media frequency pcb

Everything technical about radio can be discussed here, whether it's transmitting or receiving. Guides, charts, diagrams, etc. are all welcome.
Post Reply
radium98
no manz can test innit
no manz can test innit
Posts: 243
Joined: Fri Aug 26, 2016 7:01 pm

media frequency pcb

Post by radium98 » Fri Nov 24, 2017 7:53 pm

hi anyone have this plate of media frequence of db electronica mark can share the layout or could draw it i have the schematic if a collegue can draw it ?
IMG-20171123-WA0016.jpg
You do not have the required permissions to view the files attached to this post.

User avatar
sinus trouble
tower block dreamin
tower block dreamin
Posts: 412
Joined: Fri Aug 22, 2014 11:34 pm

Re: media frequency pcb

Post by sinus trouble » Fri Nov 24, 2017 10:02 pm

Nice bit of kit Mr Radium!
Looks like some kinda Band I or Band II receiver? As far as I know? the CA3189 is obsolete now so trying to reproduce this may be a challenge?
I am as stupid as I look! :|

radium98
no manz can test innit
no manz can test innit
Posts: 243
Joined: Fri Aug 26, 2016 7:01 pm

Re: media frequency pcb

Post by radium98 » Sat Nov 25, 2017 7:17 am

true mr sinus but i think this is could be replaced by ca3089 only 1 pin different it is not a kit it is from a professionnel 1ghz stl link mark DB eletronicca i only could get the schematic if any one have knowledge of drawing i need mixer part only i wanna experiment mixing any local vfo in experiment with band selective amp signal to get that 10.7 any ?

User avatar
sinus trouble
tower block dreamin
tower block dreamin
Posts: 412
Joined: Fri Aug 22, 2014 11:34 pm

Re: media frequency pcb

Post by sinus trouble » Sat Nov 25, 2017 7:18 pm

I couldn't find any data on the receiver you have? :(
Below is a nice example of a dual gate FET mixer! A simple Colpitts local oscillator is coupled to one side of the FET whilst your incoming signal is coupled to the other via a tuned network!
The resulting output from the FET is then tuned to select the IF!
I hope this helps?
LO And Mixer.jpg
You do not have the required permissions to view the files attached to this post.
I am as stupid as I look! :|

radium98
no manz can test innit
no manz can test innit
Posts: 243
Joined: Fri Aug 26, 2016 7:01 pm

Re: media frequency pcb

Post by radium98 » Sat Nov 25, 2017 7:44 pm

sinus trouble do you have the knowledge of drawing i will give you a pm later on .
one question is ca3189 can be replaced by ca3089 ? or u must see the drawing ?

User avatar
sinus trouble
tower block dreamin
tower block dreamin
Posts: 412
Joined: Fri Aug 22, 2014 11:34 pm

Re: media frequency pcb

Post by sinus trouble » Sat Nov 25, 2017 11:59 pm

Hello Mr Radium!
Im afraid I don't have the expertise to design a receiver for you? But the above circuit will work if you adjust values for your requirements!
Yes I do believe that the CA3089 can be used instead of the CA3189 without modification! Both devices contain IF amplifier, limiter and demodulator! Both will work aslong as you feed them with 10.7Mhz!
The circuit above would most likely need a ceramic filter to follow after the mixer IF output to clean things up before going into the CA3089!
Also if you are thinking of the Ghz range? PCB and layout become VERY critical! Knocking it up on a breadboard might not cut it! :(
I am as stupid as I look! :|

radium98
no manz can test innit
no manz can test innit
Posts: 243
Joined: Fri Aug 26, 2016 7:01 pm

Re: media frequency pcb

Post by radium98 » Mon Nov 27, 2017 7:28 am

Hello and thanks Sinus trouble no i am planning to make parts to a low band eg 144 mhz band but fm 15 khz bandwidths it really help i know very hard to make a receiver with lack of components i tried to guet the 3189 and i have collect schematic from here and there i finished a demodulator if board and a bf amp i still need a local and a mixer i will upload a schematic from a db can you explain how it work about the 3189 it was just question and dont need to use it just questioning
You do not have the required permissions to view the files attached to this post.

radium98
no manz can test innit
no manz can test innit
Posts: 243
Joined: Fri Aug 26, 2016 7:01 pm

Re: media frequency pcb

Post by radium98 » Tue Nov 28, 2017 7:24 pm

Any help with my last question guys ? about the mixer.how it work in details of the schematic of the bf960 i posted above i know 2 signals come ,one from local oscillator , and the second from the selective amplifier
lets say local equal 100mhz to simplify the other signal to the gate from selective pa is 110.7 mhz so after th e transfo i have 10.7 how is that ?

Albert H
proppa neck!
proppa neck!
Posts: 967
Joined: Tue Apr 05, 2016 1:23 am

Re: media frequency pcb

Post by Albert H » Tue Nov 28, 2017 9:42 pm

OK. It's slightly more complicated, but here goes....

To keep the numbers simple, let's say that you want to receive 100 MHz. The receiver input filters (usually voltage tuned filters these days, using varicaps) select the 100 MHz signal and pass it to the "mixer" stage. The modern way to do a mixer is with a dual gate FET, but there are several workable schemes....

There is a local oscillator in the receiver that is tuned 10.7 MHz away from the required reception frequency. This oscillator can be at 110.7 MHz or at 89.3 MHz - the difference between the local oscillator and the received frequencies is 10.7 MHz in either case. The mixer isn't perfect - it will have responses 10.7 MHz the "wrong" side of the oscillator frequency (called an "image" response) and at two times 10.7MHz and even further away from the required frequency. The input filter stage goes a long way to eliminating image response.

The output of the mixer stage is usually fed through a critically tuned circuit - tuned to 10.7 MHz. This also helps to eliminate the other mixing products..... Normally, there will be an amplifier stage at 10.7MHz driving a ceramic filter, which is also at 10.7MHz and defines the reception bandwidth - the "selectivity" of the receiver. Most of the receiver gain is then provided at 10.7MHz - the "Intermediate Frequency" - and the signal is usually amplified so far that it reaches a "limiting" level. This can be defined by a pair of back-to-back diodes or a transistor clipper (inside the IF amplifier chip) - you're not at all concerned about messing with the signal amplitude, just so long as the changes in frequency - the deviation - can be fed to the discriminator stage. Limiting also strips off interfering signals, which is why FM sounds better than AM - "No Static At All".

The last part of the RF bits of an FM receiver is the discriminator - this turns the variations in frequency back into audio. Homework: Look up "Foster Seeley Discriminator".

The reason for using this frequency-changing trick is that it's more difficult to amplify up at 100 MHz and difficult to get a discriminator to work well at that kind of frequency, so whatever frequency you tune to is converted to the industry standard frequency of 10.7 MHz. The local oscillator and the input filter are the only part of the circuit that need to be adjusted when you change reception frequency.
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

User avatar
sinus trouble
tower block dreamin
tower block dreamin
Posts: 412
Joined: Fri Aug 22, 2014 11:34 pm

Re: media frequency pcb

Post by sinus trouble » Tue Nov 28, 2017 10:32 pm

Cheers Albs! :)
A much better explanation than I could give!
Mr Radium, your schematic only shows the first portion of the circuit? Looks like just mixer, filter and IF amplifier?
The situation gets a little easier when working on a fixed frequency receiver? But even with ideal components, alignment can still be tricky!
I have a Bowman receiver and the only way I had of alignment was to monitor the IF with an oscilloscope whilst tuning for best amplitude? Im sure there are better methods?
Bowman B1RX.JPG
You do not have the required permissions to view the files attached to this post.
I am as stupid as I look! :|

Albert H
proppa neck!
proppa neck!
Posts: 967
Joined: Tue Apr 05, 2016 1:23 am

Re: media frequency pcb

Post by Albert H » Wed Nov 29, 2017 12:06 am

That's quite a pretty layout. I presume that the coils were standard Toko parts? Do you have a circuit diagram for it? The TDA1062 is a very old chip - from the late 70s!

I'll put up a receiver circuit later. It's a tried and trusted design and with minor changes can be used from Band I to Band V. When I wanted frequency agility, I'd add a PLL circuit to the local oscillator, to give a range of frequencies. One London station in the early 80s experimented with a "frequency hopping" link system. It worked - their link could change frequency by up to 8 MHz, and the link receiver would follow the changes, but the problem was the loud noises as the system frequency-hopped and the brief breaks in transmission each hour when the frequency changed!
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

radium98
no manz can test innit
no manz can test innit
Posts: 243
Joined: Fri Aug 26, 2016 7:01 pm

Re: media frequency pcb

Post by radium98 » Wed Nov 29, 2017 10:29 am

Thanls a bunch with big hug for both expertz .when i need more help i surely consult you man .my problem is i have made a local and a pll joint and also i made the demodulator that received the if my only problem now for experiment is to do the mixer part so why i only ask it .But one last question if for experiment @ a very close range i have a local 200mhz eg.and i route it according to my up scheme to the fet than a tunable lc from the other fet gate and completing the scheme should i have an output of 10.7 ?

Post Reply