Modulation meter low bars on radio

[fourstringburn]

That SSB peak is high. First get the AM peak ratio balanced out and check SSB again. There is a simple 1 pot SSB power adjustment.

 

[Limeybastard]

Wow that low deadkey really cranks up there quick! The peak at 325 is close to what you want, just get the deadkey down and a bit more peak and you're there.

What Loosecannon posted on another thread is similar to how I do it. Both pots and the RF knob all inter act with each other so it's a matter of going back and forth and re-checking.

If these newer radio's still have plastic screw heads, you can use a metal screwdriver, these are simple adjustments here. The coil adjustments require plastic trimmers that go inside of a hole to adjust a screw. These you don't want to mess with because you can really throw your radio out of balance if you don't know what you are doing.

Those visor magnifiers are nice because like you my vision is going down hill and come in handy for all types of benchwork. Go get you one!

You can try marking the pots with a Sharpie pen along with a mark on the board for a reference point.

Sharpie pen seems like a good idea. Yes, the pots I saw in the pics I took and posted earlier are philips type plastic headed ones, so I assume a normal metal screw driver would suffice?

So to sumarize, make sure radio has the RF power dialed to the lowest setting before adjusting low power dead key pot VR19, but when adusting high power dead key VR15 the RF power on the front panel of radio should be turned fully clockwise to bring it close to 400W when saying Auuuudiiooooo?

Otherwise if not, then it might exceed 400-500Watts on the high power deadkey and during modulation burn out the radio if the user controllable RF power dial on front is set to max by accident?

 

[Limeybastard]

That SSB peak is high. First get the AM peak ratio balanced out and check SSB again. There is a simple 1 pot SSB power adjustment.

Makes sense, a 8 second key down at 12'O clock position warms the back of the radio , Just glad I hadnt been using the radio much for TX as I am in process of setting up antenna. And when I did use it, was midway or lower in RF power ( which we learned recently was still too high!)

VR 15 is labelled VR15 A/F Power, does this mean AM Full power?
Cheers

 

[Limeybastard]

Was just looking at that service manual on page 19 and the following confuses me.
AM TX Power Set radio to 28.000 MHz, AM TX mode. Modulation off. Connect “short PCB” to TP7 and TP9. Set RF PWR Fully Counter Clockwise. Connect RF Power Meter to antenna jack. VR15 10W [50W] ; VR19 1W [8W] 2970DX levels shown in [ ].

Are they stating the low deadkey for the 2970DX should be 8W and high dead key 50W?

 

[Big Kahuna]

Not your radio they are talking about, that's the 2970DX not the N2 or N4.

 

[Limeybastard]

Not your radio they are talking about, that's the 2970DX not the N2 or N4.

Not your radio they are talking about, that's the 2970DX not the N2 or N4.

Yeah but those figures dont match to a 1:4 ratio do they?

 

[fourstringburn]

Don't worry about short PCB to the TP's. This is for using actual test equipment to make adjustments.You are doing it old school with voice modulation thru a mic to check PEP. For this simple adjustment, both ways of doing it can yeild the same result.

Correct, those wattage numbers are for the 25 watt 2950 radio and the older 150 watt 2970 models. They have it set for a 3:1 ratio.

After the adjustments, the RF power knob could end up anywhere in it's traveling position. For ease of usage, it would be nice if it could be a full position to 400 watts and the deadkey just right at 100 watts. If it does, then great! My radio after adjusting came out to be the RF power knob is about the 8:30 position after adjusting. This was on the 2950 so the dead key was set for 6 watts and peak was just below 25w. This is why I said when you get it right, make note of where the RF power knob is and leave it.
So yes if you bump up the RF power knob, it will raise both DK and PEP. Just always check that it is in the proper location before you use the radio or keep your power/SWR meter in-line so you will always know.

Like I said, this is a simple adjustment that won't throw your radio out of alignment. You are just adjusting the PEP and low power deadkey in relationship to the power knob setting. If the 4:1 setting ends up being fully up or down with the RF power knob, great but I wouldn't expect it.

For the starting point try the RF power all the way down, then bring up the low power pot and see if that gets you to 100 watts. If not with the low power pot full up, bring up the high power pot some because that will influence the low power also. If you still can't get close to 100w on low, then bring up the RF power knob and go again. Once you hit 100 watts low, then make sure the high is close to 400 watts. If it is more than 20 watts over, then trim the high pot some and recheck.

Because the high power and even the low power pot will influence each other, you have to keep going back and forth. If you can't get close to the the magic numbers of 100 low and 400 high, then you"ll have to start bringing up the RF knob some more and go back to the low and high pots again. Keep going back and forth and eventually you"ll get it with a little patience.

You may not hit those numbers exactly but the trick is to get it as close to that while maintaining the 4:1 ratio.

Example; 90w low and 360w high is 100 % modulation. The 40 watt less PEP really isn't going to make a difference on the other end of someone's Signal strength meter.

Since the adjustment screw heads are plastic, a regular metal screwdriver is fine.

Good luck!

 

[Limeybastard]

Don't worry about short PCB to the TP's. This is for using actual test equipment to make adjustments.You are doing it old school with voice modulation thru a mic to check PEP. For this simple adjustment, both ways of doing it can yeild the same result.

Correct, those wattage numbers are for the 25 watt 2950 radio and the older 150 watt 2970 models. They have it set for a 3:1 ratio.

After the adjustments, the RF power knob could end up anywhere in it's traveling position. For ease of usage, it would be nice if it could be a full position to 400 watts and the deadkey just right at 100 watts. If it does, then great! My radio after adjusting came out to be the RF power knob is about the 8:30 position after adjusting. This was on the 2950 so the dead key was set for 6 watts and peak was just below 25w. This is why I said when you get it right, make note of where the RF power knob is and leave it.
So yes if you bump up the RF power knob, it will raise both DK and PEP. Just always check that it is in the proper location before you use the radio or keep your power/SWR meter in-line so you will always know.

Like I said, this is a simple adjustment that won't throw your radio out of alignment. You are just adjusting the PEP and low power deadkey in relationship to the power knob setting. If the 4:1 setting ends up being fully up or down with the RF power knob, great but I wouldn't expect it.

For the starting point try the RF power all the way down, then bring up the low power pot and see if that gets you to 100 watts. If not with the low power pot full up, bring up the high power pot some because that will influence the low power also. If you still can't get close to 100w on low, then bring up the RF power knob and go again. Once you hit 100 watts low, then make sure the high is close to 400 watts. If it is more than 20 watts over, then trim the high pot some and recheck.

Because the high power and even the low power pot will influence each other, you have to keep going back and forth. If you can't get close to the the magic numbers of 100 low and 400 high, then you"ll have to start bringing up the RF knob some more and go back to the low and high pots again. Keep going back and forth and eventually you"ll get it with a little patience.

You may not hit those numbers exactly but the trick is to get it as close to that while maintaining the 4:1 ratio.

Example; 90w low and 360w high is 100 % modulation. The 40 watt less PEP really isn't going to make a difference on the other end of someone's Signal strength meter.

Since the adjustment screw heads are plastic, a regular metal screwdriver is fine.

Good luck!

What worries me, is lets say I get the 100W deadkey and 400W max modulation. But this occurs when the user controlled RF power dial did example is at 12 o clock position. What would then happen if by accident the RF dial is turned clockwise fully? Boom?
Cheers

 

[fourstringburn]

You have that same problem right now!

It's up to you to check beforehand to see it is in the correct position. Keep your power meter in-line is best and before you operate, just check your deadkey wattage to be sure it's where your final adjustment ended up and that will ensure your PEP will be in sync also. Occasionally check your meter while operating too is always good for antenna conditions as well.

Unless you hold your radio in your hand when you operate, I don't see the RF power knob moving sitting on your desk or dash if mobile.

You would have to deadkey for some time with a high SWR to really smoke the radio. Accidental bumping the High power up with the RF knob and operating at wherever the highest PEP is would take a long time before real damage would occur. Still it's best not to do it because you have a nice radio and it's quite costly.

At 4:1, it is where you have the best trade off of 100% modulation, high power without excessive heat, and the long life of the radio and it's components.

 

[Limeybastard]

Ok, ive been tweeking vr15 and vr19

So far on rf dial fully min i get 8W deadkey and with rf dial fully turned clockwise 100W dead key, all figures ballpark.

Is that better?

With user rf dial maxed out the needle almost hits 400W during modulation.

Thanks for your help. Ill do a video later?

 

[fourstringburn]

Sounds like your on track, it's an easy adjustment right?

Let's see a video.

So you said 100 watts deadkey with the RF knob fully up and the PEP with a strong AAAAUDIO is swinging up to 400 watts? if so you are good, even better due to the RF power knob being in an ideal position!

Now check your modulation meter on your modulation meter and see if that comes close to or max's out. One gripe about the RCI 2900 series is I think the metering is cheesy. I would rather see a basic Cobra 29 style meter than their numberless segment graph.

Look for VR16 just below and to the right of the High power pot (VR15), This will be labeled Mod meter and will adjust the modulation reading. If needed, set to full scale at full at full mic gain or wherever you want.

I never had to adjust SSB power. See if your radio swings up to 400 watts on SSB. If so leave it. Above the AM modulation and Low deadkey pots is VR14 labeled SSB power. This should regulate the RF power of SSB. Like the AM adjustment, it is dependent on the RF knob setting too. If SSB happens to be too low or high, mark this pot with a marker then adjust it and note the change all the while leaving the RF knob where it is for your ideal AM setting.

There should be no other pots to be adjusted after all of this. Leave the radio alone and have fun with it!

Cheers!

 

[Limeybastard]

Sounds like your on track, it's an easy adjustment right?

Let's see a video.

So you said 100 watts deadkey with the RF knob fully up and the PEP with a strong AAAAUDIO is swinging up to 400 watts? if so you are good, even better due to the RF power knob being in an ideal position!

Now check your modulation meter on your modulation meter and see if that comes close to or max's out. One gripe about the RCI 2900 series is I think the metering is cheesy. I would rather see a basic Cobra 29 style meter than their numberless segment graph.

Look for VR16 just below and to the right of the High power pot (VR15), This will be labeled Mod meter and will adjust the modulation reading. If needed, set to full scale at full at full mic gain or wherever you want.

I never had to adjust SSB power. See if your radio swings up to 400 watts on SSB. If so leave it. Above the AM modulation and Low deadkey pots is VR14 labeled SSB power. This should regulate the RF power of SSB. Like the AM adjustment, it is dependent on the RF knob setting too. If SSB happens to be too low or high, mark this pot with a marker then adjust it and note the change all the while leaving the RF knob where it is for your ideal AM setting.

There should be no other pots to be adjusted after all of this. Leave the radio alone and have fun with it!

Cheers!

I just noticed while making the video, the amps remain at 22A and stay same even when yelling audiooooo lol but the watt meter needle moves close to 400W,

I'm going to do and check what you said after this is sorted.

 

[543_Dallas]

I just noticed while making the video, the amps remain at 22A and stay same even when yelling audiooooo lol but the watt meter needle moves close to 400W,

That's normal for AM operation. The only time you'd see a significant increase in current draw with modulation is if the positive peaks were exceeding 100% and the average power is increasing with modulation. Your watt meter is reading peak envelope power. If you were to use an average reading meter like a bird the needle would just wiggle a bit with modulation.

 

[Limeybastard]

That's normal for AM operation. The only time you'd see a significant increase in current draw with modulation is if the positive peaks were exceeding 100% and the average power is increasing with modulation. Your watt meter is reading peak envelope power. If you were to use an average reading meter like a bird the needle would just wiggle a bit with modulation.

Its better than before was peaking at 50-59A from 22A baseline but then it was also going well over 400W before in AM , just safer now .

 

[Limeybastard]

PS, i think I effed up. This is radio is supposed to be 200W AM and 400ssb , rolling on the floor laughing...