| Author |
Message |
    
Freebird
| | Posted on Wednesday, June 04, 2003 - 9:24 pm: | 
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i bought a uniden washington and i want to add in the extra channels.A tech here told me he can get it to go from 26.000 all the way up to 30megs is this true can this be done? |
Tech808
| | Posted on Thursday, June 05, 2003 - 12:08 am: |
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Freebird,
A lot will depend on what chip you have in it weather you have the 858 or the 8719 chip.
There are several different channel modification's out there or even add an Expo kit for channels.
You will get 26.085 to 28.805 for the 2 switch mod on the 858 chip.
Hope this will help some.
Lon
Tech808 |
Kc0gxz
| | Posted on Wednesday, June 04, 2003 - 11:41 pm: |
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Freebird
I for one would be real curious to know how he could do that. A Uniden Washington with a 26 to 30 meg frequency range? And still oscillate? Now that's scary. Wow!! What does he know that we don't, gang?
Freebird, if you are interested in doing the frequency expansion mod (that we do on this planet) yourself, Email me at kc0gxz@aol.com. I will send you every thing you need to know. 73s.
Jeff, kc0gxz. |
Adshar64
| | Posted on Thursday, June 05, 2003 - 4:03 am: |
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I know how to do it np ie 4mhz bandwidth. Can be done with three xtal switch with 10.8758 (low)and 11.7758 (high) This will (with pll mods)give you 25.555 to 29.305 with no gaps allowing for a 10kc switch and a decent slide. Note centre normal xtal is 11.3258 instead of 11.1125 and mb8719 pin 10 lifted off ground ready for pll mods. I have 120kc (lsb normal xtal range) slide in mine with superdiode and three series inductors in vxo circuit and can tune to a desired frequency np. To get above frequencies a fourth 12.0758 xtal would need to be switched in ie four position xtal switch That will take you to 30.205. the secret in this mod is modifying the uhic007 vco.
Original varactor under epoxy coat is scraped out and replaced with genuine m-6510 superdiode same as one I have in slide (vxo) circuit. It is tricky to do and you must be careful to crush out the guts of original caractor and leave the legs exposed to solder superdiode too. Band on m-65 is at top position when fitted. The vco will cover this range now once setup with the vco tuning coil. Anyone who thinks im "full of it" just email me and i'll send you the pics showing a range and slide test on cobra 2000 display all photographed including vco mod pics etc. Xtal switch needs to be close to original downmixer xtal position with short leads and the tone control position is best spot to setup. I setup a switch on spare nb contacts to switch tone high or low, works good. One problem you may have is lazy xtal firing (not out of lock) with mode/xtal change or on-off fuction especially. A lot of this effect was tuned out with the vco coil but the on-off problem was sorted out fitting a 1000uf electrolytic capacitor from pin1 (8v)on volt switch-regulator to ground . great result there.There it is feel free to query and ask in here. Major broadband mods are needed to appreciate to outer frequencies for listening etc.Capacitor increase between mixer stages and coil taps refiited to ends is a good start.As you do these mods you lose gain so you need to find a good comprimise. Two more superdiodes can be setup on the most influential coils to provide a tuner for the frequency using two 10k pots with ferrite-cap filtered 8v supplies and diode isolation. IE as you tune say eg for 29.5 mhz you turn the two pots to tune recieve (you will hear it come up at best position) and the other pot is tuning the transmit for maximum power out etc shecked on your power meter. This method keeps good gain in the circuits. |
Adshar64
| | Posted on Thursday, June 05, 2003 - 5:43 am: |
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See superdiode - broadband mod here
http://homepages.ihug.com.au/~adshar/m65tuner.jpg
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Adshar64
| | Posted on Thursday, June 05, 2003 - 3:55 pm: |
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See Photo's of above mod here
http://homepages.ihug.com.au/~adshar/2000.html
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Adshar64
| | Posted on Thursday, June 05, 2003 - 5:00 pm: |
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Also the fact its a uniden washington tells us its a mb8719 chassis. Early President washington basestations were 858 chassis and identified by only two buttons under the ch knob whereas the mb8719 chassis later has three buttons there. |
Freebird
| | Posted on Saturday, June 07, 2003 - 2:57 pm: |
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i was wondering can the same thing be done to the uniden madison?im not sure if the uniden madison has the same chip or not?  |
Freebird
| | Posted on Saturday, June 07, 2003 - 4:15 pm: |
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well im going to buy a uniden madison with the 8719 chip so i guess it will do the same mods? |
Adshar64
| | Posted on Saturday, June 07, 2003 - 6:21 pm: |
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yes Madison is same type of chassis as cobra 2000 with minor component differece |
Arcangelny
| | Posted on Sunday, June 29, 2003 - 8:20 am: |
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Who sells the super diodes you spoke of... (values/part numbers?) I remember copper used to sell a little swinger diode that did the same thing, but I don't see it listed anymore... |
Adshar64
| | Posted on Sunday, June 29, 2003 - 8:20 pm: |
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Genuine superdiodes no longer available(please someone prove me wrong)however this company supplies a replacement.
http://www.freesantaferia.com/parts.html
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