Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Dec Mon 10, 2018 8:17 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 78 posts ]  Go to page Previous  1, 2, 3, 4
Author Message
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 08, 2017 7:09 am 
Member
User avatar

Joined: Nov Sat 26, 2011 4:09 am
Posts: 9182
Location: Texas. USA
ab5ni wrote:
.... The other day I was looking at a part-15 transmitter circuit that somebody posted, and it was based on the LM386. I was like, "Man, that is one noisy chip!" There has to be a better circuit out there for doing this, Tube. ...
You're not building a phono preamp and even the default gain of 20 is really too much. It's been built by scores of people and not one has complained about 'noise'.

It's perfectly fine for a part 15 transmitter.


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 08, 2017 7:29 am 
Member
User avatar

Joined: Jun Sat 17, 2017 4:22 am
Posts: 1106
Location: Lafayette, LA.
Howdy Flip,

Flipperhome wrote:
ab5ni wrote:
.... The other day I was looking at a part-15 transmitter circuit that somebody posted, and it was based on the LM386. I was like, "Man, that is one noisy chip!" There has to be a better circuit out there for doing this, Tube. ...
You're not building a phono preamp and even the default gain of 20 is really too much. It's been built by scores of people and not one has complained about 'noise'.

It's perfectly fine for a part 15 transmitter.


Well, you guys can use the LM386, and I'll use Bluetooth, and everyone will be happy :D.

73,

Randy AB5NI

_________________
I eat spaghetti code out of a bitbucket while sitting at a hashtable - pay for the meal with cache!


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 08, 2017 8:02 am 
Member
User avatar

Joined: Nov Sat 26, 2011 4:09 am
Posts: 9182
Location: Texas. USA
ab5ni wrote:
Howdy Flip,

Flipperhome wrote:
You're not building a phono preamp and even the default gain of 20 is really too much. It's been built by scores of people and not one has complained about 'noise'.

It's perfectly fine for a part 15 transmitter.
Well, you guys can use the LM386, and I'll use Bluetooth, and everyone will be happy :D.

73,

Randy AB5NI
:lol: Well, I've used Bluetooth, the LM386, and various tube AM (and FM) transmitters. Each has their appeal. I'm proudest of the tube FM transmitter but the LM386 is the slam dunk simplest I've seen for a decent range AM job.


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 08, 2017 8:27 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 29438
Location: SoCal, 91387
ab5ni wrote:
Problems arise when you want to try and hear DX stations during the nighttime hours, past sundown. Most of stations here in the States will be low-power, 1-KW stations, and most of them will be at or barely above the noise floor. If that isn't bad enough, you can also have tremendous amounts of fading, with other stations popping in and out, interfering with the station you are trying to copy. Now, add to that numerous heterodynes caused by competing stations on the same frequency. On the AM, MW BCB, this is what you'll hear in the US 95% of the time.

No argument there, but what else is there to DX? FM? digital TV?

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 08, 2017 11:01 am 
Member
User avatar

Joined: Jun Sat 17, 2017 4:22 am
Posts: 1106
Location: Lafayette, LA.
Hi Fifties,

fifties wrote:
No argument there, but what else is there to DX? FM? digital TV?



All modes can have some DX pop up out of the blue. I've seen it on VHF and UHF TV. It doesn't happen all that often, but when it does, it's quite amazing. At those frequencies, the DX signal is usually bouncing off of clouds in a storm system and tropospheric ducting. Being a ham-radio operator, I've also heard and worked numerous DX stations around the world via shortwave. You can talk to stations around the world on as little as 50 mW's with proper conditions.

I used to talk to Yuri, 4K1F, in the Antarctic quite frequently with only a few watts on 40 meters using CW (morse code). He was running QRP (low power) as well, which only goes to show that you can talk to and hear a lot DX with the proper band conditions.

73,

Randy AB5NI

_________________
I eat spaghetti code out of a bitbucket while sitting at a hashtable - pay for the meal with cache!


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 08, 2017 5:24 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 7978
Location: Beautiful Downtown Burbank CA
ab5ni wrote:
The other day I was looking at a part-15 transmitter circuit that somebody posted, and it was based on the LM386. I was like, "Man, that is one noisy chip!" There has to be a better circuit out there for doing this...


I've built several '386 transmitters and never noticed a problem. Perhaps you could look over this schematic and make some improvements? http://oi67.tinypic.com/2ugynpx.jpg


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 08, 2017 6:31 pm 
Member
User avatar

Joined: Jun Sat 17, 2017 4:22 am
Posts: 1106
Location: Lafayette, LA.
Mike Toon wrote:
ab5ni wrote:
The other day I was looking at a part-15 transmitter circuit that somebody posted, and it was based on the LM386. I was like, "Man, that is one noisy chip!" There has to be a better circuit out there for doing this...


I've built several '386 transmitters and never noticed a problem. Perhaps you could look over this schematic and make some improvements? http://oi67.tinypic.com/2ugynpx.jpg


Quite easily. Get rid of the LM386 and use high-quality, low-noise, discrete components. Also, there are probably numerous, low-noise op-amps out there that will do a very good job in this application.

73,

Randy AB5NI

_________________
I eat spaghetti code out of a bitbucket while sitting at a hashtable - pay for the meal with cache!


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 08, 2017 6:43 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 7978
Location: Beautiful Downtown Burbank CA
Schematic please. Simple low parts count of course.


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 08, 2017 7:35 pm 
Member

Joined: Apr Thu 14, 2016 8:25 pm
Posts: 411
Location: pensacola fl
Hi all. Felix you are right on. I am an engineer who builds and maintains commercial am stations here. Am can out perform fm. Less bandwidth used to do it. Stereo am if done right will surprise you. You can build your own transmitter for it and a receiver as well or use a commercially built am stereo radio and widen its bandwidth.


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 08, 2017 8:04 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 29438
Location: SoCal, 91387
ab5ni wrote:
Hi Fifties,

fifties wrote:
No argument there, but what else is there to DX? FM? digital TV?



All modes can have some DX pop up out of the blue. I've seen it on VHF and UHF TV. It doesn't happen all that often, but when it does, it's quite amazing. At those frequencies, the DX signal is usually bouncing off of clouds in a storm system and tropospheric ducting. Being a ham-radio operator, I've also heard and worked numerous DX stations around the world via shortwave.

I suppose so, and I used to DX analog TV, but with the conversion to digital, those days are pretty well over with. AFA shortwave, sadly it's diminishing as time goes by.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 08, 2017 9:03 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 19321
Location: Warner Robins, GA
ab5ni wrote:
Howdy Tube,

That is always an option, but for me, it's the mystery of tuning the airwaves that is exciting.

73,

Randy AB5NI


I too sometimes like tuning the airwaves.

ab5ni wrote:
Howdy Tube,

If I ever go this route, I think I'm going to add Bluetooth to my eventual collection and just stream period radio broadcasts to my radios that conform to that era. Seems like a better solution.

73,

Randy AB5NI


Give WRDV a listen sometime.

http://www.wrdv.org/

They play a lot of the period correct music for antique radios.

When I listen to my radios I normally will stream WRDV and use Stereo Tools to process the audio a little and the resultant sound quality to me is as good as if not better than a lot of commercial AM stations.

Far as streaming the music you could build a part 15 AM transmitter and add the bluetooth receiver to it.

That way the audio can play on every antique radio you have which can receive the signal without having to connect to a different bluetooth receiver each time you want to listen to a different radio or move one bluetooth to each radio you listen to.

Will also enable listening to whatever you are streaming on radios without an external input so that you don't have to add one and will permit playing the same thing on multiple radios at one time if for instance you have other radios in other rooms and are doing things throughout the house and want to hear what you are streaming.

ab5ni wrote:
Quite easily. Get rid of the LM386 and use high-quality, low-noise, discrete components. Also, there are probably numerous, low-noise op-amps out there that will do a very good job in this application.

73,

Randy AB5NI



If the LM-386 was really a problem in the application it is used in, I do think the design would have surely been changed to a better OP-AMP long before now.

I myself use a two tube part 15 6GY6 AM transmitter.


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 08, 2017 11:41 pm 
Member
User avatar

Joined: Jun Sat 17, 2017 4:22 am
Posts: 1106
Location: Lafayette, LA.
Howdy Tube,

Tube Radio wrote:
I too sometimes like tuning the airwaves.


I love tuning the band. Also, I'm starting to wonder that if we don't do something about it and the AM stations start to slowly fade away, the FCC might try to step in and see if they can go for a band grab. Greed is always in the background lurking.

Quote:
Give WRDV a listen sometime.
http://www.wrdv.org/
They play a lot of the period correct music for antique radios.


Awesome. I was wondering if their was a stream or station out there doing this type of thing. Thanks for the link.

Quote:
When I listen to my radios I normally will stream WRDV and use Stereo Tools to process the audio a little and the resultant sound quality to me is as good as if not better than a lot of commercial AM stations.


Cool. I was planning on doing the same thing. I'm just a bit late to the game :D.

Quote:
Far as streaming the music you could build a part 15 AM transmitter and add the bluetooth receiver to it.
That way the audio can play on every antique radio you have which can receive the signal without having to connect to a different bluetooth receiver each time you want to listen to a different radio or move one bluetooth to each radio you listen to.


Hmm. Interesting idea. I'll think about it, Tube.

Quote:
Will also enable listening to whatever you are streaming on radios without an external input so that you don't have to add one and will permit playing the same thing on multiple radios at one time if for instance you have other radios in other rooms and are doing things throughout the house and want to hear what you are streaming.


Well, I was thinking about adding Bluetooth to them so that I can have the added advantage of selling them to the retro-mod crowd, should I ever decide to get rid of some of my radios to make room for more :D.

Quote:

If the LM-386 was really a problem in the application it is used in, I do think the design would have surely been changed to a better OP-AMP long before now.
I myself use a two tube part 15 6GY6 AM transmitter.


Now, I like the sound of using tubes for the transmitter :D. All I can say is this: If and when I decide to go the the "Part 15 transmitter" route, I'll either go tubes or the low-distortion op-amp route. Should I go for the op-amp, I'll redo the LM386 schematic and post a revision for those who are interested.

73,

Randy AB5NI

_________________
I eat spaghetti code out of a bitbucket while sitting at a hashtable - pay for the meal with cache!


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sun 09, 2017 12:32 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 19321
Location: Warner Robins, GA
You're welcome.

Adding Bluetooth that way would definitely be good when selling them.

If you go the tube transmitter route I have a schematic I can email you.


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sun 09, 2017 1:31 am 
Member
User avatar

Joined: Jun Sat 17, 2017 4:22 am
Posts: 1106
Location: Lafayette, LA.
Howdy Tube,

Tube Radio wrote:
You're welcome.

Adding Bluetooth that way would definitely be good when selling them.

If you go the tube transmitter route I have a schematic I can email you.


Sounds good. What I'm also thinking about doing is designing a programmable power strip. The way I see things, I won't be able to have all my radios plugged in at the same time, but what I can do is add Bluetooth and an Arduino to a power strip, and tell the thing which socket to make active. Then all I'd have to do is use multiple, intelligent power strips, and then write a program that talks to all of them. Then I'd tell a strip to turn on a socket, play a radio for a few hours, and the turn on the next and do the same thing. After that strip has played all those radios, I talk to the next strip, cycle through those radios, on and on, until my entire collection has been heard :D. Letting my radios play a few hours apiece -- with period music :D -- would be a good way to keep all electrolytics in tip-top shape, and should I hear something funky come out of one of them, I can throw it on the bench for a look-over.

73,

Randy AB5NI

_________________
I eat spaghetti code out of a bitbucket while sitting at a hashtable - pay for the meal with cache!


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 29, 2017 2:57 pm 
Member

Joined: May Tue 05, 2009 10:21 pm
Posts: 314
Location: West Windsor, NJ 08540
Hi Everyone,

I found a very interesting article about the history of the many different versions of the simple TRF AM receiver chips.

From the mid 1970's onwards, if you wanted to build a simple AM radio, chances are the circuit you would use was based around the ZN414.

n the 1980's, two more versions of the IC appeared in an 8pin DIL package. These were the ZN415 and ZN416 and were simply a ZN414 with an audio stage capable of driving low impedance headphones.

Eventually, Ferranti went the way of many semiconductor companies, and the ZN414/ZN415/ZN416 were no longer being produced. However, all was not lost as the Asian manufacturers had cloned it under a number of different types. First was the YS414 and then came the MK484, LMF501T, TA7642, and various other xx7642 types. The MK484 and TA7642 are the most common types these days.
It would be interesting to know the development of the ZN414. It is possible the concept came from one of two places. In the U.S, National Semiconductor had their LM372 in the late 60's.
Functionally, this is a very similar IC. However, it has a low input impedance, requiring a tapping on the aerial coil when used for a TRF receiver, and runs off a higher supply voltage. The LM372 has a gain of about 60dB (slightly less than the ZN414), is in a different package, and has more of its internal circuitry available to the outside world. It was intended to be used as an IF amplifier/detector, but Electronics Australia published a TRF circuit with it operating in the broadcast band, fed from a ferrite rod aerial, as one would with a ZN414. A later project saw it used in a 27Mc/s superhet remote control receiver.

The complete article that includes many schematics is located at: http://members.iinet.net.au/~cool386/zn414/zn414.html


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jul Sat 29, 2017 8:58 pm 
Member
User avatar

Joined: Jun Sat 17, 2017 4:22 am
Posts: 1106
Location: Lafayette, LA.
Howdy Frank,

Wonderful article here and on that site, dude. Ever think about writing a definitive book on the subject? If so, please let us know, as I would love to read it.

73,

Randy AB5NI

_________________
I eat spaghetti code out of a bitbucket while sitting at a hashtable - pay for the meal with cache!


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jun Fri 08, 2018 10:27 am 
Member

Joined: Sep Sun 04, 2016 9:26 am
Posts: 35
Location: North Queensland, Australia.
G'day all, just popping in to say g'day and say that my MK484 AM tuner is still working fine and sounding great. For a while I thought that it was a bit 'noisy/ hissy', but the noise turned out to be coming from my computers power supply audio line. Just isolate the audio line when unneeded and no noise! The little MK484 circuit is great and works very well. Regards, Felix.


Top
 Profile  
 
 Post subject: Re: The MK484 as a high quality AM tuner.
PostPosted: Jun Fri 08, 2018 11:23 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 19321
Location: Warner Robins, GA
Most likely that is a ground loop.

Can be easily cured with a couple 1:1 audio transformers of at least 10K primary and secondary impedance with their secondary in series and the primary becomes the audio input. You then have stereo to mono or one transformer can be used and a couple resistors used to combine the stereo channels.


Top
 Profile  
 
Post New Topic Post Reply  [ 78 posts ]  Go to page Previous  1, 2, 3, 4

All times are UTC [ DST ]


Who is online

Users browsing this forum: Google Adsense [Bot] and 2 guests



Search for:
Jump to:  
























Privacy Policy :: Powered by phpBB