Uniden Washington (MB9719) Channel Mod

[unit_399]

8113 -

If your rig has the 11.3258 xtal, then this should work for you.



Cut the trace to pin 14, and bridge the cut with a 4.7k ohm resistor. Connect a spst switch between pins 9 and 14 as shown. Closing the switch will give you channels 41 - 45 on channel selector positions 37 - 40.
73s.

- 399

 

[8113 Northern MN]

I have a 11.3258 crystal available right in front of me. Ill have to check out this mod. Thanks a ton!

 

[ExitThirteen]

This is the conversion I do with the Uniden Washingtons and Cobra 142GTL's. I don't swap out the 11.1125 mhz crystal, it's not necessary. I just leave it in the radio and utilize the 11.1125 crystal.

I use this switch configuration as shown for my channels. This setup will get you 192 channel capability, (26.175-28.085) with no skips other than the usual "A" channels.

Both toggles must be double throw, center off. I illustrated a DPDT center off and a SPDT center off, but you can use DPDT center offs for both, don't matter.

Make sure you do the resistor mod on pin 14 that Unit 399 illustrated in a previous post to get your bank of 4 channels (26.775-26.805, 27.415-27.445, 28.055-28.085).

Hope this helps!


~Cheers~

 

[sonoma]

will this version work on the cobra 148gtl by chance and get the channels you have listed.

 

[ExitThirteen]

Yes, change the 11.325 mhz crystal out for a 11.1125 mhz crystal, and the channels will work out the same.


~Cheers~

 

[sonoma]

we have some drivers at the shop that wants to run the cobra 148 radios and want 26.735 on the radio. normally we find a L kit to put in them. this would be the easist way to go since the L kits are hard to find now. thanks alot for your input. they run a lot of the galaxy 959 and 949 radios since the P5 wire gets them 26.735 off channel 8 and cobra 29's with a A+ kit to get the lower side of channel 19.

 

[ExitThirteen]

Are they the older side mic 148's? I know my conversion will work on those, but I can't guarantee they will work on the new front mic style 148's that have the RCI8719 PLL's in them, since I've never modded a newer 148 yet for that kind of coverage.



~Cheers~

 

[sonoma]

they are all the older side mic radios with the mb8719 PLL. we do not even mess with the front mic ones that people want channels in. they do good to run after a mild peak and tune. then the PLL does not mod very well either. put a lescomm kit in one is all so far.
thanks Exit13 for the info. will have to see what happens on one.

just read where the pin 9 to 14 with a 4.7k resister works for the 11.3258 crystal.per unit399 posted the info on it. well looks like it may be play time to see which will all work.

 

[sonoma]

Yea Sonoma someone else mentioned the lescomm kit to me locally while chatting on the rig. Im less inclined to buy things then I am to either find someone elses homebrew method or create my own. I own an electronics business so I have access to literally endless amounts of any kind of components you can imagine lol

over on cbtricks we have a person in Australia that can make any circuit a person wants to make a radio do all kinds of frequency's. right now she has been working with a design with Loosecannon on a PLL circuit for a radio of his.so far to indepth to do for a customers radio. last post he did was he was changing some parts to a different design to do what he is wanting. just waiting to see how he comes out. she even rights her own programing to the chips she uses. very amazing what she can do. she and her family have a radio repair business over there.

 

[ExitThirteen]

There's two ways you can get the 4 channel banks.

Unit 399 described one method, that involves cutting the trace on pin 14, putting a 4.7k resistor across the cut, and wiring a switch between pin 14 and pin 9.

The other method (the method I use) is to cut the trace on pin 14, and simply wire a switch across the cut.

Both of these methods will work on either the 11.325 crystal, or the 11.1125 crystal.

I've been experimenting with channel expansions for a while using Arduinos to control the programming of the PLL, and allow crystals to be swapped in and out using diodes and/or relays. Using the Arduino for this purpose, I've been able to go from 26.175 up to 28.705+ with continuous coverage, no skips. Quite fun, actually!


~Cheers~

 

[sonoma]

I have a Philly made 148 on the bench right now I bought non working off ebay and have it now working so just need to peak and tune it to make sure all is working just fine and will try your channel mod on it to see if I get what I am looking for.
thanks again for the info.

 

[8113 Northern MN]

Wow I stepped away from this discussion to do some remodeling on the shop and didnt realize so much had been said. Looks like I have some awesome different things to try.


While I have your attention and such great commentary....I am looking to buy a 50MHz oscilloscope for factory resetting some radios that had other mods in them which are no longer working and I would like to reset everything and get it back running. I was searching through Amazon and came across http://www.amazon.com/DDS-3x25-Arbi...405978150&sr=8-39&keywords=50MHz+oscilloscope . Was reading through and trying to find out if this would work with using it for tuning a CB. Been searching around and looking for advice. Im looking to spend >$200 and find something that is USB/PC conrolled. Is this good or anyone know of something better?

 

[AudioShockwav]

and simply wire a switch across the cut.

I got in the habit of always adding a 3.3 or 4.7k across the cut, this prevents the pin from floating.
I did a conversion on a radio one time and found that the pin I had the switch on would go hi sometimes during tx, adding a pull down resistor stopped the problem.
Made me think about it trying to troubleshoot the problem.

 

[ExitThirteen]

Good point Jeff! There is that possibility that certain pins can float if you isolate them. Some pins you can get away with it if it has a bypass cap to ground, but you're spot on with your post! Funny thing is, I use to put resistors across pins years ago. Don't know why I got away from it.

Good stuff!


~Cheers~

 

[mechanic]

Arduino

There's two ways you can get the 4 channel banks.

Unit 399 described one method, that involves cutting the trace on pin 14, putting a 4.7k resistor across the cut, and wiring a switch between pin 14 and pin 9.

The other method (the method I use) is to cut the trace on pin 14, and simply wire a switch across the cut.

Both of these methods will work on either the 11.325 crystal, or the 11.1125 crystal.

I've been experimenting with channel expansions for a while using Arduinos to control the programming of the PLL, and allow crystals to be swapped in and out using diodes and/or relays. Using the Arduino for this purpose, I've been able to go from 26.175 up to 28.705+ with continuous coverage, no skips. Quite fun, actually! ~Cheers~

I'm just starting with Arduinos, do have any pointers in this direction? Any info on what you are doing?

Thanks 73 mechanic