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If you read this, You'll get some great laughs.

Cruiseomatic

Dark side of the Sun.
Dec 28, 2011
110
3
28
So lately I've been having some questions come up after dealing with what I have on some rigs and wondered, If it is possible, Would it work, Should I do it, Etc...

First is, If they (OEMs) wax a couple of the cans to keep their tune, Could you possibly wax all of them instead and put some around the VR trimmers aswell so everything holds it tune? Right kind of wax that is.

Second is, Modulation limiters. Here lately, clipping them has become a big issue. But we all know what happens when you do and when you don't. And clipping that diode disables the entire AMC circuit, Yes.
So, Instead of clipping it or lifting a leg which I prefer, Why not put a resistor inline with it to cut down how much voltage it receives so it doesn't slam back so hard? I have two radios currently, BOTH will touch 14-15 watts then get slammed back to 5-7 and a meter that shown it at only 40-45%. I also have two techs that one, who did the alignment swear they're at 100% using his scope and SA. Another who hasn't ever seen them said the meter used is junk and wrong. But wait, They'll kiss 15 but the meter showing only 40-45% is wrong.... Lets do some math. If you take 45% of 15, What is that? Correct 6.75. Here, I even had google confirm my "old school" math.
https://www.google.com/search?q=8%+of+15+is+what&rlz=1C1EODB___US623US623&oq=8%+of+15+is+what&aqs=chrome..69i57.4104j0j1&sourceid=chrome&ie=UTF-8#q=45%+of+15+is+what
Now, if I'm "averaging", meaning it stays close to that for the most part, 6-7 watts PEP output but will hit 14-15 before limiter kicks in, That tells me, I AM running 45% total mod and the meter was not lying but that the "tech" did not tune as he said he did. He did specify though that instead of an almost industry standard of 1kHz at 30 mv, He did 1 kHz at 10 mv. Claims it doesn't matter as the AMC kicks in at 3mv so it is adjusted properly. He also said to do a RX alignment, He goes by a SINAD meter and not "factory procedure". I also have a power imbalance. One side will do slightly more than the other. For example: 40 will do 7 watts PEP but 1 will only get to 5. Also, DK levels are different on both sides. Hell, Both radios do different levels yet were aligned the same... One can't even key up on 36-40 without twitching hard like it isn't getting enough power to fully key. But later on it will but has a delay of about a half second. $40 per radio and they're still basically stock. He wants me to send them back so he "Can look at them." Afraid to at this point. But anyway. So I did a small very unscientific test. Carefully noting current position of VR so to return it when done, I used my phone and a 1khz test tone with full phone volume right at mic screen. Not only does the AMC ignore the tone and some tones(Sweeping) push the radio further than others, but once the VR goes so far, so does the output and further turning does nothing. SO, without clipping it, Could one use say a 1K resistor inline with diode instead? I did put the VR back as it was set. But have a few other rigs I'd like to try this on. Namely one thats already been clipped and has been for years. I actually have videos of what they're doing....

Third, Where can one get a SA and scope or a combined unit without spending a two weeks paycheck for it? Even a SDR type would be fine for me. Gives the same results.

You're dying from laughter now aren't you? Thought so. Now, I'll kick back and watch everyone put in their thoughts and opinions on all this.
 
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ok i read through that monstrosity and have a couple of points for you to consider.

first, you are trying to interpret things using your observations over what test equipment tells you.
why?
If it's because you don't trust your tech, then find one that you do trust.

If i understand your statement about your power output correctly (i believe you left out a couple of details like what your deadkey is set at) then it sounds like the problem is not with your techs, but with your antenna and your meter.

first, the "power imbalance". If your tech is worth his salt, he is tuning your radio using a dummy load, and dummy loads are pure 50 ohm resistance regardless of the HF frequency.

chances are when you take your radio to the tech that tuned it, it will show the same power output on 1 and 40.
this means that your antenna acts different on channel 1 than it does on channel 40.
all antennas do this to some degree.

second, the modulation percentage.
let's assume that you have a 4 watt deadkey. using your meter in AVG mode, at 100% modulation, it should read 6 watts.
In PEP mode, it should read 16 watts.

from what you posted, it sounds like your radio is tuned to 100% modulation, and your modulation meter is not accurate.
modulation meters sold for the CB market are not accurate and should not be used for quantitative testing.
it's really just something for you to use as a reference to see if your mic battery went dead or something like that.

as for the wax thing, yes you could just wax the entire PC board and nothing would ever move.
would that prevent the radio from going out of tune eventually? no. not a chance.

component values change over time for a variety of reasons and that is precisely why they put adjustable components in your radio.


as for adding the resistor in line with the diode, sure, you could do that and change the response curve in some way, but you really don't need to.

think about it like this, the VR that sets the modulation is not at max when it is adjusted for 100% modulation, so bumping it up from there is the same thing as adding the resistor you are talking about.

LC
 
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He did specify though that instead of an almost industry standard of 1kHz at 30 mv, He did 1 kHz at 10 mv. Claims it doesn't matter as the AMC kicks in at 3mv so it is adjusted properly.
Turn the knob up to 11, have him do it at 40mV haha, nope 30mV would be my "guess" reading the friggen manual and all, if that is what it says anyway....

Maintaining a near-constant 100% without overmod while talking can be tricky w/out the right mic, tune, or "processing" (voice).
Have you tried running a power mic?

P.S. what model radio is this thread about?
https://www.w8ji.com/amplitude_modulation.htm
 
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So much for email notifications, Lol.

ok i read through that monstrosity and have a couple of points for you to consider.

first, you are trying to interpret things using your observations over what test equipment tells you.
why?
If it's because you don't trust your tech, then find one that you do trust.
(Its not that I don't "trust" him, I've never used him before.)

If i understand your statement about your power output correctly (i believe you left out a couple of details like what your deadkey is set at) then it sounds like the problem is not with your techs, but with your antenna and your meter.
(One radio has a deadkey of 2 and the other is 2.5)

first, the "power imbalance". If your tech is worth his salt, he is tuning your radio using a dummy load, and dummy loads are pure 50 ohm resistance regardless of the HF frequency.

chances are when you take your radio to the tech that tuned it, it will show the same power output on 1 and 40.
this means that your antenna acts different on channel 1 than it does on channel 40.
all antennas do this to some degree.

second, the modulation percentage.
let's assume that you have a 4 watt deadkey. using your meter in AVG mode, at 100% modulation, it should read 6 watts.
In PEP mode, it should read 16 watts.
(In AVG mode, It reads same as DK. In PEP, it "swings" to 14-ish then slams back down to around 6 once limiter cuts in.)

from what you posted, it sounds like your radio is tuned to 100% modulation, and your modulation meter is not accurate.
modulation meters sold for the CB market are not accurate and should not be used for quantitative testing.
it's really just something for you to use as a reference to see if your mic battery went dead or something like that.
(While thats true, Its gives some loose idea of what you're doing. Would love to get one for amateur radio and use it.)

as for the wax thing, yes you could just wax the entire PC board and nothing would ever move.
would that prevent the radio from going out of tune eventually? no. not a chance.
(Not to worried about it loosing tune as I am vibrations from mobile environments shaking the components enough to break the PCB pads loose.)

component values change over time for a variety of reasons and that is precisely why they put adjustable components in your radio.


as for adding the resistor in line with the diode, sure, you could do that and change the response curve in some way, but you really don't need to.
(What kind of curve would it change? Response time? Cut in current level?)

think about it like this, the VR that sets the modulation is not at max when it is adjusted for 100% modulation, so bumping it up from there is the same thing as adding the resistor you are talking about.

LC

Trying like Hell to figure this out because I have a 68 that had its diode cut for years. It would do 14-ish all the time. Put limiter back in as a test and AMC would kick is as it should and brought it down to around 7-8. Using a tone, I adjusted the VR until PEP no longer rose then backed it down maybe a watt. Still has almost half turn to go. Same PEP as before with cut diode and sounds the same. Still get great reports with it if not better ones. WITH the limiter in and still getting full PEP of 14-15. Why can't these two do that? And why is it one can't key on 36-40? Thats what I don't get. If the 68 can be tuned for 100 and still do full PEP with limiter as without, Why are these 78's having such a hard time? And yes, The RFI slugs are still in although one was missing. I reinstalled one from a parts rig. And the 68 does need a alignment as the RX is pure trash and I'm sure the emissions are outrageous.
 
Turn the knob up to 11, have him do it at 40mV haha, nope 30mV would be my "guess" reading the friggen manual and all, if that is what it says anyway....

Maintaining a near-constant 100% without overmod while talking can be tricky w/out the right mic, tune, or "processing" (voice).
Have you tried running a power mic?

(No, I haven't as I've always had the thought that a good and properly tuned radio doesn't need a bulky power mic to have clean loud audio. Thats a trucker thing really since they all have to be the loudest and have 60 Kw to get out to the guy next to him.)

P.S. what model radio is this thread about?
https://www.w8ji.com/amplitude_modulation.htm
 
What i was trying to explain to you is that cutting the diode and turning the AMC pot are doing the same thing.
yes, clipping the diode takes the VR completely out of the circuit, and turning the VR all the way up basically does the same thing.

when you were experimenting with your 68, you were doing the same thing by replacing the diode and using the VR.

without an oscilloscope, you really cant make any real measurements by which to judge the differences made by adjusting the pot.

again, stop paying attention to your modulation meter, as it is just confusing you because it is not made to do this type of testing.

if you have a radio that keys 4 watts on channel 1, and won't key up at all on channel 36-40, then you absolutely have a radio problem, and it's not just your antenna.

It's starting to sound to me like your tech(s) might not be the experts they claim to be, and your only solution is to take the radios to someone who does know what they are doing.

the problem here is that there are too many variables at play and without seeing the radio for myself, i can't tell you what you might be misinterpreting.

I will say that from my experience it sounds like your radios just need a proper alignment/ tune-up.

they should all be capable of making 20 watts PEP or so, and should easily do 16 watts from a 4 watt deadkey.
LC
 
I'm just experimenting with it. I know its not the "proper" way but its a start. And the VR on the 68 was far from wide open. One 78 will DK around 2-3 on Ch.1 but 36 through 40 and it has Hell trying. Actually have a video of it doing this.
They were sent in for exactly that, a tune-up and alignment. Having MOSFET finals stock they should easily do 20.
The "tech" wants me to send them back to him so he can "fix" a problem that should of been detected before they left. I asked for a video of what they're doing when I sent them but never got the video. Spent $40 a radio for this. The RX is perfect and spot on but TX sucks. The tech was a "Mikes Radio Repair". Communication is lacking at best usually. I got the shipping label a few days ago and just not sure if I should send them back or just ask for a refund on all this. I've got many radios needing various types of work and from his videos, I thought this is the guy I need. Now I'm wondering. Most of the work I can do but its the RF that I need help with. Looking for a scope and SA for myself but can't find one that is even close to affordable.
 

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