That site is still up? I haven't updated it in years. I too have used a
tuner. On short antennas, it can make a good deal of difference. On longer
ones, it doesn't seem to matter much. The transformer is the way to go.
Easy, works well and you don't have to mess with it.

"Mark S. Holden" wrote in message
...
Radio Man wrote:
Mark...Can you be specific on what type and/or impeadance of the
transformer you are using? Also what antennas are you using it on?

I mostly use 9:1 impedance matching transformers I wound myself
according to the directions on CW's web site.

http://www.kc7nod.20m.com/new_page_1.htm

On antennas:

#1 is out at the moment because of a lightning strike a few weeks ago
and I've been too busy to get it replaced - but it was a 65' random wire
made with #14 wire that's 225 feet away from my house (and farther from
the neighbors) The coax is underground. It gets practically no RFI.
I'm sure it would work almost as well if it was 60-70 feet away from the
house, but I don't have tall sturdy trees there.

Here's a web site with a discussion of this type of antenna.

http://www.anarc.org/naswa/badx/antennas/low-noise_antenna.html

#2 is a triangular horizontal loop antenna that's partially over the
house. It was made with about 150 feet of #14 wire. Loops are low
noise designs, but my house is filled with gizmos that cause rfi, so
it's not my favorite. It has a 4:1 impedance matching transformer.

#3 was my first antenna at the house - it's 40 feet of wire stapled to
the rafters in my attic. It's closer to the RFI and I haven't used it
in years. 9:1 transformer.

#4 is my current camping and vacation antenna. It's a 3 meter folding
whip originally intended for a PRC-25 or PRC-77 with a 9:1 impedance
matching transformer that mounts onto a photographic tripod. It works
quite well.

#5 is an Electro-Metrics ALR-25 Loop. I still need to create a control
box to switch bands on it electrically, but ultimately, this may become
the "portable" antenna for places I can drive to where I need to use an
indoor antenna. This has it's own impedance matching circuitry built
in.

I have some extra #43 ferrite's on hand that are a little smaller than
the one CW's design calls for. They work well. If you'd like one, you
can have it for the price of a small padded mailing bag and a couple of
stamps. Contact me directly for details.

On Tue, 21 Sep 2004 01:15:42 GMT, John Steffes
wrote:

We use an antenna tuner to feed our W8JK antenna for use for shortwave
reception for two reasons:
1. The 8JK has a high impedence input so it is fed with 300 ohm ladder
line; thus the use of the tuner (in this case) acts as a balanced
transformer.
2. The 8JK was "cut" for 20 meters. For use on other frequencies, the
tuner acts (with adjustment) as a conjugate match that provides a 50 ohm
input to the receiver.

Results of the tuner appears to peak signal strength as the impedence of
the receiving antenna is transformed by the matching provided by the tuner.

Tuners are passive in nature; that is, they require no amplifier
electronics and associated power. They may be unbalanced input to
balanced output (or vice versa) or unbalanced to unbalanced
input/output. Preselectors on the other hand are active devices. They
vary in design and may provide matching as well as gain.

The selection of the device you choose will depend on the type on
antenna system you employ.

In any case, good luck!

John

John,
I'm not sure I understand why you feel a preselector is an "active
device"? From everything I've learned, active devices are such things
as transistors, IC's, hybrids etc or a reference to a circuit that
requires power to operate. The preselectors I've seen are 'passive'
in that there are no semiconductors and no power required - excluding
models that also have a built in pre-amp. Rather they are basically a
'tank' circuit that with a combination of inductance and capacitance
create a 'bandpass' so only frequencies in a given range easily pass
through the preselector to the receiver.

Am I missing something in either your explanation or my understanding
of a preselector?

Howard

"John Steffes" wrote in message
...
We use an antenna tuner to feed our W8JK antenna for use for shortwave
reception for two reasons:
1. The 8JK has a high impedence input so it is fed with 300 ohm ladder
line; thus the use of the tuner (in this case) acts as a balanced
transformer.
2. The 8JK was "cut" for 20 meters. For use on other frequencies, the
tuner acts (with adjustment) as a conjugate match that provides a 50 ohm
input to the receiver.

Results of the tuner appears to peak signal strength as the impedence of
the receiving antenna is transformed by the matching provided by the tuner.

Tuners are passive in nature; that is, they require no amplifier
electronics and associated power. They may be unbalanced input to
balanced output (or vice versa) or unbalanced to unbalanced
input/output. Preselectors on the other hand are active devices. They
vary in design and may provide matching as well as gain.

The selection of the device you choose will depend on the type on
antenna system you employ.

In any case, good luck!

John

Thanks John. Very informative post.

Howard,

The preselectors we have dealt with have been , in general, active. They
have used positive feedback to increase the "Q" of the resonant tank
circuit providing greater selectivity. It is reasonable to accomplish
this using no positive feedback (bandpass design) as you suggested.

John

Howard wrote:
On Tue, 21 Sep 2004 01:15:42 GMT, John Steffes
wrote:


We use an antenna tuner to feed our W8JK antenna for use for shortwave
reception for two reasons:
1. The 8JK has a high impedence input so it is fed with 300 ohm ladder
line; thus the use of the tuner (in this case) acts as a balanced
transformer.
2. The 8JK was "cut" for 20 meters. For use on other frequencies, the
tuner acts (with adjustment) as a conjugate match that provides a 50 ohm
input to the receiver.

Results of the tuner appears to peak signal strength as the impedence of
the receiving antenna is transformed by the matching provided by the tuner.

Tuners are passive in nature; that is, they require no amplifier
electronics and associated power. They may be unbalanced input to
balanced output (or vice versa) or unbalanced to unbalanced
input/output. Preselectors on the other hand are active devices. They
vary in design and may provide matching as well as gain.

The selection of the device you choose will depend on the type on
antenna system you employ.

In any case, good luck!

John


John,
I'm not sure I understand why you feel a preselector is an "active
device"? From everything I've learned, active devices are such things
as transistors, IC's, hybrids etc or a reference to a circuit that
requires power to operate. The preselectors I've seen are 'passive'
in that there are no semiconductors and no power required - excluding
models that also have a built in pre-amp. Rather they are basically a
'tank' circuit that with a combination of inductance and capacitance
create a 'bandpass' so only frequencies in a given range easily pass
through the preselector to the receiver.

Am I missing something in either your explanation or my understanding
of a preselector?

Howard

On Tue, 21 Sep 2004 09:22:41 GMT, John Steffes
wrote:

Howard,

The preselectors we have dealt with have been , in general, active. They
have used positive feedback to increase the "Q" of the resonant tank
circuit providing greater selectivity. It is reasonable to accomplish
this using no positive feedback (bandpass design) as you suggested.

John


John,
Thanks for the reply, nice to know I wasn't off-base in my thinking.

Howard

Howard wrote:

On Tue, 21 Sep 2004 09:22:41 GMT, John Steffes
wrote:

Howard,

The preselectors we have dealt with have been , in general, active. They
have used positive feedback to increase the "Q" of the resonant tank
circuit providing greater selectivity. It is reasonable to accomplish
this using no positive feedback (bandpass design) as you suggested.

John


John,
Thanks for the reply, nice to know I wasn't off-base in my thinking.

Howard

A shortwave preselector can be either active or passive. The former
usually has an amplification stage followed by an impedance matching
output circuit in addition to the tuned circuit(s). The passive type has
only the tuned circuits. Some preselectors can be both active or passive
if the amp' circuit can be turned off (lowered to unity gain) or
completely bypassed. The main advantage of any preselector is it's
bandpass filtering (tuned circuit) which provides a means of removing
signals outside the frequency range (band) that the user wants to hear.
This is particularly useful for receivers (usually portables) that don't
have a good antenna input circuit to accomplish this filtering process
internally.


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