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Broad Description:
(about) 24" diameter. Passive 6 position switch at base covering
150khz-30mhz. Mil-spec &/or calibrated to Standards. Described Uses:
magnetic field testing, direction finding or as a part of a noise
isolation kit. Some are old - military surplus from the 50's and some
are being made new.

A couple makes/models:
Empire LP-105
PRD AT-1026/URM-85
CU-890/URM-85

I've seen the first two on eBay in the last few months selling
$200-$300. I can post the links if you want to see what I'm talking
about. Googling, there is scant little on these things. I found a
schematic for the CU-890/URM-85, a specialty RF shop that will rent an
LP-105 for $200/wk or sell it used for $600 and indications of other
manufacturers still making these types of loops new.

What's with these things? Can they/why can't they be used for LW/MW/SW
listening?

-Mark/airchecklover

Mark,

I've seen those military surplus loops on Ebay from
time to time. I'm no expert, but I don't see why they
wouldn't work on at least MW and SW if tuned to the
proper frequency. $600. is a little steep for me.

There's also a guy in Australia (PK's Loop Antennas)
who sells MW loop antennas for around USD$50. I have
one and it works very well; can pull in DX stations on
any average radio. Would probably work great with a
higher-end radio. He also makes LW loops and will
custom-build them for other frequency ranges if asked.


Keith

--- In loopantennas@..., "airchecklover" <mdh@...> wrote:

Broad Description:
(about) 24" diameter. Passive 6 position switch at base covering
150khz-30mhz. Mil-spec &/or calibrated to Standards. Described Uses:
magnetic field testing, direction finding or as a part of a noise
isolation kit. Some are old - military surplus from the 50's and

some

are being made new.

A couple makes/models:
Empire LP-105
PRD AT-1026/URM-85
CU-890/URM-85

I've seen the first two on eBay in the last few months selling
$200-$300. I can post the links if you want to see what I'm talking
about. Googling, there is scant little on these things. I found a
schematic for the CU-890/URM-85, a specialty RF shop that will rent

an

LP-105 for $200/wk or sell it used for $600 and indications of other
manufacturers still making these types of loops new.

What's with these things? Can they/why can't they be used for

LW/MW/SW

listening?

-Mark/airchecklover

I have used EMC loops, both passive and active in design. The passive
loops are OK for shortwave/Medium wave listening but can be
insensitive due to their broadband passive design.

The active broadband EMC loops use a lot of gain in the amplifier to
overcome the insensitivity of such a compact loop. In my experience
the noise floor of these active loops is quite high and thios makes
them a poor choice for DX work.

These types of loops are generally designed for near field operation
and were not designed with Shortwave DX work in mind. They will work
OK with Medium Wave due to the greater signal strengths of such
signals. The problem will then be Intermodulation products in the
active loop amplifier.

Just my 5 Cents worth.

Fraser

EMI/RFI antennas in general, not just loops, are designed for maximum
bandwidth and not efficiency. A capacitor tuned loop is the opposite end of
the spectrum from an amplified LF/MF/HF loop. An EMI test requires sweeping
broad frequency spans, and the less bandswitching, or tuning of the antenna
necessary the better, because that makes the test more efficient. The
efficiency and selectivity that are prized by someone trying to pull in a
weak signal in the presence of a strong one is just the opposite of the
efficiency desired by the EMI test engineer.

From: keith beesley <keith1226@...>
Reply-To: loopantennas@...
Date: Sun, 24 Jun 2007 01:56:34 -0700 (PDT)
To: loopantennas@...
Subject: Re: [loopantennas] Anyone know abt these LF-MW-HF loops?


Mark,

I've seen those military surplus loops on Ebay from
time to time. I'm no expert, but I don't see why they
wouldn't work on at least MW and SW if tuned to the
proper frequency. $600. is a little steep for me.

There's also a guy in Australia (PK's Loop Antennas)
who sells MW loop antennas for around USD$50. I have
one and it works very well; can pull in DX stations on
any average radio. Would probably work great with a
higher-end radio. He also makes LW loops and will
custom-build them for other frequency ranges if asked.

Keith