI Vinton VA, WKPA WLNI WZZU Lynchburg VA, WMNA/WMNA-FM Gretna VA,
WOWZ Appomattox VA
http://members.cox.net/dalehcook/starcity.shtml

"If you want a real instrument, get a Boonton/Measurements Model 59."

Boy, I will second that. I have a number of grid dip meters. The 59 is my
favorite and blows all the others away. It is as close to perfection as
anything should be.

Colin K7FM


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COLIN LAMB wrote:
"If you want a real instrument, get a Boonton/Measurements Model 59."

Boy, I will second that. I have a number of grid dip meters. The 59 is my
favorite and blows all the others away. It is as close to perfection as
anything should be.

Colin K7FM

The Measurements 59 is a great little GDO. Two things you must be
aware of, though: First is the coil sets are all slightly different
in terms of their stray capacitance and inductance. As a result each
set is serialized to the 59 frame it belongs with. The second is the
frequency tics were hand penned onto the dial during calibration.
Don't try and clean the dial!

-Chuck Harris

Dale H. Cook ) writes:
On Tue, 18 Jan 2005 06:08:14 GMT, "COLIN LAMB"
wrote:

Years ago, I decided to convert one of my Millen tube jobs to a solid state
one

When I got done, the 2 highest bands were off calibration.

That's because the inter-electrode capacitance of the tube is part of
the tuned circuit.

I don't know if the poster was referring to it, but QST ran an article
in a December issue, I think 1972 but it might have been 1971, by someone
from Millen about their work on making a solid state version.

They used the same coil set and tuning capacitor, though I don't recall
if they changed the dial.

It was not a conversion article, not a construction article, but about
what they needed to do in order for the solid state version to put out
a flat output, with few false dips. It was interesting to read, at the
time.

Michael VE2BVW

"I don't know if the poster was referring to it, but QST ran an article in a
December issue, I think 1972 but it might have been 1971, by someone from
Millen about their work on making a solid state version."

You get a gold star on the memory test. It was December of 1972. I think
it was titled "Anatomy of a Grid Dip Meter", and it was written by the chief
engineer at Millen, who had led the conversion team. It is a worthwhile
read for anyone who thinks of converting an rf device to solid state. In
particular, the simple rf choke became a substantial barrier. The end
result was multiple rf chokes and ferrite beades placed in just the right
order to work at all frequencies. I recall Millen worked for days on the
"simple" task of creating something that would work as an rf choke on all
frequencies.

Colin K7FM



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Is there anyone left who is familiar with calibration of a Millen 90651 grid
dip meter? ....

The Millen grid dipper was never a calibrated ,or accurate device, to
get an accurate reading ,tune a receiver to the desired frequency and
set the dipper to the receiver ,You will be anble to get "in the ball
park" Good Luck W4PQW

Hmmmn. Never calibrated?

I have a chart from "James Millen Mfg. Co., Inc" dated 1-31-50 and
titled "Calibration of low frequency inductors for James Millen
#90651 or #90661 Grid Dip Meter".

--Myron, W0PBV.
--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

The Millen grid dipper was never a calibrated ,or accurate device, to
get an accurate reading ,tune a receiver to the desired frequency and
set the dipper to the receiver ,You will be anble to get "in the ball
park" Good Luck W4PQW

Hmmmn. Never calibrated?

I bought my 90651 new in 1955. It was
considered the best GDO *because* of
its good calibration. The accuracy was
very good for a time when frequency
counters were laboratory curiosities.

73, John - K6QQ