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Author Topic: Anyone like the "DipIt" dip meter from QRP Project?  (Read 21846 times)
ND9B
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Posts: 49




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« on: August 24, 2013, 06:59:11 PM »

This is supposed to be a modern replacement for the old Grid-Dip meter. Is it worthy of a place in the ham shack?

(BTW, It's a kit. I like kits.)

Bobby Dipole ND9B
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KA4POL
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Posts: 1901




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« Reply #1 on: August 24, 2013, 09:59:45 PM »

Be honest, you are just waiting for someone to say: Yes.
It looks nice, but honestly I prefer my VNWA3 networkanalyzer which cost about 400 bucks more.
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VU2NAN
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Posts: 237




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« Reply #2 on: August 24, 2013, 10:11:29 PM »

For a homebrewer there's more fun to be had homebrewing a one- or two- transistor dipmeter!

73,

Nandu.
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KB1WSY
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Posts: 631




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« Reply #3 on: August 25, 2013, 06:34:19 AM »

The description of the circuit is here: http://www.qrpproject.de/UK/dipit.htm.

I have never heard of the technology used in this design, but I don't know much! It seems that the dipper induces a 400 Hz audio modulation tone in the RF tuned circuit that's being tested, and the dipper then detects this tone to get a sharp match on the center frequency. It is claimed that this gives a sharper (thus more accurate) dip than the traditional RF-absorption method. I would be curious to hear whether anyone has had experience of this system. I've always thought of GDOs as fairly approximate devices.

I've read a lot of negative comments about some of the early solid-state dippers such as the Heath "tunnel" model. I've also noticed that some of the modern dippers on the market nowadays are relatively expensive: even the MJF "economical model" is $149. Why these high prices? It's one of the few pieces of equipment that has become much more expensive in real terms, over the years.

Bobby doesn't say whether he already has an old-fashioned tube dipper. Those are a lot of fun and very affordable given the large number of them still around. I bought a beat-up Eico 710 and restored it to new condition, which is almost as much fun as building a kit. It works great and is surprisingly accurate.

73 de Martin, KB1WSY
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G3RZP
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Posts: 4358




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« Reply #4 on: August 25, 2013, 09:20:59 AM »

In about 58 years of playing with radios, I've never used a GDO, and never felt I needed one. I did have a play with a Heathkit Tunnel dipper at work, and found it practically useless. They can useful for tuning traps for antennas, though. However, the only time I made any traps, they were for changing a Mosley beam to cover 12 and 17 rather than 10 and 15, and the traps  being in metal tubes needed a different approach.
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ND9B
Member

Posts: 49




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« Reply #5 on: August 25, 2013, 10:32:59 AM »

The description of the circuit is here: http://www.qrpproject.de/UK/dipit.htm.

I have never heard of the technology used in this design, but I don't know much! It seems that the dipper induces a 400 Hz audio modulation tone in the RF tuned circuit that's being tested, and the dipper then detects this tone to get a sharp match on the center frequency. It is claimed that this gives a sharper (thus more accurate) dip than the traditional RF-absorption method. I would be curious to hear whether anyone has had experience of this system. I've always thought of GDOs as fairly approximate devices.

I've read a lot of negative comments about some of the early solid-state dippers such as the Heath "tunnel" model. I've also noticed that some of the modern dippers on the market nowadays are relatively expensive: even the MJF "economical model" is $149. Why these high prices? It's one of the few pieces of equipment that has become much more expensive in real terms, over the years.

Bobby doesn't say whether he already has an old-fashioned tube dipper. Those are a lot of fun and very affordable given the large number of them still around. I bought a beat-up Eico 710 and restored it to new condition, which is almost as much fun as building a kit. It works great and is surprisingly accurate.

73 de Martin, KB1WSY

I also have an Eico 710, and had a Knight Kit model years ago. I don't know about the solid-state dippers, but I found my tube types devilishly hard to dip. Even coupling as close as possible, I often wondered if I was seeing a dip or just imagining a dip! The DipIt claims to be much more sensitive with very little coupling required. As a plus, there is no sensitivity adjustment and it has a digital frequency display. Anyway, I just ordered one. I'll report back once I've tried it.

Bobby Dipole ND9B
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KD0REQ
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Posts: 848




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« Reply #6 on: August 25, 2013, 12:07:14 PM »

back in the day, I haywired a dipper that was useful for eating batteries.  bzzzzt!

when I built my trap dipole, I had to break down and got an old Lafayette 6CW4 job.  like tuning an old transmitter, there are multiple dips, because there are multiple harmonics.  but if you get a deep dip, you have probably found the fundamental.  all the secondaries tend to be shallow and not broad.

as if you can tell with the iffy tuning.  I suspect the old boasted-of dippers like the Millen have some gear reduction that counts for something in trying to hit a frequency instead of sail past it like dusting the cop car in the weeds on a deserted highway.
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G3RZP
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Posts: 4358




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« Reply #7 on: August 25, 2013, 02:00:02 PM »

I haven't done the sums as to how much AM would be impressed on a signal. Suppose a 10 MHz signal modulated +/- 0.2 or +/-20kHz with a circuit with a Q of 20 and a 3dB bandwidth of 500kHz? I haven't bothered to do the sums, but what difference in amplitude would result? It suggest that a low Q circuit would not  respond well - although the same applies to some extent to a usual GDO.
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VA2PBJ
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Posts: 156




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« Reply #8 on: August 26, 2013, 05:33:46 PM »

Has anyone ever tried to convert a mfj-207 into a dip meter? It does have all the similar functions.
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7 3 Peter VA2PBJ
KH2G
Member

Posts: 236




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« Reply #9 on: August 30, 2013, 08:11:05 PM »

I have used a variety of dippers for many projects and have heard many complaints by users. Trick is to couple as loosely as possible and still get a dip. Too tight and now or very sloppy dip and too loose, no dip. You must also be cognizant of surrounding objects that may affect the circuit under test.
Regards,
Dick KH2G
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K8AXW
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Posts: 3636




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« Reply #10 on: August 31, 2013, 12:10:34 PM »

I,ve used both the GDO and the Heath kit Tunnel Dipper.  I found the Tunnel Dipper just so much junk.  The old
GDO that used those minature tubes quite useful.  Back in the day we didn't have the selection as we do today.

At any rate a "dipper" can be quite useful when building resonant circuits.  As with any piece of test gear it's essential to know how to use it and understand it's limitations.

Personally, I would seriously consider buying the Dipit if I intended to play with resonant circuits.
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G3RZP
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Posts: 4358




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« Reply #11 on: September 01, 2013, 02:18:23 AM »

That's two of us found the Tunnel Dipper useless then. In any case, it's likely the tunnel diodes aren't working by now anyway.
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G3RZP
Member

Posts: 4358




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« Reply #12 on: September 02, 2013, 09:21:30 AM »

I did eventually do the sums. At 10MHz with a Q of 20 and a 0.2% frequency variation, the modulation depth is 0.6%.
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SM6XUN
Member

Posts: 15




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« Reply #13 on: September 21, 2013, 10:41:27 AM »

I have built it years ago and still use it frequently,
it works great, better feel than with a regular GDO although i would also like a analog meter.
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KB1GMX
Member

Posts: 707




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« Reply #14 on: September 21, 2013, 01:25:52 PM »

Funny I have a Eico 710 and a solidstate dipper and both get used depending on 120V ac available.
Getting a dip is not hard and my 710 was built by me back around 1965.  For many years that
and a crappy rf generator were my signal sources and I did a lot of building and testing with just that.

Measuring antennas depends on getting coupling, a one or two turn loop on the feed connector
usually did the trick.

The heath tunnel dipper was a problem as it was terminally weak (very low RF power).  Most solidstate
ones I've built and used worked well as tube units without the tether.

I looked at the Dipit, good idea and maybe a help but it depends on the Q of the circuit under test
and some stuff have very low Q like a dipole at the end of 50ft or coax.


Allison
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