Herculodge

Manly Watch Deal of the Day: Invicta Russian Diver for $69.99

 

 

Excellent price for a 52mm Invicta Russian Diver. 

Ed Explains Some of AM Band's Advantages Over FM Band

 

As nice sounding as FM is, it can only transmit a realtively short distance, ie, "line-of-sight." Your FM radio must be ain a clear direct line from the transmitter, which the curvature of the earth limits.

FM has trouble going around mountains and buildings and suffers from distortions due to reflections--called Multipath distortion---similar to the old "ghosts" you used to get in TV pictures. AM can go thousands of miles and is generally impervious to (non-metallic) walls and and hills and structures.

In fact, by bouning off the ionosphere, AM signals can frequently "skip" around the world, as AM DXers know and love. FM can never go very far and maintain any quality.

Neil Evaluates AM Performance on His Many Radios

Neil gives us a break down of his radios' AM performance. 

Manly Watch Deal of the Day: Invicta Quiotaur Russian Diver for $89 and Free Shipping

 

 

Excellent price on this Invicta Russian Diver with 52mm bezel and blue dial. 

Some Easy to Understand Technical Facts About the AM Band on Your Radio

How good, or bad, is the AM band, especially in the context of my complaint that the Sangean K-200 sounds muffled on AM? It all depends. Here are some solid technical facts from our readers:

Gary writes:

Excessively muffled sound on AM is mainly due to:
1. An IF filter that is too narrow.
2. A poorly designed audio stage, a poor speaker, or inappropriate equalization. Full range bass and treble controls can often help.

It's true that FM has much wider bandwidth than AM, but it's also true that not all radios sound muffled on AM.

Ed adds:

AM radio has more than enough quality for voice. A telephone has less than a 3 kHz bandwidth, and yet you can still instantly recognize the voice of any of your friends or family. The trouble is when little speakers are bass-boosted ("voiced") in order to sound a little warmer on music, it winds up making voices sound boomy/muffled.

Demetri adds:

AM's source material's upper end is hard limited at 10khz. With single filter radios, the filter width must balance good adjacent channel rejection with fidelity so some fidelity is sacrificed in most designs. Also, the radios that sound good probably also artificially raise the high end to give that 10khz every chance to sound as good as possible.

FM source material is limited to 15khz for each channel so you get quite a bit more on the high end. Also the channel spacing is much wider on FM so the filters will not limit the fidelity as much.

Remember FM as 108-88=20Mhz to play with but AM only has 1.710-.530=1.2 MHz to fit all those stations.

An example of a high performance AM radio from Brian AKA Scooby:

My SSTran AM transmitter broadcasts a rather wide bandwidth signal. When coupled with a good tube radio, such as my 1956 Blaupunkt set, the sound is astonishingly good. The Blaupunkt in question has both AM and FM. I won't deny that the FM still has a very slight edge in fidelity, but the average listener that hears it thinks that the radio is playing FM instead of AM from my SSTran.

The flip side to this is that commercial stations aren't allowed to broadcast using the bandwidth my SSTran uses. Not to mention that the AM is still prone to interference, no matter how wide the broadcast bandwidth or quality of the AM receiver.

Mark Roberts adds:

Don't forget about the sharpness of the bandwidth filtering. Vintage radios, pre-ceramic filters, had very gentle roll-off, giving them a pleasing mellow sound. Modern ceramic filters are sharper and can have side effects beyond restricted frequency response. My AM HD tuner has an extremely sharp cutoff at 5 kHz, the proverbial brick wall. There are all sorts of knock-on effects and distortion that result. It has a little better fidelity than the typical AM radio but it sounds awful, sort of like the way network radio broadcasts used to sound -- even if they were on an equalized line -- before they went to satellite delivery. 

Must AM Band Sound Bad? A Debate

 

Neil and I have been complaining about AM sound being muffled on the Sangean K-200. Steven writes:

The AM sounds muffled because... it's AM.

Not trying to be snotty, just pointing out that AM sound quality has always been intrinsically inferior to that of FM, and since 1989, transmitted AM audio bandwidth has been further limited (to 10.2 KHz, vs 15 KHz for FM) to allow more transmitters to be accommodated. And that's before factoring in AM's disadvantages in when it comes to rejecting noise from fluorescent lights, electric motors, etc, that tend to mask high frequencies and muffle things even further.

That's why music broadcasters fled AM and it has become mostly the domain of right-wing punditry and sports-talk blather, where the shouting can be heard above the muffled audio quality.

Herculodge Response

I'm not convinced that AM is SUPPOSED to be hopelessly bad. If I use my Panasonic RF-888, for example, the AM sounds supreme, clear, and majestic. It's not just an AM problem. It's a radio problem.

Neil's Sangean K-200 Working Well in the Kitchen

 

So far so good with my K-200. I agree the AM audio is a little muffled, but I found that because of the speaker port design it is very dependent on placement. I have it on top of the fridge in the kitchen, and the acoustics work much better there. FM reception is phenomenal, and I use the night light and egg-timer all the time.

AM Reception on the Sangean K-200 Has a Muffled Quality, But FM Sounds Fine

My wife is now using the Sangean K-200, primarily as an alarm clock. I noticed that my earlier impressions that the speaker is distorted and muffled is only on AM, not FM. So I think the issue is more with AM reception than the speaker itself or perhaps the interaction between the two. 

Nice Example of a Panasonic RF-1150 Bidding on eBay

 

 

Here's a nice working condition Panasonic RF-1150 with the Gyro AM antenna intact. 

Dorpmuller Says No to the Grundig S450: Cheap Build Quality

 

 

 

 

I checked one out at a RS and what a chintzy, rattling POS. Cheap plastic. Like "made in hong kong", ca. 1960's. Real junk and the display cover was broken off in the box. Felt like it would crumble if I set it down a little too hard.