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Thread: Are there actually any 900 MHz Astro Spectras out there?

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    Default Are there actually any 900 MHz Astro Spectras out there?

    Model charts show M04W* models should be in the 896-941 range, but I've yet to find one on the used market. Was this perhaps something that never actually got released?

    Thanks,

    Jim, KY1H


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    There were analog 900 spectras but the Astro line never had them as far as I'm aware. I had visions of setting up my analog spectra as an Astro 900 but there's no provision for that band in the firmware from what my limited probing could find out.

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    there was a post in September of 2015 about changing the band limits in the Astro Spectra CPS the op said the 900 band was there just needed to be moved oob for Ham band.
    never did hear how that project turned out maybe he will let us know.

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    Quote Originally Posted by kd5ual View Post
    there was a post in September of 2015 about changing the band limits in the Astro Spectra CPS the op said the 900 band was there just needed to be moved oob for Ham band.
    never did hear how that project turned out maybe he will let us know.
    Id love to take up the 900 MHz Astro spectra challenge. Its just getting the donor hardware up here is so bloody expensive.

    One could try to engineer a 900 MHz codeplug, or simply mod an 800 MHz codeplug for extended programming. The tuning freqs would also need adjustment. Some hardware mods would also be required, such as replacing the front end filters or simply bypassing them.

    If it worked, it would be a conventional-only mod as theres definitely no 900 MHz channel table support in the 3600 or 9600 firmware builds.

    Off-topic comment: hams really need to learn more about the 900 MHz (33cm) band. Range is very impressive with even low power and a pair of yagis. Height helps too, obviously.

    Ive done about 22 miles (35km or so) using two HTs at 1W, with about 60-70 feet of HAAT between the points.

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    I found out the table I was looking at on Batlabs is sort of generic, even though it is supposssed to be for the Astro Spectra. There are other bands listed there including low band and over 1GHz that Motorola never manufactured for the Astro Specta line. So it appears a home brew mod as others have mentioned is the only hope if one wants a Spectra at 900MHz.

    Thanks,

    Jim
    KY1H

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    Quote Originally Posted by Mars View Post
    I’d love to take up the 900 MHz Astro spectra challenge. It’s just getting the donor hardware up here is so bloody expensive.

    One could try to engineer a 900 MHz codeplug, or simply mod an 800 MHz codeplug for extended programming. The tuning freqs would also need adjustment. Some hardware mods would also be required, such as replacing the front end filters or simply bypassing them.

    If it worked, it would be a conventional-only mod as there’s definitely no 900 MHz channel table support in the 3600 or 9600 firmware builds.

    Off-topic comment: hams really need to learn more about the 900 MHz (33cm) band. Range is very impressive with even low power and a pair of yagis. Height helps too, obviously.

    I’ve done about 22 miles (35km or so) using two HTs at 1W, with about 60-70 feet of HAAT between the points.


    I think the tuning freqs and getting the vco to cooperate may be the challenge, for front end filters the DFC5R915P026BTP or DFC6R933P033BTP would work fine the latter is available on that auction site, and only one needed per radio.

    Mars if you are interested I would be willing to make a hardware donation just need to know where to send it

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    VCO, RX front end/preselector, and PA would all carry over from an analog donor radio just like analog-Astro conversions in other bands, and the VCO mod for 902/927 operation is already well-covered. The only hardware modification potentially required would be to the 800 MHz donor Astro RF board.

    If this ever got off the ground it would be a fantastic way to repurpose 800 MHz Astro Spectras and 900 MHz analog Spectras, both of which are selling for scrap prices these days.
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    Are you sure you can't use the RF board out of an analog spectra? I could've sworn that's what I did for one of my band conversion units. Dropped an 800 command board and vocon into a VHF analog body and tuned it up on VHF just fine. It's been a few years but I definitely did not have a VHF astro RF board at the time.

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    Im willing to take a look at this project, and collaborate with others. But not right now. In the middle of some important career objectives for the next 4-6 weeks.

    I am confident progress can be made. The most difficult part will be working on a custom s-record, inclusive of new tuning ranges/frequencies. It is not as simple as modifying CPS for extended programming.

    The project can be compartmentalized, and many of us can work on subsections of it.

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    Quote Originally Posted by motorola_otaku View Post
    VCO, RX front end/preselector, and PA would all carry over from an analog donor radio just like analog-Astro conversions in other bands, and the VCO mod for 902/927 operation is already well-covered. The only hardware modification potentially required would be to the 800 MHz donor Astro RF board.

    If this ever got off the ground it would be a fantastic way to repurpose 800 MHz Astro Spectras and 900 MHz analog Spectras, both of which are selling for scrap prices these days.
    My comment about the vco was based on Mogman's post from 2015

    I have an analog Spectra on 900 Ham

    as for the RF board we need to compare the 800 and 900 spectra rf boards and then compare to the Astro 800 to see what changes need to be made.

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    Mars is right on the undervalued nature of 33 cm. I have used the old 15 and 30W ex-trunking Spectra radios at 925.5 MHz simplex with good results. Best DX was 385 miles using 4' grid pack antennas and TPL 100W amps. I've had contacts over 100+ miles from home with a dish to a mobile station just using 30W each way.

    I've wondered about a 900 MHz Astro Saber. I understand many of the 800 MHz AS SMD RF modules are the same as those used in the 800 MHz Jedi series and idly wondered (leaving aside the CP issue) if a 900 MHz module transplant were possible.
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    Quote Originally Posted by axel View Post
    Are you sure you can't use the RF board out of an analog spectra?
    If you want it to do P25 (which is the real benefit of this project) you HAVE to use an Astro Spectra RF board. The A/D DSP conversion takes place on the RF board, not the command board or VOCON.
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    Quote Originally Posted by motorola_otaku View Post
    If you want it to do P25 (which is the real benefit of this project) you HAVE to use an Astro Spectra RF board. The A/D DSP conversion takes place on the RF board, not the command board or VOCON.
    Then I guess we'll he hax0ring/converting/studying some of those useless 800 MHz astro spectras. Shame, since I threw about 5 of them out last year. Doh.

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    Quote Originally Posted by motorola_otaku View Post
    If you want it to do P25 (which is the real benefit of this project) you HAVE to use an Astro Spectra RF board. The A/D DSP conversion takes place on the RF board, not the command board or VOCON.
    Are the RF boards in the Astro Spectra similar to the Spectra RF board in that you have the bandsplit jumpers on the board? I should know the answer to that question, as I should have recapped my Astro Spectra RF boards like I have on the Spectras. I realize some other components will most likely need changing, but just thinking. But then you would also need to change the preselector and maybe the VCO boards as well.

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    I heard Motorola came out with this really great improved and simplified antenna connector, it looks just like an ordinary nut and bolt. Perhaps it could be fitted onto a Spectra as well, it would help with the higher 900MHz freqs.

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    Quote Originally Posted by kc9mmm View Post
    Are the RF boards in the Astro Spectra similar to the Spectra RF board in that you have the bandsplit jumpers on the board? I should know the answer to that question, as I should have recapped my Astro Spectra RF boards like I have on the Spectras. I realize some other components will most likely need changing, but just thinking. But then you would also need to change the preselector and maybe the VCO boards as well.
    I have never personally tried to switch bands on a Spectra RF board of any flavor. My cottage industry was moving R1 UHF Astros up to R3 with the aforementioned PA, VCO, and preselector swaps from a donor R3 analog radio, and the UHF Astro RF board covers all four UHF ranges. I’ve heard the move from 800 to VHF is trivial, but I’ve never tried it. I can say it’s not as simple as just moving a few jumpers.
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    I wish there was more 900 use, I have an XTL2500 900 radio sitting on the shelf collecting dust, would be great to get some use out of it!

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    Default Are there actually any 900 MHz Astro Spectras out there?

    Same boat, bro. Ive tried getting some local fellows interested, but so far no biters.

    On that note, I was playing with a 7580 a few days ago. I got it talking to my XTS2500 on 927.5000 Simplex. 7580 tuned up perfectly at 2.5W output, 4.5 kHz deviation (I hate narrowband) and RX sensitivity was about .20uV for 12dB SINAD.

    It also took a 927/902 pair no problem. Same specs. 7580 appears to be a winner. Very efficient PA too. Only 1.1A at 2.5W. Less than an amp at 1.0W.

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    Wow did not know anyone picked up on the 900 ASD project, Mine did "work" but never got around to figuring out the softspot tuning issue.
    A couple things.
    1 yes you must use an ASD (Astro Spectra Digital) RF board, I have never been able to get an ASD to boot with an analog (Spectra) RF board, it will give you a 01/90 hardware failure.

    2 the so called band "jumpers" are only zero ohm resistors and they do NOTHING but give a visual indication of what band the RF board is built for, I have converted a ton of the 800 boards to VHF, only a dozen or so components need to be changed including adding the transistor and associated components to allow "splinter" frequencies to be programmed on VHF, so it must be a late board that has provisions for this, Motorola just leaves off these components in the UHF and 800MHz versions as they just are not needed.
    I have dropped 800MHz boards directly into a VHF radios with no noticeable problems except you cannot program splinter frequencies, I figure the radio must do some type of boot test to see if it is equipped. I did a test removing one of the resistors to basically disable that transistor and the radio "knew" it was not there and would not allow splinter frequencies to be programmed.

    3 No hardware changes should be necessary except the VCO mod , use the 900MHz analog Spectra's VCO and front end and the rest from a 800MHz ASD.

    What happened was the 900MHz XTL's got cheap enough to make this project not as desirable as before, and they work like a hose.

    Oh yes, I think Jim was looking at the "generic" Motorola model list that also shows a low band ASD among others that never were.

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    Sorry, Brain fart, of course you also need to use the 900MHz PA.
    The TX power and mod was way out of whack on my test radio because it was so far away from its tuning soft points.
    Also when I dropped the 800MHz boards directly into a VHF without modification it was only a test, so I did not do an alignment or see if any other issues would develop, most of the component changes were simply resistor and capacitor value changes except for adding the transistor and associated components.
    That is why only the VHF radio had the 2.5KC added to the data tag, the UHF and 800MHz radios would do splinter frequencies with the original RF boards

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    Mogman, would you have a list of the cap/resistor values you swapped out? I realize one could probably cross reference service manuals for this purpose. Just trying to expedite/organize any efforts.

    As for the tuning/whacko values, yes, the s-record contains this information. I know it can be modified. The only thing I'm not sure of is the VCO crossover frequency and whether or not it's required to be referenced/understood by the firmware itself. If it's just a matter of ensuring the VCOs (RX/TX) are locking and firmware/brains aren't involved with that process, I think we should be good.

    The out-of-whack deviation/balance stuff (and possibly oscillator reference) would all be related to the radio operating outside of the defined tuning ranges, and there may also be "soft limits" defined somewhere. A "soft limit" is are defined upper/lower frequency range, where tuning values are referenced. Once outside of those ranges, things go screwy. We fixed this in the ASTRO Spectra Plus. This is something I would love to work on, by maping the tuning blocks of the ASTRO Spectra. I know of someone who may already have the info. Cough cough Alp....ha. cough. it would be great to get this figured out.

    And if any of the mentally ill people at MSI are reading this, no, we're not nefariously reverse engineering/DMCA/Criminal Copyright Infringement violating your products. This is a 23-year-old radio and we wish to make it work on ham radio frequencies. No private financial gain or commercial advantage will be taking place. Getting that out of the way before the mouth breathers down there get any ideas.

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    No problemo!!! Had to convert it to a JPG. This is for a 800 to VHF conversion, don't think any mods would be needed for 800-900MHz conversion Board mod.jpg

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    Sorry I ran out of editing time and got kicked off, Q670 can be seen above U602, these component pads must be there for the conversion to VHF I think all boards rev C and up have them.
    With these mods you can build a VHF ASD from a VHF Spectra and an 800MHz ASD
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    Quote Originally Posted by mshelby View Post
    I wish there was more 900 use, I have an XTL2500 900 radio sitting on the shelf collecting dust, would be great to get some use out of it!
    I think the same thing on almost a daily basis. I have even begun gathering things for the project then stop myself as I think is this going to be yet another machine that only myself and one other talk on? Because I have 3 other machines where we can do that.

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    Part of the problem is lack of subscriber units (mobiles and portables) on 900 MHz. Commercial convertibles include EFJ 5100 (5300 mobiles too?), XTL and XTS2500's, and older analog Spectras. That's one of the reasons this thread and ones like it are important, the more subscriber units we can get out there the better the band can be utilized. And "use it or lose it" is the name of the game these days!

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