Files for 160mW WBFM PLL Transmitter

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Post by Admin on Wed Apr 03, 2019 8:46 pm

Hi Abby,
Nice to see you active so soon Very Happy Very Happy 
Thank you very much for the information. I really appreciate that.

I have loads of projects that could benefit from cheap PCBs (I now lack time).
The only possible hangup could be the Swedish import fines and duty on all China products. I will see if they can ship via Singapore, or Germany, the same as AliBaba do  Cool

Best regards from Harry - SM0VPO (EA/SM0VPO)

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Post by Abby123 on Wed Apr 03, 2019 8:27 am

dare4444 wrote:10 pcbs for $2 and $12 shipping from Hong Kong

I know that there is a WellPcb company in China that produces PCBs and PCBAs, less than 100 * 100.
3 pieces, only $1.

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Post by dare4444 on Sun Dec 09, 2018 5:08 pm

The complete article looks good. I wanted a simple two stage transmitter with an usable power output. The 2n2219 oscillator is delivering between 25 - 30mW and this eliminates the need of a driver stage. The sound quality is not up to the par though but it is not noticeable in normal hobby use. The power oscillator might be the culprit as RF voltage on the varactor diode is kind of high. I have designed another 700mW FMTX. Will submit the circuit soon.. it has better sound quality and higher output power and has two 2n3904 transistors in oscillator and buffer stages and two cascaded 2n3866 RF amplifier chain with the driver operating in class AB and final in class C mode

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Post by Admin on Sat Dec 08, 2018 9:53 pm

Hi Joy,

I have now published the project on the homepages, in the TX section.
I have also updated the libks to the messageboard. It was as I thought, the index page was linked directly, but ll the other 227 pages were linked to a common file (so that I only needed to replace it once :-).

BR Harry

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Post by Admin on Thu Dec 06, 2018 7:04 pm

Hi Joy,
Everything looks perfect! 
Great, then I shall publish it shortly, but I will remove the paragraph numbers. I took the liberty of adding a couple of lines to explain what the project was all about, and a link to your previous project. When I have the time I will add a link in the previous project to this project  Smile

There’s an error in the link to the forum on your start page. It should be http://sm0vpo.forumotion.com
I am aware that the URL has changed, and I updated it a couple of days ago, late in the evening/early morning. It should be working fine now.

I used to have a bit of trouble with changing the forum address, since the link was in so many different projects. But now they are all linked to /board.htm in the root directory so I only needed to change it in one place  Very Happy

Anyway, thank you for the notification. Really appreciated.

Best regards from Harry - SM0VPO


Last edited by Admin on Thu Dec 06, 2018 7:06 pm; edited 1 time in total (Reason for editing : Changing to gooder grammer and correcting some spolling mistaikes.)

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Post by dare4444 on Thu Dec 06, 2018 2:39 pm

Everything looks perfect! You can go ahead and add the project to your home pages. The forum is not opening from the link on your main page. It opened from the newsletter link in my email. There’s an error in the link to the forum on your start page. It should be http://sm0vpo.forumotion.com

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Post by Admin on Sun Dec 02, 2018 7:38 pm

http://213.114.131.21/_new/160mw-tx.htm

Hi Joy,
I have added the 160mW project to the above URL. The homepages are not yet linked to it.
Please review it and let me know if you have any comment.

When you are happy with it I will take away the sentence/paragraph numbers and link it to the homepages.
Notice that I have added a link to your pevious project.

BR Harry

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Post by dare4444 on Fri Nov 30, 2018 2:33 pm

Thank you I have saved your notes for future references. Have a good time at your company meeting. Once the teeth are fixed then it should get easier.

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Post by Admin on Thu Nov 29, 2018 10:16 pm

Hi Joy,
You are aware that I have been sick for about 10 days, andI was feeling better by Tuesday, but yesterday (Wednesday) I had an operation at the dentist. To be honest that was the last thing I wanted.

The doc said he would give me something to make me a bit more relaxed, so I drank the potion. 10 minutes later I was feeling dizzy. I had no breakfast so the drug had a large impact. Interesting that he put two "rawl-plugs" in my jaw, the same as you do with hanging cupboards on the wall, but these are a bit smaller and made of titanium. He drilled the jaw-bone and screwed these things in, but I didn't really feel much, didn't even know he used a drill  Surprised I thought the procedure went quite fast, felt like 15 minutes or so, but he said it took over two hours! He said that at one point I began snoring  Sleep

But now I have a load of pain and a huge swelling in the side of the face. Penicillin and pain killer have been added to my daily meds. It will be like this for about 5 days more. But he cannot screw the new teeth into the plugs until the bone has grown a bit. He explained the posts are like self-tapping screws. They sit nice and firm, but they will not yet take me eating pork-scratchings. The bone has to grow around them, until about next February. As I understand it, the new teeth are a bit like the screw-in feet you get in Ikea furniture, only smaller.

Maj-lis is still in Spain, she comes here in nine days, and I want to have your project finished by then. Tonight I have downloaded the files and started processing them.

One small comment is that your text seems to lack some form of introduction, explaining what the project is all about, based on ... etc (reference to your other TX project?). What were goals and what were you trying to achieve, and so on?

The text you have given is very informative, but it seems to jump right in the deep end, if you know what I mean. Your first line of text for the project begins with "Carefully adjust VC1 for PLL lock". Do you have any observations or precautions at any stage f the build? Just a few suggestions. It could also begin with what the project actually is.

I suggest I take what I have got and put together a web page, then give you the link to review. This time I will number the sections so that there will be no confusion if you want to insert text somewhere, or have a particular text string edited. I will leave gaps in the numbers, the same as one used to do with the old BASIC programs (line numbers in increments of 10). So if, for example, you want to insert new text between lines 220 and 230, then you number the new text 225. Absolutely no confusion  Smile Then when the review is finished and you are happy with it, then we can remove the line numbering and I can publish the document for you.

Audio sounds a bit distorted with increased output power? Why is that? 
You guessed it. High-level RF to the oscillator also changes the varactor capacitance during each cycle of RF. This can cause:

1 - The sinusoidal RF waveform can begin to become trianguar
2 - With higher RF volages on the varactor then the AF sensitivity can change

If you use a vary large tuning inductor and a small tuning capacitor then the impedance and RF voltage is high. Using a lower impedance can lower the RF voltage, as well as reducing any possibility of mutual coupling between the oscillator and final stages.

It could also be caused by hitting that point where the synthesiser sees lower modulating frequencies as a frequency error, and the loop filter passes the lower frequencies.. Put your oscilloscope on the control voltage fed back to the VCO (between the VCO and the loop filter). Sweep your AF signal generator from 20Hz to 16kHz and see if there is any audio superimposed on the control loop voltage.

One little trick I learned was that R24 is 22K and with C21, you have an RC time of 200ms. This may allow some ripple below about 50Hz modulating frequency, rising sharply at 20Hz. R24 could be increased a little, but this will make the lock-time longer. If there is any ripple, then try using a 100K + 4.7K in series at R21, but put a pair of back-to-back signal diodes (1N914, 1N4147, etc) across the 100K resistor. In normal operation you will have better low frequency modulation response, but if there is a large disturbance to the loop then the diodes will conduct and bypass the 100K = 20x faster lock time.

In the filters I designed I used a short time-constant before the "biggie" (R24 + C21). The overall effect is the same, but with a short filter first then there is less ripple fed to the "biggie" so the double-diode technique is more effective. But I can see that there has gone a lot of thought into your filter design, so the AF quality you mentioned is probably somewhere else.

Sorry, just a few ramblings from a 67-year old brain bouncing a few ideas  Basketball

Very best regards from Harry - SM0VPO

PS - Tomorrow evening I will be in Stockholm having the company Christmas lunch. I may not be able to chew on much with these stitches in the gums, but I can probably have a good suck of the fish  Wink

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Post by dare4444 on Sat Nov 24, 2018 11:47 pm

Audio sounds a bit distorted with increased output power? Why is that? I have noticed that audio sounds best when it's a colpitts or inverted Harley oscillator. Is it due to low RF power on the varactor diode? In my circuit the varactor is connected between collector of the oscillator and ground. Does it induce some distortion as RF voltage levels are high on the collector?

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Post by dare4444 on Sat Nov 24, 2018 7:41 pm

Hi Harry, how's your health now?
I made some modifications and now getting almost double the power output or 360mW at 12V.

For better matching of oscillator stage to PA, I added a low inductance coil (2T 26SWG on 8mm dia. air core) between the 27p capacitor and the base of the 2n3866 final. I also changed L2 to 7T 20SWG 8mm dia. air core and VC2 with a 56p fixed capacitor. As the output power is now higher, I also increased the value of R13 feeding the 74AC74 divider to 680ohm.

This completes the modification for 2X power output.

Please add this info at the bottom of the article.

Thanks. Hope you are feeling better now. There's a breathing technique in yoga known as pranayama for better health. In India millions of people are reporting benefits from doing pranayama regularly. You might want to check it out. My mom's health is getting better because of pranayama so ya it kind of works.

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Post by dare4444 on Wed Nov 21, 2018 1:32 pm

10 pcbs for $2 and $12 shipping from Hong Kong

https://jlcpcb.com

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Post by dare4444 on Tue Nov 20, 2018 2:58 pm

Hi Harry, my ugly bug construction boards are never compact and neat due to R&D and frequent changes to the circuit until I am satisfied. So there is a lot of 'hacking' involved.

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Post by Admin on Tue Nov 20, 2018 6:59 am

dare4444 wrote:Yes the ugly bug construction works so well for RF circuits. It's quick and fast.
It is that, indeed. It can also be made very neat and compact, but we can discuss that later. I never had a lot of success above about 100MHz with PCBs. But I have used PCB for lower frequencies with a copper land for the higher frequencies, as a "module".

dare4444
Start taking a zinc supplement. It strengthens the immune system. And if you like eggs, eat 3 egg yolks a day if you can for B-vitamins, selenium, and folate and it should improve your overall energy levels. Dr. Paul Jaminet in his book Perfect Health Diet suggests this. Get well soon.

Thank you very much for the advice. I hate eggs. The Spanish eggs have a funny taste to them and I seem to have developed a real dislike for all eggs. I only use them as a glazing when I am baking pastry. But I have started eating loads of fruit, especially citrus fruits.

Last night I had no sleep as I had coughing attacks. Feels like something stuck in the throat. Probably scar tissue!!

BR Harry

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Post by dare4444 on Tue Nov 20, 2018 12:30 am

Yes the ugly bug construction works so well for RF circuits. It's quick and fast.

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Post by dare4444 on Tue Nov 20, 2018 12:29 am

Start taking a zinc supplement. It strengthens the immune system. And if you like eggs, eat 3 egg yolks a day if you can for B-vitamins, selenium, and folate and it should improve your overall energy levels. Dr. Paul Jaminet in his book Perfect Health Diet suggests this. Get well soon.

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Post by Admin on Mon Nov 19, 2018 10:11 pm

Hi again Joy,
Once again this looks really "Heath-Robinson" but it is a great example of what you can do with "dead-bug" construction.

I will download the files later in the week and have it ready for your review, probably around Friday. At the moment I am sick and about to go to bed (about an hour late :-( ). I was as sick as a dog over the weekend and I just laid in bed, sweating and coughing. But I had to spend some time on the computer to answer your massage.

Congratulations on the project. Another high performer :-) Who needs PCB*s  Very Happy

BR Harry - SM0VPO

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Post by dare4444 on Mon Nov 19, 2018 6:56 am

Harry, let me know if the design is sound and if I followed all the standard RF practices like impedance matching, decoupling, etc. I tried not to overload the oscillator. The coupling capacitor is only 27p between the two stages. Audio sounds excellent.

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Post by dare4444 on Sun Nov 18, 2018 8:09 pm

Hi Harry,

Files for 160mW WBFM PLL Transmitter. Please add this under your transmitters section.

https://ibb.co/cfO6Kf (160mW WBFM PLL TX spectrum output)

https://ibb.co/gFJSjf (Prototype board)

https://ibb.co/gBLMc0 (RF section schematic)

https://ibb.co/dggSH0 (PLL Control section schematic)

https://ibb.co/e4rKzf (Close up of L1 and 1/4 turn tapping from V+)

https://ibb.co/gwCDN0 (RF power meter for tuning. Tune VC2 for maximum peak voltage. Po = [Vpeak + 0.6V diode loss squared] / [50ohm load * 2]

https://ibb.co/mMJjh0 (50ohm dummy load for power measurement)


Carefully adjust VC1 for PLL lock. The PLL lock indicator LED should turn on. VC2 should be adjusted for maximum output power on 96MHz.

Second and third harmonic levels are -24dBc and -29dBc respectively. This particular prototype is delivering 170mW at 12V and 210mW at 13.5V DC.

When power is initially switched on, the PLL takes about 2 seconds to lock. Two 74AC74 (74F74) high speed flip flops have been used as divide by 16 prescaler. It is further divided by 8 in CD4040 and fed to PLL comparator CD4046 which in turn generates the control voltage to keep the 2n2219A oscillator on frequency. CD4060 is the reference frequency oscillator and outputs 750KHz to CD4046. A BB910 varactor diode has been used. It can be replaced with a 16V 400mW zener diode but BB910 gave better sound quality. The final stage uses a 2n3866 and operates in class B mode. It provides 10dB power gain and boosts 20mW from the oscillator stage to 160mW after the low pass filter. A three pole low pass filter consisting L5 and two 27p capacitors cleans up the output before it is fed to an antenna or external RF amplifier.

A 27p capacitor is feeding the PA stage from 1/4T tap off L1. It can be increased to 47p for 200mW power output at 12V.

RFCs 1, 2 and 3 are 1.5uH or 70T of 39SWG wound on a 10k 1/4W carbon film resistor. Without RFC3, audible tone was heard from the CD4060 crystal oscillator. R8 and C9 add 50uS pre-emphasis. C9 is five 100n capacitors in parallel. C9 should be increased to 750n for 75uS pre-emphasis. It depends on which part of the world you are in.

The transmitter was built on a 4cm X 3cm copper clad board using ugly bug construction method. Keep all leads as short as possible. Use 12V hum free regulated power supply. It is advisable to house the transmitter in a small metal box. Use a matched ground plane or dipole antenna mounted 20 to 30 feet above ground and clear of obstruction to obtain the maximum range from this low power WBFM PLL transmitter. A 78cm long wire antenna can be used but load the output with a 470ohm resistor and then connect the wire antenna. The 470ohm resistor will improve linearity as the wire antenna is not exactly 50ohm impedance and also protect the PA stage by keeping VSWR low.


Last edited by dare4444 on Mon Nov 19, 2018 9:00 pm; edited 4 times in total

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