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455kHz & 10.7MHz stuff

Online Super zHero

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455kHz & 10.7MHz stuff
« on: August 06, 2015, 11:24:58 AM »
I'd like to open a new topic dealing with these two frequencies.  They have been discussed in other radio threads here in Comm Eng but are deeply embedded and hard to find.

These two frequencies are of course used in Broadcast AM and FM radios as described in many topics by our radio guru- Bravokilo.  I will not go into details about them here but rather just touch on projects around them.

To start with, here's a signal injector that can be used in troubleshooting AM radios:




Online Super zHero

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Re: 455kHz & 10.7MHz stuff
« Reply #1 on: August 06, 2015, 11:30:06 AM »
Here's what the 455kHz resonators look like:




I don't have any 10.7MHz ones (yet).

Offline bravokilo

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Re: 455kHz & 10.7MHz stuff
« Reply #2 on: August 06, 2015, 01:09:15 PM »
Pahengeeeeeeeeeeee, sabi ng kambing.

What can I say? Good thread, you started Super Z. Related to the AM/FM IF amp ICs, plenty in the market. The one easy to find in discarded radios and even new ones from Newport (P25), is the TA2003. Of course we have a separate thread for the 2003. Here I will support Super on discussing the 455 kilohertz and and 10.7 megahertz intermediate frequencies in communications circuits. It is quite timely actually and complimentary to our "hot" topic (hinde sa Pangpalinaw ha....), na Regenerative radio receivers.

WELL:

     - THE ORIGINAL RADIOS WERE CRYSTAL SETS
     
             - the AC signal was "detected" by a crystal, which was nothing more than converting it to DC. The DC fluctuated with
                the original information modulated in the TX by way of changing AMPLITUDE or signal strength.
             
             - these sets lacked SELECTIVITY and the incoming AC signal was not amplified. Most of the amplification was on
                the audio stage which also amplified noise.
   
      APPEARED THE REGENERATIVE RADIOS.

             -  Armstrong tumbled upon the REGENERATIVE receivers and it was instant success throughout the world. The AC
                 was enhanced by way of mixing it with an oscillator in the radio oscillating at the same frequency. It was a giant
                 leap in radio at that time. We have thread on Regen radios both tube based, FET based or simply bipolar tranny
                 based.
              - the local oscillator can be tickled to the right level. Tuning and selectivity improved but amplication of the original
                signal remained an enigma.

     - AN IDEA THAT DID NOT TAKE OFF

               - one early concept was to have a series of TUNABLE RF amp stages. This meant each staged had to be tuned to
                  the desired frequency. THERE WERE JUST TOO MANY VARIABLE CAPACITORS.


     - THE ANSWER: SUPERHET

                - fortunately frequencies can be added, subtracted, divided, and multiplied. The concept of the superhet
                  was to subtract 2 frequencies.
 
                - The first frequency is the incoming signal, the second frequency is locally generated on the receiver.

                 - when these two f's are mixed, the difference can be extracted. A series of FIXED TUNED ampifiers pick up
                    the differential frequency(they are tned to this differential frequency) which is then detected to audio.

                  - the differential frequency chosen was 455 kilohertz. So, the yellow, white ans black canned transformers
                    in your AM broadcast band radio are all tuned to 455 khz. Once fixed tuned, they need not be adjusted
                    in tuning to different radio stations. The incoming antenna and the local oscillator are controlled by a ganged
                    pair of variable capacitors. As the incoming freq. is raised, the f of the LO is also raised maintaining the same
                    differential frequency ( and VV).

                    THAT IS HOW RADIOS ARE KEPT COMPACT BY HAVING ONLY TWO VARIABLE CONDENSERS.


Re: 455kHz & 10.7MHz stuff
« Reply #3 on: August 06, 2015, 01:49:57 PM »
Subscribing..
sir Super zHero, meron ka bang complete file nito?




Online Super zHero

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Re: 455kHz & 10.7MHz stuff
« Reply #4 on: August 06, 2015, 01:54:19 PM »
Wala eh,,,, hinahanap ko nga dito sa forum (contributed by BK).  Got this one from Googling.

Online Super zHero

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Re: 455kHz & 10.7MHz stuff
« Reply #5 on: August 06, 2015, 02:31:15 PM »
There's an article and project here using the 455kHz oscillator for a homemade metal locator:
http://www.zl2pd.com/miniMetal.html

Click on link above for larger diagram.
Image result for mini spot 455khz

Offline bravokilo

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Re: 455kHz & 10.7MHz stuff
« Reply #6 on: August 06, 2015, 04:30:36 PM »
Remember, any AM radio produces 455 khz dun sa collector ng mixer tranny or dun sa output ng yellow traffo. It is also modulated since you can hear the music or the announcer talking. For that matter, we can actually use any of the IF traffo to make a 455 oscillator. The red oscillator coil can oscillate in the AM band region. Incoming signal ranges from 540 to 1640 Khz. The local oscillator then has to track 540-455 to 1640-455. That is roughly 100 khz to 1300 khz. That is why we can use the red traffo to make a 1khz oscillator.

What I do when I test an RC receiver to oscillate the transmit xtal and the local oscillator xtal, the difference is 455 khz.


For the upper band ( I don't want to say FM band), 10.7 Mhz is the Intermediarte Frequency.

 

Offline bravokilo

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Re: 455kHz & 10.7MHz stuff
« Reply #7 on: August 06, 2015, 04:33:48 PM »



Here is another one

Offline bravokilo

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Re: 455kHz & 10.7MHz stuff
« Reply #8 on: August 06, 2015, 04:36:38 PM »


Offline bravokilo

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Re: 455kHz & 10.7MHz stuff
« Reply #9 on: August 06, 2015, 04:39:05 PM »
The Q1 and Q2 circuit from Super can be used to modulate the above circuit.

Offline bravokilo

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Re: 455kHz & 10.7MHz stuff
« Reply #10 on: August 06, 2015, 04:45:51 PM »


Here is for generating 10.7 Mhz.

Offline bravokilo

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Re: 455kHz & 10.7MHz stuff
« Reply #11 on: August 06, 2015, 04:51:18 PM »
REply numbe 8 shows a BFO. It sands fro Beat Freqauency Oscillator. When you connect it to the antenna of your ordianry SW rado, you will hear the single side bands.

Offline >>>^żżż^<<<

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Re: 455kHz & 10.7MHz stuff
« Reply #12 on: August 06, 2015, 07:48:47 PM »
subs...... ::)
http://www.elab.ph/index.php?topic=52236.0 TF?
http://www.elab.ph/index.php?topic=41860 ? ? ? DIY traffo Test Build Uli
http://www.elab.ph/index.php?topic=33717  I2c / spi programmer
http://www.elab.ph/index.php?topic=37150.0 Lcr esr makikigulo rin ba kayo ??? Test Build
http://www.elab.ph/index.php?topic=29963.0 Esr collection na malamig
http://www.elab.ph/index.php?topic=25854.0 Basic C++ Programming Tutorials by Prof Asimo
We only live once,treasure those we love, make friends not enemies and keep our family closer. And we will be at peace.
FISH

Online Super zHero

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Re: 455kHz & 10.7MHz stuff
« Reply #13 on: August 06, 2015, 09:05:05 PM »
Another BFO circuit, this one using the popular MPF102:

http://www.geojohn.org/Radios/MyRadios/S120/S120.html


Offline bravokilo

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Re: 455kHz & 10.7MHz stuff
« Reply #14 on: August 10, 2015, 03:22:55 PM »
I think any of the IF traffos will work. yellow, black or white. But the first one posted by Super has an internal modulation, the pair of tranny. It should be incorporated here here. For example, without the modulator, nothing will be hear if the 455 khz osc is inseted into an AM radio.

Offline bravokilo

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Re: 455kHz & 10.7MHz stuff
« Reply #15 on: August 10, 2015, 03:33:05 PM »
The Loadstar brand Signal Gen I got from E Gizmo last Saturday has 455 khz and 10.7 Mhz marked on the scale. Assuming I would spend P100 each for each frequency, yung presyo I paid of P1600, minus P200 na. Better grab one habang mayroon pa. I think 3 or 4 units left. The advantage of the SG is we would also know where the IF is tuned and moving the dial, the signal goes through. It has an internal modulator and an input jack for ext. mod. May Low and High and may fine tune.

This SG can be converted to al all band receiver as it can serve as a tunable local oscillator. It goes up to 150 Megs and up to 450 Mhz in harmonics.

May radio IC which has a 10.7 Mhz input. Google KA22471, which means I can make a coil for the amateur band(VHF) which is around 144 Mhz. The local osc is the signal gen set to less 10.7 Mhz. The differential which is 10.7 M will go through the IC and can pick up the amateurs.

Offline zirlou21

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Re: 455kHz & 10.7MHz stuff
« Reply #16 on: August 11, 2015, 03:13:07 AM »
 :) :) :)

...gud day mga masters sa AM/FM comm,sirBK &Super.

...pwede ba tayo makagawa ng freq converter para sa US.StdFM broadcast to Jpn.std FM  radio reciever.
...kase may mga surplus na japanese car stereo digital ang tuning dalawang channel lang sa pinas masagap 88.3 at 89.9mhz.
...may gawa galing china mabibili sa raon yun nga lang sablay.
...by the way ang jpnFM ay 76-90mhz(bw=14mhz) ang US-FM ay 88-108mhz(bw=20mhz).
 any idea mga sir.thnx
...NO OFFENSE pls..usapang teknikal lang,walang personalan.....

Online Super zHero

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Re: 455kHz & 10.7MHz stuff
« Reply #17 on: August 11, 2015, 07:06:51 AM »
Long time no see, zirlou.....
Di pa ako nakakakita ng Jap FM radio kaya wala pa akong input.

Offline >>>^żżż^<<<

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Re: 455kHz & 10.7MHz stuff
« Reply #18 on: August 11, 2015, 07:15:15 AM »
Nasa baba talaga freq nya parang nasa 89 lang yata tayo naman nasa 88 to 106 something kaso bihira ang istasyon na lumagay sa freq below 89 sa mga lugar natin.
http://www.elab.ph/index.php?topic=52236.0 TF?
http://www.elab.ph/index.php?topic=41860 ? ? ? DIY traffo Test Build Uli
http://www.elab.ph/index.php?topic=33717  I2c / spi programmer
http://www.elab.ph/index.php?topic=37150.0 Lcr esr makikigulo rin ba kayo ??? Test Build
http://www.elab.ph/index.php?topic=29963.0 Esr collection na malamig
http://www.elab.ph/index.php?topic=25854.0 Basic C++ Programming Tutorials by Prof Asimo
We only live once,treasure those we love, make friends not enemies and keep our family closer. And we will be at peace.
FISH

Online Super zHero

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Re: 455kHz & 10.7MHz stuff
« Reply #19 on: August 11, 2015, 07:21:56 AM »
Sige,,, duon ninyo pag-usapan sa FM thread ni BK....