Tait T500 Series

[StormShadow]

Hi I've just been working on a few old Tait T500 radios.

Two of the radios I have tuned to 145.000 MHz

The other radio is a VHF low band... I know this radio will easily cover 70 MHz but I can't help but wonder whether this can cover 50 MHz for 6 meters instead of 4 meters?

Regarding the other two Taits I've got on 145.000 MHz Both radios have 2 channels, eventually I'll be modding them for more channels but for now I'm just going to set them up on the 2 channels they have already.

Channel 1
RX 145.800 MHz
TX 145.200 MHz
Channel 2
RX 145.500 MHz
TX 145.500 MHz

On the other radio I want:
Channel 1
RX 145.800 MHz
TX 145.200 MHz
Channel 2
RX 145.550 MHz
TX 145.550 MHz

I had a look on David Pye's website to try work out the diode matrix board. The TX side of the diode matrix board was really easy to work out but the RX side is really confusing.

I was wondering if anybody knew how to work out the RX side of the diode matrix board?

RX
N9 - 128MHz
N8 - 64MHz link open
N7 - 32MHz link open
N6 - 16MHz link open
N5 - 8MHz link open
N4 - 4MHz
N3 - 2MHz link open
N2 - 1MHz link open
N1 - 500kHz link open
N0 - 250kHz
A5 - 200kHz
A4 - 100kHz link open
A3 - 50kHz
A2 - 25kHz
A1 - 12.5kHz
A0 - 6.25kHz
This would come to 123.600 MHz but if I add 21.4 I'll get 145.000 MHz

Well here is the TX side of it
N9 - 128MHz link open
N8 - 64MHz
N7 - 32MHz
N6 - 16MHz link open
N5 - 8MHz
N4 - 4MHz
N3 - 2MHz
N2 - 1MHz link open
N1 - 500kHz
N0 - 250kHz
A5 - 200kHz
A4 - 100kHz
A3 - 50kHz
A2 - 25kHz
A1 - 12.5kHz
A0 - 6.25kHz
This would be 145.000 MHz simple.

[wires]

How did you get on re aligning the tx and rx on the radio the selfs, from memory it's a case of adjusting voltages at test points?

[StormShadow]

I set the diode matrix board up for 145.000 MHz then I adjusted the VCO to lock on to 145.000 MHz on both RX and TX

[StormShadow]

I'm still having problems working out the RX configuration

The RX is aligned perfectly on 145.000 MHz but if I want to get 145.800 then I have to re-solder or unsolder a few tabs on the matrix board but the question is witch ones? that's where my problem is

I know I won't have to worry about this when I do the 100 channel mod as I will be replacing the 2 channel diode matrix board with a new EPROM board witch will be programmed by a computer. I have the circuit diagram for the new board witch the E-proms will fit on to.

In the meantime I just thought it be nice to be able to use one of the 2 channels to see how the radio performs

OK I have also a VHF Low Band Tait T500 witch I've found out that this radio can go all the way down to 48MHz perfect for 6 Meters

I plan on doing the same 100 channel mod to this too. I'll put in a few 49MHz frequencies in but the rest will be 6 Meter frequencies I may have to extend the channel range to fit in all the repeater channels as well as the simplex channels I want.

This will be my first time programming EPROMs so it might take a while.

I'm just wondering if their is any universal radio EPROM programming software about?

[mr_h4ck3rm4n]

im unsure but if i remember right you need to subtract 21.4mhz from your rx freq and then make your calcs for the diode matrix.,

sound old radios.


found this for the uhf
http://davidmpye.co.uk/node/13

cheers

[FERNOX]

I have just dug an old T500 out of my cupboard, but it wont power up, its not a fuse problem any idea were to look first for fault in radio, cheers

[StormShadow]

I'd check the Diode, its handy to have a multimeter so that you can test.... I'd start at the power point and work your way through, if your getting no power to the radio it could be something simple.

[Admiral]

Bridge N4 N0 A3, unsolder N3 N2 N1,