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AM Antenna Question.

TubesGalore

TubesGalore

Active Member
I fired up my Pioneer SX-626 that I just received for the first time this evening. FM reception was poor, receiving only the local FM station. I attached a simple dipole antenna hung in the window and now reception is great.

Same problem with the AM, only receiving the local station. The original factory AM antenna is in place. Would a dipole also work for AM or do I need some kind of loop or other type antenna? What do you use for AM?

Thanks.

Tom
 
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I use a crappy loop antenna and it seems to work much better than the factory one on my Onkyo. I can easily pick up all of the local stations now where before it was pretty iffy on a lot of them.
I've never tried to use a dipole with AM so maybe give it a shot and see what happens.
 
If the "loopstick" (LOL) is pressed flat against the back of the receiver that could explain poor reception. If so, swing the loopstick out and away from the back of the receiver. You could also try a length (6', 10', ++) of wire and attach it to the non-ground AM antenna terminal. An AM dipole comparable to the standard FM "T" would be approx. 100x longer tip-to-tip (100 MHz / 1 MHz = 100).
 
I followed loopstick's suggestion and checked the AM antenna. Sure enough it was up against the receiver. Once placed away reception improved greatly. I believe it can still be improved because when I put mu hand on the antenna reception improves even more. I'll experiment with positioning the receiver or go with the loop antenna or wire.
 
Take a look at a magnetic loop antenna for AM Broadcast reception this is one from Grundig. There are others with more-or-less the same design. Note the antenna trimmer on the side this makes a huge difference.

They are also easy to build. http://www.radiomagonline.com/misc/0082/shielded-loop-antennas-for-the-am-band/35342

http://smile.amazon.com/Eton-GRUNDI...8&qid=1426784954&sr=1-2&keywords=loop+antenna

41azedTuR8L.jpg
 
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The Terk & the "Grundig" shown earlier are broadly similar and probably of equivalent performance -- and that level of performance is indeed pretty good.

http://radiojayallen.com/select-a-tenna-vs-terk-am-advantage/

The Select-A-Tenna was a good, relatively inexpensive tuneable AM loop -- they're no longer made, but it shouldn't be too hard to find one at a hamfest, antique radio fleamarket, or even on eBAY.


Onkyo T-4055 AM-FM stereo tuner receiving WBZ-AM (Boston) on a spring afternoon from about 120 miles away (& thanks to an inductively-coupled Select-A-Tenna!). by mhardy6647, on Flickr

Photo shows an Onkyo T-4055 AM-FM stereo tuner receiving WBZ-AM (Boston) on a spring afternoon from about 120 miles away (& thanks to an inductively-coupled Select-A-Tenna!).

EDIT: Not sure if anyone directly addressed the nature of AM vs. FM when it comes to antennae. The bottom line is that the wavelength of the transmitter "carrier wave" for AM is much greater than that for FM. This has many different implications for reception (not to mention the use of different modes of transmission to encode analog audio data on an AM vs. FM carrier!) -- for the current discussion, it relates to the length of wire required for a properly-tuned antenna.

Midband in the standard AM broadcast band is about 1.0 MHz (1000 kHz): this corresponds to a wavelength of 934 feet (300 meters).
Midband in the US commercial FM broadcast band is about 98 MHz; this corresponds to a wavelength of "only" about 10 feet (3 meters).

The appropriate length of an antenna is thus about 100 times less for FM than for AM!

The AM loops, of course, have their antenna wire coiled in... well... a loop. This isn't just for compactness -- there are electrical properties of a properly made coiled loop antenna that are exploited by the Terk, the Grundig, and the Select-A-Tenna... but explaining that concisely & accurately is beyond my pay grade :-)

EDIT^2: I used this gizmo to calculate wavelengths, being the lazy blighter that I am: http://www.csgnetwork.com/freqwavelengthcalc.html
 
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transmaster said:
Take a look at a magnetic loop antenna for AM Broadcast reception this is one from Grundig. There are others with more-or-less the same design. Note the antenna trimmer on the side this makes a huge difference.
Click to expand...

Amazon also has this version - appears to be the same thing, slightly cheaper.
 
The longer the wire the better the reception on AM for the most part. Keep it away from anything that will have electrical interference.
 
As a late teen (AM was king) I had a buddy who ran an antenna wire out his BR window, wrapped around a screw-in insulator stuck in the eave then on to the next insulator eventually going around the whole house :)
 
Assuming that the dipole on the back can't be rotated laterally, try turning the receiver on it's feet, you will likely find a sweet spot with improved reception. Of course this rarely coincides with out desired orientation for the equipment, hence why an external is the way to go...
 
Wavelength is not the only difference between AM and FM. They are different animals. FM tends to travel "line of sight".
AM tends to folllow the ground contours, and also under certain conditions can bounce off coluds or the ionisphere.
AM not being as direction/point-to-point oriented needs it's antenna type while AM is less picky.
BTW, isn't 300' the average 1/4 wave length for AM, thus a 300' wire works well. For directed pickup, the options get expensive.
 
In 1986 I had a Hallicrafters SX-110 multiband receiver(c. 1961) that worked well with the standard 25' copper wire aerial kit from Radio Shack. It came with two ceramic insulators & some entry wires going into the house. The antenna wire went out my bedroom window & was strung out to the end of a clothesline pole in the back yard. The shortwave reception was pretty good, & I believe the AM was good as well. So would a 300' length of wire be a major improvement over the 25' wire? It's been a long time since I fired up the Hallicrafters(15+ years) & I have only used the set top loop on my two 1995 Pioneer receivers for any AM listening that I do. If the expected benefit was great I might try exchanging the loop for the wire.
 
woodj said:
Wavelength is not the only difference between AM and FM. They are different animals. FM tends to travel "line of sight".
AM tends to folllow the ground contours, and also under certain conditions can bounce off coluds or the ionisphere.
AM not being as direction/point-to-point oriented needs it's antenna type while AM is less picky.
BTW, isn't 300' the average 1/4 wave length for AM, thus a 300' wire works well. For directed pickup, the options get expensive.
Click to expand...

Absolutely -- I didn't think it was worth going into wave propagation in the context of this thread, much less the difference in frequency vs. amplitude modulation (not to mention mono compatible FM multiplex stereo encoding) ;-)

300 feet is 1/4 wavelength for 820 kHz, according to http://www.csgnetwork.com/freqwavelengthcalc.html
 
The AM loop antennas are great for finding different AM stations far from your location because they are directional. By rotating them around you can discover all types of different stations, especially at night when "skip" occurs. My wife enjoyed to listening to Ireland in the wee hours!
 
Sandstrom said:
Assuming that the dipole on the back can't be rotated laterally, try turning the receiver on it's feet, you will likely find a sweet spot with improved reception. Of course this rarely coincides with out desired orientation for the equipment, hence why an external is the way to go...
Click to expand...

This was a handy feature for a table / nightstand radio. The radio stayed put in its own footprint and just the antenna changed direction. This concept never got much traction in the audio world. :)

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