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Bushpilot169
Junior Member
Username: Bushpilot169
Post Number: 21
Registered: 2-2004
| | Posted on Monday, July 05, 2004 - 10:17 pm: | 
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Just wondering? I was looking at some past posts
and saw some super swing mods for the cobra 25 &
29 using 220uf el cap & 100 ohm res. Will this
mod work on a uniden pc76wxl? if so what is the
jumper that i change? In the mods for the cobra it
said the jumper is in front of the final.
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Bushpilot169
Junior Member
Username: Bushpilot169
Post Number: 23
Registered: 2-2004
| | Posted on Tuesday, July 06, 2004 - 3:16 pm: |
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just to let everyone know that it will work. i did an expearment last night on a uniden pc76wxl,
i looked for the jumper that was in front of the
final, # jv 101,put in a 470uf ele cap, then put
a 100ohm res across the legs. i then gave it power and prayed, well it worked, i got a 1 1/2
dead key & 35 watt swing.
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Spaz
New member
Username: Spaz
Post Number: 5
Registered: 6-2004
| | Posted on Tuesday, July 06, 2004 - 8:40 pm: |
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I've tried the supermod on many 25's 29's 68's & 78's. The best over all I found was a 47ohm barefoot and a 68ohm with amp. Seemed I lost modulation with a 100ohm. |
Mr_cobra
New member
Username: Mr_cobra
Post Number: 1
Registered: 10-2004
| | Posted on Sunday, October 10, 2004 - 3:11 am: |
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I have a SS3900 and a Uniden Grant LT, I need mod info to get a low dead key ~ 1 watt, and swing everything, somebody fix me up. |
Tech548
Moderator
Username: Tech548
Post Number: 312
Registered: 5-2004
| | Posted on Wednesday, October 13, 2004 - 10:32 pm: |
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Mr Cobra
Here is the NPC modification for the Grant and Cobra-148. Study it well.
1. Remove TR-24. Do not cut R-131.
2. Add a solder bridge to the solder side of the board that effectively jumps R-196. This is a quick way of replacing R-196 with a jumper (reducing its value to zero ohms), and also increases the range of VR-10 (A/M dead-key power) so that the dead-key can be set to 1.5 watts later on.
3. Add a 10uF 25 or higher volt electrolytic cap to the following points: The positive leg goes to the trace that connects to pin 9 of the IC-6 (the audio IC), and the negative leg goes to the R-194/D-63/R-228 junction. This is the NPC mod that compresses the negative modulation peaks and allows the average power to increase based on the modulation percentage.
4. To set the driver bias to 50mA, power up the radio, put it in LSB or USB, set the mic gain to minimum, remove the wire from test point 8, insert a milliamp meter in series between the test point (which is positive) and the wire, key the mic, and adjust VR-9 until the meter reads 50mA.
5. To set the final bias to 100mA, the same instructions apply as in step 4 except the test point will be TP-7 and the adjustment is VR-8.
NOTE: On some of the newer radios the final bias can't be set higher than about 50mA. The reason is that the value of R-179 has been increased in order to decrease the effective range of VR-8. To solve the problem, replace R-179 with a 500 to 1000 ohm resistor.
6. Once the final bias has been set, unplug the DC power cord. Put the final bias wire back on the test point. Now cut the final bias wire about 1/2 inch above the connector. Strip and tin 1/8 inch of the wire. Also tin the cathode (banded) leg of D-55 (the reverse polarity diode), and solder the wire to D-55. This assumes the test point connector is at the end of the wire that is furthest from the final transistor. On some of the newer models the test point connector is at the end of the wire closest to the final transistor. On those models, completely unsolder the wire at the end opposite the test point connector and solder it to D-55. This is the mod that converts the RF final stage to linear in all modes.
7. Power up the radio, put it in the A/M mode, key the mic, and set VR-10 (A/M) dead-key power adjustment) for about 1.5 watts into a dummyload... "Not" into an antenna.
8. Tune the RF chain coils (L-38 and L-45 through L-48) for maximum peak (modulated) output power in the center of the band (that would be Channel 20 on a stock radio and Channel 40 on one that has the popular expanded frequency range of 26.815 to 28.045). If you have a favorite frequency that is more than 30 channels from 19 or 40, then do your tuning on that channel.
9. Now check the dead-key power again. It should be around 2 watts or higher. Since this is only a single final radio, use VR-10 to turn the dead-key down to around 1.5 watts.
"WARNING" I CAN'T STRESS THIS ENOUGH. Do "not" over do the dead-key! You have to keep in mind that the carrier power increases up to 10+ watts with modulation, which means there is absolutely no point in having the dead-key set any higher than is required to "reliably key a RF amplifier". Most amps will easily key with as little as 1/2 watt of dead-key power. If you over do the dead-key, the transmitted audio will sound weak because the negative modulation peaks will never reach 100%. In other words, setting the dead-key too high will be defeating the purpose of this modification.
Final Results: If tuned correctly, the "dead-key power" should be 1.5 or 2 watts very maximum. The average "modulated power" should be 10-12 watts. And the "maximum peak power" should be around 18-22 watts--give or take a watt or two.
Jeff
Tech548 |
Inspector
Member
Username: Inspector
Post Number: 94
Registered: 12-2001
| | Posted on Sunday, October 17, 2004 - 8:02 am: |
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FYI On a lot of other boards, the "heavy swing" mod or RC/NPC mod has been dumped-on severly. I feel this is due to the impropper instalation of this mod in a lot of radios. If it is done correctly, it can work as it is supposed to, but a lot of techs go overboard with the "swing" and it defeats the purpose of the mod. Perhaps the propper implimentation of this mod for the RCI/Galaxy type radios can be posted here...just for the record. |
Audiophile73
Junior Member
Username: Audiophile73
Post Number: 21
Registered: 5-2004
| | Posted on Thursday, October 28, 2004 - 1:58 am: |
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i don't know how the heck that uniden did 35 watts |
Jon666
Intermediate Member
Username: Jon666
Post Number: 289
Registered: 11-2003
| | Posted on Thursday, October 28, 2004 - 6:42 pm: |
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me either being a single final radio
thats impossible
jon |
Inspector
Intermediate Member
Username: Inspector
Post Number: 104
Registered: 12-2001
| | Posted on Monday, November 01, 2004 - 8:09 pm: |
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As A follow-up to my previous post, here is a repost of Tech 8541's post that puts things in perspective...The NPC-RC mod is the most used mod in export radios today. It has been around for years, but it is set up wrong and actually labeled wrong (depending on form used) by 90% of the techs using it.
The npc where the limiter is removed and the final/s volted -IS- an actual npc. but after reading this I hope you all will see that unless you have the right equipment it is unacceptable for a clean signal (which is the reason for using the npc without clipping the limiter). Even when set right, a 1w carrier with 35-45w (single or dual final) of swing is not good.
For the npc where the limiter is left intact and and the final/s is not volted, a stock radio set at 100% mod by the factory, needs nothing but the npc components... Well, the high power carrier needs reducing to keep the pos peaks from flattopping, but the lower power setting needs nothing but the npc components. This mod is also not truly a npc mod, but a ppe (positive peak expansion) mod. There is no compression of the negative peaks, since the neg peaks still hit 100% mod without the AMC being adjusted, but the pos peaks will hit 125-300% pos mod (depending on resistor value used).
The reason is because the amc is only triggered on the neg peaks. The AMC is turned off on the post peaks, but it tracks on the positive peaks by an rc circuit.
Here is a galaxy 77hml at 100% mod and a 1.25w carrier as an example....
For a 1.25w carrier the collector of tr51 is at 2.50vdc. the emitter of tr49 is at 2.54vdc. when audio is applied for 100% mod, the collector of tr51 swings from 0-5v (5vp-p). the emitter of tr49 swings from 2.49-2.59v (0.1vp-p).keep in mind that the emitter of tr49 only swings 0.1vp-p as this will be revisited later. The AMC samples the neg peaks and keeps them at 100% mod.
Now when a 1n914 diode/390ohm res npc (ppe)is used, things begin to change. The banded end of the diode goes to the collector of tr51 and the res goes to the emitter of tr49. The neg peaks still hit the 100% mod I had set the radio for in the last step, but the pos peaks go to about 200%. Remember how the voltage on the col. of tr51 goes to 0 but the voltage on the emit of tr49 only goes to 2.49v. So when the col. of tr51 goes 0.6v lower than the emit of tr49, the diode is turned on and -tries- to pull the col of 51 back up but the AMC is set to -make- the voltage of the collector of 51 hit 0 (100% neg mod). To do this more audio must be dumped into 49. This is evident by remeasuring the voltages at the emiter of 49 with a scope. it was 0.1vp-p with audio, now it is 0.2vp-p. Since the amc only samples the neg peaks, that same 0.2vp-p is present on the pos peaks, and since only 0.1vp-p is needed here, the pos peaks go past 100% (about 200% here). So as you can see, there is no compression of the negative peaks (npc). There -can't- be if the neg mod is hitting 100% before and after the modification without amc being adjusted. But there is positive peak expansion (ppe). This is all done by a way of fooling the limiter/amc... You can add this to any stock radio and it will work properly as long as it was properly set at the factory for 90-100% mod. You also need to keep the carrier at no more than 3.5w for single final radios and 5w for dual finals for the 390/914 npc(ppe)... for a 560/914, 5w carrier for single and 7w carrier for dual finals.
As for the npc where the limiter is removed and finals VOLTED, there -is- neg peak compression since there is no limiter present to react and -force- the neg peaks to 100%. BUT you have to have a scope to set it correctly, and how many of you have one??? You may also have to play with resistor values or mic gain to get it to work properly (once again you still need a scope)...You might as well just clip the limiter, since if you don't have the right equipment you're in the same shape, but with about 5min-30min (depending on your soldering skill level) more work to do. Also, why volt the finals when with both mods you have to reduce the high power carrier for them to work properly? The regulator is being "spared" by reducing the carrier power (which is the same reason for "volting" the finals).
Anyone who wishes to post this on other forums has my permission. I'm not doing this to call anyone out or for self recognition, but i'd like to see this get around for techs who don't quite understand what is going on with this/these mods (especially since this is the most popular mod out there). This mod was meant to run clean radios with increased pos mod, so it should be understood how to do it properly. I'm not a "mad scientist" saying it works because I say so. I laid down the facts to prove it.
richard byrd
--------------
Richard A. Byrd Jr.
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Bullfrog13x4
New member
Username: Bullfrog13x4
Post Number: 1
Registered: 3-2006
| | Posted on Saturday, April 15, 2006 - 8:16 pm: |
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this is for you guys that cant find it
"galaxy/ranger swing mod"
here you go
find the high power vr there will be a resistor connected to the sweeper leg of the vr raise one leg of this resistor and install a 1n4001/1n4007 rectifier diode in line with these two points with the bandend end facing away from the vr that is it, DO NOT PULL THE LIMITER!!
retune/alighn the radio
if you cant achieve the modulation level you want DO NOT remove the limiter. if the redio is a cobra/uniden it will be a diode if the radio is a galaxy/ranger it will be a transistor butt the idea is the same, simply pull the emmitter leg from the board and install resistance in between the two points, i use a variable to make it adtustable and less stress trying to find the right size of fixed resistance. |
Bullfrog13x4
New member
Username: Bullfrog13x4
Post Number: 2
Registered: 3-2006
| | Posted on Saturday, April 15, 2006 - 8:32 pm: |
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this is for you guys that cant find it
"galaxy/ranger swing mod"
here you go
find the high power vr there will be a resistor connected to the sweeper leg of the vr raise one leg of this resistor and install a 1n4001/1n4007 rectifier diode in line with these two points with the bandend end facing away from the vr that is it, DO NOT PULL THE LIMITER!!
retune/alighn the radio
if you cant achieve the modulation level you want DO NOT remove the limiter. if the redio is a cobra/uniden it will be a diode if the radio is a galaxy/ranger it will be a transistor butt the idea is the same, simply pull the emmitter leg from the board and install resistance in between the two points, i use a variable to make it adtustable and less stress trying to find the right size of fixed resistance. |
Wareagle
Junior Member
Username: Wareagle
Post Number: 39
Registered: 12-2001
| | Posted on Sunday, September 21, 2008 - 11:18 am: |
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For killer super mod use 470pf capacitor and 220 ohm resistor,i did this with a 1969 final and have 3/4 watt deadkey and 25watt swing with awsome modulation!!!!!!!!! |
Bruce
Senior Member
Username: Bruce
Post Number: 4825
Registered: 9-2003
| | Posted on Monday, September 22, 2008 - 8:21 am: |
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Times have changed I can remember the DRAKE and HEATHKIT controlled carrier modulation of the 60’s and 70’s which caused your power output to wildly swing. It was fronded upon and soon discarded.
Now people build it back into radios I guess things just never change just go in circles.
INTRESTING .......
On 6 since 66
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Norm
Junior Member
Username: Norm
Post Number: 27
Registered: 9-2002
| | Posted on Sunday, December 27, 2009 - 8:45 pm: |
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THIS IS SOME GOOOD WORKE MEN. 0N 9 ECNIS 99 |
Bft_driver
New member
Username: Bft_driver
Post Number: 2
Registered: 12-2012
| | Posted on Monday, December 17, 2012 - 3:31 am: |
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Is the PPE mod ok to do on the current mosfet final EPT3600 style board radios? |
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