Batboard

gday all, have this xtl5000 going fine up to 477.150mhz then i get the Fail001 at 477.175 .. i would like to have up to 477.500 atleast? any tricks to make it lock here? the rx is fine still . cheers all

shadowman

Not without board-level mods, and I'm not sure that's possible on an XTL (haven't looked... seriously, it's doing 90MHz in its stock config and you can usually squeeze another 5-8MHz out... that's pretty damn good).

He probably wants to get UHF CB and the NSW GRN system in one radio. At least that seems to be the most often recurring issue I see coming from his part of the world.

Bottom line is, on some radios it works and on some others it doesn't. No one that I'm aware of has explored modifying the VCO in an XTL radio, but I'm sure you'd wind up losing a few MHz off the bottom end to get all of 477 MHz.

yeah not interested in the GRN... as i have a uniden scanner for that purpose .. i just want to get the uhfcb all in:) what i have foudn out tho it works fine up to ch30 or so when cold. but once the unit has been on for a period of time and has warmed up a little it operates fine up to 478mhz:) wich is fine cheers for the replies guys greatly appreciated.

Shadowman

If you wanted to do it right you could probably find someone on this side of the pond to swap your R-split radio for a S-split.

i have an S split (450-520MHz) XTL5000 id swap as long as yours is Q split (380-470). Let me know if you would be interested... the particulars are below:

My radio has firmware 15.00.09 and has a flashcode of 580208-801484-4
G51 - SMARTZONE Systems Operation
G806 - ASTRO Digital Operation
G173 - SMARTZONE OMNILINK Multizone Operation
G361 - ASTRO 25 9600 Baud Trunking Systems Operation
G114 - Enhanced Digital ID Display
G298 - OTAR with Multikey
W947 - Packet Data Interface
G193 - ADP Encryption Software DSP Based Only
W391 - P25 Radio Authentication

Hello everyone, I came accros this post when looking for info on the XTLs VCO. There does not seem to be a lot if information on it. I am looking to do what shadowman was trying to do. I would love to squeeze just a few mhz out of the TX side of the VCO to allow say 480mhz TX on a 380-470 unit. I would care if I lost 20 or 40 MHZ off the low end.... I am just wondering if anyone has ever made any progress with this???
ev..

Install S-split board, reprogram, good to go.

I too would love to see some information on making this adjustment, as with ev, I don't really care about losing 20MHz from the lower end of the range but that last 1MHz at the top is really missed with our UHFCB bandplan here down under?

I have seen some radios which will happily go to 478MHz and others that won't so I suspect it is just a matter of a variance in the factory adjustment?

Andrew

So as yet, no one has managed to find out what makes the VCO tick so to speak?

There doesn't appear to be anything in the Tuner software which relates to adjustment of the VCOs, only a Reference Oscillator adjustment.

From the detailed service manual:

Transmitter frequencies are generated from two VCOs, Q5825 and Q5826.
• Q5825 supplies frequencies in the range 380 MHz up to (but not including) 425 MHz.
• Q5826 supplies frequencies in the range from 425 MHz to 470 MHz.

Simple math tells us that each VCO "officially" covers a range of 45 MHz but in practice it must be something closer to 52 - 53 MHz? I can't see any physical adjustments for the VCOs on the board so I assume there must be a higher level "Depot" version of the tuner program that may allow access to softpot adjustments for the VCOs? Either way you would obviously have to adjust both VCOs or you would end up with a (Fail 001) gap in the middle of the radio's range?

BTW, do NOT be tempted to 'play' with the Reference Oscillator or your radio will transmit off-frequency across the entire range!

Andrew

Its easy - you bend the voltage on the negative VCO steering line which shifts the tuning range up a tad.

MattSR wrote:Its easy - you bend the voltage on the negative VCO steering line which shifts the tuning range up a tad.

...and this is done how?

Andrew

You know, it wouldnt bother most of us if there was a fail 001 hole in the middle somewhere.... As Bigfella said, its just that last couple of Mhz at the top that is all we need. And also, a friend has one that will go just to 480 with no tweaking, so there cant be much in it...
Ev..

So is ir really easy? how do you adjust the voltage on the VCO, if there is a way, we are all holding our breath...

Ev.

Bigfella237 wrote:

MattSR wrote:Its easy - you bend the voltage on the negative VCO steering line which shifts the tuning range up a tad.

...and this is done how?

Andrew

Andrew, The mod above only applies to the ASTRO Spectra. You use a resistor to change the voltage on the line. This doesn't seem to apply to the XTL series though as the VCO section is totally different.

Cheers,
Matt

ASTRO Radio Tuner also allows access to the Tx VCO Crossover Frequency which may also be useful for squeezing an extra MHz or two out of the top end, unfortunately ASTRO25 tuner software does not for some reason.

Andrew

As the term 'VCO' implies, the range of a vco is controlled by the applied voltage.
Some require tiny pieces of copper to specific tuning elements on the substrate to warp the range up or down, and others require the addition of a resistor and/or copper to shift the frequency.
A conductive pen found at radio shack has been used with good success, as does those tiny 'specks' of copper added.
The conductive pen 'trick' has been used a lot for doing the VCOs in the 900 Maxtrac radios, but I am sure there are others as well.

The addition of conductive material changes the resonant frequency and the voltage change is a function of that addition, as well as a range of voltage that are useful.