On Thu, 10 Mar 2005 12:24:15 -0500, clvrmnky
wrote:
I've been looking more seriously at the balun/tuner/ground offerings out
there. Seems to be a fair amount of contention out there about whether
antenna tuners work for SW.

Hi OM,

I am sure that is the gospel in rec.radio.shortwave. There is little
there that qualifies as dependable information - except what station
was being heard (and then, this information is obviously iffy).

If I can lessen the abuse my otherwise sensitive front-end is taking
from the wire, then maybe it's worth a try. That is, I'm
hoping/guessing that such a device will help my radio not hear a strong
signal 10-15kHz on either side of the mark, swamping out stuff I might
otherwise hear near these stations.

No, no tuner is going to have that much Q unless you get a very small
loop to go with it. Then, you are better off tuning the loop instead.
All-in-all you need to twist a knob somewhere. There are several
merits of using tuners with longwires. The chief among them is that a
tuner will depress the strenght of local AM stations that will desense
your receiver (even if you are not even tuned anywhere near that AM
station's frequency - such is its power and the weakness of receiver
front ends).

In this regard, homebrew is good because it allows me to experiment for
cheap.

By all means, do it.

Hmmm. I understand that a balun is really a type of matching
transformer, and that the specific nomenclature used is really just to
distinguish the various use, application and materials of the transformer.

This is all true, but bears very little on your needs.

All the designs for homebrew longwire X:1 baluns I've seen are step-down
transformers using specific types of ferrite material.

Those are conventional transformers, not chokes, not BalUns (or
UnUns).

Of course,
typical use often has one side of the primary and secondary going to a
good RF ground (for balanced application, anyway), which I do not have.

May as well divorce yourself from those explanations. A tuner will do
the job of transforming AND filter out the crap. A tuner is a
variable transformer. If you have a single wire coming in to the
tuner, add a hank of wire to the tuner's ground connection [hank = 20'
±6dB].

My thinking is that since I'm going to be experimenting with different
wire antennas this summer, why not try a few different matching
techniques as well?

Matching at the antenna, or matching at the receiver? Unless you have
long arms, or many antennas for each band, it is simpler to match at
the receiver.

The lack of good RF ground is going to be a challenge, and may preclude
any of this. I've got lots of wire, however, so I'm willing to give a
weekends up to try different things.

Returning to the need for a BalUn, properly a choke, for your
application. It is useful for reducing house noise from getting mixed
with your signal. Conventional transformers won't do that (unless you
add a choke at their output on the signal downstream).

73's
Richard Clark, KB7QHC