Anti-Jamming Shortwave Antenna System?
Ali N.
site:
http://www.krsi.net/us-en/antijamming.asp
which claims to present an 'anti-jamming' antenna for use by listeners
of this radio station who are located in Iran. The actual radio
studios are apparently in California, broadcasting on 17510 KHz.
Can somebody with a better knowledge of antennas and electronics
explain the principle behind this design, and whether it will actually
work!? Are there other types of 'anti-jamming' antennas around?
Ali
Albert P. Belle Isle
Ali,
If I recall correctly, this is a copy of a design (and its description
and photograph) that was put out for Radio Free Europe/Radio Liberty
users to employ when wanting to listen to RFE/RL broadcasts in the
face of Soviet jammimg.
The design was, I believe, done by professional engineeers tasked to
come up with one that employed easy-to-obtain materials.
I've heard that this noise-canceller is as good as one of the MFJ
Noise Cancellers, but "twitchy" in its tuning-by-positioning.
It's the same principle: a second antenna to phase-out a strong
interfering signal. As it says on the bottom of the page:
>Note: If the jamming signal comes from the same direction as the radio signal, this
>system will not provide any benefit.
just like an MFJ or any other such canceller.
Your radio uses frequency filters to eliminate signals not on the same
frequency; this adds a spatial filter to remove same-frequency signals
that come at you from different directions.
Whether the noise is accidental from your local power company's
poorly-maintained insulators, or intentional from the government's
high-power jammers makes no difference.
Good listening,
Al
Albert P. BELLE ISLE
Cerberus Systems, Inc.
================================================
ENCRYPTION SOFTWARE with
Forensic Software Countermeasures
http://www.CerberusSystems.com
================================================
RadioGuy
Ali N. <al...@post.com> wrote in message
news:51990af0.02102...@posting.google.com...
Thanks for the link. The featured antenna is a variant of the
CTL (Coplanar-Twin-Loop). I have seen this identical
construction article on the VOA/IBB web sites first starting about
two or three years ago then appearing elsewhere.
This special and unusual antenna was designed by a research
scientist at Stanford Research Institute; Dr. O.G. Villard. If you want a
paper to read with substantially more information on the theory and
construction of the antenna authored by the inventor see the article in QST,
'The Coplanar-Twin-Loop Antenna' September 1988, pages 29-35. You can get
reprints at ARRL Headquarters. The paper claims a null depth on sky-wave
(yes, that's sky-wave) signals of around 20 dB.
There was a very nice write-up in WRTH describing different models of the
CTL plus a few construction details but the article I have doesn't give a
publication date. I suspect it was an issue around 1989 or a couple of
years after. It was the issue that contained a review in 'Equipment Test
Bench' on the Grundig Yacht Boy 220.
I've seen references to the antenna in a couple of other publications as
well.
You got my interest up to try and build the antenna described in the
link; I need something to null out VOA/Radio Marti---those signals
are so wide that sometimes that they jam nearby broadcasters.
R.
-----
N8KDV
RadioGuy wrote:
1990 (I think) and the 1993 WRTH.
RHF
"Antenna for Reducing SkyWave Interference"
Written by Dr. O. G. Villard, Jr.
http://www.hard-core-dx.com/nordicdx/antenna/special/reducin1.html
NOTE: This design is for ShortWave "SkyWave" Signal Reception.
This is from a prior posting to this NewsGroup.
"Home Brew Noise Canceling (Anti-Jamming) Antenna"
~ RHF
=QUOTE=
Howdy RHF:
Thanks for the link. The featured CTL (Coplanar-Twin-Loop) may be one
I
haven't seen as of yet. However, there was one described on the
VOA/IBB web
site I looked at a couple of years ago.
This special and unusual antenna was designed by a heavy duty research
scientist at Stanford Research Institute by O.G. Villard. If you want
a
paper to read with substantially more information on the theory and
construction of the antenna authored by the inventor see the article
in QST,
'The Coplanar-Twin-Loop Antenna' September 1988, pages 29-35. You can
get
reprints at ARRL Headquarters. The paper claims a null depth on
sky-wave
(yes, that's sky-wave) signals of around 20 dB.
There was a very nice write-up in WRTH describing different models of
the
CTL plus construction details but the article I have doesn't give a
publication date. I suspect it was an issue around 1989 or a couple
of
years after. It was the issue that contained a review in 'Equipment
Test
Bench' on the Grundig Yacht Boy 220.
I've seen references to the antenna in a couple of other publications
as
well but I will have to search them out.
Do a search for the Coplanar-Twin-Loop' for more info. You are right,
It
looks like a simple loop but it isn't.
Thanks, you got my interest up to try the CTL described in the
link---it
will be awhile before I get to it though.
R.
= = = RHF <rhf-...@usa.com> wrote in message
news:3ef6beca.02100...@posting.google.com...
"Home Brew" Noise Canceling (Anti-Jamming) Antenna
This Antenna was Originally Designed as a simple and easy to build
Anti-Jamming Antenna for Radio Free Europe Listeners. They also
Claimed that this Antenna should work with reducing 'man made' local
noise.
http://origin.rfaweb.org/front/sira/
? Has anyone ever built this antenna and tried one of these to reduce
household noise?
? Anyone have any Reports of Successes in Helping to Eliminate Noise
around the shack?
~ RHF
=UN-QUOTE=
= = = al...@post.com (Ali N.) wrote in message > news:<51990af0.02102...@posting.google.com>...
Hal Turner Sucks
>Subject: Re: Anti-Jamming Shortwave Antenna System?
>From: mikey...@earthlink.net
>Date: 10/26/02 7:05 AM Central Daylight Time
Telamon
al...@post.com (Ali N.) wrote:
The basic answer to your question is that the antenna is not sensitive
in all directions and in some directions receives very poorly. If you
are in a situation where two stations are transmitting on the same
frequency in different directions from your location you can orient the
antenna so that it poorly receives the station you don't want to hear
(the jammer) while picking up the station you want to hear more
efficiently.
--
Telamon
Ali N.
Ali
> = = = al...@post.com (Ali N.) wrote in message >
news:<51990af0.02102...@posting.google.com>...
> The latest issue of Monitoring Times makes reference to the following site:
>
> http://www.krsi.net/us-en/antijamming.asp
>
> which claims to present an 'anti-jamming' antenna ...