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Modulation meter low bars on radio

Limeybastard said:
Did you notice the vr dead key pots and amc were clockwise to increase resistance ?
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Yes, That's typical on most radio's. I believe I mentioned that earlier that the pot adjustments are reverse.

Leapfrog just posted a real good explanation of the different kinds of limiter mods.

I discourage doing mods like that but they have their purpose for some people.
 
fourstringburn said:
Yes, That's typical on most radio's. I believe I mentioned that earlier that the pot adjustments are reverse.

Leapfrog just posted a real good explanation of the different kinds of limiter mods.

I discourage doing mods like that but they have their purpose for some people.
Click to expand...

The chasis where b754 is attached to, did you notice the frame getting very hot there with the amp cover renoved that is.

Also, will you be doing a amp switch mod on yours?
 
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Over the course of making adjustments it got right up there heat wise. I wouldn't say it got very hot.

I'm curious if the fact your RF power knob being all the way up is still volting up the circuit creating excessive heat even though the high/low pots are keeping the deadkey/PEP in check.

One thing we didn't see on your video was your SWR reading. This can affect your adjustments.

A 2.1 SWR reading represents a 11% power loss which can be around 44 watts with your radio. A 1.5 SWR is a 4% loss. Most single window meters have the percentage loss in the SWR scale, I didn't see it on yours.

This is why I prefer cross needle meters because you see the SWR, Forward, and Reflected power loss all at once and there is no pre-calibration setting, just key the radio.

I mentioned earlier if you have a dummy load to make adjustments so your results won't be skewed by any antenna mismatch.

I was pressed for time to do mine yesterday so I didn't use my dummy load but I did set mine with reflected power loss from a 1.4 SWR.

I'll make another video when I get home tomorrow night and run my radio into a dummy load.

I use the oil can type dummy load.
 
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One meter shows higher swr using same dipole in attic its connected to , but the funny thing is the smaller swr meter that is showing the higher swr below shows same swr level as larger swr meter for my trucks magmount, how weird is that.?

Ch40 slightly higher reading on the smaller meter both ch1 and 40 show over 2.




 
fourstringburn said:
Just received my N2. I did have to adjust the AMC pot because it was too far down and the peak modulation was dropping off too soon. Now the modulation holds at it's peak until unkeyed or a long pause.

Here is a clip showing the deadkey after adjusting. The factory settings were peaking over 250 watts PEP and a low deadkey around 10w to 80w. Never could dial in a 25 watt deadkey and 200 watt PEP out of the box.

The first part shows the meter on average power and the low power scale. Notice the SWR isn't 1:1 so you have to subtract the reflected power. This is true with all meters, you have to subtract Reflected power from the Forward power to get the true power reading. The low deadkey is about 25w after subtracting the Reflected power.

The 2nd part has the meter switched to high power and Peak power and shows right about 200w after you subtract the Reflected power. After a little adjusting with the AMC, I got a nice 4:1 deadkey/swing ratio.

The RF power knob ended up in the 9:00 position.

Note: the camera is looking up at the meter at an angle so the readings appear slightly higher than what they really are.

Click to expand...



So the left needle is showing watts and right needle swr?

And if you were to turn your RF knob to 5 0'clock what would the output become?
 
Limeybastard said:
So the left needle is showing watts and right needle swr?
Click to expand...
No!

With cross needle meters the left shows Forward power and the right shows Reflected power. The SWR is where the 2 needles intersect.

Cross needles are better once you get used to them. They require no SWR calibration and you see it all at once. You do have to manually subtract any Reflected power from the Forward but you're supposed to do this on single needle meters too.

Assuming the scale is 1Kw, Pic one shows an SWR of 1.8 with Forward power of 500w and 40 watts reflected. Actual power is 460 watts. You can easily figure the other 3 yourself.

See example below. Where the X is circled is the SWR.

SWR.gif
 
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fourstringburn said:
It appears both show 1.5 or less so you're fine.

Can't say why the quirkiness on the 1 meter.
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By the way, not sure if I mentioned this, thise hi and low deadkey pots clockwise reduces flow I get it, but the modulation pot clockwise increases modulation, any reason why this pot is setup differently?

Youd think righty tighty clockwise would be closing the flow?
 
Limeybastard said:
So the left needle is showing watts and right needle swr?

And if you were to turn your RF knob to 5 0'clock what would the output become?
Click to expand...
Here is an updated clip of my radio first going thru a dummy load, then the antenna. You can tell the difference because the right needle ( the SWR ) is flat with no movement and with the antenna is slightly off the flat mark.

I turn up the deadkey from the lowest setting to show how far up it goes, it goes up to a 100 watts. Notice I check deadkey with the meter on average power, this keeps the needle movement steady with little or no influence from background noises. It also makes a faster needle movement easier for tuning because the needle falls fast after you unkey.

You can see the Peak swing with audio modulation is hovering around 200 watts with 50 watts of deadkey. I forgot to show SSB but I adjusted it so the audio peaks are the same.

 
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