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Author Topic: Coils for a PACO G-15  (Read 3679 times)
K5CQB
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« on: July 28, 2011, 07:39:36 PM »

I recently bought a PACO G-15 grid dip meter without coils.  I downloaded the manual but it really doesn't have any info on the coils.  The plug on the meter has three pins for the coils.  Does anyone here have a coil schematic or some advice on winding my own coils?  

The tuning capacitor is a dual gang and I do not know its value nor does the schematic show it.  On the manual schematic it shows one of the pins (one side of the coil) going to one of the capacitor gangs and the other pin (other end of the coil)  going to the other gang.  Looking under the hood I can see this and the third pin goes straight to ground.  The schematic doesn't show this.   

Thanks,
Jim
k5cqb
« Last Edit: July 28, 2011, 08:12:24 PM by K5CQB » Logged
W4OP
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« Reply #1 on: March 08, 2013, 01:07:03 PM »

Hi Jim,
I am in the same boat. Did you ever find coil details for the Paco?

Dale W4OP
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K5CQB
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« Reply #2 on: March 08, 2013, 01:57:55 PM »

Hi Dale,
Sorry but I have not found any schematic or plans.  I tried to make one up based upon a picture I found but it was so long ago that I can't remember if it worked or not.  After a while it was put on the back burner. 

Jim K5CQB
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WB6BYU
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« Reply #3 on: March 08, 2013, 03:25:28 PM »

You could wind a coil of some standard inductance (1 to 5uH, perhaps) and
measure the oscillation range with a frequency counter.  From that you can
calculate the capacitance variation and the required inductance for each
band.
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W4OP
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« Reply #4 on: March 08, 2013, 04:11:05 PM »

The manual and schematic are on the Bama site. It turns out that although the coil socket has three terminals, the ground is not used with the standard GDO coils. I made up a socket and wound a coil and my GDO works fine. I'll eventually work out the coils so each band  is calibrated.
Very nice sensitive unit.
The coil socket pins are 0.5" center-center and the pin diameter is 0.094". I made my test coil by turning down 3/4" phenolic rod but leaving the base at 0.75" and embedding brass pins into the base section.
GL,

Dale W4OP
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W9GB
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« Reply #5 on: March 08, 2013, 04:33:17 PM »

Quote from: W4OP
The coil socket pins are 0.5" center-center and the pin diameter is 0.094". I made my test coil by turning down 3/4" phenolic rod but leaving the base at 0.75" and embedding brass pins into the base section.
GL,
Dale -

Molex uses .093 crimp terminals (pins and sockets) for their popular nylon connectors,
 so that is a potential DIY source.
http://www.molex.com/molex/products/family?channel=products&chanName=family&key=standard_093

w9gb
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W4OP
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« Reply #6 on: March 08, 2013, 08:26:26 PM »

You and I think alike Greg- that is precisely what I used to initially test the meter for oscillation!
I folded the barbs back a bit to get the necessary insertion depth.
Tnx,

Dale W4OP
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VK2TIL
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« Reply #7 on: March 08, 2013, 09:09:50 PM »

I think the chart on p9 of the manual could be used to work-out the inductance of coils E, F & G; this might be a useful short-cut.

For example, 100pF in // with coil E resonates at 26 dial divisions; the frequency will be the frequency corresponding to coil D at 26 divisions.

The inductance of coil E can then be calculated.

A similar procedure would find the values of coils F & G.

Once you have the inductance of one or more coils, the value of the variable capacitor can be calculated from the dial markings; the inductance of the remaining coils can then be calculated.

I think this should work.

The pin plugs may be microphone - connector standard like this;

http://www.altronics.com.au/index.asp?area=item&id=P0949

(They have a "proper" designation number but I can't remember it at present  Sad  ).

I have converted female connectors of the kind shown in the link to male connectors with brass pins inserted into the female receptacles and held with epoxy; this was for a cable for a Boonton power meter which uses a two-pin connector of this kind but with reverse gender.
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K5CQB
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« Reply #8 on: March 09, 2013, 11:48:07 AM »

WOW!  This is great.  Dale thanks for the info on the coil ground, that was what stumped me in the beginning.  Also thanks for reviving this thread.  I will try and get back to the PACO and get it running.
Jim
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W4OP
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« Reply #9 on: March 09, 2013, 06:04:04 PM »

I just turned down a 3/4" phenolic rod on the lathe so that the base remained 0.75" but the coil winding section was 0.5".
I used 0.093" brass rod for pins. The overall look is very commercial- I can send pix to anyone interested.
The Paco is quite a good GDO- with sharp dips from a couple inches away from the L-C tank. Not as good as my my Measurements, but nothing is.
Anyway, in order for the coil to track the dial  properly, it is going to have to have the same form factor  and wire gauge as the originals. Likely due to  different turn-turn capacitance. My coil is very close at the 4MHz low end but off by a MHz at the 10MHz hi end. This really is not an issue as a counter loosely coupled to the GDO coil will read the exact frequency.

Dale W4OP
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W9GB
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« Reply #10 on: March 09, 2013, 07:08:57 PM »

Quote from: W4OP
You and I think alike Greg- that is precisely what I used to initially test the meter for oscillation!
I folded the barbs back a bit to get the necessary insertion depth.
I was reading some Herb Brier articles from 1950s CQ magazines this evening.

The .093" pin was supposed used for ICM FA-9 crystals (their magazine advertisement)
 to fit WW2 surplus FT-243 sockets -- so that is another potential source.

HC-4/U - Crystal same as FT-243, 2 pins, spaced 0.486" and .093" diameter.
HC-17/U - has same pin spacing and pin diameter as above.
http://www.af4k.com/crystal_holders.htm

w9gb
« Last Edit: March 09, 2013, 07:14:28 PM by W9GB » Logged
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