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AM random length antenna information?

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Posted on November 5, 2014 at 13:18:28
cootcraig
Audiophile

Posts: 116
Location: SE Colorado
Joined: October 23, 2005
 This is slightly lazy, as I did not find enough details on a quick search of this forum. I'm having great results with my rhombic FM and chimney mounted external TV antennas. Next up is to try out an external AM antenna. The lazy part is I'm looking for details on the antenna installation and building an antenna tuner.

 

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RE: AM random length antenna information?, posted on November 5, 2014 at 14:31:50
6bq5
Audiophile

Posts: 4390
Location: SF Bay
Joined: August 16, 2001
 AM is largely non directional and weather dependent - though location (terrain, building density and construction methods- of buildings) will affect reception, in addition to the noise environment...
The link below may provide you with more info-
Happy tuning


Happy Listening

 

Long Wire Antenna , posted on November 6, 2014 at 04:28:15
1973shovel
Audiophile

Posts: 10117
Location: Greenville SC
Joined: February 25, 2007



"The relatively simple long wire antenna can be used as an extension to a radio's existing antenna, or connected to the radio receiver terminals.

The basic long wire antenna system consists of:

Heavy gauge insulated wire or 4 gauge copper wire for the antenna.

Wire situated at least 2.5 meters high (i.e. above head height).

The wire should be at least 20 meters long with no joins.

Insulators are installed at each end of the wire to ensure the house and tree (or post) is isolated from the antenna.

The antenna should be placed away from any objects that may interfere with reception.

The feed line is soldered to the antenna wire. There must be a loop in the feed line just before it enters the house so rainwater drips off.

The feed line is connected to the antenna terminal of the radio. A separate wire runs from the earth terminal to the earth spoke.

If the radio does not have terminals, the feed line can be attached to the radio's own antenna."

The above information, along with the graphic, was lifted off some other site, a LONG time ago. I can't vouch for its performance or, more importantly, its safety. It seems pretty straightforward, however.

I bought the Radio Shack Shortwave antenna kit shown below some years ago, but never used it. Radio Shack doesn't carry it anymore, but maybe you can find one on ebay or elsewhere. The picture's not mine, or I'd give you the RS part number.





Giving in to convenience, I spend about $40 on one of these, the Terk AM Advantage tunable AM antenna, but wasn't very impressed with it.








 

RE: Long Wire Antenna , posted on November 6, 2014 at 08:42:19
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 "I can't vouch for its performance or, more importantly, its safety.'

Unfortunately, as shown, it is UNSAFE! Atmospheric electrical activity can destroy the equipment and/or the residence. :>((

A lightning arrestor needs to be added near the building entrance point. A satisfactory lightning arrestor can be made from a non-resistive spark plug.

Install a knife switch in the lead in line, just after the line enters the building. The switch should be open when the radio is not in use and the radio should not be used during an electrical storm.


Eli D.

 

RE: AM random length antenna information?, posted on November 6, 2014 at 10:53:25
Awe-d-o-file
Dealer

Posts: 21037
Location: 50 miles west of DC
Joined: January 10, 2004
 Height isn't very important for AM. Some say noise is less when lower. Feed it with coax though as when unshielded wire passes all the noise generation in your house can make it really noisy and ultimately not very usable.

I have lots of AM and ham antennas I made and installed.



ET
ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

RE: Long Wire Antenna , posted on November 6, 2014 at 11:53:33
tesla
Audiophile

Posts: 3180
Location: San Diego County, California
Joined: October 25, 2000
 That diagram is exactly what my Dad and I built when I was a kid. Stretched it from one side of the house to the other side, used it with my kit-built Philco crystal radio. Never worried about lightning, we just didn't get it where I grew up. Worked great, finally took it down in my late teens, when my crystal radio days were long gone.



Proudly serving content-free posts since 1984.

 

Long Wire? Vs Random length, posted on November 6, 2014 at 12:31:28
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 an AM BCBand long wire antenna is of the order of 300metres long! Few of us even with farms are going to put up such.

We can if we have a house on a block build a 'random wire', but adding a spark arrestor is VITAL.

Adding an antenna tuner isn't. Unless you want the quietest possible sound and have wide audio bandwidth AM tuner stage.

An antenna tuner consists of a tapped coil over a ferrite rod perhaps and a vane capacitor.

Mine has just one tapping and I use the cap, since a techie set it up.


Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

What didn't you like about the Terk, mate!?, posted on November 6, 2014 at 20:03:15
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 As I am getting on in years - I may not rebuild my 25ft high up random to the neighbours chimney, and might get one of the CCrane AM 'tennas (with a remote tuner indoors) and stick the 'tenna out under the clear roof of the deck.

TIA
Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

In a nutshell, Timbo?, posted on November 7, 2014 at 04:38:03
1973shovel
Audiophile

Posts: 10117
Location: Greenville SC
Joined: February 25, 2007
 Performance.

I was playing around with late night DXing. I considered installing the Radio Shack shortwave antenna kit I mentioned elsewhere in this thread. But I wouldn't have left it hooked to the radio, and fishing the wire in from outside on the occasions I wanted to DX hardly seemed worth the bother.

Many sites recommended a no longer made tunable AM antenna, which I forget the name of. I started reading about the Terk, and some said it was "just as good" as the one I had been looking for, used.

When the Terk is dialed to the frequency the radio is tuned to, I get a very brief interruption (for want of a better word) of the audio from the speaker, which would seem to indicate that it's not broken. But that's about all I get. Stations don't seem any clearer, stronger, no less static, etc.

I thought perhaps the lack of improvement was because I was trying to use the Terk with an inexpensive Sony clock radio I use in the bedroom. The Sony has no provision for an external antenna hook-up, so I tried it with the antenna in close proximity to the radio. For those who may not be aware of it, that is how these AM antennas are supposed to work.

Figuring I'd get better performance with direct hook-up to a better radio, I tried a few others I have, which do have external antenna terminals. I tried it with a GE Superadio (noteworthy for its AM performance), a Marantz 105 and Yamaha T-80 AM/FM tuners. The ferrite rods / loops of those radios worked just as well as the Terk.





 

RE: "A lightning arrestor needs to be added near the building entrance point", posted on November 7, 2014 at 04:52:01
1973shovel
Audiophile

Posts: 10117
Location: Greenville SC
Joined: February 25, 2007
 That's a great piece of advice, Eli, and one I wasn't aware of. When I did my searches of outdoor AM antennas some years ago, a ground rod was mentioned. As was disconnecting the lead-in wire from the radio when the antenna wasn't in use. But I never came across the spark plug lighting arrestor.

Quite frankly, the whole long wire antenna project seemed to be more trouble than it was worth, for the one AM station I hoped to receive. I've got about fifty other projects which interest me more, including rebuilding a pair of Dynaco MKIIIs, which I've been putting off for far too long.

Maybe after I retire I'll try an outdoor AM antenna. I'm saving your post, so that I won't forget the necessity of the lightning arrestor.

Thanks.

 

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