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Modifying Low Band CDM1550 onto 10m 29 MHz

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g8tzl2004
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Modifying Low Band CDM1550 onto 10m 29 MHz

Postby g8tzl2004 » Thu Aug 24, 2017 4:30 pm

Anybody successfully programmed a low band 29.7 - 36 MHz CDM1550 onto 10m?

I have been doing some research and there is very useful info on modding 50 MHz, 220 MHz and 450 (to 440 MHz) CDM's - especially using CHIRP (W9CR) which involves modifying the tuning piers as well as the band limits.

With the 10m CDM1550, I only need to take the radio 200KHz out of band (compared to -10 MHz and +4 MHz with the 450 MHz and 50 MHz CDM's).

Does the old "shift key" trick work with the CDM's like it does with the Maxtracs allowing you to program down to 29.5MHz just by holding in the shift key?

Will I need to adjust the tuning parameters given that I am only going 200KHz out of band (rather than 10 MHz)?

Any other hints from anybody that has successfully modded a 10m CDM?

Thanks

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Astro Spectra
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Re: Modifying Low Band CDM1550 onto 10m 29 MHz

Postby Astro Spectra » Fri Aug 25, 2017 12:55 am

The shift key thing doesn't work AFAIK but the superb web site of Bryan W9CR sets out what you need:

http://wiki.w9cr.net/index.php/Waris

I used the old CP tool and a hex editor because ... I'm old.

The recommended way today is to use the Chirp application.

I only use my radio above 29 MHz on a couple of frequencies so it didn't need anything special other than a routine alignment.

g8tzl2004
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Re: Modifying Low Band CDM1550 onto 10m 29 MHz

Postby g8tzl2004 » Fri Aug 25, 2017 1:06 pm

I have a few questions about modifying a CDM to 10m:

Are there any issues in selecting a 28 MHz frequency band edge rather than say 29.5 MHz?

Does a 29.7Mhz CDM require any front end alignment? I think my 10m Maxtrac did not have any front end alignment. I think my 2m VHF CDM has very broad front end alignment. I think you just align on one mid frequency and then input default fixed values for all the other VHF front end tuning points...as the front end tuning is very broad.

Do I need to alter the front end tuning points (or "piers")?

If I do need to alter the front end tuning points, do the tuning points need to have a fixed standard gap between each of the 7 tuning values. With the 450 MHz CDM, W9CR subtracred -10MHz from all the tuning points. With a 6m CDM, +4 MHz was added to all the tuning the points. So what should I do with a 10m CDM which I only need to program 200 - 300KHz out of band? Is a smaller change (ie -300KHz) preferred over a bigger (say -2Mhz) change...especially since the 29.7 MHz CDM are designed to only work over a very small frequency range ie 29.7 - 36 MHz....ie 6 to 7 MHz maximum theoretical coverage. You need 3 different radios to cover from 29.7 MHz to 50 MHz (29.7 - 36 MHz, 36 - 43 MHz and 43 - 50 MHz) whereas a VHF CDM overs from 136 to 174 in one radio (ie 38 MHz range)?

Thanks

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Astro Spectra
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Re: Modifying Low Band CDM1550 onto 10m 29 MHz

Postby Astro Spectra » Fri Aug 25, 2017 2:13 pm

g8tzl2004 wrote:...what should I do with a 10m CDM which I only need to program 200 - 300KHz out of band?


Astro Spectra wrote:I only use my radio above 29 MHz on a couple of frequencies so it didn't need anything special other than a routine alignment.


What I said, 29 MHz and up performed perfectly with nothing other than a routine alignment.

g8tzl2004
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Re: Modifying Low Band CDM1550 onto 10m 29 MHz

Postby g8tzl2004 » Fri Aug 25, 2017 2:36 pm

But did you alter the first or all of the tuning piers....or just leave the tuning piers alone?

I guess the first tuning point (or pier) is around 29.7 MHz. According to the CHIRP app, if you program in a frequency below 29.7 MHz, the CPU gets confused as it is unable to perform a correct linear interpolation for the tuning values as it wants to see a value above and not below 29.7 MHz...so you need to lower the tuning piers to include the new band edge as well as hex edit the frequency band edges.

Did you align the front end when you set up your CDM on 29.000 MHz and above?

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N9NU
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What radios do you own?: HT-1250 x 3 | CDM1550 | More..

Re: Modifying Low Band CDM1550 onto 10m 29 MHz

Postby N9NU » Wed Sep 06, 2017 7:15 am

Wait....the CHIRP programming app works with Motorola radios? I didn't see any of them listed.

I have a CDM 1550 (low band) and would love to mod it for 10M



Tim S Dickerson, CEM
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Tim S Dickerson, CEM - ARS N9NU
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g8tzl2004
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Re: Modifying Low Band CDM1550 onto 10m 29 MHz

Postby g8tzl2004 » Wed Sep 06, 2017 7:37 am

Check out W9CR's wiki and You Tube videos.

My 10m CDM is a Euro version with different firmware so the chirp app will not (yet) work.

I'm still unsure whether I need to mod the tuning points or just the band limits?

Jay
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Re: Modifying Low Band CDM1550 onto 10m 29 MHz

Postby Jay » Sun Oct 08, 2017 6:39 pm

I've done several CDMs and HT's to 10m FM, all with old school hex mods. Real PIA, but it works and you don't have to modify your CPS when you are done, and can pass the radio along to others who can still program it. None of them required any alignment after the fact, but I only opened it to 29 MHz and pretty much stuck to 29.5 Mhz and above for operating. Great fun to run a CDM on 10m FM.

George
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What radios do you own?: X9000, HT1550XLS, MTS2000, etc

Re: Modifying Low Band CDM1550 onto 10m 29 MHz

Postby George » Tue Oct 31, 2017 5:35 am

Okay, I'll ask...what is CHIRP? Where is it available?

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tuckerm
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Re: Modifying Low Band CDM1550 onto 10m 29 MHz

Postby tuckerm » Tue Oct 31, 2017 5:24 pm

George wrote:Okay, I'll ask...what is CHIRP? Where is it available?

http://chirp.danplanet.com/projects/chirp/wiki/Home
Schrodinger's Radio: It is simultaneously too loud and too quiet, but you will never know which until someone transmits.


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