Batboard

We all know that IMBE tx is pretty tight to the radio's band split, while analog is more fogiving. Has anyone done the conductive pen modification on a VCO to get IMBE to work either at a higher or lower freq. I know the radio doesn't show out of lock when IMBE fails but wondering if modifying the vco will change that. Where I am thinking is the VHF astro spectras that are 146-174. It would be nice to have them down to 144.0000 on IMBE but generally they dont. I don't mind loosing a little on the high end as I dont go about 163 anyway.

The range 1 vhf's are rare while the range 2 vhf's are plentiful.

Thanks

Jason

it's not normally a matter of VCO lock.

it's a matter of the tuning frequencies in the EEPROM.


without the proper tuning frequencies to do an alignment, you're screwed.... regardless of whether the VCO locks up or not.




doug

So lower the vco crossover freq and you think it would work?

Jason

I just tested a fairly new (serial number 412CFG..., 2.5 kHz RF board, 1MEG, T04KLF..., R11.24.00, N08.03.02) 110 watt Astro Spectra 146-174 model in the ham band.

The P25/IMBE TX seemed to work pretty well all the way down to 144.000. An IFR2975 showed the modulation fidelity to be around 3-4%, which is a bit high, but not too bad. Output power was just over 100 watts, too.

P25 receive didn't seem to be affected at all down at 144.000.

VHF's have always been more forgiving than UHF.

the 450 meg models are much more sensitive to alignment -- and without hacking the tuning softpots, you can't change the radio alignment at 440/444 Mhz... only 45x.000... which isn't close enuf.


sometimes it works first try - sometimes it doesn't



doug

batdude wrote:VHF's have always been more forgiving than UHF.

You're also not pushing quite as far... 2MHz out-of-band and 7-10MHz are entirely different things...

I have noticed that both the Astro Spectra and Astro Spectra Plus VHF both exhibit the same issue.

batdude wrote: the 450 meg models are much more sensitive to alignment -- and without hacking the tuning softpots, you can't change the radio alignment at 440/444 Mhz... only 45x.000... which isn't close enuf.

sometimes it works first try - sometimes it doesn't

doug

Let's say I wanted to guess at entering some numbers to see if I could bump the IMBE transmit operating range down. Which softpots would I need to work with?

I have so far built 2 R-split Astro Spectras with VCOs yanked from 450-482 analog Spectras. One locks all the way down to 440 and will transmit & reveive IMBE at 446 with no problems. The other goes out of lock and won't transmit IMBE at 446, but it will receive.

It is not only the VCO unlocking but IMBE deviation and mod balance soft pots that you have to worrk about.

I tried both versions R04.01.01 and R07.00.01 of ASTRO 25 Mobile CPS, and neither will even let me enter an out of band frequency for a VHF Astro Spectra Plus. I wanted to try the same experiment with 144-146 MHz P25 operation on a 146-174 radio, but I guess that's out...

Has anyone even got a 146-174 Astro Spectra Plus to program below 146?

515 wrote:I tried both versions R04.01.01 and R07.00.01 of ASTRO 25 Mobile CPS, and neither will even let me enter an out of band frequency for a VHF Astro Spectra Plus. I wanted to try the same experiment with 144-146 MHz P25 operation on a 146-174 radio, but I guess that's out...

Has anyone even got a 146-174 Astro Spectra Plus to program below 146?

Yes, you need to edit the CPS exe file. Look under the Astro CPS out of band on this site for instructions.

In the w3 I have in the truck:

It received imbe just fine down to 144.600 (I didn't test lower)

However it doesn't transmit anything ledgible below 146.000 (I tried it on 145.450, and 145.49)

Everyone I talked to about it, told me the same thing about the softpot values.

I bet if I threw a 136-162cp in there it would be fine though.


.

Has anyone figured out how to hack the softpot tuning settings for the ASTRO Spectra or XTS3000 CPS?

I have an ASTRO Spectra that will work fine on 440 analog but in IMBE it transmits a carrier but no audio. I am looking to mod the tuning freqs to allow me to take these radio into the ham band.

XTS3000 is a 450-520
ASTRO Spectra is a 450-XXX radio.

Thanks,

Have you tried to just load an R split (438 to 470 IIRC) codeplug in? Obviously you would need to completely re-align the radio. You know the RF section works down to 440 in analog. My UHF Astro SPECTRA(corrected) started life as a standard Spectra range 3 UHF (450 to 482). The VCO was modified to work down to 440. When I did the upgrade I just used an R split codeplug. Well your RF range may vary without any VCO mods, as long as it is aligned correctly it should work IMBE in the working RF range.

With the XTS3000 I don’t think you would have much RF range below 430 to 435, and probably your RF performance would fall off 7 to 10 megs out of band.

I just upgraded an S split 3000 to IMBE for a friend, and I’m very surprised that it will work IMBE TX/RX down as low as 441.2, and maybe lower. I have not tried to 440 yet.




Jim

mine cut off ast 445.xxxx


after vco mod

all good down to 441

n7maq wrote:My UHF Astro Saber started life as a standard Spectra range 3 UHF (450 to 482).

You meant Astro Spectra, right?

Anywho, I scored a 438-470 analog motorcycle and a 438-470 Astro codeplug, so I got the whole kit 'n caboodle going. The radio I mentioned earlier that TXed IMBE down to 446 quit doing so after I swapped VCOs with another one, so it would appear that out-of-banding is contingent on both alignment AND VCO flexibility. My experience has been that later-model (i.e. black tag) analog Spectras seem to be wider-banded than older white-tag radios as-is, so if you can seek one of those out for your parts donor.


On a slightly-related topic, has anyone laid hands on a 450-520 XTL5000 and tried going out of band with it yet?

motorola_otaku wrote:

n7maq wrote:My UHF Astro Saber started life as a standard Spectra range 3 UHF (450 to 482).

You meant Astro Spectra, right?

Yes I meant Astro Spectra

Jim

motorola_otaku wrote:On a slightly-related topic, has anyone laid hands on a 450-520 XTL5000 and tried going out of band with it yet?

Yes I had one for sale here a little while back and there were no takers so I sold it on the 'Bay.

It did analog and IMBE Tx/Rx from 440-520 no problems. Good sensitivity 0.15uV @ 12db SINAD all the way down to 440MHz since it had the W12 preamp option.

I have an XTL2500 450-520. I did the out of band mod listed for the ASTRO Saber CPS listed on the main page and it works great. I have used it as low as 441.825 with no issues at all.