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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 3rd Mar 2021, 12:24 pm   #1
Malcolm T
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Default Grid dipper

I have just recently pulled a piece of old test kit from my collection a
Tradiper Model TE-15 Dip oscillator . It still works and seems to be fairly accurate after all these years . However i never really got to use it fully to get to know its capabilities or foible,s.
Just how accurate is one of these GDO,s then ? and what are its limitations.
If i set my receiver up on CW frequency should the GDO oscillator come up right bang on a frequency or within a few 100 Hz . There is a small VR inside on the PCB that is connected to the base of a tranny that sits across one of the plug in coil sockets that is connected to the coil socket. I,m not quite sure if this is a zero setting for the accuracy or what , i assume since the 70s things might have changed with some components ?.
Just how is it possible to test and set up the accuracy of a GDO.
I want to check the inductance of home wound air coils for my aerial / antenna and thought this may be a good way of doing it , ie with a GDO.
Any assistance appreciated.
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Old 3rd Mar 2021, 12:49 pm   #2
Terry_VK5TM
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Default Re: Grid dipper

If you are talking accuracy of the dial re frequency markings, they are so-so.

Listening to the dipper signal on a known calibrated receiver dial was a common way of getting a somewhat more accurate frequency reading.

I posted a manual and schematic for the TE-15 in a thread on here some time ago.

Found it:
https://www.vintage-radio.net/forum/...08&postcount=5
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Old 3rd Mar 2021, 12:50 pm   #3
Julesomega
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Default Re: Grid dipper

You should find it is withing a few hundred kHz on the HF bands. You can judge the dial resolution from the pictures on Radiomuseum

The frequency is pulled by anything conductive near the coil, in particular by any other tuned circuits.

edit: crossed with Terry's
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Old 3rd Mar 2021, 2:05 pm   #4
Junk Box Nick
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Default Re: Grid dipper

I have a TE-15. It hasn't been used in years and dusted it off recently as I am considering making an HF aerial cut to resonance.

I checked it against my FRG-7 and noticed that the sensitivity control pulls the oscillator frequency about. Zero beating on the FRG-7 and not touching the sensitivity I used the TE-15 to check how far off the tuning was on another set. I got my answer – way off!

The dial on the TE-15 seems generally ‘within the region’ which is probably all that can be expected.

It seems more accurate, and far less cumbersome, than my old Heathkit GD-1U that years ago got nicked from my shed, along with some other obscure radio items, back when I lived with my parents. Someone knew what they were looking for...
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Old 3rd Mar 2021, 2:36 pm   #5
G6Tanuki
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Default Re: Grid dipper

I wouldn't expect you to be able to reliably set or read a typical GDO dial to better than 1% - I've only ever used a 'dipper' for things like making sure coils in things like frequency-multiplier stages or RF/IF tuned-circuits are tuned to the right harmonic, or that a tunable LO is set on the 'right' side of the signal-frequency circuits.

Expect errors when the tuned-circuit 'pulls' the GDO - I came badly unstuck with this once when trying to tune up a 3.6MHz mobile antenna using a GDO and had to bodge the loading-coil to replace the 'excess' turns the GDO suggested I removed.

Check your GDO with a frequency-meter while it's actually in-use!
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Old 3rd Mar 2021, 6:08 pm   #6
Bazz4CQJ
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Default Re: Grid dipper

I have a TE-15 in my motley collection. It was probably one of the cheaper GDO's that appeared on the market, but certainly up to 30MHz, mine works quite well and the calibration is not bad. As commented above, the sensitivity control pulls the frequency, so always work with the sensitivity adjusted to the level where the meter is on the "SET" mark, and that will minimise that problem.
I wouldn't expect the accuracy to be better that some kHz; even if it's spot on at some point on the scale, it may well deviate elsewhere. You could buy a cheap digital frequency counter to operate alongside it.

B
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Old 4th Mar 2021, 10:11 am   #7
Malcolm T
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Default Re: Grid dipper

Well , thanks for the reply's . I wasn,t expecting too much from it certainly not
atomic clock standard LOL.
But it does function and its close but not any way spot on. The print on the dial and the cross hair line has got to be a few Khz wide any way but for generally getting something close i suppose its ok.
No doubt another piece of test kit from yesteryear. At least its a useful signal source .

I have just tried it out on a 40mm diameter air coil ( white pvc pipe former ) i wound for a mobile vertical many years ago on a lathe , placed a 10pf across it and the dip occurs at about 6500Khz so either my maths was out some years ago or its the dipper , hmmm interesting.
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Old 4th Mar 2021, 10:58 am   #8
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Default Re: Grid dipper

10pF sounds very small for 6500Khz.
My Te15 is reasonable to find the area of interest by the dial, then listening on an rx if accuracy is required.
Rob
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Old 4th Mar 2021, 12:10 pm   #9
Malcolm T
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Default Re: Grid dipper

It was the closest cap to hand , i just used it for that reason.
The initial goal was to determine the inductance of the air coil without an online calculator.
But i,ve since been onto a calculator and it comes out to 41 microhenries.
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