900Mhz Astro Spectra?

ssybert · Post by **ssybert** » Wed Oct 06, 2004 4:58 am

I was brainstorming last night trying to find a way to get a 900mhz astro Spectra. I dont NEED astro, I just want to be able to use my current W3 head on 900.

Here's what I came up with:

Get a WORKING 900mhz ANALOG radio.
Remove the MLM and swap in an astro vocon and command board.
Get an S-record for an 800mhz radio and hack the last programmed version down to an earlier DOS version.
Push the S-record into the radio
Hack the RSS to allow freq's up into the 33cm band.
Viola! 900mhz ASTRO Spectra!

Am I missing anything? This SHOULD work, right?

CTAMontrose · Post by **CTAMontrose** » Wed Oct 06, 2004 6:09 am

ssybert wrote:Get an S-record for an 800mhz radio and hack the last programmed version down to an earlier DOS version.

this part intreages me.. tell me more...

ssybert · Post by **ssybert** » Wed Oct 06, 2004 6:19 am

Well, (I think) someone with lab 9.05 can downgrade the last programmed version of a radio by modifying it's s-record. I person offered their services to me once and with a copy of my s-record they were able to back me down to 8.5RSS. I think it was done via lab but I could be wrong. Regardless, it can be done. The only reason this portion is required is because the newer CPS stuff can't (yet) be band modded. The older dos RSS is EASY.

I'm real excited about trying this... I think I'm going to start buying things up. I can't see any reason this wont work. Dual radio UHF/900 Astro W3. I must say, I think I'll be the first ever

ASTROMODAT · Post by **ASTROMODAT** » Wed Oct 06, 2004 9:22 am

"I must say, I think I'll be the first ever."

Therein lies the problem: There will be nobody to talk with, especially if you don't modify a Quantar to also run 900 IMBE.

Larry

ssybert · Post by **ssybert** » Wed Oct 06, 2004 9:35 am

Well, the intention is not to run astro, just to allow me to run a dual radio with my W3 HHCH. I've currently got an Astro Spectra UHF W3 setup. To USE the W3 HHCH, both radios need to be ASTRO radios. I wont be running astro on the 900 because that radio will be for ham use only. Not too many IMBE repeaters around let alone converted quantars

I hate the A3 head, dont want another HHCH up front and would like to play around with the dual radio stuff a little. What better way

It is likely nobody has done this but there are alot of guys with more insight than me that can say "Oh yeah, that should work but you'll need to do this too" or "nope, can't do it because this doesn't do this" or something.

Post by **wavetar** » Wed Oct 06, 2004 10:49 am

It may be even easier to go the opposite route...get a used 800MHz Astro Spectra, last programmed with DOS RSS. Hack it into the 900MHz band, and swap out the RF/PA boards from an old analog 900MHz Spectra. No RSS version to worry about.

Todd

CTAMontrose · Post by **CTAMontrose** » Wed Oct 06, 2004 10:53 am

yeah thats what i was thinking as well..

if it was that easy, everyone would be buying VHF analog spectras and just adding the astro stuff and be getting Astro Spectras on the cheap.

ssybert · Post by **ssybert** » Wed Oct 06, 2004 10:57 am

It IS that simple. I've done it to atleast half a dozen radios. Me and a couple buddy's have gotten low split UHF astro spectras and mid split ANALOG spectras for conversions. Remove the MLM from the analog and swap in a Vocon/command board from the astro. Push in the appropriate S-record for the band radio the ANALOG is and the ANALOG is now an ASTRO.

the result is an ASTRO on the RIGHT band and an analog on the WRONG band.

As a matter of fact, the radio in my truck used to me a low UHF split A7 which is now an ASTRO W3 with nothing more than the W3 front panel, vocon and command board

CTAMontrose · Post by **CTAMontrose** » Wed Oct 06, 2004 11:00 am

hmmm

how much is a VOCON / command board typically?

ssybert · Post by **ssybert** » Wed Oct 06, 2004 11:02 am

they're not easy to find... vocon can go anywhere form $100.00 - 250.00 and I dont usually see command boards.

The easiest thing to do is buy one of each radio, swap the NON-RF boards (MLM & Vocon/command board) and sell the resulting analog for whatever you can get.

You can get the astro radios on less than useful bands pretty cheap.

I think I answered my own question about the 900 stuff. It looks like it's going to work. I'll post results when I finish granted I can secure the parts I need.

ASTROMODAT · Post by **ASTROMODAT** » Wed Oct 06, 2004 11:13 am

A high split ASTRO converted to operate in the low split range has more issues than just being able to force a codeplug in the lower range. Its front end has filters with really tight skirts that are laser trimmed to the upper versus lower range. Sure, you can force it to accept programming frequencies that would otherwise be out of range, but you get poor receiver, and exciter, performance. What's the point of using a commercial radio to take advantage of its great sensitivity and selectivity, and then countermand all of this by forcing it into out-or-range frequencies?

Larry

ssybert · Post by **ssybert** » Wed Oct 06, 2004 11:30 am

Wrong.

Take a 403-430 ASTRO Spectra. useless, right?

Take a 450-482 ANALOG Spectra. Useful, but better if it were ASTRO

Now, REMOVE the MLM from the 450-470 ANALOG Spectra.

Remove the Vocon and Command board from the 403-430 ASTRO.

Put the Vocon/Command board FROM the 403-470 ASTRO radio INTO thr 450-470 ANALOG RADIO.

The Analog 450-470 Radio is now an ASTRO Radio with a 403-430 vocon.

The nice thing about these vocons & command boards is they are universal. There good on any band! You could have used an 800mhz radio ASTRO as a doner and it would still work!

now when you power it up it's going to give you a solid FAIL 001. Nothing will work. the programming in the vocon is in the 403-430 range and the RF section of the radio is 450-470.

ok, simple enough to fix... force in an S-record from a similar radio IN THE RANGE OF THE RF SECTION of the previously ANALOG radio and viola! The radio will come up like it was always an astro. Some tuning may be in order but thats really all there is to it.

The RF portion is STILL operating within the same band so there's no de-sense.

Scott.

CTAMontrose · Post by **CTAMontrose** » Wed Oct 06, 2004 11:30 am

i think hes talking about keeping the RF parts together with the original split

converting an ASTRO low split into an ANALOG low split and vice versa, just moving over the logic required to convert the radio, not the bandsplit.

ASTROMODAT · Post by **ASTROMODAT** » Wed Oct 06, 2004 11:38 am

Correct. I was talking about situations where folks take a 450-482 ASTRO Spectra and try to get it to operate in the 438-470 MHz band (e.g., to operate in the 440-470 MHz Ham band). It doesn't work well, as both the RX Front End and the Exciter work like heck when you try to do this.

Larry

ssybert · Post by **ssybert** » Wed Oct 06, 2004 11:40 am

Agreed. I've got a 450-482 ASTRO Spectra and I forced it down to 440 and it was horrible. my portable on the front seat recieved 10x better. I've since removed all out of band freq's from the spectra as they're absolutely useless in there.

CTAMontrose · Post by **CTAMontrose** » Wed Oct 06, 2004 11:40 am

just to be clear you would also have to change out the control heads as well....

keep only the componets that are RF related correct?

ssybert · Post by **ssybert** » Wed Oct 06, 2004 11:43 am

Ahh... Yes. I forgot all about that becuase I was thinking back to my W3 which needed replacing anyway from the radio's original A7. I THINK I remember reading someplace a standard analog head could be made to work with astro radios... I can't remember though. But for all intensive purposes, yes. The head does need to be swapped out for a W series which is compatible with the model # in the s-record your forcing in.

ASTROMODAT · Post by **ASTROMODAT** » Wed Oct 06, 2004 12:04 pm

Seems like it would be a lot easier to sell your incorrect band radio on eBay, and get the proper banded ASTRO radio.

BTW, this brings up why it is so important to get the original sales receipts/proper tags, etc. on eBay radios. Otherwise, you have no idea how many Ham radio operators and others have screwed around with who the heck knows how many multiple radio mods, and screwed up what started out as a great radio.

This is why I generally hate and distrust most (not all) eBay radios. You really have no clue as to what it is that you are really buying. Kind of like having unprotected sex with a stranger---no matter what they say to you at 3:00 AM when you get back from the local bar to your bachelor's pad, you have no frikin' idea what you're messing with! (Until you visit your Motorola authorized MD to get checked out.)

Larry

ssybert · Post by **ssybert** » Wed Oct 06, 2004 12:08 pm

Well, it wouldn't be cheaper to buy the right band split when the price of a range 2 UHF astro is like 4 times the price of a range 1.

situations like that make the most sense... or if you have parts lying around

ASTROMODAT · Post by **ASTROMODAT** » Wed Oct 06, 2004 1:44 pm

Or if you are doing it for the fun of it, as a hobby. Then it's theraputic.

Larry

Post by **xmo** » Wed Oct 06, 2004 4:31 pm

Boy - now you guys have got ME thinking!

I have a VHF analog Spectra. I also have an extra 800 Astro Spectra. I would like to have a VHF Astro Spectra. I would also be perfectly happy to have the 800 radio be an analog unit when the project is done!

I think I'm going to give this a try! I may even have an extra one of those Astro Spectra Plus conversion kits - that would be way cool - a VHF Astro Spectra Plus.

ssybert · Post by **ssybert** » Wed Oct 06, 2004 4:59 pm

Whats the Plus conversion do?

Don't happen to have a command board kicking around do you?

Post by **xmo** » Wed Oct 06, 2004 5:55 pm

The Spectra Plus conversion converts the radio to a Spectra Plus which is basically the same feature set as an XTL5000.

The kit does come with a pretty nice flash code that includes Smartnet, Smartzone, IMBE, Astro25 trunking & multikey.

For conventional use that may be not a big attraction - but the nice thing is the kit comes un-initialized - so installation in whatever frequency band radio is a snap without having and special 'secret' software or LAB tools. Also - the Plus might work with those jazzy new heads they're coming out with!

Converting analog Spectra MLM's from one band to another is already a documented process - so the project should be possible.

Sorry - no command boards laying around.

Post by **batdude** » Wed Oct 06, 2004 6:20 pm

uh, pardon moi

but the RF board between astro and analog spectra isn't even in the same ballpark... this is why i haven't been interested in converting some of these radios before... when the RF board is $500+, kinda pointless

doug

ssybert · Post by **ssybert** » Wed Oct 06, 2004 7:04 pm

Want a minute... The UHF ranges are the same aren't they? All the radio's I've done were UHF. I haven't played with 800 or VHF.

Even if the RF ranges are different, as long as you program frequencies within the range of the RF section of the hybrid radio things should be fine shouldn't they?

I just thought of a new problem with making a 900mhz astro.

Now, if I take a 900mhz ANALOG and put a vocon/command board into it it WILL power up. It's going to give me a FAIL 001 because someplace in that S-record there is either a range specified or something that the radio must try to lock on because it knows it wont work even without keying up.

SO... Here's the problem I just thought of... If I change the freq. ranges in the RSS to ALLOW 900mhz freq's to be programmed into my 800mhz S-record in my 900mhz analog (now astro) radio, the S-record is still going to have some kind of band limit spec. in it (850-896 for example) and the 900mhz RF components will not lock up in that area.

Does anyone know if it's possible to hack the S-record and change what the band limits it "thinks" it is? I think this is going be a problem as the 800mhz limits the S-record has stored someplace will conflict with what the 900mhz RF components can handle.

Ideas? I knew I'd find some problems.

Post by **batdude** » Thu Oct 07, 2004 4:53 am

the RF board is NOT common between the analog and astro spectra.

this is the problem.

and i am not going to plug a couple hundred $ vocon into an analog RF chassis "just to see if it will work"... maybe someone with some spare parts or the time to research the various pins/voltages on the RF board header connector can do this...

ssybert · Post by **ssybert** » Thu Oct 07, 2004 6:16 am

Did you read this whole thread? I've done it. It does work.

What are the exact band limits of the 3 ranges of an ANALOG spectra and an ASTRO?

As long as the freq's programmed fall between the band limits of the NEW RF boards, there shouldn't be any attenuation problems.

Still curious about the s-record problem I posed last night. Anyone have any ideas?

CTAMontrose · Post by **CTAMontrose** » Thu Oct 07, 2004 6:25 am

Analog:

VHF
Range-1 136-162 MHz
Range-2 146-174 MHz
UHF
Range-1 403-433 MHz
Range-2 438-470 MHz
Range-3 450-482 MHz
Range-4 482-512 MHz

ASTRO

K 146-178 (i thought this was 136-178, but this is according to the main pg
Q 403-437
R 438-482
S 470-520

Microwave Mike · Post by **Microwave Mike** » Thu Oct 07, 2004 7:51 am

The Astro UHF RF Board IS common for all three UHF splits. The VCO, Rf front end and PA section are band limted.
The part numbers for Spectra and Astro Spectra boards are different, but the boards seem the same, except the RF board. I have done Q split conversions to R split using Spectra and Astro blends. The conversion to 900 Mhz should be the same as converting a Standard Spectra to 900 Mhz.The Rx front end will have to have the block filter replaced and the VCO will have to be worked on.

mm

Motofanatic · Post by **Motofanatic** » Thu Oct 07, 2004 8:08 am

uWave Mike is correct, there is one Astro RF board for all UHF splits.

Doug is also right, you cannot convert a analog Spectra to an Astro Spectra without also changing the RF board to an Astro RF board.

Ssybert is probably doing this, but just never stated it I assume.

The only way to find out if you can make an 900MHz Astro Spectra is to try it because there are no 900MHz Astro RF boards. In the detailed service manual, there are only 3 bandsplits for the Astro RF board: VHF, UHF and 800 each with their own respective part #'s.

Notice there is no 900MHz Astro RF board. You will have to just try it with an 800MHz Astro RF board and see if it can work at 900MHz.

ASTROMODAT · Post by **ASTROMODAT** » Thu Oct 07, 2004 8:58 am

As Doug pointed out, by the time you changeout the $500 ASTRO RF board, the economics of such a conversion make no sense (even if your opportunity cost is zero).

Larry

carbineone · Post by **carbineone** » Thu Oct 07, 2004 9:44 am

ssybert said in his post that he has done it with an analog uhf rf board apparently this works to some extent guys. Now if someone could put one of those radios on an analyzer and see how well it does.

carbineone · Post by **carbineone** » Thu Oct 07, 2004 9:55 am

Sorry after reading more careful I understand what you guys are saying.
The astro rf board for uhf is common for all splits and he is putting the astro rf board in an analog spectra of a different uhf bandsplit. Sorry it's
a little confusing. That is a neat trick though.

CTAMontrose · Post by **CTAMontrose** » Thu Oct 07, 2004 10:04 am

i dont think he said he was changing out the RF boards... from what i read it was command board/vocon/interconnect/control head

he also said that the command board and vocon could be put into any other band...

my take is that he has taken all non band specific parts and transferred them.

i AM a bit confused as most are saying that it wont work, but he is saying that he has done it several times.. me wishes i had a Q band laying around...

ASTROMODAT · Post by **ASTROMODAT** » Thu Oct 07, 2004 12:35 pm

ASTRO Spectra RF board does NOT = analog FM Spectra board.

That's the point he seems to be missing.

Larry

carbineone · Post by **carbineone** » Thu Oct 07, 2004 1:18 pm

Yes does not = astro rf board but he says it works. If it works with the regular board then what's the problem.

ASTROMODAT · Post by **ASTROMODAT** » Thu Oct 07, 2004 2:14 pm

Since we all agree that the ASTRO Spectra RF board is not = to the analog Spectra RF board, I guarantee you that there is a good and valid technical reason for this. The fact that it appears to work O.K. (such as for Ham radio use and the like) is by no means an endorsement that you will enjoy proper radio performance with this swap. Otherwise, Motorola would surely manufacture only one flavor of RF boards (Digital versus Analog), and thereby realize substantial product savings. Consolidating to a single RF board for the ASTRO Spectra and Analog Spectra would generate savings for Motorola on their BOM for manufacturing, as well as generate savings for ongoing maintenance, spares, repair costs, etc. There is definitely an issue here, whether we folks on the Batboard happen to know the details of the deltas, or not.

Larry

carbineone · Post by **carbineone** » Thu Oct 07, 2004 2:27 pm

I want to thank ssybert for posting this mod. If it works to a degree it is still a neat trick and some of us would like to play around with it. Not everyone can afford to buy all Moto factory fresh stuff. This board should encourage a little more experimenting instead of just saying go buy it from Motorola. Not starting any arguments just giving my opinion.
Thanks

ASTROMODAT · Post by **ASTROMODAT** » Thu Oct 07, 2004 2:39 pm

Point well taken, carbineone. I completely agree with your comments, as I am a Ham and I grew up on Heathkits and modified Motracs, etc, for Ham use. My only observation is that everytime I have fooled with going outside of Moto's stock approach, one invariably finds trouble. Remember the old days of the Micor repeater? The 450-470 repeater worked like krap if you tried to tune it to the 440-450 Ham range, without replacing the Exciter board with the 420-450 version (or without replacing probably a dozen or so discretes on the stock exciter board). The thing lit up the spectrum analyzer like a Christmas tree, ahead of the factory passband duplexers. There were also big problems with the circulator and related circuitry as I recall, and the RX was not very sensitive, or you would lose the great selectivity specs of the Micor. The 420-450 off-shore Micor repeater had more circuitry deltas from a standard 450-470 Micor than you could shake a stick at. While you could definitely get the stock 450-470 Micor repeater to work reasonably well on the 440 Ham band, there were plenty of issues and lots of work to correct them. In the end, it was easier (and almost as good) to use the ICOM 4020 repeater and be done with it. Its selectivity and sensitivity were remarkably good, and it was extremely reliable. I wish ICOM would hurry up with its IMBE gear!

Larry

Motofanatic · Post by **Motofanatic** » Thu Oct 07, 2004 2:46 pm

Ok, Larry pretty much hit it on the head in his post 3 above this one so I won't repeat it.

I will say that I'd hate for someone to spend money (even a little bit for this "experiement") only to come up disasspointed so I'll clarify why and what won't work.

The Astro Spectra RF board is not a Analog board. That means it does not have any analog audio output coming out of it. That is because the Vocon expects a digital signal from the Astro Spectra RF board to then demodulate in its DSP as a standard FM analog signal or a digital (CAI, VSELP, IMBE, etc.) signal.

A Analog Spectra RF board does not output this digital signal and never will. If there is any hope of something being produced, the best you will achieve is an analog FM demodulated signal being passed up to the Vocon/Command Board and that's it. You will not be able to receive any digital transmissions using a Analog Spectra RF board with a Astro Spectra Vocon/Command board.

If your desire is to have a analog only Astro Spectra, then this experiment may be worthwhile. If you truly need to have a digital Astro Spectra that can receive CAI, IMBE, VSELP, etc. then you will need to find or buy a Astro Spectra RF board appropriate for the band you are operating in.

carbineone · Post by **carbineone** » Thu Oct 07, 2004 2:53 pm

That answers it perfect thanks for the info.

ssybert · Post by **ssybert** » Fri Oct 08, 2004 7:26 am

Guys...

The only radio's I've tried this to are UHF radios. T-band to Mid, low split to Mid... It all works fine. I did not swap any RF boards between the radios, just the logic. After making an Analog radio an astro by swapping IN a Vocon/command board I pushed in an S-record in the bandsplit of the new "hybrid" and it works. it needs to be tuned up a little but secure works, Astro works, secure astro works, Everything appears to work perfectly. I understand what you guys are saying about passing digital/analog... well, isn't EVERYTHING analog at that level? just becuase it's not VOICE it IS NOISE. The RF components dont know the difference between voice and data. The """"DATA"""" at that stage is NOT 1's and 0's it's NOISE. It still needs to go through a D/A converter BEFORE it's REALLY digital. Therefore, the only difference between the two RF boards can really only be that one might be more finely tuned, better components, things that will help preserve the EXACT value of the signal, it being potentially "digital". The analog only RF board could be less that "perfect" because the signals it passes can afford to be slightly damaged, altered, etc. without any noticable degregation to the end result. Maybe the "astro" RF board isn't REALLY necessary, just Motorola going the extra mile to ASSURE their signal is nothing but 100% with 150% quality products to gurantee it?

ASTROMODAT · Post by **ASTROMODAT** » Fri Oct 08, 2004 1:02 pm

ssybert, I think you are trivializing the magnitude of the delta. My sense is that your proposed lash-up (e.g., using an analog FM RF Spectra board in a modified analog Spectra to try to perform as an ASTRO Spectra) flat out will not work in IMBE mode. Try it and prove me wrong, but I'm betting that it will not work in IMBE mode.

Larry

ssybert · Post by **ssybert** » Fri Oct 08, 2004 2:31 pm

Larry,

Of the radios I've upgraded, a few... 3+ anyway... maybe more... All work IMBE. I can gurantee this. I know for sure they work becuase the guys I did the upgrades for wanted them upgraded for that purpose.

I dont know about quality, noise, etc... but bottom line, when I TX with a modified spectra on an IMBE channel, my XTS decodes it perfectly. Other authentic Astro's decode it as well as other modified astros. My 785D also decodes it

This I know for sure

Scott.

Post by Pj » Fri Oct 08, 2004 3:42 pm

Um, I am a little late to this discussion, but a well known batlabber here took my 15 watt 800 Astro Spectra and I am 99.99999999% sure he swapped out the PA deck with a 35watt Spectra PA deck.

Tx/Rx 100% IMBE and analog.

Of course I skipped a few posts, so this just may not apply...but I thought I would put this little piece of unnessary information out there.

Post by **xmo** » Fri Oct 08, 2004 3:54 pm

The issue is not transmit - it's with receive.

The difference between the analog Spectra RF board and the Astro Spectra RF board is that the Astro board has a different IF chip. Most of the other circuitry is the same and the connections are so similar that there is no worry about letting smoke out.

The big difference between the two is that the Analog IF IC has a single ended demod out that connects to the command board on J500-4. The Astro board has a differential output on J500-4 and J500-3. On the Analog board J500-3 is labled spare.

These connections route through the command board to the VOCON. The big question is - what is the result of driving the differential inputs on the Astro VOCON with single ended IF demodulated data?

Maybe it works OK for C4FM but would have issues for CQPSK. If I do try a conversion - I'll put it on the bench and run some BER tests to see what happens.

Post by **xmo** » Fri Oct 08, 2004 4:14 pm

Actually - there is another option here - don't change the RF board.

On feature of Spectra is that the RF boards are really all the same RF board with minor component changes. The Spectra series is probably the only radio family to ever use the same IF frequency for all the commercial RF bands [the IF frequency is actually patented by Motorola for this application].

In the case of VHF vs. 800 there is one jumper change, 6 resistors and one cap. Surface mount stuff - but not an insurmountable challange.

grinthock · Post by **grinthock** » Fri Oct 08, 2004 10:45 pm

So one good question while on the bench. Is that pin that's labelled SPARE, REALLY a spare? Or do they just label it that way (because it's "not used") that's something a scope could tell us.

At first I was thinking the RF section provides the audio/IF output to the rest of the unit, but XMO you are suggesting that the IF levels that it outputs to the VOCON may be different?

All of this is very interesting, so question being, are all VOCON's the same? Could someone get an unknown vocon (from an unknown radio) and put it in, forcing in an S-Record (probably need a good tune job)

The argument regarding RF board looking different doesn't mean much, companies change designs yet they are still 100% compatible / the same

As for the people discussing cost, I havn't seen very many Astro Spectra's (VHF) go cheap, but analog spectra's for less than 200usd (or even 100USD) are not unheard of. I've also seen VOCON's around for dirt cheap too, that being said, even if you purchased it new, you would still be ahead cost wise.

So I havn't seen clean clear answers to some important questions here.

1) These RF boards are different (appearance) but are they different electrically and RF Wise., so they have same input and output specs

2) Does this work across VHF/UHF/800/900 so that you could yank a VOCON/Command and move it from any into any

3) Let's make assumptions that tuning would be necessary

4) We need the service manuals from one of each to compare specs

5) Who has done it, and if you have, document what you did, how you did, and what you went from/to.

6) Let's talk about what's been done, not what people think or speculate.

Motofanatic · Post by **Motofanatic** » Sat Oct 09, 2004 6:45 am

Grinthock, please don't take this as directed to you. Your post merely provided a good outlined Q&A platform for me to reply to.

I'm baffled by how confused some people are on this thread and how much they misread or skim over the other posts.

What Larry, xmo and myself have posted is correct. You are not going to achieve 100% Astro Spectra operation (in all digital/analog Tx/Rx signalling/data/audio aspects) if you use an analog Spectra RF board with a Astro Vocon/Command board. The Astro Spectra RF board is DIFFERENT electrically (in a major way) from an analog Spectra RF board.

Repeat: The Astro Spectra RF board is DIFFERENT electrically (in a major way) from an analog Spectra RF board.

With that being said, I will use grinthock's questions below to summerize:

grinthock wrote:At first I was thinking the RF section provides the audio/IF output to the rest of the unit, but XMO you are suggesting that the IF levels that it outputs to the VOCON may be different?

In a Astro Spectra RF board, there is no concept of an analog output to the Vocon. The output on the 2 pins xmo refer to is a current loop containing 16-bit I/Q (In-phase/Quadrature) digitized output that comes out of the ABACUS chip. This is sent over to the Vocon where it uses the DSP (or ADSIC) to demodulate the I/Q data as either FM analog audio, or digital (CAI-IMBE/VSELP) audio. If you put a scope on these 2 pins and inject an analog FM signal into the Astro Spectra's receiver, you will NOT see or hear the analog modulation. These two I/Q data pins from the Astro Spectra RF board are carrying data at a 20KHz rate (according to the service manual)

grinthock wrote:All of this is very interesting, so question being, are all VOCON's the same? Could someone get an unknown vocon (from an unknown radio) and put it in, forcing in an S-Record (probably need a good tune job)

These 2 pins carrying the I/Q signal between the Vocon and the Astro Spectra RF board are the same (as far as voltage level and timing). However, I am sure there are different Vocons as they improved on the revision of the board. (e.g. 512K vs. 1Meg Vocons)

grinthock wrote:The argument regarding RF board looking different doesn't mean much, companies change designs yet they are still 100% compatible / the same

xmo was referring to the physical differences between the Astro Spectra RF board and the analog Spectra RF board. There is a clear and evident difference between those two having different part #'s and design. Of course, there are half a dozen Astro Spectra RF board REVISIONs as you refer to which are just revision improvements upon the same design.

grinthock wrote:So I havn't seen clean clear answers to some important questions here.
1) These RF boards are different (appearance) but are they different electrically and RF Wise., so they have same input and output specs

Please refer to my replies above

grinthock wrote:2) Does this work across VHF/UHF/800/900 so that you could yank a VOCON/Command and move it from any into any

Without changes? No. However once a Vocon has the correct codeplug for the bandsplit it is needed to operate on, it will work correctly. The Vocon is only frequency dependant based upon the the codeplug that is loaded into it. The Command board has no frequency dependant parts on it.

grinthock wrote:3) Let's make assumptions that tuning would be necessary

Yes, if a Vocon is changed from one bandsplit to another (even within the same band - i.e. UHF-Low to UHF-T), it will need to be realigned

grinthock wrote:4) We need the service manuals from one of each to compare specs

You need to have the detailed service manual to see the differences between the VHF, UHF and 800MHz Astro Spectra RF boards if you are going to convert from one band to another (meaning from 800MHz to UHF for example)

grinthock wrote:5) Who has done it, and if you have, document what you did, how you did, and what you went from/to.

I have. I used the Detailed and Basic Astro Spectra Service Manuals. I have converted 800MHz Astro Spectra RF boards for use as a UHF Astro Spectra and a VHF Astro Spectra by buying the correct SMT parts and moving/replacing the parts as documented in the Detailed Service manual. I have converted analog VHF/UHF/800 Spectras into Astro VHF/UHF/800 Spectras buy replacing the analog MLM/command board AND analog Spectra RF board with the Vocon/command board AND Astro Spectra RF board with appropriate control head changes.

grinthock wrote:6) Let's talk about what's been done, not what people think or speculate.

I wholeheartedly agree. Lets hope any further replies to this thread will be after people carefully read all the posts in their entirety. This board is valuable because of the accurate information posted. People should not be mislead into thinking something will work based on speculation or incomplete testing.

ExKa|iBuR · Post by **ExKa|iBuR** » Sat Oct 09, 2004 8:01 am

xmo wrote:Actually - there is another option here - don't change the RF board.

This interests me.

So basically what you're saying XMO, is that it would be possible for me to take, say, a UHF Astro Spectra, swap out some parts on the RF board, take an S-Record from a VHF Astro Spectra, get the radio re-turned, and whala, I'd have a VHF Astro Spectra?

If that's the case, that might be a decent alternative to getting a "real" VHF or whatever band you want astro. Getting a radio tuned up isn't really that hard if you have the right gear, or know the right people.

Now that being said, for anyone who has done what xmo mentioned, how much of a PITA is it to swap out the parts, and which ones are they?

Keeping with the original post...if you wanted to swap out parts to make a 900MHz astro - obviously Motorola never made a 900MHz version, so could you still modify a VHF/UHF/800 board?

-Mike

900Mhz Astro Spectra?

900Mhz Astro Spectra?

Re: 900Mhz Astro Spectra?

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Astro Spectra 900 Mhz.......ah...it can be done.

Doesn't anybody read carefully anymore?