Why?

[Hawkeye351]

LC,
I've found that NPC on certain radios will make that passthrough regulator scorching hot, which weakens the regulator eventually.

Whereas, the simple swing mod (diode added to existing resistor at the carrier control VR) doesn't make it run hot.

They both produce decent quality after alignment and tune, but the NPC is more demanding on that regulator.

I'm not dissing the NPC, it works great in some radios, and not others. Same goes for the simple swing mod, it'll work great in some radios, and not others.

If I can get by without adding more of a demand from that passthrough in order to give a little more swing, then that's the route I take.

Sometimes it's not just about looking good on a watt meter or scope, sometimes it's about current draw and heat buildup.

 

[loosecannon]

I appreciate the reply.

when you say NPC, are you including volting the final along with it?
i never do that, but many do, so i feel like i should clarify so we are on the same page.

Im also a little confused about what you mean by "certain radios" as the NPC as it pertains to galaxy/ranger/connex/etc... is the exact same mod on the exact same circuit. As im sure you know these are all the same design packaged in a different case and it's been this way for 30 years or more by now.

I guess the reason im trying to understand your stance on this is because i've been NPCing these chassis for almost as long as the mod has been around and have never scorched nor had a failure on the AM regulator.

could there be a difference in how either of us does this mod?
what value resistor do you use in the NPC?
where would you set the deadkey on say, a 4 watt radio when you do this mod?

Ive seen the scope patterns for both and i found the NPC to be tuneable for a beautiful negative peak but with the swing mod it would always clip somewhat.

thanks for any input/enlightenment you can offer on this.
LC

 

[Hawkeye351]

If I do the npc, then I'd use a 330 ohm resistor along with the diode. But this guy's way of NPC is a 100 ohm and the diode.

Yes, I know mostly all these exports have the same board, and mostly the same parts, but I've noticed some of the radios work fine with the NPC, while others didn't, even though they're basically the same radios.

He told me the reason he likes the NPC is because it works great in his dx88 without ever running hot, but every time he does the NPC to this 4800 the regulator gets scorching hot. The 4800 wasn't getting hot with the little swing mod I installed, but it's running hot again with his NPC.

He sent me 2 videos the other night trying to show me on his watt meter (watt meter, lol), that my swing mod made his amp key high and swing backwards. The other video he says was the same setup but with his NPC.

I observed closely and noticed a few things that seemed suspicious.

1. The lighting in the room was the same in both videos.
2. Nothing on his desk was moved from one video to the next.
3. The window blind has the same sneak a peak fold in it.
4. The outdoor lighting through the blinds was identical.
5. On the watt meter with the first video, with what he says was my swing mod, was showing 190w key swinging back to 160w.
6. On the watt meter with the second video, with what he says is his NPC, was showing 160w key swinging forward up to 190w.

Did y'all catch that?
One video, supposedly with my mod showed a deadkey out the amp of 190w.
On the other video, supposedly with his NPC showed completely opposite, exactly opposite of mine.

My take away from those videos is, he recorded both at the same time and didn't replace his NPC back to my swing mod. All he did on the first video was crank the variable power up on the radio to make the amp key higher, which will result in back swing. And on the second video, all he did was drop the variable power back down so the amp will key lower, resulting in forward swing.

Think about it:
My way he says keys "190w" and swings back to exactly "160w".
His way he says keys "160w" and swings up to exactly "190w".

The simple swing mod doesn't increase the deadkey from the radio, nor does it make an amp deadkey go up.

I think his conscience is eating away at him now, cause every since he sent those 2 videos to me, he hasn't texted or called since. Guess he knows I'm not stupid and I caught on to that trick.

 

[loosecannon]

LOL he sounds like quite a character.

Does the 4800 have the board version that uses SMT like the 2950DX?

Because i found that the NPC didn't work well in that version, but i also found that it wasn't needed because you almost couldn't make the thing not swing up to max.

I can't remember what resistor value i found works best, but it's in my notes.
I think it was 390ohms.

I usually experiment with a trimmer first, then measure and replace with the closest stock value part.

It's been a long time since ive done the "swing mod" version. are you able to keep it from clipping on negative peaks with this mod?

I have been trying to explain to people that the NPC is not useful unless you are lowering the deadkey of the radio for a long time and some just won't get it.

the way i put it to them is that the radio has a maximum PEP that it can achieve at 100% modulation, and if you want to get more than 100%, you'll have to lower the deadkey in order to provide the headroom needed.

thanks for the replies!
LC

 

[Hawkeye351]

Yes, by realigning the RF stage will usually clean it up. Then if I want a little less AMC attack, I will strap a 22k ohm resistor across the AMC timing cap leads.

All my radios, after doing the simple swing mod along with the alignment and possibly a 22k across the AMC cap will drive the snot out of any amp. I'm always hearing guys questioning how I'm able to make this old radios drive amps harder than they've ever seen. I'm always honest with them by telling them it's all in the alignment, primarily the VCO voltage, especially the buffer(s) and the oscillators. I just add the simple swing mod to please their eyes on their watt meters and to allow full swing regardless of carrier level.

Yes, you are correct, it is a 390 ohm. I've read your write up on another thread on this. Although it's a 390, I still use a 330, just personal preference.

Thank you for your conversation. I enjoy conversing with you guys.