I've always liked the compact size. I have both the TRC-453 and the TRC-465. I also have the older TRC-451. Very similar pc board and layout, but bigger. I collect older CB's and fix them up then put them on a shelf.
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trc 465 mods
- Thread starter doctor
- Start date
You and me both ! Buy, cuss, fuss, mess, and finally fix/fine tune and then sit on a shelf. Better half thinks I'm nuts ! (Maybe I am)
I like the older radios myself. My main base radio is a 1977 Royce 1-642, plus I have a Galaxt Saturn base as well as q Royce 1-632 Mobile I talkon from time to time. It's more interesting to be a littlt nuts IMHO.
Been playin around with this little guy over the Christmas break. A trc-452.. A friend gave it to me "for parts", but I just cant scrap a workin radio lol
Wired it 4 pin cobra, stuck in the blue led's, and wired in some extra channels through the anl switch. After tuning, 3w swinging to 10.. Loud little radio with the old cobra coffin mic..
Wired it 4 pin cobra, stuck in the blue led's, and wired in some extra channels through the anl switch. After tuning, 3w swinging to 10.. Loud little radio with the old cobra coffin mic..
ok, what am I missing here? am only, 23 channel... how is this related to modding the 465?
Its not...so what? Its a 7 yr old thread. They were talkin 'bout old radios in the few previous post before mine.
Btw, the trc 452 is 40 channel. Thanks for your input...
It is good to revive these older posts, keeps 'em alive!
The 465 and PC122 chassie are nice to convert. I have used the crystal swap and had good contacts on 10 meters. The N kit is good also if you can find one.
mechanic
The 465 and PC122 chassie are nice to convert. I have used the crystal swap and had good contacts on 10 meters. The N kit is good also if you can find one.
mechanic
Back from the archives...
How specific are R-151 and R-152 at 8.2k? I have the 2.2k, but my stock skips from 6.8k to 10k. Am I going to have to order more resistors?
No, 6.8K would be fine - besides, you can MODIFY R152 by using lower values - but don't go too far, for the Limiter really uses the two resistors as a means of Attack and Decay measures for Limier - you don't want to sound too "compressed" or mono-tone from the releasing action tends to make a pumping effect because the divider is not balanced.
Do you really need me to Discuss?
(This is my work from CB Tricks Site I saved from destruction - but that is Just My Opinion and I'm supplying you this reprint...)
To Locate that "paring"The parts listed are drawn and referenced to the schematic. The reasons for C 113 listed twice in two different orientations denote the differences from the board chassis that was used in both year, make and Brand using this type of PCB design.
When R151 is greater than R152, the bias developed by the base regions' VR5 and D34 of Q29 will flow predominately through R152 and ground. This sets the limiters original reference level and when Q503 produces a level of audio that averages below this threshold level set by the Base region, Q29 will switch on and begin to conduct - heavily.
The values of capacitance and resistors in the AMC/ALC amp sections, make the limiter amp transistors work as Class-A devices. When the RMS values of the sense level threshold R151 and R152 provide, fall below a set-point established by VR 5, the limiter in Q29 AMC amp section starts to conduct. This sense line uses R151 to tap into what TP 8 uses from Q503.
When the AM Regulators' set output [by VR 10] is providing more audio waveform than a straight-DC bias level - as if you were producing a modulated carrier, R151, R152 and VR 5 pre-set sense this and voltage varies on the emitter of Q29. When audio drive RMS value becomes excessive - [e.g. DC bias drops], the emitter has something to dump what the collector has into the line Q503 and TP8 share - how much is determined by VR5 and D34. The more Q503 produces in Audio - reduces the RMS/Average level - which means the carrier envelope can be reduced to too low of levels for the Driver and Final to operate safely in [remember the 5.6 volts setting]. Q29 works more in the negative region where the original bias voltage of 5.6 volts could drop too-low and cause saturation when modulation levels start making Q503 drop closer to 0 volts - which can cause a reverse bias condition [base to collector] and damage.
This comes from personal Experience!
During my time with the wonderful group on the rec.radio.CB NewsGroup, there was a considerable level of heated debate and conversation about the use of Limiters, and the Justification that users had about using them or getting rid of them. This series of pages is not to remove the limiter, far from it. I'm discussing ways to use it to your advantage and one of the MAIN reasons I became a believer in use of the limiter in this radio is due to RECEIVE and using this vehicle in a mobile environment.
The audio line is active in the radio and up through the mic cord - EVEN WHEN THE RADIO IS UNKEYED [receiving] - this can create a problem with Ground loops and Noise Pickup.
Aside from the extra heating generated by excessive modulation...
The mike element is disconnected at the handset by a switch inside the handset itself.
The line to it is left floating at whatever potential that may exist at the radio to the handset.
Ok, end of Reprint...
Now for a little more insight...if you're still reading this...
The Limiter is a simple COMPARATOR - its' adjustable - but can be a bit too aggressive in the stock radio for many - and it's why many people rip out the limiter - and never realize the Limiter also helps to keep OUT the noise you can pick up from the Mic.
The Limiter works or uses power from the DROP in a power level compared to the Limiters' PRE-set FIXED power level. (Your 70% Mod tune-up setting)
You have a 5.6 volt "setting" you use to set Carrier to 4 watts thru the AM Power control.
The Limiter's AMC adjust pot, uses this "reference" to compare to the Audio and Bias that goes to the Driver and Final. And is why you need to send a Modulation level percentage (like 70%) to make the Differences between Carrier "Steady state" and Audio Envelope in the BIAS - the amount of DROP in Bias can be considerable so they make the Limiter work harder when there is a greater DIFFERENCE.
The energy used is developed by R152 and R152 - a Divider - making it (the Divider) have a higher value helps to keep the Limiter working by supplying the difference power to the limiter circuit - only less power is present to work the limiter. Keeping R151 and R152 in play but not too low in value, allows the power to flow into the circuit and to prevent the Driver and Final from getting too much audio and not enough BIAS because we take less energy from the AM Regulator to work with - the Limiter still works, only to a lighter / lesser degree.
Do you really need me to Discuss?
(This is my work from CB Tricks Site I saved from destruction - but that is Just My Opinion and I'm supplying you this reprint...)
To Locate that "paring"
- Study the graphic above and locate R151 and 152 - by AMC and AM Power controls and Q29 You can also use the larger graphic above showing the location of R151
- C113 is worth mentioning here because of the values of capacitance are different between the years and gave different results in rise and fall or attack time and decay of the limiters' action on the mic audio
- TR27[Q27] needs to remain in place.
I do not recommend the limiter be removed from this radio.
It serves a SECONDARY PURPOSE that shunts Microphone audio and any RF noise from the Mic Cord from mixing into receive audio via audio line and keeps RF noise from finding another way into the radio to mess with the RECEIVERs IF and RF amps and Detector.
- At least...try this mod BEFORE you give up and remove the limiter.
When R151 is greater than R152, the bias developed by the base regions' VR5 and D34 of Q29 will flow predominately through R152 and ground. This sets the limiters original reference level and when Q503 produces a level of audio that averages below this threshold level set by the Base region, Q29 will switch on and begin to conduct - heavily.
The values of capacitance and resistors in the AMC/ALC amp sections, make the limiter amp transistors work as Class-A devices. When the RMS values of the sense level threshold R151 and R152 provide, fall below a set-point established by VR 5, the limiter in Q29 AMC amp section starts to conduct. This sense line uses R151 to tap into what TP 8 uses from Q503.
When the AM Regulators' set output [by VR 10] is providing more audio waveform than a straight-DC bias level - as if you were producing a modulated carrier, R151, R152 and VR 5 pre-set sense this and voltage varies on the emitter of Q29. When audio drive RMS value becomes excessive - [e.g. DC bias drops], the emitter has something to dump what the collector has into the line Q503 and TP8 share - how much is determined by VR5 and D34. The more Q503 produces in Audio - reduces the RMS/Average level - which means the carrier envelope can be reduced to too low of levels for the Driver and Final to operate safely in [remember the 5.6 volts setting]. Q29 works more in the negative region where the original bias voltage of 5.6 volts could drop too-low and cause saturation when modulation levels start making Q503 drop closer to 0 volts - which can cause a reverse bias condition [base to collector] and damage.
- For best results - note the two values and make both resistors of equal, Higher value and this will provide a greater range of adjustment and less sensitivity from an overactive limiter.
I use 8.2K [Grey-red-red] for both and have good results. Too high and this mod doesn't work, too-low and no limiter action. - The above will provide you a means to cushion the effects of overdriven microphones and/or overzealous operators that have given you radios with the limiters ripped right out or their sockets on the board. It simply increases the range of operation this circuit [the AMC] provides and does give the operator a level of protection not achieved when they remove the limiter transistor to give them their so-called dominance of the airwaves at the cost of receiving a Worked All Neighbors [WAN] award for their efforts and the subsequent gathering of people from the neighborhood at the operators front door wanting a piece, if not just peace, with their neighbor.
This comes from personal Experience!
During my time with the wonderful group on the rec.radio.CB NewsGroup, there was a considerable level of heated debate and conversation about the use of Limiters, and the Justification that users had about using them or getting rid of them. This series of pages is not to remove the limiter, far from it. I'm discussing ways to use it to your advantage and one of the MAIN reasons I became a believer in use of the limiter in this radio is due to RECEIVE and using this vehicle in a mobile environment.
The audio line is active in the radio and up through the mic cord - EVEN WHEN THE RADIO IS UNKEYED [receiving] - this can create a problem with Ground loops and Noise Pickup.
- I'm well aware of people that simply don't care and how these people would want to sound like the others that are making a mess, and try to regain control of a channel and many of them remove the limiter for the sole purpose of trying to be on top of a pile. Not the best way - but they feel that way. I'm trying to keep you, the reader, from going too far and causing more headaches with your neighbors.
Aside from the extra heating generated by excessive modulation...
The mike element is disconnected at the handset by a switch inside the handset itself.
The line to it is left floating at whatever potential that may exist at the radio to the handset.
- This makes an excellent antenna for picking up blower noise and alternator whine.
Radio Shack [Realistic] was aware of this during the early years and added a dead short jumper wire at the handsets switch to short out the mic audio line when unkeyed. Since mic cords have a shielded cord, the noise pickup was less when using these handsets. - The use of D34 in the above circuit engages the limiter when the radio is in RECEIVE mode. D34 turns on the limiter for this purpose - to eliminate a potential problem with noise in the receive that was-not/is-not because of the receiver - it was the mixing of amplified noise from the open line to the outside environment and it mixes with the receivers own detected signal - at the Audio Chip.
Ok, end of Reprint...
Now for a little more insight...if you're still reading this...
The Limiter is a simple COMPARATOR - its' adjustable - but can be a bit too aggressive in the stock radio for many - and it's why many people rip out the limiter - and never realize the Limiter also helps to keep OUT the noise you can pick up from the Mic.
- Noise - RFI - in handset and cord and ambient RF noise level - that will still get into the Audio stream - there is no other way to turn of the Mic's audio and it's noises in Receive unless you have a limiter in place.
The Limiter works or uses power from the DROP in a power level compared to the Limiters' PRE-set FIXED power level. (Your 70% Mod tune-up setting)
You have a 5.6 volt "setting" you use to set Carrier to 4 watts thru the AM Power control.
The Limiter's AMC adjust pot, uses this "reference" to compare to the Audio and Bias that goes to the Driver and Final. And is why you need to send a Modulation level percentage (like 70%) to make the Differences between Carrier "Steady state" and Audio Envelope in the BIAS - the amount of DROP in Bias can be considerable so they make the Limiter work harder when there is a greater DIFFERENCE.
The energy used is developed by R152 and R152 - a Divider - making it (the Divider) have a higher value helps to keep the Limiter working by supplying the difference power to the limiter circuit - only less power is present to work the limiter. Keeping R151 and R152 in play but not too low in value, allows the power to flow into the circuit and to prevent the Driver and Final from getting too much audio and not enough BIAS because we take less energy from the AM Regulator to work with - the Limiter still works, only to a lighter / lesser degree.
- We can do the opposite, by making R152 much - much lower but the Limiter CLAMPS quicker and you can wind up with a Mono-tone-"ish" result because the Limiter tracks the envelope too aggressively more so than it's original settings.
The schematics for Uniden PC122 shows R148 as 22k, where in the PC122XL shows it to be 68k. Also, in TRC465 it is 68k. I lowered R148 in my PC122 to 15k or even 10k, this speeds up the release time of C113, or "bleeds off" the voltage stored on this cap. C113 is the sample and hold capacitor where both the AMC and ALC come together. Too low of a value of R148 and the AMC/ALC "pumps".
This is also where I got the idea in the first place to put a 10k across C133 in the Galaxy style radios where there is no AMC/ALC "bleeder" resistor across that sample and hold cap, or across C147 in a RCI2950 (early, not DX), or in RCI2970, a 22k. In a Cobra 148 or Grant MB8719, C109 is the cap, and I used a 22k. Most of this was found by trial and error.
This is also where I got the idea in the first place to put a 10k across C133 in the Galaxy style radios where there is no AMC/ALC "bleeder" resistor across that sample and hold cap, or across C147 in a RCI2950 (early, not DX), or in RCI2970, a 22k. In a Cobra 148 or Grant MB8719, C109 is the cap, and I used a 22k. Most of this was found by trial and error.
I'm sorry I know this is an antique subject but I just bought two of these antique radios the other day LOL. The chip switch and adding upper channels went perfectly as described. But I have not been able to get any lower channels. Any suggestions would be greatly appreciated. Thank you
My old 465 has an Expo kit. It has 39 above 40 and 39 below 1. It has one channel of overlap. Channel 1 in "high" toggle is 27.405. Channel 40 in low is 26.965. Other than that it works great. Opened clarifier as well. Great old rig...same as PC122