I have an older Uniden PC68XL (made in Philippines, ser#95002515), and am wondering if there's any"swing mods" to adjust the dead key between 1 watt or less to max power for this radio, like there is for cobra 29's?
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Uniden pc68xl help
- Thread starter fastfreddie1269
- Start date
I suppose you can get a resistor and a capacitor to help with that, but I felt that the audio was distorted after doing it. What worked better for me was stacking 4 diodes in series near the AM transformer.
Otherwise, here is a guide to do it with a capacitor and a resistor near the final.
Cobra 29 Swing Mod
Otherwise, here is a guide to do it with a capacitor and a resistor near the final.
Cobra 29 Swing Mod
Here's what we use.
https://www.ebay.com/itm/1164725379...pid=5336136228&customid=&toolid=10001&mkevt=1
Kinda pricey, but maintains the full modulated peak output of the radio at all carrier settings down to a half Watt. Designed to save labor, not to pinch pennies.
73
https://www.ebay.com/itm/1164725379...pid=5336136228&customid=&toolid=10001&mkevt=1
Kinda pricey, but maintains the full modulated peak output of the radio at all carrier settings down to a half Watt. Designed to save labor, not to pinch pennies.
73
I'm very interested in the dk module you referred to on ebay, but the circuit board in the Uniden pc68xl is a little different than the Cobra 29. So, would the module work in the pc68xl, and where would I install it? What jumper, etc. Thanks!
I'm working on a version with hookup details for the PC68XL. Found some pics of the procedure. I don't know how many different circuit-board layouts were used in that model number, but the plan is to post a sale ad for that model. I should probably post it here, too.
Soon.
We always say that.
73
Soon.
We always say that.
73
It should definitely work. The green wire that comes off the module is just going to a ground point, but the same exact spot of where it gets installed still holds true.
So JV17 (grn arrow) is the equivalent of J36 in the Cobras?It should definitely work. The green wire that comes off the module is just going to a ground point, but the same exact spot of where it gets installed still holds true.
Attachments
Let me go look in my PC68XL to have a look underneat. Honestly, if its a ground point, you are golden and ready to go. Will come back with a picture underneath of what that one is you are pointing to.
To confirm, Yes, JV17 is the jumper that is the same as J36 on a Cobra 29 etc.. I uploaded 2 pictures. The 2 circles in each picture is the ground point on the actual circuit board. The yellow arrow you pointed to, is a chassis ground, which I would not tap into. So you have either choice on the 2 I circled for the circuit board ground.
You can always double check with a multimeter to be sure its on a circuit board ground. Hope it helps.
I uploaded 2 pictures. The 2 circles in each picture is the ground point on the actual circuit board. The yellow arrow you pointed to, is a chassis ground, which I would not tap into. So you have either choice on the 2 I circled for the circuit board ground.You can always double check with a multimeter to be sure its on a circuit board ground. Hope it helps.
Ok, thanks. It helps a lot!To confirm, Yes, JV17 is the jumper that is the same as J36 on a Cobra 29 etc..
You can always double check with a multimeter to be sure its on a circuit board ground. Hope it helps.
View attachment 75606
View attachment 75607
For a clean swing, remove R44, then solder the anode of a 1N4148 or 1N400(#) to JV17 and the cathode (stripe side) to the positive side of a 10uf (25v+) electrolytic cap, ground the negitive side.
Install 1 of the bottom legs of a 1k (102) VR into the R44 hole closest to C49 and the top leg to where the new diode and capacitor meet.
Turn the mic gain all the way down then adjust the new VR to your desired dead key. With the mic gain at normal your PEP and audio will be exactly as it was before, but the envalope growth will be more than enough to get 100% (or more) out of a low drive amp.
This can be done to any radio with this style "buffer amp"(Cobra 25/29, Uniden PC66/68/76/78...). I call it the "Swing-A-Roo"...
Install 1 of the bottom legs of a 1k (102) VR into the R44 hole closest to C49 and the top leg to where the new diode and capacitor meet.
Turn the mic gain all the way down then adjust the new VR to your desired dead key. With the mic gain at normal your PEP and audio will be exactly as it was before, but the envalope growth will be more than enough to get 100% (or more) out of a low drive amp.
This can be done to any radio with this style "buffer amp"(Cobra 25/29, Uniden PC66/68/76/78...). I call it the "Swing-A-Roo"...
To add to my last post:
Setting the deadkey through the amp into a scope to get 100 to 125% growth (after amp) is what I found to be the sweet spot between "Loud Enough" and "Kazoo". It will be way more from the bare radio, swinging 18 watts from 0.5 will distort the receiving radio, but swinging 100 watts from 20 will not.
Setting the deadkey through the amp into a scope to get 100 to 125% growth (after amp) is what I found to be the sweet spot between "Loud Enough" and "Kazoo". It will be way more from the bare radio, swinging 18 watts from 0.5 will distort the receiving radio, but swinging 100 watts from 20 will not.