----- Original Message -----
From: "Scott McClements" <kc2pih@gmail.com>
To: "TowerTalk" <towertalk@contesting.com>
Sent: Thursday, March 20, 2008 8:10 PM
Subject: [TowerTalk] Using a dip meter
> Hi,
>
> Being a new ham, I have never used a grid dip meter or
> actually seen
> someone use one. I've read the historical movement from
> people using
> grid dip meters to "SWR analyzers". I've also read that
> using a a real
> grid (tube) dip meter is the way to go.
>
> That being said, I need to determine the resonant
> frequency on some
> parasitic elements for a cubical quad I am building. Not
> having time
> to scour the used market for recommended makes/models, I
> bought the
> MFJ-201 Dip Meter new. Ok, time to test this thing out -
> I read the
> vague owner's manual and headed outside to try to dip my
> 75 meter
> loop. I made a small loop in the wire in a corner close
> to the ground
> and moved the coil on the MFJ dip meter around the loop
> (in the loop)
> after setting the sensitivity as directed by the manual. I
> spun the
> thumb wheel all the way from 2.0Mhz up to 8Mhz.
>
> No dips - no nothing. Same experience I had when I tried
> using the dip
> adapter coil for my MFJ-259B (which I have read is also
> worthless).
>
> Ok - what am I doing wrong? The owners manual talks about
> "loosely
> coupling" to the circuit under test. What does that mean
> exactly? Is
> this MFJ-201 just as useless as the MFJ-259B with the dip
> adapter?
>
> -Scott, WU2X
What you are describing is a perfect application for a dip
meter. It should work fb.
The quad loop must be continuous, with no insulators.
The small loop that you formed must not be shorted upon
itself. It should be maybe 3/4 inch diameter. Bring the dip
meter coil up close, coils co-axial, for the initial dip,
and then move it as far away as you can, with the coils
still co-axial, for best accuracy. Use a communications
receiver to monitor the oscillator frequency for best
frequency resolution.
The dip should be very sharp, so when you say you "spun" the
thumbwheel over a 6 Mhz range, maybe you were going too
fast.
There's no reason why this shouldn't work.
Dave Hachadorian, K6LL
Yuma, AZ
.
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