JP,

Fixed Loop On-a-Roof - Great for Monitoring that Hard-to-Get
AM/MW Radio Station [ On-the-Roof / In-the-Attic / Out-in-the-Yard ]
http://groups.yahoo.com/group/Shortw...a/message/9430

For that type of single AM/MW Radio Station "On-Frequency"
Monitoring an Out-Side Fixed 'Tune' Loop Antenna can
be very effective for providing a Clear and Clean Signal
for Operational Monitoring of the Transmitter's 'actual'
{Over-the-Air} Broadcast Signal.

Usually getting the Element of the Loop Antenna at least
Three Feet above the Roof (Five Feet is better) will get
the Loop out of the Building's RFI / EMF Noise Envelop.

1. Build the Loop Antenna Element (Hula-Hoop) with a
Weather Proof Box for the Fixed Tuning Capacitor and
Coax Cable feed-in-line to the Radio / Receiver.

2. Located, Position and Tune the Loop Antenna Element
for the best Signal of the "Target" AM/MW Radio Station.

3. Listen and Enjoy 'that' AM/MW Radio Station 24/7 )

READ - One Station "Fixed" Out-Side AM/MW Loop Antenna
http://groups.yahoo.com/group/Shortw...a/message/5065

READ - Two AM/MW Antennas for AM/MW DXing
http://groups.yahoo.com/group/Shortw...a/message/3446


just an idea - iane ~ RHF

Interesting. I had often wondered about that subject but I was to lazy
to google it. So you would have to tune the loop (going outside) for
every station you wanted to hear? That doesn't sound any good to me.

Can't you tune the loop from inside? It wouldn't make any sense if you
couldn't. {?}

In article .com,
"BCBlazysusan" wrote:

Interesting. I had often wondered about that subject but I was to lazy
to google it. So you would have to tune the loop (going outside) for
every station you wanted to hear? That doesn't sound any good to me.

Can't you tune the loop from inside? It wouldn't make any sense if you
couldn't. {?}

Some loops are designed to be tuned remotely but I don't know of a
commercial one you could buy. On scheme is to send a DC voltage down
the coax to the remote antenna that varies the capacitance of a
variactor diode to tune the antenna.

--
Telamon
Ventura, California

Telamon wrote:

In article .com,
"BCBlazysusan" wrote:

Interesting. I had often wondered about that subject but I was to lazy
to google it. So you would have to tune the loop (going outside) for
every station you wanted to hear? That doesn't sound any good to me.

Can't you tune the loop from inside? It wouldn't make any sense if you
couldn't. {?}

Some loops are designed to be tuned remotely but I don't know of a
commercial one you could buy. On scheme is to send a DC voltage down
the coax to the remote antenna that varies the capacitance of a
variactor diode to tune the antenna.

I believe this is one
http://www.ccrane.com/antennas/am-an...m-antenna.aspx

craigm

In article , craigm
wrote:

Telamon wrote:

In article .com,
"BCBlazysusan" wrote:

Interesting. I had often wondered about that subject but I was to lazy
to google it. So you would have to tune the loop (going outside) for
every station you wanted to hear? That doesn't sound any good to me.

Can't you tune the loop from inside? It wouldn't make any sense if you
couldn't. {?}

Some loops are designed to be tuned remotely but I don't know of a
commercial one you could buy. On scheme is to send a DC voltage down
the coax to the remote antenna that varies the capacitance of a
variactor diode to tune the antenna.

I believe this is one
http://www.ccrane.com/antennas/am-an...m-antenna.aspx

That site seems to be down right now.

--
Telamon
Ventura, California

Does higher bands mean like 160m is higher than 75m or 3.885MHz is
higher than 1.945MHz?

Would your Idea be practical Telamon considering the reverse voltage
capacitance of a varactor is limited to a small swing in PF? Maybe
lots of diodes in parallel?

Ack Ack, 12:59, back to work.

73
NEO

RHF wrote:


Usually getting the Element of the Loop Antenna at least
Three Feet above the Roof (Five Feet is better) will get
the Loop out of the Building's RFI / EMF Noise Envelop.


What technical foundation exists for this type of statement?

craigm

CraigM,

Why - Elevate the Antenna Element 3-5 Feet Above the Roof ?
http://groups.yahoo.com/group/Shortw...a/message/9443

Just basic practical experience on my part and
what I have read and been told over the years.

FWIW - Elevating the Antenna Element 3-5 Feet 'above' the
Roof may not always work in providing a Stronger Signal and
Less Noise in all situations - but often it does.

In general this statement applies to any Antenna Element
around a House or Building or their Roof Line and Attic.

Where 'possible' get the Antenna Element :
* Off-the-Surface
* Away-from-the-Surface
* Out-and-Up-in-the-Air
A few Feet of Space {Distance} Does Matter

The Why - It just may result from the simple fact that as
the Distance {Space} from a Source-of-Noise Increases
the Signal Level of the Noise Decreases.

So 'if' there is some Wiring or Equipment (Source-of-Noise)
in the Attic Area : The Surface of the Roof would be closer
and the Noise Stronger then if it were detected another 3-5
Feet away (Up Higher in the Air).

Note - This 'assumes' a non-metal Roof Surface that may act
as a Shield for any Noise emanating from the Attic of House.

It goes without saying that 'if' there is Electrical Equipment
on the Roof like Swamp-Coolers or Air-Conditioners then it
is always a good idea (were practical) to place the Antenna
Element away from such potential Sources-of-Noise.

In Conclusion - It remains my recommendation that "Elevating"
the Antenna Element 3-5 Feet 'above' the Surface of the Roof
is the better place for it to be for a Cleaner RF Signal and
Reduced Noise from the interior of the House.

as always - iane ~ RHF

In article , craigm
wrote:

RHF wrote:


Usually getting the Element of the Loop Antenna at least
Three Feet above the Roof (Five Feet is better) will get
the Loop out of the Building's RFI / EMF Noise Envelop.


What technical foundation exists for this type of statement?

Most any building materials have a dielectric constant higher than air
(1) and tend to bend the electric field lines around the house. The
field lines generated inside penetrating the outside tend to head toward
earth.

--
Telamon
Ventura, California

In article .com,
"N9NEO" wrote:

Does higher bands mean like 160m is higher than 75m or 3.885MHz is
higher than 1.945MHz?

Would your Idea be practical Telamon considering the reverse voltage
capacitance of a varactor is limited to a small swing in PF? Maybe
lots of diodes in parallel?

Ack Ack, 12:59, back to work.

Well a couple of things come into play.

Local noise goes up, along with atmospheric, and loops tend to have
greater local noise rejection over a voltage type. This is especially
true for a shielded loop. There is no loop advantage in atmospheric
noise save for lightening storm noise so it might make a better summer
antenna.

The lower in frequency you go the signals tend to be directionally phase
stable and so with a loop receive pattern you can null signals.

The higher in frequency you go the less advantage there is in a loop
over a dipole but it will work just fine.

I think paralleling diodes to get more capacitance than what one diode
can provide will work. Can't think of a reason why it would not work.

--
Telamon
Ventura, California