Batboard

Hello:
I have converted a maxtrac 900 privacy plus trunking radio to a Maxtrac 900 16ch conventional radio by blanking reinitiating with the 900 conv eprom and it went well and works great after calibration and setup.
I read and did do the conductive pen mod in the vco and have again succeeded in the mod but it only gives you the 902 repeat6er input and the 927 area rx.
But works great.
I read an article on modding the maxtrac 900 for full ham band 33cm to get all the freqs from 902 thru 928 MHz plus by doing a 15 volt dc vco steer line mod.
My question is does anyone know if you still need to do the conductive pen mod as well in the vco or is just tyhe15 volt full band mod only needed so skip the conductive pen mod ???
I found both mods talked about on batlabs and another on repeater builder but the two articles left me wondering if I needed to do both yet or just the one for 15 volts to get full band operation.
I did change out the factory murata filters for the took 915 ham filters so im set to go there.
The radio does tx in the 902 area but nothing from 903 up to about 924 then tx again and rx but no rx in 902 but tx yes for repeater inputs.
Looking to do a full coverage tx rx mod for all freqs 902 thru 928 plus now.
Thank you
Satelite

You WILL have to use the conductive pen on the VCO. Similar procedure to what you already did but you will need to make sure it works over a wider range.

One half of the VCO operates ~39 MHz lower than the receive frequency and that half also handles low TX freqs. The other half of the VCO handles high TX freqs (talk-around). Each was designed to handle the 6 MHz frequency span 896-902 or 935-941. So now you want each half of the VCO to handle more than a 25 MHz frequency span. There will be problems.

The firmware switches the VCO half at 903 MHz, which is why you do one half for talk-around and the other half for RX and normal repeater input TX. You can alter the firmware to move the switching frequency. You may have to alter the circuit so it selects one half for RX and the other half for all TX.

Bob M.

Hello:
Thank you for the reply.
I have changed the normal 900 murata filters out for the took ham filters for everybodys info for tx rx in the ham 33cm 900 hz band.
Yes I have already done the vco steering line mod first with the conductive pen but my pens liq didn't dry after 12 hours with a 60 watt bulb hovering over it so it cleaned it off and soldered a strip line and did get the steer line voltage to settle at 6.6 volts for 902 MHz tx and at 928 MHz was 3.3 volts during tx so for needing the 2 to 7 volts mod I got it easily enough.
Yes I did see the vco tx 902 to 902.9 then nothing for tx again till 922 MHz and txd through and up to 932 MHz and from the looks of it most likely higher yet but did not test any higher.
I found twice the mention and instructions on modifying the radio so that it could tx rx from 902 thru 928 as a full ham band 900 mod by using a 15 volt mod for the vco which gets around the vco shift at 903 and allows one half of the vco to do the 903 and up from what it was understood by myself.
I did get a hold of one of the authors to that one post on it and he claims to have done it and successfully got full tx and rx for the entire 900 ham 33cm band from 902 thru 928 mhz.
My question was now since I did the normal vco mod and got just the repeater inputs 902 to 902.9 MHz and repeater outputs and simplex from 922 thru 928 plus was can I get tx rx in the middle freqs missing above ?
Apparently from the 15 volt vco mod and rf bd mods I can so it says.
But the normal vco mod shift that gives you inputs and repeater outputs plus the high end simplex freqs is in one article and then the full ham band tx rx mod is mentioned in yet another post which left me wondering if they stood alone as mods or did I need to do the first vco conductive pen mod then further mod the rf bd to get the balance of the band ???
I may have to try just the 15 volt rf bd mod for full band and see without the conductive pen mod to find out.
My thought is since the maxtrac 900 as a conventional already has the entire ham 900 spread in it as is just that the way Motorola designed it to sw at 903 to the other half of the vco to do the rest just limited by components for its normal biz band freq spread so by doing the 15 voly rf bd mod im supposed to be able to get full band tx rx operation.
May have to try to text the author again for the answer .
But I figured id give it a try here for answers and clarification since the bd does have some pretty savvy techs here - just gotta get them to put some finger tips on the key bd
Thank you
Satelite