John Plimmer,

I would agree for the Shortwave Listener (SWL) who does
not want to get in to a lot of extra boxes in the Shack and
the resulting confusion of : ? Which Knob To Turn Next ?

The simple Matching Transformer between the Antenna
and the Coax Cable feed-n-line is the single best item
to add to the External Antenna to Coax to Radio System;
except for a good earthen Grounding Point.

NOTE - It is Interesting that you identify the use of
the 9:1 Matching Transformer for the lower reaches
of the spectrum AM/MW Band Tropic Bands and
such and the use of a 4:1 Matching Transformer
for above 10 MHz.

Question - Which respect to which type and size of
Antenna or Antennas do you make this statement ?

i want to know - iane ~ RHF

RHF
In earlier years I must have owned every type of antenna
tuner/preselector that was on the market.
The MFJ I found were so badly made of such cheap parts that they were
frankly awful.
Then I had an expensive Japanese Mizuho and finally a ham made me a really
nice one tube amplifier/tuner.

I must say though, that for use on holidays with my portables the old Grove
Mini Tuner was great. A really useful little box of tricks that did wonders
for maximising signals off a short wire 30/40 foot long (I'm not in favour
of hanging too much wire on a portable).

But then I started experimenting with the simple home brew magnetic matching
transformers and they outperformed all the fancy knob twiddling
tuners/preselectors by far, apart from there ease of use (no knob twiddling
and nothing to adjust at all).

I did experiments with various magnetic matching transformers I had and
found 9:1 the best for my needs on the BCB mediumwave band and the Tropical
bands. The 4:1 matching transformers worked well listening to international
broadcasters above 10 Mhz.

The 9:1 magnetic matching transformers I mainly use with my 1000 foot
beverage antenna's, but it also worked superbly on my suburban Windom
antenna which was only 55 foot long but I managed to get it up 40 foot high.

I don't think the length of wire attached to the magnetic matching
transformer matters at all - I have used them from 50 foot long on holidays
from hotel rooms to 1000 foot long beverages on serious DXpeditions. I think
what matters is that 4:1 favours reception in the upper HF band and 9:1 is
very good lower down the band.

Some of my pals who own Drake R8 series RX's run their longwires direct into
the shack and couple up to the 500 Ohm input of the Drake. But to me that is
silly, as if you look at the Drake workshop manual you will see that the 500
Ohm input on the Drake is terminated into a 9:1 transformer anyway, so it
is much better for noise abatement to terminate your longwire 30/40 foot
away from the shack/building and then run a coax into the RX and terminate
it into the 50 Ohm connector on the RX.

--
John Plimmer, Montagu, Western Cape Province, South Africa
South 33 d 47 m 32 s, East 20 d 07 m 32 s
RX Icom IC-756 PRO III with MW mods
Drake SW8 & ERGO software
Sony 7600D GE SRIII
BW XCR 30, Braun T1000, Sangean 818 & 803A.
GE circa 50's radiogram
Antenna's RF Systems DX 1 Pro, Datong AD-270
Kiwa MW Loop
http://www.dxing.info/about/dxers/plimmer.dx

"RHF" wrote in message
oups.com...
John Plimmer,

I would agree for the Shortwave Listener (SWL) who does
not want to get in to a lot of extra boxes in the Shack and
the resulting confusion of : ? Which Knob To Turn Next ?

The simple Matching Transformer between the Antenna
and the Coax Cable feed-n-line is the single best item
to add to the External Antenna to Coax to Radio System;
except for a good earthen Grounding Point.

NOTE - It is Interesting that you identify the use of
the 9:1 Matching Transformer for the lower reaches
of the spectrum AM/MW Band Tropic Bands and
such and the use of a 4:1 Matching Transformer
for above 10 MHz.

Question - Which respect to which type and size of
Antenna or Antennas do you make this statement ?

i want to know - iane ~ RHF
.
.
. .
.

In article ,
"John Plimmer" wrote:

RHF
In earlier years I must have owned every type of antenna
tuner/preselector that was on the market.
The MFJ I found were so badly made of such cheap parts that they were
frankly awful.
Then I had an expensive Japanese Mizuho and finally a ham made me a really
nice one tube amplifier/tuner.

I must say though, that for use on holidays with my portables the old Grove
Mini Tuner was great. A really useful little box of tricks that did wonders
for maximising signals off a short wire 30/40 foot long (I'm not in favour
of hanging too much wire on a portable).

But then I started experimenting with the simple home brew magnetic matching
transformers and they outperformed all the fancy knob twiddling
tuners/preselectors by far, apart from there ease of use (no knob twiddling
and nothing to adjust at all).

I did experiments with various magnetic matching transformers I had and
found 9:1 the best for my needs on the BCB mediumwave band and the Tropical
bands. The 4:1 matching transformers worked well listening to international
broadcasters above 10 Mhz.

The 9:1 magnetic matching transformers I mainly use with my 1000 foot
beverage antenna's, but it also worked superbly on my suburban Windom
antenna which was only 55 foot long but I managed to get it up 40 foot high.

I don't think the length of wire attached to the magnetic matching
transformer matters at all - I have used them from 50 foot long on holidays
from hotel rooms to 1000 foot long beverages on serious DXpeditions. I think
what matters is that 4:1 favours reception in the upper HF band and 9:1 is
very good lower down the band.

Some of my pals who own Drake R8 series RX's run their longwires direct into
the shack and couple up to the 500 Ohm input of the Drake. But to me that is
silly, as if you look at the Drake workshop manual you will see that the 500
Ohm input on the Drake is terminated into a 9:1 transformer anyway, so it
is much better for noise abatement to terminate your longwire 30/40 foot
away from the shack/building and then run a coax into the RX and terminate
it into the 50 Ohm connector on the RX.

--
John Plimmer, Montagu, Western Cape Province, South Africa
South 33 d 47 m 32 s, East 20 d 07 m 32 s
RX Icom IC-756 PRO III with MW mods
Drake SW8 & ERGO software
Sony 7600D GE SRIII
BW XCR 30, Braun T1000, Sangean 818 & 803A.
GE circa 50's radiogram
Antenna's RF Systems DX 1 Pro, Datong AD-270
Kiwa MW Loop
http://www.dxing.info/about/dxers/plimmer.dx

"RHF" wrote in message
oups.com...
John Plimmer,

I would agree for the Shortwave Listener (SWL) who does
not want to get in to a lot of extra boxes in the Shack and
the resulting confusion of : ? Which Knob To Turn Next ?

The simple Matching Transformer between the Antenna
and the Coax Cable feed-n-line is the single best item
to add to the External Antenna to Coax to Radio System;
except for a good earthen Grounding Point.

NOTE - It is Interesting that you identify the use of
the 9:1 Matching Transformer for the lower reaches
of the spectrum AM/MW Band Tropic Bands and
such and the use of a 4:1 Matching Transformer
for above 10 MHz.

Question - Which respect to which type and size of
Antenna or Antennas do you make this statement ?

I thought about this and I think I have an answer to the rational
behind Johns assertion of different transformation ratios work better
depending on frequency. I think he is actually seeing transformer
efficiency at work rather than the wire impedance changing over
frequency. The higher ratios of 9:1 require more turns then the 4:1,
which can cause a roll off in high frequency response. Depending on
winding technique the roll off can be severe. Transformer cores also
have a frequency response that must be considered. The question is has
he had the opportunity to test the frequency response of the
transformers he used?

The 4:1 could be the right impedance if the wire is low to the ground
by the way.

Another possibility is that the earth under the wire has a conductivity
that varies with frequency. Conductivity change over frequency should
not be enough to explain a change of 450 to 200 ohms of the wire over
frequency.

The horizontal single antenna is one element where the other element is
the ground under it. This is an unbalanced Marconi type antenna. As a
RF current induced on the wire above ground; the E field from the charge
connects to the ground under the wire. The distance from ground
determines the impedance of the wire with air as the dielectric. This
impedance characteristic is similar to how a capacitor operates where
the closer the plates are to each other the impedance and decreases and
the value of capacitance increases. Surface area, dielectric and plate
spacing all affect the capacitor response.

The two things you can control for antenna wire impedance is wire
diameter and height above ground. The higher the wire the higher the
impedance of the wire similar to capacitor plate distance. The smaller
the wire diameter the higher the impedance of the wire similar to
capacitor plate area. See how that works?

Regarding the Drake 500 input I agree with his comments of AC power
operation and note an exception for battery operation it should work
fine as long as you also connect the radio ground to a ground stake or
radial under the wire. I'm sure Drake wound a good UNUN in the radio
front end.

--
Telamon
Ventura, California

On Fri, 28 Apr 2006 17:58:46 GMT, Telamon
wrote:

In article ,
"John Plimmer" wrote:


The horizontal single antenna is one element where the other element is
the ground under it. This is an unbalanced Marconi type antenna.

No it isn't. A Marconi antenna i s a 1/4 Wave vertical working
against a ground screen to form a virtual center fed Dipole.