Uniden 66XL help and tune tips

[NZ8N]

Remove the cap/resistor mod, replace with a wire, restoring JP6. Repeak the radio.
Now, here is my "Swing Mod".
Remove R44.
Take a 1N4148 diode, Anode side to JP6, and Cathode side to a 10uF @ 50v Electrolytic cap (or was that a 47uF ?? 100uF ?? but still at 50v), negative side of the cap soldered to Ground on the top of the can of L14.
Run a variable resistor, 1k like the RF Gain pot, from the diode/cap you just installed, other end to where the back hole of where R44 used to be.
The bigger the cap value, the longer the circuit stays charged in between words.
The positive peaks of the audio charge the capacitor through the diode, providing voltage to the TX Buffer transistor, TR9.
With the RF Gain pot all the way up, it is like there is no modification, but when you turn the RF Gain pot all the way down, or anywhere in between, the RF Carrier "follows" the audio. The more you talk, the higher the carrier becomes, but in between words, the carrier drops to whatever setting you have it set at.

 

[NZ8N]

on that little cap on the bottom of the board, can you tell us which two components are being connected by it?

LC

That green cap is from the Collector of the final to ground. What value is it, CB590? Bend it the other way to see what value it is.

 

[loosecannon]

i like that idea NZ8N.
is this something that you just came up with or something you've been using for a while?

CB590,

the reason L13 doesn't have a slug in it is because it's just a coil to keep RF off of the DC voltage supply to the collector of the driver. a slug would do nothing for it.

my guess is that small cap is C45, which would be somewhere around 33pF.
LC

 

[NZ8N]

I came up with that idea over 20 years ago when we needed an "Advertiser Radio" to park up the road near the Interstate, with a Digital Voice Recorder (DVR, or Watergate) and a prerecorded message advertising our shop. I used a 555 timer circuit set to fire the DVR about every 10 minutes or so, and the radio, a Cobra 25 LTD, which was set in TX the whole time (shorted jumpered mic plug), although I may have had the 555 trip the DVR, which in turn would key the radio, I can not remember that particular detail. In between message firings, there would be no carrier, or maybe just enough signal to hear from 5 feet away.
This works on Cobra 29 style radios too, pull JP32 and feed the voltage into the left trace that JP32 was connected to, to do the same thing.
This can have the "windshield wiper effect" on receivers on the other end, with the carrier dropping low in between words.

Now, mind you, I have not worked in a CB shop in purt dern near 20 years, though, so this is all from memory. I used to work in a shop in North East Ohio, near Youngstown.

I used to make DVR's from ISD chips, chipcorders like Memo Mate key fobs, and other such. I still have a few samples of the dead bug style o9nes I had made, I even used sound toy boards I retrofitted with the record and other such functions of the chips.

 

[kopcicle]

https://www.worldwidedx.com/threads...e-key-for-the-cobra-29-radios-no-joke.240485/

the right way

 

[Low_Boy]

View attachment 32967

Remove the cap/resistor mod, replace with a wire, restoring JP6. Repeak the radio.
Now, here is my "Swing Mod".
Remove R44.
Take a 1N4148 diode, Anode side to JP6, and Cathode side to a 10uF @ 50v Electrolytic cap (or was that a 47uF ?? 100uF ?? but still at 50v), negative side of the cap soldered to Ground on the top of the can of L14.
Run a variable resistor, 1k like the RF Gain pot, from the diode/cap you just installed, other end to where the back hole of where R44 used to be.
The bigger the cap value, the longer the circuit stays charged in between words.
The positive peaks of the audio charge the capacitor through the diode, providing voltage to the TX Buffer transistor, TR9.
With the RF Gain pot all the way up, it is like there is no modification, but when you turn the RF Gain pot all the way down, or anywhere in between, the RF Carrier "follows" the audio. The more you talk, the higher the carrier becomes, but in between words, the carrier drops to whatever setting you have it set at.

I love this swing mod.

 

[NZ8N]

No offence Kop, but that is a variation of the "Cap/Resistor Swing Mod" above with the TIP transistor acting as a variable resistor, my circuit does not need a TIP transistor heat sunk to the chassis.
How does that TIP transistor circuit look like on the scope pattern? I tried it years and years ago, I didn't like the looks on the scope.
Mine looks like a normal peaked radio (preferably with AMC) on a scope.

There's always more than one way to skin a cat.

 

[kopcicle]

How does that TIP transistor circuit look like on the scope pattern? I tried it years and years ago, I didn't like the looks on the scope.

Just reduced carrier...
Looks like crap if the limiter is removed

 

[Mk121]

Good info NZ8N. I will have to give that a try.

 

[CB590]

Looking at an Expo 100 kit online for $35. Thoughts on that for this little monster?

I like 26.915 and some other like 415 and such.

 

[Shadetree Mechanic]

https://www.worldwidedx.com/threads...e-key-for-the-cobra-29-radios-no-joke.240485/

the right way

I have that peel and stick in my 29, works great.

 

[NZ8N]

The Expo "S" kit and any derivative thereof, has a design flaw. TX is fine, but they tell you to bypass the first IF filter with a capacitor? Can you say bleed over?

 

[CB590]

The Expo "S" kit and any derivative thereof, has a design flaw. TX is fine, but they tell you to bypass the first IF filter with a capacitor? Can you say bleed over?

so this won't work properly?? And what about and older -S model. Found them as well.

 

[Handy Andy]

From The Desk Of:
Handy Andy:

I love this swing mod.

Good to see my efforts back in the CB Tricks days were not a total loss...


If anyone recognizes the above drawing styles, wanted to just say a big thanks for proving that these mods do work...

Wish you all, including those that don't like me....(Ha Ha)...a Merry (albeit belated) Xmas and a Happy New Year...

Back to business...and family matters...

 

[CB590]

From The Desk Of:
Handy Andy:



Good to see my efforts back in the CB Tricks days were not a total loss...
View attachment 32981

If anyone recognizes the above drawing styles, wanted to just say a big thanks for proving that these mods do work...

Wish you all, including those that don't like me....(Ha Ha)...a Merry (albeit belated) Xmas and a Happy New Year...

Back to business...and family matters...

I for one missed ya. Happy New Year back at ya.