Ham radio allignment without a SSG Is there an Ic capable of tone modulation? - Page 1
Forum section: electronics / beginners

author: pitpat
author_rank: Contributor
timestamp: September 28, 2021, 04:38:29 pm
content: Hi there, i need to reallign an old Icom V200t.As stated in the service manual I need to provide with a SSG a signal that has:level 1mV (-47dbm)modulation 1kHzdeviation +-3.5 kHzTo measure the SINAD (I do have the sinad sw)Now, can I avoid to go in the search of an instrument that can provide those values and get some sort of IC that can do all of the above?I do have an Oscope but other than this application I do not find a reason to also own a signal generator.Thaks a lot for the timeFederico.

author: bob91343
author_rank: Super Contributor
timestamp: September 28, 2021, 10:58:13 pm
content: You can borrow a generator or use a signal from a repeater.

author: CJay
author_rank: Super Contributor
timestamp: September 29, 2021, 02:05:41 pm
content: Why not use the PC to generate the tone and the oscilloscope to check/set the amplitude?

author: pitpat
author_rank: Contributor
timestamp: September 29, 2021, 04:54:00 pm
content: Hi thanks for the reply!That was my original plan but what about the deviation? isn't the signal required to be FM?

author: xrunner
author_rank: Super Contributor
timestamp: September 29, 2021, 05:12:23 pm
content: Quote from: pitpat on September 29, 2021, 04:54:00 pmDo you have a spectrum analyzer? If so, you can check the deviation using the bessel null method by looking at the transmitter's output spectrum. But without the SA, I don't think you can get there.

author: bob91343
author_rank: Super Contributor
timestamp: September 29, 2021, 05:46:41 pm
content: In my garage I have a Lampkin deviation meter that should solve the problem.

author: CJay
author_rank: Super Contributor
timestamp: September 29, 2021, 06:18:13 pm
content: Quote from: pitpat on September 29, 2021, 04:54:00 pmMy bad, yes, you need to modulate a carrier with the tone form the PC. To do that you could use something like an Si5351B (I think) which has a VCO input that can be used to FM the output.You'd need to use something like an Arduino to control the Si5351 chip

author: bob91343
author_rank: Super Contributor
timestamp: September 29, 2021, 08:50:45 pm
content: Part of the problem is measuring the deviation.

author: pitpat
author_rank: Contributor
timestamp: September 30, 2021, 07:48:38 am
content: Quote from: CJay on September 29, 2021, 06:18:13 pmOh thats a cool IC! thanks a lot!About the deviation, can't I just use an Oscope? 3.5khz is well below the 20Mhz upper limit of my scope.I can buy a nano vna (also needed for another project of mine) if that might help.

author: Kerlin
author_rank: Regular Contributor
timestamp: September 30, 2021, 09:20:12 am
content: Your a licensed ham so you must be familiar with a 1 FET collpits RF oscillator. Make it stable by using npo ceramics and good passives.Make it variable using a varicap to avoid frequency variations due to hand capacitance. Put a 2N2222 buffer on it.Run it into a another hard driven buffer to produce square waves out then use a multiplier stage to freq multiply it, filter it and buffer it. Five transistors at $0.30 each and a few passive bits. Use a cheap freq meter or a freq meter kit to see where its on.Use a resistive pad as an attenuator.Have done this. Made it unsurprisingly stable by putting it all in an aluminium (for RF shielding) box with a one watt resistor that is producing above room temperature heat.Turn it on wait one hour and its stable. RF done.Use a twin T oscillator (one transistor) at freq some where around 1khz to deviate the RF gen you have made. Deviate it by feeding the sine wave into the Varicap thats used for adjusting the RF freq on the Collpits oscillator.Align it buy looking at the sine output from the radio on a CRO. If you don't have a CRO then make a sharp filter for the audio freq, rectify it, amp it and display it on a meter. Or even have a go at doing it by ear, it will for sure get it working well enough to have contacts.Gaining intuative experience in RF is what makes hams masters of RF and allows you to develop and practice what other electronics people call "The Black Art".Being a Black Art practitioner is a totally massive advantage in professional life.People stand back just stunned when you can show good RF skill, worth getting it.Get a pdf copy of the ARRL handbook and spend time reading it, as a licensed ham you must be familiar with most of it.Googled and found the manual herehttps://www.rigpix.com/protrx/icom_icv200t.htmMost probably much more available on the net.

author: xrunner
author_rank: Super Contributor
timestamp: September 30, 2021, 11:13:35 am
content: Quote from: pitpat on September 30, 2021, 07:48:38 amNo.You seriously need to do a little research on your own now. Come on - you have the internet at your hands. Search this -"How to measure FM deviation"

author: bob91343
author_rank: Super Contributor
timestamp: September 30, 2021, 04:22:54 pm
content: A deviation meter or a spectrum analyzer can measure deviation.

author: pitpat
author_rank: Contributor
timestamp: September 30, 2021, 05:06:33 pm
content: Hi, what a reply thanks a lot! Yes I do need to study a bit more on the subject, as a matter of facts the ham radio license where i live require more of the bureaucratic stuff than the actual technic...Is there any chance that you have the schematics for such a circuit? Put togheter a generic culpitt oscillator shouldn't be a big problem, making it variable might be...I'll eventually get there, for now I'll have a good read of the AARL handbook.Thanks again!

author: pitpat
author_rank: Contributor
timestamp: September 30, 2021, 05:25:44 pm
content: Thanks y'all for the replies, yes I had a google session and read abot deviation measurement.I'll try to find an instrument capable of measuring it, if I also manage to make a circuitry that output a measurable signalIt's all new stuff for me and I do know that an experieced radio technician could easily reallign my radio but its just not how I do things, whats the point if I dont risk to break something?

author: bob91343
author_rank: Super Contributor
timestamp: September 30, 2021, 05:51:40 pm
content: pitpat, I like your attitude. You are trying to improve, to learn, to rise above your current capabilities. That's one of the most important parts of amateur radio, and it gets pushed aside by too many who just want to play with the knobs and collect QSOs.I have some very nice test equipment. I use it not for its intended purpose but rather to play with the capabilities. I look at the spectrum of a signal, AM or FM or CW, and see what the sidebands are like and how strong the harmonics are. I have learned a lot about Fourier and Bessel, and it has helped me understand what my radios do. I even built, with the help of another ham, a digital readout for my old Kenwood analog radio. I diagnosed a fault with one of my antennas.I hope you will continue on your quest for understanding. Read more books, enroll in an engineering program, or whatever you enjoy. Don't worry about the opinions of others.

author: pitpat
author_rank: Contributor
timestamp: September 30, 2021, 06:46:10 pm
content: Thanks Bob!I've always been actracted to the practical side of the world. If something moves I want to know how it does it, disasseble tweak and understand.I wasn't initially really actracted to electronic, mostly just to the practical side untill I was introduced to the theory behind it by the academic world and realized how beautiful is.I am currently taking my engeenering school and it really helped developing my passions.I'm slowly starting to collect some test equippment on my workbench, mostly to be repaired, but as student I try to keep it low and buy only the things I need the most.

author: Kerlin
author_rank: Regular Contributor
timestamp: September 30, 2021, 09:45:16 pm
content: Must be something wrong with the internet there.Agree with comments that you need to seriously do some internet searches.I had no problem with finding a sites with circuits and information on building your own deviation meter with a few dollars of parts.

author: bob91343
author_rank: Super Contributor
timestamp: September 30, 2021, 11:30:05 pm
content: I think he is less interested in building test gear than he is in understanding how stuff works. He's on the right track with engineering classes. Building someone else's project may be useful at the moment but knowing the theory behind it is a much more powerful thing.Currently I am reading a big fat book named Handbook of Physics. This is an amazing tome, with revelations on nearly every page, stuff I thought I knew but only touched the surface. The book was published about 55 years ago but nearly everything in it is still current. I have learned about scientists of whom I had been unaware, and most important, have gained some insight as to the way to think. I am humbled by this book but do not recommend it for the faint hearted, as it goes deeper than most would like.

author: Kerlin
author_rank: Regular Contributor
timestamp: October 01, 2021, 05:55:55 am
content: Since we are wandering off topic and I think he is pretty much done and answered anyway.I am interested in such books Bob.When I was a teen an engineering graduate named Tim found his graduate thesis project and presented me with it.It was based on some research he found in an old library in some ancient library books, over 120 years old.The way he described those books to me was awesomely fascinating.They covered experiments on putting electrical signals into the brain. Tim told me they were experimenting with things that could not be done now by using homeless people.His device used head probes to hook up to the brain.It was able to generate brain waves. The shape, frequ and amplitude were variable.He gave the device to me but refused to give me the paper on it as he wanted to continue the work on it one day.He claimed that he had some good success with reducing pain with it and was considering developing it to use in medical operations.As a teen I thought I had come across some pure electronics Alchemy.Tell me more about your book - whats it called, who by, how old.

author: pitpat
author_rank: Contributor
timestamp: October 01, 2021, 08:23:22 am
content: Hi Kerlin, good morning!Yes I didn't explain myself very well, I was asking for the actual circuit you were talking to so that i could do some research based on that. Actually I was more intrested in the actual rf generator circuit, dont get me wrong you gave me a lot of hints to study on, I was just curious since you said you already done something similar.About your friend's research, I've read somewere about a research about using some circuitry to neuro-stimulate the brain to navigate the poor things by remote.Biomechanics is a topic that really fascinates me, I recently had a class and got the opportunity to have some lab experimentation with EEG to locate sources of pain on post traumatic patients. Really cool stuff...PS. Found it:https://ibionics.ece.ncsu.edu/assets/EMBC_12.pdf

author: CJay
author_rank: Super Contributor
timestamp: October 01, 2021, 01:52:08 pm
content: Quote from: Kerlin on October 01, 2021, 05:55:55 amSounds like a biphasic pulse/waveform generator, coincidentally a TENS machine is also a biphasic pulse generator.

author: TimFox
author_rank: Super Contributor
timestamp: October 01, 2021, 03:47:33 pm
content: A "real" standard signal generator (SSG) includes modulation capability and (very important) good shielding to achieve extremely low leakage, so that the low signal outputs with high attenuation settings are legitimate.In the past, to check FM deviation of a carrier within the bandwidth of my 7603 analog oscilloscope with delayed time base, I carefully set up the trigger and delayed time base so that I could see the extremes of the next zero crossing after the trigger zero crossing. This gave me the difference between minimum and maximum period, which allowed straightforward calculation of the frequency deviation. Delayed time base has perhaps become a lost art since then.

author: fourfathom
author_rank: Super Contributor
timestamp: October 01, 2021, 04:06:45 pm
content: With an audio tone as the modulation source, you can use a cheap SDR as a spectrum analyzer and use the Bessel null procedure to determine the deviation. Here's an SDR that will work at the VHF frequencies of the Icom radio:https://www.amazon.com/RTL-SDR-Blog-RTL2832U-Software-Defined/dp/B0129EBDS2/(about $30 -- you can find cheaper, but I like this one). A PC soundcard/dongle can generate the required variable frequency and amplitude tones.

author: bob91343
author_rank: Super Contributor
timestamp: October 01, 2021, 06:16:30 pm
content: Kerlin, as I said, the book is called Handbook of Physics, published around 1965. I don't see it as a handbook but more as a survey of the entire field of physics. It attempts to bring together the various specialties into a sort of unified whole.It was written by a large group of scientists including some famous ones. It's probably 1000 pages or maybe more. One chapter was written by Bardeen, one of the inventors of the transistor. He covers all the way from basic semiconductor physics to diodes and transistors and rectifiers and FETs and lots more. Not just a survey but quantitative information with graphs and equations and an attempt to explain how everything works.You have to be a serious student to get through this. Many times certain principles are assumed known by the reader. Not all parameters are satisfactorily defined but over all I think it's worth your time. I searched the web but didn't see any references to this book. If you are interested I will get it and give you the ISBN and other data on it.

author: Kerlin
author_rank: Regular Contributor
timestamp: October 02, 2021, 02:48:24 pm
content: Ah yes you did give the name.I was suffering from the thing I see a too much of on forums, a lack of reading comprehension. I read it as a handbook on physics, instead of that being the actual title of it.Pipat.As I covered in my post the circuit is a collpits oscillator.Again I googled it for you, again. I just googled collpits oscillator - not hard?If you dont like that one there are many more.http://vu2lvj.blogspot.com/2014/03/a-2-stage-colpitts-variable-frequency.htmlYou can use many types of FET in that circuit including MPF102.

author: Kerlin
author_rank: Regular Contributor
timestamp: October 02, 2021, 04:09:11 pm
content: Before you ask. That link is to a variable oscillator for the 7mhz band.To get it to work at a higher frequency you need a smaller coil and a smaller variable capacitor. Maybe 6 turns on 5mm and a 0 to 50 pf variable capacitor.It can be calculated using the normal formula for tuned circruits 1/2 pi root LC. To save you the trouble of the mathematics you can use a tuned circuits calculator that you will find on the net.If you refer back to my post on how to do make this then you will see that this oscillator needs to run at 147 Mhz divided by 2 or 3, depending on wether you use a double or a tripler (both only use one transistor). I can't exactly remember but I think a tripler is easier to get running than a doubler.So your oscillator will run at 49 Mhz.Get that running first build this oscillator stage.You can of course buy cheap DDS signal generators which is one other simple way of doing this.You really need to get a pdf copy of the ARRL handbook of the net and read it. You will find it has a section on frequency multiplication.In your first post I notice you mention that you come in to electronics from the practicle side.This is a common mistake. There is no such thing as practicle side verses theory side. You need both and the theory is the most important.In Melbourne Australia at the moment we are locked down at home.It has worked ok as we have only had around 1000 deaths (which is still to many).Some are watching a web camera that is showing the nest of some rare Peregrine falcons. Many around the world are watching it.They are the fastest animals on the planet they have been measured at 390k kmph.I watched a replay of the chicks from last year which showed the first flight of the young birds.Fastest animal on the planet a mighty falcon but these ones can't yet fly.They walked over to the edge of the building looked over, made a lot of noise, then just jumped off 32 floors up.Take the jump, NOT OFF A BUILDING, into electronics, in this case RF. Build the oscillator stage.Later on when you are into heavy software you will have earned the right to jump off a building.

author: pitpat
author_rank: Contributor
timestamp: October 03, 2021, 02:43:01 pm
content: Hi Kerlin, Thanks a lot for the patience! I just bought a copy of the ARRL Handbook as you suggested.So, let's see if I got this right in order to close this thread.To measure the SINAD I have to generate a signal with a carrier of 144Mhz modulated to 1Khz and Deviated max to +-3.5 Khz.Note that my radio works in the ham vhf band so 144-146Mhz the one you found the service manual for is the 80Mhz version not sure if that changes anything.Now with the colpit oscillator I make a 147Mhz and then divide it by 3 (why not directly on 144Mhz as needed for the carrier?)Filter it and attenuate it to the requested level and then feed in to the "tank" of the oscillator a 1khz sine generated with a twin T oscillator as you suggested.Finally get the signal into the antenna line and measure the SINAD from the speaker output.Am I right? I'm still a bit confused about deviation in general...

author: xrunner
author_rank: Super Contributor
timestamp: October 03, 2021, 03:07:12 pm
content: Quote from: pitpat on October 03, 2021, 02:43:01 pmJust a note ... the standard FM deviation in the 2 meter ham bands (at least in the US) is +/- 5 kHz. The Icom IC-V200T (professional land mobile rig) does 5 kHz deviation "according to the version"Check here -https://www.rigpix.com/protrx/icom_icv200t.htmIf the one you have does not do 5 kHz deviation it isn't going to sound good to other hams using standard ham rigs ...

author: pitpat
author_rank: Contributor
timestamp: October 03, 2021, 05:00:29 pm
content: Thanks xrunner, yes the deviation should indeed be +-5khz according to the manual.Another thing, shouldn't be better to feed the modulation signal to a buffer instead that directly to the oscillator?

author: xrunner
author_rank: Super Contributor
timestamp: October 03, 2021, 05:11:34 pm
content: Quote from: pitpat on October 03, 2021, 05:00:29 pmYes, all the radios I've adjusted I go into the microphone input stage (the service manual instructions will say that). Something like 50 to 100 mV is usually about right.

author: bob91343
author_rank: Super Contributor
timestamp: October 03, 2021, 05:56:00 pm
content: I think the publication date is more like 1967.