Antenna for shortwave reception
 

John Smith wrote:
flashdrive wrote:

...
Has anyone ever successfully reverse engineered the pre-amp of a
Wellbrook loop? It might be possible to dissolve the encapsulating
material (epoxy?) to reveal the PCB and componants. Otherwise a
medical scanner (seriously) might reveal some useful information.

My question would be, "Why go to the trouble?"

Indeed, grab a DC - 1Ghz MMIC device (make sure you don't get an SMC
component, unless you like soldering under a microscope), stick a proper
filter for the freqs/bands in front of it, and feed its' input with a
well designed loop ... if you need EXTREME gain, you can cascade a
couple of MMICs.

Regards,
JS

I do SMD rework occasionally, with MagEyes. You'd use a power amplifier
for a pre-amp?

Shortwave Radio Listener (SWL) Antennas -versus- Amateur RadioAntennas
 

Telamon wrote:
In article
,
Telamon wrote:

In article ,
Dave wrote:

John Smith wrote:

However, in side-by-side comparisons on 10-6-2m antennas I have built,
comparing a 5/8 against the 1/2 (construction methods/materials and
matching components identical) ... the actual difference, in the real
world, must be less than the width of a meter needle in the readings ...
or, put simply, I no longer deal with the extra length required of the
5/8 ... your mileage may vary ...

The advantage of a physical height (antenna length) between 180 and 215
degrees (see previous post regarding the magic number being around 195
degrees) is improved take-off angle and reduced skywave-groundwave
interaction, not dramatic nearfield voltage increases.
Regarding Mr. Smith's comments above my experience and others is the
opposite. 5/8 is a much better performing antenna than a 1/2 wave for
local VHF and UHF communications. Well worth the effort to build a 5/8
wave antenna over a 1/2 wave. The 5/8 had some kind of series load coil
part way up the whip where the 1/2 wave match/compensation was done at
the base so the whip was solid. Sorry I can't more specific then that as
those experiments were many years ago.

Mr. Smith is still lost in space.

Here is an example of the 5/8 wavelength antenna I recall using in the
center of the page. The one I used was permanent mount not magnetic
though. The van roof it was installed on was the ground plane.

http://www.new-tronics.com/main/html/mobile_vhf.html

When this antenna was changed for a 1/2 wave a lot of coverage was lost.
This was before cell phones so I had to start using pay phones a lot.


The one with the center coil is a collinear. It is 2 stacked verticals
with a "delay" between.

Transmitting with a "Beverage" Antenna and/or a Ferrite Rod Antenna
 

On Dec 29, 5:52*am, Dave wrote:
John Smith wrote:

Now, let me give you a mechanical example, so those willing and/or able
may grasp the concept, in fact, let me give you a couple:

1) The neighbors light is shining in my window(s), it is too bright too
sleep--I place a thick blanket over the window--WAALAA, "masked" the
problem!

2) The neighbors stereo is too loud. *I plug my ears, again, WAALAAA,
problem fixed!

3) [add your own example here]

telemundo is an argumentative idiot with a poor working knowledge of
what discussions he engages in *... *:-(

But then, if you don't possess the knowledge/experience to be able to
realize this, no one can blame you for being fooled ... later.

Regards,
JS

- Telemundo is a subsidiary of General Electric.
-
- Your analogies don't hold up.
-*You cannot transmit with a Beveridge
- and you cannot transmit with a ferrite loop.

Dave -says- You cannot transmit with a Beveridge and

Dave that is "Beverage" Antenna
http://en.wikipedia.org/wiki/Beverage_antenna
and sure you can Transmit with it.
http://www.qsl.net/k2hq/bev.htm
http://www.kkn.net/~n2nc/bev_arrays/
http://members.cox.net/kb1gw/bev-page.htm
http://www.n0hr.com/hamradio/66/10/ham_radio0.htm
http://www.seed-solutions.com/gregor...n/Beverage.htm

-IF- You really wanted a Beverage Antenna for very
Directional Transmitting : Single-point on a Single
Frequency : You might try one at 1.5 WL or 3 WL

Dave -says- you cannot transmit with a ferrite loop.

Sure you can Dave and Ferrite Rod Transmitting
http://www.st-andrews.ac.uk/~www_pa/...rt7/page5.html
Antennas are just about every where you go . . .
http://www.radio-electronics.com/inf...od_antenna.php
-think- Low Power Very Directional Transmitting
Antenna RFID Detection Exit Door Systems in
many Retail Stores : Some/Many of these use
Ferrite Rod Transmitting Antennas {Transponders}.
http://www.elnamagnetics.com/library/rfant.pdf

Dave even Arnie Coro "DXers Unlimited" [RHC]
says it can be done ;-}
http://www.radiohc.org/Distributions...s/01-1222.html
"you can build a ferrite rod loop antenna"

The Characteristically 50 Ohm Impedance Coax Cable is 'only' 50Ohms Nominal when . . .
 

On Dec 29, 12:37*pm, Telamon
wrote:
In article
,



*RHF wrote:
On Dec 28, 8:36*pm, Telamon
wrote:
In article ,
*John Smith wrote:

SNIP

I never even commented on where the placement of the matchbox would be,
and, as everyone knows, anywhere along the line you can place it. *The
best place would be between the coax (feedline) and the antenna-

Right. That's because you are to stupid to understand a concept until
someone rubes your nose in it. This would not even occur to you until
someone else brought it up.

-that is, taking for granted that the match from your rig to the
feedline is perfect.

SNIP

You are really worried about the match of 50 ohm *coax to your radios 50
ohm output? Now that's funny.

IIRC - The Characteristically 50 Ohm Impedance
Coax Cable is 'only' 50 Ohms nominal . . .
Until you attach something to it.

SNIP

Nope. The cable itself has a characteristic impedance of some design
value. The spacing and size of the conductors along with the dielectric
constant of the insulator between them dictates the impedance of the
coax.

You are confusing the characteristic impedance of the coax with its
ability to be an effective transmission line. The coax only behaves as
an effective transmission line when both ends of it are terminated at
its characteristic impedance.

--
Telamon
Ventura, California

Telamon,

OK -restatement- The "Measured" {by You} 50 Ohm
Impedance Coax Cable is 'only' 50 Ohms nominal*
* Until you attach something to it.

-IF- You then attach a Transmitters Output that is
a Nominal 50 Ohms to one end of the Coax Cable
and then the 'other' end will still "Measure*" about
50 Ohms.
* This is what the Antenna will see.

However -if- You attach an Unknown "Z" Antenna
and Ground to one end of the Coax Cable; then the
'other' end may "Measure*" near or far from 50 Ohms.
* This is what the Transmitter will see.

Unknown "Z" Antenna = Random Wire Antenna

as always . . . i may be 'w-r-o-n-g' - iane ~ RHF

Shortwave Radio Listener (SWL) Antennas -versus- Amateur RadioAntennas
 

On Dec 29, 1:35*pm, John Smith wrote:
RHF wrote:
...
JS,

Good Antenna Building Concept :
You Can't Talk To Them -unless-
You Can First Hear Them. ~ RHF
*.

Well, I'd like an antenna like this one (see URL, below.) *He comes into
my location in the low valley of CA like a door buster, from his secret
location in NV. Jumping the high Sierra Mountains in a single leap! *grin

- http://www.smeter.net/w6obb/antenna-farm.php
-
- Regards,
- JS

JS - Yeah some people have the money
to Do-It-Up right. ~ RHF

5/8 WL Antennas ?
 

Dave wrote:

...
A "counterpoise" is not a ground plane.
...
"Buckets of irony littered the lobby"

Oh no, here we go again with more magical/mystical antenna physics and
supernatural powers ...

Generally, a ground-plane is not referred to as counterpoise, but it
certainly IS one; it "balances" an unbalanced antenna by providing the
mechanics where the counterpart of the wave may be mirrored.

And, although every ground-plane IS a counterpoise, not every
counterpoise need be a ground plane ... again, DUH!

Regards,
JS

Shortwave Radio Listener (SWL) Antennas -versus- Amateur RadioAntennas
 

Dave wrote:

...
http://www.new-tronics.com/main/html/mobile_vhf.html

When this antenna was changed for a 1/2 wave a lot of coverage was
lost. This was before cell phones so I had to start using pay phones a
lot.


The one with the center coil is a collinear. It is 2 stacked verticals
with a "delay" between.

If I remember correctly, from running comparisons thought antenna
prediction softwares, 1.5db is about the most "gain" which can,
theoretically, be had between a 1/2 and a 5/8; and, not even "all that
gain" (i.e., max 1.5db) is gained in such a narrow point or swath of
pattern so as to account for "a lot of coverage lost." And, rarely, if
ever, is the theoretically reached, in my humble experience.

Something is obviously wrong with that whole statement ... perhaps a
"chit poor" 1/2 is being compared to a reasonable performing 5/8?

Regards,
JS

Antenna for shortwave reception
 

Dave wrote:

...
I do SMD rework occasionally, with MagEyes. You'd use a power amplifier
for a pre-amp?

For some? ABSOLUTELY!

Like, is the loop completely shielded? How efficient of a loop are we
speaking of? Etc.

But in all cases, yeah, I would provide for much more amplification
factor than I will ever need, why not? I mean, do I really need the 454
with blower in my "toy car?"

Regards,
JS

Antenna for shortwave reception
 

John Smith wrote:
Dave wrote:

...
I do SMD rework occasionally, with MagEyes. You'd use a power
amplifier for a pre-amp?

For some? ABSOLUTELY!

Like, is the loop completely shielded? How efficient of a loop are we
speaking of? Etc.

But in all cases, yeah, I would provide for much more amplification
factor than I will ever need, why not? I mean, do I really need the 454
with blower in my "toy car?"

Regards,
JS

And, certainly, I am assuming, you are using "power amplifier" in
correct context, when dealing with low power devices--as opposed to the
5kw POWER AMPLIFIER behind, and NOT in front of, my rig?

Regards,
JS

W6OBB Art Bell's 5-Acre Antenna Farm in Pahrump, Nevada
 

On Dec 29, 7:18*pm, Dave wrote:
John Smith wrote:

- - his secret
- - location in NV.

- 9041 Desert Lane
- Pahrump, NV 89048
-
- http://maps.google.com