Astro Spectra Plus (VHF K-split) acts strange

[HA5BRG]

Hi there,

A few months ago I have purchased an Astro Spectra Plus unit from E-bay. The radio was sold as parts or not working.

Radio's specs:

Model: T04KLH9SW3AN
Flashcode: 580008-000480-2
HOST: R08.01.03
DSP: R08.01.03
Vocon: 4 MEG
CPS used: R20.00.00

The radio was sold as parts without any accessories, but when I opened up the radio it seemed untouched and nothing was missing. Even the Vocon was in place! I have checked all modules, panels, connectors but everything was just fine so I gave it a try and powered it up connected to a dummy load.

Guess what?

It was working fine. Powered up immediately, passed self check and it was fine both in Rx and in Tx. I hooked it up to my PC and read it with the CPS. Codeplug can be read and write without any issues. My CPS (PatMob.exe) was previously modified to accept frequencies below 146 MHz (to accept VHF frequencies from 136-174 MHz). I have entered some frequencies below its official lower bandsplit limit, freqs for local simplex channels, like 144 and 145 MHz values. Accidentally I have set the Tx Mode to ASTRO (what I have not noticed at that moment). Since everything was fine, I have attached the radio to my main VHF antenna and pushed the PTT button to see what happens. In next few seconds I almost had a heart attack....one of my friends answered back: "Hey Tom, is that you in P25? I read you loud and clear"....

What the.....FFFF....???? How is that possible? The radio was not modified physically, the codeplug was not hacked....how is this possible? How can it work below 146 MHz with normal digital deviation levels? The other ham station is 30 miles away from me...

How is this possible? Maybe some of you can answer this. I have no idea. This shouldn't work but it IS working. But how? I always thought that there is a straight deviation limit below and above each band limits, the radio's firmware itself cuts the deviation below 1 kHz (2.75-2.85 kHz is needed to have a proper level used by P25). The limit was always a P.I.T.A. when I was working with older VSELP and IMBE gear.


Thanks in advance.

 

[Alpha]

I'm guessing it's due to the Plus not having the artificial deviation restriction outside of the normal operational band limits like the regular Astro Spectra has. I have not played with the Pluses enough to be sure of that, however.

That whole P25 limit thing was total BS anyhow, since at he other end of the band it gracefully extrapolates the last known tuning value out beyond the end of normal operation - making it obvious that the limiting was unnecessary and (IMHO) just added out of spite as an afterthought since analog works just fine there.

Either that or your radio is REALLY badly tuned and the deviation is cranked up way too high so he is getting enough to make it work...

 

[HA5BRG]

The cranked up deviation at 146 MHz in K-split VHF radios can be successfully used to bypass that artificial lower band limit what you have mentioned too. But only in very very ancient VSELP units. When it comes to legacy Astro firmware R04 (first IMBE) and newer this method WILL NOT work.

I have used a Motorola service monitor to properly align the radio. I am 100% sure that all parameters meet the factory values provided by the DSM or the BSM.

I will keep experimenting with the radio. If Motorola stepped away from this bullsh*t artificial limit at the AS+ family, these radios will have much higher value for HAMs, I think.

 

[Mars]

Guys, I hate to be the bearer of bad news, but the AS+ does indeed have a soft-limit. And I can verify if it's not modified, you will have issues. Just because it's working, doesn't mean it's working properly.

The soft limit is defined in the TUNE partition at block 4399, offsets 0-3. (4 bytes). In the VHF R2 version, the default data is 01 BD 8E 80. (146.00000). In the R2 K-split radio, it should be changed to something like 01 A5 24 80 (138.00000).

The math works like this: Take your desired lower limit frequency, multiply it by 2, then put that into a base converter (or programmer calculator) and convert it to hex. If your desired lower limit is 137.41250 MHz (x2), your decimal number would be 27482500, which converts to 01 A3 59 84.

HA5BRG, your soft-limit may have already been modified by someone (previous owner?).

To access the TUNE partition, you will require a proprietary Motorola engineering tool which has been floating around. I can not offer further support for that tool, other than providing the data above, which needs to be applied to accommodate the changes.

 

[HA5BRG]

That's not bad news at all. I will keep these info in mind, it maybe come handy some day.

I have some special tools, maybe it will the job, but I don't have any OEM cables for the radio. I've been searching the HKN6155 cable for a while, with no luck.

 

[HA5BRG]

Is it possible to read a radio's tuning partition data and clone it into another?

 

[Mars]

Is it possible to read a radio's tuning partition data and clone it into another?

No, not with regular CPS. Not with Depot CPS either, for that matter.

An unnamed tool is used for that type of operation, but I'm not sure what the purpose would be as it would also overwrite digital tuning values.

 

[HA5BRG]

Let that unknown program remain unknown here and unnamed too.

In the meantime I am facing another issue: the radio has good Tx but poor Rx. It looses Rx after a few minutes it gets warm. I have replaced all items. The VOCON seems faulty somehow. I tried to put it into other radios. Seems faulty in other units.

Any tips?

 

[Mars]

What split is the radio, and what frequency are you experiencing the poor RX with? Has the preselector board been modified for the preamp version? If so, check to make sure there are no cold solder joints on the resistors.

 

[HA5BRG]

The radio is a K-split VHF unit. None of the panels were modified AFAIK.

I had some luck yesterday 8with the same radio). I did find the root cause of this problem. Some kind of microscopic (yes, I could only find it with a microscope) metallic dust was stuck on the VOCON, between two pins of an IC. This had short circuited a tantalum capacitor on the RF Board. After all these were fixed, the radio works fine.

 

[PRC148]

The radio is a K-split VHF unit. None of the panels were modified AFAIK.

I had some luck yesterday 8with the same radio). I did find the root cause of this problem. Some kind of microscopic (yes, I could only find it with a microscope) metallic dust was stuck on the VOCON, between two pins of an IC. This had short circuited a tantalum capacitor on the RF Board. After all these were fixed, the radio works fine.

Wow good find.