Uniden 66XL help and tune tips

[NZ8N]

Read the install instructions.
They want you to bypass the 1st iF filter, a 10.695 MHz filter, and use a capacitor across it, because the IF is no longer in the same place.

I will go over it later, after i get home from work tonight, and do the math, and a write up.

About 10-11 months ago, I had a brainstorm, and came up with a universal kit that should work on anything, even a Uniden pro510.

 

[CB590]

Read the install instructions.
They want you to bypass the 1st iF filter, a 10.695 MHz filter, and use a capacitor across it, because the IF is no longer in the same place.

I will go over it later, after i get home from work tonight, and do the math, and a write up.

About 10-11 months ago, I had a brainstorm, and came up with a universal kit that should work on anything, even a Uniden pro510.

it's ok. Don't bother. I'm kinda a plugnplay guy. I don't do circuits. Feel free to post if you want for others. Was just a wild thought for a compact 25/66 with upper and lowers.

 

[Crossbow]

From The Desk Of:
Handy Andy:

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...

Happy New Year Andy. So good to see you are back and hope all is going well. I for one miss seeing the amazing help you always gave on this site!

 

[Shadetree Mechanic]

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...

Happy New year Andy!

 

[Shadetree Mechanic]

Read the install instructions.
They want you to bypass the 1st iF filter, a 10.695 MHz filter, and use a capacitor across it, because the IF is no longer in the same place.

I will go over it later, after i get home from work tonight, and do the math, and a write up.

About 10-11 months ago, I had a brainstorm, and came up with a universal kit that should work on anything, even a Uniden pro510.

That sounds interesting, that would be great for the Cobra29 that is on its way to me.

 

[NZ8N]

The Cobra 29 series has a different PLL than the 25's do.
The PLL in a 29 uses an offset mixer of 15.360 MHz, or 3/2 of 10.240 MHz (the reference oscillator of most PLLs used in CB), that when injected with a higher or lower offset frequency, like 15.810 Mhz for "Uppers" or 14.910 MHz for "Lowers", the PLL will track the new frequency band. Hence, the Expo 100 "A" kit or any clone of, will work great for that radio.
The VCO frequency for Channel 1 Receive is 16.270.
16.270 - 15.360 = .910 MHz, which is what the PLL is programmed to lock to on CH 1 RX.
To get "Uppers, we change the offset frequency to 15.810. The VCO now goes to 16.720 on Channel 1.
. VCO . - . offset
16.720 - 15.810 = .910 again!

To get lowers, the new offset frequency is 14.910.

The Cobra 25 series, uses a PLL that can directly "read" the VCO frequency, so there is no offset mixer to fool into changing bands.

But, I figured out a way to do it for a 25 series and other radios that have "impossible to crack" PLLs. I haven't finalised the design yet.

Just today while I was at work, I had another idea on how to fix the Receive IF problem with the Expo 100 "S" Kits that I mentioned above, which I have to do some research on before I release my findings.

 

[loosecannon]

wow so much good stuff in this thread!

first, NZ8N, is this supposed to be like a controlled carrier sort of thing?
I can see how when the deadkey is all the way down, like half a watt or so, that you'd get the rushing sound, but if you set it for, say, a 2 watt deadkey, could the radio still swing up to its 16 watt PEP peaks and look good on the scope?
if that's the case, then how did the negative peaks get kept below 100%?

certainly not bashing, just learning. im going to try this myself sometime in the near future, but thought i'd ask anyway.

next, CB590, can you post a link to that kit you posted a pic of?
im curious to read about it.

there are some ideas in the works for freq mods to this type of radio.
(not by me)

and lastly but not leastly,
Happy New Year Andy.
good to see you around.
I am interested to know how things have been going, so please PM me if you don't want to post it all here.
LC

 

[NZ8N]

LC, the capacitor has an idling voltage of 13.8v or whatever the audio transformer and D10 feeds the Final and Driver. The cap charges to 25 or so volts only on the positive peaks of the audio, which after going through the variable resistor, powers the TX buffer transistor. When there is no audio to feed it, it drops the voltage to the TX buffer, to whatever you have it set for. So, when you put audio into it, it goes to the maximum voltage, which is the same as it would be if you turn the variable up all the way.
Basically, I am modulating just the carrier envelope to each word or sound, and the Driver and Final modulate the audio onto this varying carrier.

 

[loosecannon]

thank you for the explanation.

i really need to try this one some time soon.
LC

 

[NZ8N]

https://www.ebay.com/itm/113716845232

Here is the link to the "S" Kit clone. DJ56 (DSS56) is on here, haven't seen him on here in a while though.

 

[CB590]

wow so much good stuff in this thread!

first, NZ8N, is this supposed to be like a controlled carrier sort of thing?
I can see how when the deadkey is all the way down, like half a watt or so, that you'd get the rushing sound, but if you set it for, say, a 2 watt deadkey, could the radio still swing up to its 16 watt PEP peaks and look good on the scope?
if that's the case, then how did the negative peaks get kept below 100%?

certainly not bashing, just learning. im going to try this myself sometime in the near future, but thought i'd ask anyway.

next, CB590, can you post a link to that kit you posted a pic of?
im curious to read about it.

there are some ideas in the works for freq mods to this type of radio.
(not by me)

and lastly but not leastly,
Happy New Year Andy.
good to see you around.
I am interested to know how things have been going, so please PM me if you don't want to post it all here.
LC

kit with both h/l

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/113716845232

Kit with pics of circuit and how to install on CB

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/113714553377

Here is someone selling an older -S kit

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/233377112236

 

[NZ8N]

The "S" kits would work, if the 10.695 MHz crystal filter were switched out to the new IF frequency for each band, like for 1 band up (27.415 - 27.855), the new IF would need to be 11.145, and the new injection frequency would be 10.690, where the original injection frequency would be 10.240.



The VCO is locked, so the IF and Injection Frequencies would have to be switched in and out to match.

They are telling you to bypass the 1st RX IF filter with a 100pf cap, which would about kill the selectivity. Bleed over, anyone?

 

[CB590]

Well as far as turning down the dk on my existing 66xl. Just found a friend that has a pretty nice 66xl that has not been hacked at all and is all stock and has 0 mods.

Would that in the groups opinion be a better setup for me??

I just want an option to turn down my DK to like 2-3w and say swing to 8 or 9w without popping my 203 amp in my truck if I decide to do that??

 

[NZ8N]

Pull the cap/resistor mod out, see what the color code is of the resistor, change it to the next higher value, should drop the carrier like you want it to be.

If it is
Brown Black Black (10 Ohms), change to a
Red Red Black (22 Ohms), or
Orange Orange Black (33 Ohms), or
Yellow Purple Black (47 Ohms).

I have even seen up to 100 Ohms (Brown Black Brown) work in some cases.

 

[Handy Andy]

@CB590

If you need a little push...

This thread - Cobra 29LTD channel mod questions/help may help provide a direction to help you with selecting more of a CERAMIC IF filter than to stick with the usual (now, but back then - er, ruled too expensive) Xtal filter.

The problems you might get using Xtal (read you will if you're into extreme ends of the bands of coverage) is the limited width of frequencies' you will have available in tuning range in using the Xtal versus CAP approach.

Well, Xtals are like caps (ok, work with me here before you pounce) only they RESONATE at a vary narrow range of frequencies in and around the NATURAL resonance the quartz "thingy" has. They are used because they "peak out" at a specific range and have a sharp cutoff.

CERAMIC IF Filters are similar to the Xtals and were (still are) used in radios. They provide some selectivity peaking but offer more passband in BANDWIDTH than Xtal. True - you'll get noise - yes, but, to not to try it, you may miss out on something easier to work with in a smaller package to replace the Xtal.

They come in two types - one a 150kHz bandwidth - you see these in AM radios and most shortwave types that even used a BFO (for SSB detection and CW and TTY) and 300kHz for FM.

But WAIT!
Here's the GOOD NEWS!
You already use a 150kHz CERAMIC Filter!
​

Why AM is narrower than FM - due to the nature of the signal. The IF strip needed only to decode audio from the sideband (Diode detector) but it couldn't remove noise spikes that were also included

FM used "carrier" power as a means to clip the impulse and spike noises usually present - and tracked the CHANGE OF FREQUENCY thru a discriminator - and the result you hear, was the audio - all done by "tracking" the rate of change (Deviation) - not the envelope information contained in the sidebands of typical AM stations (Amplitude).

So in light of your problem, instead of developing a circuit full of caps, in both series and parallel configurations - the CERAMIC IF Filter may provide the BANDWIDTH without the need to suffer the noise abatement problems around using a simple Cap-based filter network.

Hope this helps!