Batboard

I have a standard VHF 146-174 Spectra that I may just wind up trying to convert to an Astro Spectra, since I can't seem to find a decently priced VHF Astro. A few of the frequencies that I need to talk on are out of the band limits of the 146-174 split. I have one channel in the 139 mhz area, and two around 141 mhz. I know there are edits for other programs to allow their respective radios to go out of band, but I'm just curious if either standard Spectra RSS or Astro Spectra RSS/CPS can be modified to allow a 146 split radio to behave as a 136 split radio.

Thanks

Hex editing of Spectras has been covered extensively on this Board previously. Also, try batlabs.com and see what info is there on the same subject, bandwidth limitations, etc. etc. etc.

http://batlabs.com/spectra.html
http://batlabs.com/astromob.html

I don't think you can convert a Spectra to an Astro Spectra under any conditions. The old Spectra is a completely different animal and has no digital communications capabilities whatsoever.

Tom in D.C. wrote:I don't think you can convert a Spectra to an Astro Spectra under any conditions. The old Spectra is a completely different animal and has no digital communications capabilities whatsoever.

Sure you can. All you need is a new RF board (although I believe there's been discussion on the board prior as to what component changes are necessary to make a Spectra RF board compatible with an Astro Spectra) and a new command board and vocon to replace the old command board and MLM, and finally a new control head. Force feed a SRecord (if necessary to match the new model and band), full alignment, and you're good to go.

The Q split Astro Spectras that you could get on Ebay complete for cheap worked great for the conversion. There are also cheap VHF Astr Spectra boards out there for around $20.00 but they will not do the 2.5KHz steps. I have done the conversions for well under $100.00 in parts.


Jim

akardam wrote:(although I believe there's been discussion on the board prior as to what component changes are necessary to make a Spectra RF board compatible with an Astro Spectra)

Interesting. I suspected and just confirmed from the detailed service manual that the actual A-D/D-A conversion takes place on the RF board, at U301. So even if the Astro controller board will talk to an analog Spectra RF board and be able to process its output, P25 or VSELP ain't happening.

I'm also skeptical whether a 146-174 radio will work well down at 139 or 141, with or without a VCO mod. But I guess if a 450-482 radio can be coerced to work down at 441 it's possible.

So I suppose if I want to create P25 capable (Astro) Spectra, I'd need to find pretty much all new boards, including the control head, except for the PA? Seems like I'm trying to find a needle in a haystack by pieceing this together...

Your VCO, preselector, and PA boards can be recycled from an analog Spectra. The RF board, command board, VOCON, and control head are Astro-specific.

What you really need is a 136-162 radio. Luckily for you the range-specific components are the ones that can come from an analog radio, so what you need to find is a 136-162 analog Spectra. The VHF RF board works across the whole 136-174 range and the command board and VOCON aren't range-specific at all.

btrains wrote:So I suppose if I want to create P25 capable (Astro) Spectra, I'd need to find pretty much all new boards, including the control head, except for the PA? Seems like I'm trying to find a needle in a haystack by pieceing this together...

I have purchased the Q split (403 to 43?) Astro Spectras complete for under $50.00 on eBayAstro . That will give you the command, VOCON, and control head. Then all you need is a VHF RF PCB, for the older boards that will not do 2.5KHz steps they run around $20.00 each. If your legacy Spectra is now working down to 139MHz without any problems you MAY be able to get away with it in analog, but I doubt you would get digital more than two or three megs out of band. My experience with the low and mid power units has only been to 144.5 TX, high power units do not like to do digital at all out of band. As Otaku pointed out your best bet is to go with a J split (136 to 162). Just because your VCO is locking now, it may not with an Astro command board calling the shots, plus you RX probably is not what it needs to be at 139MHz.

Jim