Hi all,

someone have a schematic for a medium wave pll with cd4060 / cd40103 /cd 4046 and a 4608 kHzxtal?

Many thanks in advance

Roberto iw2evk
Milan (italy)

iw2evk wrote: ↑Fri Dec 13, 2019 12:49 pm Hi all,

someone have a schematic for a medium wave pll with cd4060 / cd40103 /cd 4046 and a 4608 kHzxtal?

Many thanks in advance

Roberto iw2evk
Milan (italy)

Try this Roberto:
viewtopic.php?f=11&t=1598
Have fun now!

Thanks,

i've found this schematic, but use a xtal for fcc channeling (10 khz step) https://antiqueradios.com/forums/viewto ... ynthesizer
i suppose i must due use a xtal 9,8304 for 9 khz channeling , right?

iw2evk wrote: ↑Sat Dec 14, 2019 12:50 pm Thanks,

i've found this schematic, but use a xtal for fcc channeling (10 khz step) https://antiqueradios.com/forums/viewto ... ynthesizer
i suppose i must due use a xtal 9,8304 for 9 khz channeling , right?

The 4060 in that diagram divides by 1024 - for 9Khz you'd need a 9.216Mhz crystal. Our friends at https://www.amateurradioshop.nl have 9.216, 10.24 and 4.608Mhz crystals for 40 cent each, AND they have all the chips. They have a kit for an AM pll for €20 if you want a nice circuit board... https://www.amateurradioshop.nl/webshop ... uwkit.html

The little "transmitter" at https://www.amateurradioshop.nl/ is VERY low power. You can improve its performance with a small bipolar transistor amplifier between the 4053 and the output filters. I have one here, and it has a useful range of about 600m when connected to a random length of wire outside my office window. I've set it high up the band, and as a "home broadcaster" it's fine for feeding your old valved radios with stuff that you want to hear. It's NOT going to make a "pirate radio station".

I'm working on a cheap and simple MW box at the moment, which uses PDM for efficiency. The output is Class E (actually close to C) and is about 90% efficient when loaded correctly. Details to follow

Albert any chance of sharing what that transistor stage might look like? I have one of those amateur radio.nl boards and am interested in amplifying it a little, but unsure of component values etc for adding that transistor

Ciao,

try this simple 2n2222 stage with heatsinks (output about 1,5-2 Watt)

Ciao,

try this simple 2n2222 stage with heatsinks (output about 1,5-2 Watt)

iw2evk, thanks for that.

I wonder though how to match such a stage to the transmitter Albert refers to, or whether you could just disconnect C16 and couple it through that?

(schematic here BTW: https://www.nfor.nl/radioforumservice/p ... AM_Osc.pdf )

I assume a pretty high impedance output. The presence of R5 interests me on the output network, it would be a Pi network if a capacitor was there instead

Its a nice little unit for the use Albert suggests, just in its unmodified form you can struggle to cover your property with it when you have brick walls to contend with. A boost to its output would make it pretty nice

Whath you thinks about using this linear module 3w out ?

https://www.banggood.com/it/1MHz-1000MH ... rehouse=CN

Looks nice but needs a 50 ohm input and will be 50 ohm output. 50 ohm output for these kind of transmitters isn't so good as it takes a lot more effort to properly match them to an electrically short antenna at such low frequences

see here for preamplificator and power stage of am trasmitter on medium wave home made

https://drive.google.com/drive/folders/ ... xyTJSAK0mM

The PDM design is now well advanced. I've got 20 Watts carrier power and it peaks at just over 80 Watts (about 105% mod). It uses two cheap IRF-series FETs, one for RF output and the other for the modulator. The modulator works at about 70kHz, and varies the mark / space ratio of an oscillator. The variable-width squarewaves switch the modulator FET, and the filter network at the output of the FET converts the density of the squarewaves to a varying DC voltage for the PA supply.

There are two problems with the design at the moment, but I've found a way around the worst of the two. The lesser problem is my use of a little coupling transformer between the PLL logic output and the RF final amplifier. I can't find a way of getting rid of this little nuisance - its presence makes the drive circuit simple to the slightly weird PA, and the final FET operation is properly independent of the PLL - preventing unwanted coupling of big signals into little circuitry!

The bigger problem was that the original idea required the use of a P-channel FET for the final (or the modulator), but this wasn't terribly practical since N-channel are more robust and more widely available. I got around the problem in a fairly novel way, using a fixed +36V supply through an RF choke to the drain of the N-channel FET, and (effectively) modulating the PA ground voltage with the modulator FET! I saw something similar done in a valved rig years ago (there's nothing new under the sun!), and the use of an output matching transformer means that the PA "ground" is isolated from the real ground, so the output LPF can be done in the usual way.

I still have some residual 70kHz ripple in the carrier at full modulation (the 70kHz spurs are at -66dBc - more than I'd like), so I have to work on the modulator filter some more. I might need a further coil (though I hope not).

In the end, this will be a cheap, easy to build rig. There will be two RF transformers to wind (not a huge number of turns), two modulator chokes to wind, one RF choke to wind and two output filter coils...... It's designed to be used anywhere in the MW band, but you'll have to make the output filter suit the part of the band you're using. If you don't mind winding an insane number of turns on to toroids, it could be used down on long wave too. Efficiency is much higher than is usual with AM gear, and nothing (so far) runs hot! The modulation sounds pretty good as it is, but I mean to add some envelope feedback to further improve the modulation quality. I'm also going to add audio input filtering, so that the response is right for a MW channel, but I'll put in a bit of "presence" boost to make it nicer to listen to.

Circuit details to follow soon!

Albert H wrote: ↑Sun Dec 15, 2019 4:36 am The little "transmitter" at https://www.amateurradioshop.nl/ is VERY low power. You can improve its performance with a small bipolar transistor amplifier between the 4053 and the output filters. I have one here, and it has a useful range of about 600m when connected to a random length of wire outside my office window. I've set it high up the band, and as a "home broadcaster" it's fine for feeding your old valved radios with stuff that you want to hear. It's NOT going to make a "pirate radio station".

I'm working on a cheap and simple MW box at the moment, which uses PDM for efficiency. The output is Class E (actually close to C) and is about 90% efficient when loaded correctly. Details to follow

Albert I assume you added an extra transistor to yours - would you mind sharing what you did exactly? I have one of these boards exactly for the purpose you describe and would love to get a little more out of it

Thinking about it, the specs state 12-15v. But looking at all of the datasheets, the ICs seem good with up to 20v supply. I might stick 18v into it and see what it does - its a higher voltage for the CD4053 to switch, which should translate to higher voltage to the antenna...This is definitely the case when switching up to 15v from 12v.

Maybe that stage will just bolt on - I wouldn’t have thought so to be honest.

For anyone interested, The unit does work and works better off 18v - higher voltage observed at the antenna as a result

Here's the little "PA" I added to one of these boards. The range increased from about 40m to around the block!

Albert, thank you so much for this! I’ll enjoy putting this together over the hols. Merry Christmas to you sir!

Adam

Hi Albert, well so far not much luck with this circuit. I etched a few little PCBs to test it on.

What im finding is it is VERY easy to overmodulate and cause distortion. I cant get the audio near to the level it was at on the standard board, and range is poor. I am seeing quite high antenna voltages though (via a multimeter and probe circuit), so its doing something....

Few questions if I may,

-For the 1mh and 2.2mh chokes I have used small axial leaded epoxy inductors - should this be ok?

-Im sending the signal straight from the 4053 into the circuit via the 0.1uf capacitor shown on the diagram. I tried using the original 470pf capacitor instead and it seemed to be slightly better

-The output is fed back to the output filter, including the 100k resistor to ground. This resistor is interesting as Ive never seen a resistor on a Pi network - perhaps a pulldown resistor for the 4053? Maybe i'll try placing this after the 4053 as it was originally and sticking a capacitor in its place.

Id really appreciate any suggestions you have, I will definitely be experimenting some more as it would be lovely to get it working well

EDIT - perhaps I'll scope the modulation and see what its looking like, maybe its not behaving linear. Perhaps some adjustments to the biasing at the base?

All the best
Adam