Dave Platt wrote:
The MFJ 269 with the dip-meter coils, is probably the least-sensitive
and least-usable dipmeter I've tried to date. It really isn't good
for very much at all.

Thanks,

Hopefully it won't have to be very good. I need it to make a trap antenna,
I found what I want for 180 UKP (plus shipping and taxes), but simply can't
afford it. In fact, buying the $20 coils is a stretch at this time.

I have plenty of coax and plastic pipe is easily available.

I don't think the coil construction is terribly critical, though,
since the coil inductance is not being used as part of the oscillator
tuned circuit. The MFJ uses only two coils to cover a wide range of
frequencies, rather than the half-dozen or so coils used by real
tank-circuit dippers.

It did seem awfuly cheap, the same range in their dip meter was covered
by at least five coils.

You can try simply winding a few turns of hookup wire on a convenient
tubular form, hooked up to an RCA or BNC or PL-259 glued to the end of
the form, and see if you can get an adequate dipping for your
purposes.

Ok, thanks, it may be exactly what I need.


The higher-frequency MFJ coil seems to be about 4 or 5 turns of wire -
length is about 1/2" and diameter is somewhere around 3/8". The
lower-frequency coil is somewhere around 12-14 turns of wire,
close-wound on a 1/2"-diameter plastic form.

This sounds good to me, I should be able to duplicate that.

As dippers go, the Heathkit HD-1250 solid-state model (it's a
dual-gate-MOSFET-based gate-dipper rather than a grid-dipper) is
better than the MFJ. It's not great, but it's probably adequate for
most purposes.

Heathkit? What's a heathkit? I have not seen one in the nine years I've
been here. A friend supposedly has a heathkit HF rig in boxes from when he
moved here, 25 years ago, I'm sure he hasn't even turned them on in
at least five years.


The Measurements/Boonton Megacycle Meter is the ne plus ultra of
dippers, as far as I know. It's big and perhaps a trifle clumsy, but
it has a strong oscillator which *really* dips nicely with even very
loose coupling to the circuit being measured. If you ever run across
one, grab it.

In a country there are no hamfest, no swap meets, no ham radio stores,
and you need to get permission from the Ministry of Communication to
buy a new rig (pro-forma, but it must be added to your license),
I expect that I'll never run across one, even if I hunt it down. :-(


73,

Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
IL Voice: (07)-7424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838
Vist my 'blog at http://geoffstechno.livejournal.com/