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Recommended VHF transceiver to use on NB 12.5 kc splinter frequencies

 

Hi folks,
I'm in Wa. state and WWARA has authorized me a NB rpt. pair 146.6875 out / 146.0875 in. (2.5 kc / 12.5 kc ch. spacing)
My rpt. is a Motorola Quanter.
I now am searching for compatible radios that will operate on the "splinter" fxs.?
The radios must have the proper "IF" filters on rec. for NB.
I have heard that the Motorola CM300 "May" be usable for NB use.
I have a few Mot ASTRO Spectra mobile trunk mount radios. I have read that if they are labeled "2.5 kc" they may be usable.
I have not checked the Astro Spectra radios yet. (FCC id #)
Any ideas of compatible radios for me to tell our radio club about? (So they can utilize the rpt...LOL)
I appreciate any guidance or transceiver advice.
Tim
AE7TH
Vashon Is. Wa.?
 

When the FCC (AKA Motorola) mandated narrow band for Part 95 services, they forgot that a small number of VHF channels, primarily VHF mutual aid channels required 2.5 KHz resolution.
?
Because manufacturers could continue to sell older model radios for a time, there are exceptions in that some VHF radio equipment may not properly resolve certain channels, which require the radio to resolve to 2.5 KHz channel steps.
?
(From my website:)
?
Examples are

VCALL -10 155.7525 MHz,
VTAC - 12? 154.4525 MHz and
VTAC - 14? 159.4725 MHz

These channels cannot be evenly divided by radio synthesizers, which do not resolve to 2.5 KHz.
Additionally, there are other VHF channels on these "7.5 KHz channel centers" which may be
troublesome.
?
I think you will soon realize that a lot of commercial VHF radios sold decades ago will be incompatible with your channel center.
?
?
--
The Real RFI-EMI-GUY
 

I meant to say Part 90 services.....
--
The Real RFI-EMI-GUY
 

Hello Tim,

For mobile radios, the M1225 and CM300 will both work for narrow band. I would be very sure the P1225 and CP300 portables will also.

Mick - W7CAT

----- Original Message -----
From: "TIM HARDY via groups.io"
To: [email protected]
Sent: Sunday, March 16, 2025 07:07:14 PM
Subject: [repeater-builder] Recommended VHF transceiver to use on NB 12.5 kc splinter frequencies

Hi folks,
I'm in Wa. state and WWARA has authorized me a NB rpt. pair 146.6875
out / 146.0875 in. (2.5 kc / 12.5 kc ch. spacing)
My rpt. is a Motorola Quanter.
I now am searching for compatible radios that will operate on the
"splinter" fxs.
The radios must have the proper "IF" filters on rec. for NB.
I have heard that the Motorola CM300 "May" be usable for NB use.
I have a few Mot ASTRO Spectra mobile trunk mount radios. I have read
that if they are labeled "2.5 kc" they may be usable.
I have not checked the Astro Spectra radios yet. (FCC id #)
Any ideas of compatible radios for me to tell our radio club about?
(So they can utilize the rpt...LOL)
I appreciate any guidance or transceiver advice.
Tim
AE7TH
Vashon Is. Wa.




--
Untitled Document
 

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Almost any Kenwood with the model TK-7xxx will do those splits.
The Kenwood repeaters TKR-750 and 751 will also do those splits.
Roger, N5QS



On 3/16/2025 8:07 PM, TIM HARDY via groups.io wrote:

Hi folks,
I'm in Wa. state and WWARA has authorized me a NB rpt. pair 146.6875 out / 146.0875 in. (2.5 kc / 12.5 kc ch. spacing)
My rpt. is a Motorola Quanter.
I now am searching for compatible radios that will operate on the "splinter" fxs.?
The radios must have the proper "IF" filters on rec. for NB.
I have heard that the Motorola CM300 "May" be usable for NB use.
I have a few Mot ASTRO Spectra mobile trunk mount radios. I have read that if they are labeled "2.5 kc" they may be usable.
I have not checked the Astro Spectra radios yet. (FCC id #)
Any ideas of compatible radios for me to tell our radio club about? (So they can utilize the rpt...LOL)
I appreciate any guidance or transceiver advice.
Tim
AE7TH
Vashon Is. Wa.?
 

The Motrola?CDM series will also narrowband and are great mobile radios
The CDM 1250 and CDM 1550 (my favorite)

Lloyd KO4L

On Sun, Mar 16, 2025 at 11:14?PM n5qs via <ygroup=[email protected]> wrote:
Almost any Kenwood with the model TK-7xxx will do those splits.
The Kenwood repeaters TKR-750 and 751 will also do those splits.
Roger, N5QS



On 3/16/2025 8:07 PM, TIM HARDY via wrote:
Hi folks,
I'm in Wa. state and WWARA has authorized me a NB rpt. pair 146.6875 out / 146.0875 in. (2.5 kc / 12.5 kc ch. spacing)
My rpt. is a Motorola Quanter.
I now am searching for compatible radios that will operate on the "splinter" fxs.?
The radios must have the proper "IF" filters on rec. for NB.
I have heard that the Motorola CM300 "May" be usable for NB use.
I have a few Mot ASTRO Spectra mobile trunk mount radios. I have read that if they are labeled "2.5 kc" they may be usable.
I have not checked the Astro Spectra radios yet. (FCC id #)
Any ideas of compatible radios for me to tell our radio club about? (So they can utilize the rpt...LOL)
I appreciate any guidance or transceiver advice.
Tim
AE7TH
Vashon Is. Wa.?



--
Lloyd M. Mitchell (KO4L)
 

As you are no doubt finding out, the average ham radio has 25kHz IF filtering and +/- 5kHz (or more) TX deviation with little or no modulation limiting.

Your choices for equipment that can resolve to 2.5kHz channel steps will be limited.




Quoting "TIM HARDY via groups.io" <w7trh@...>:

Hi folks,
I'm in Wa. state and WWARA has authorized me a NB rpt. pair 146.6875 out / 146.0875 in. (2.5 kc / 12.5 kc ch. spacing)
My rpt. is a Motorola Quanter.
I now am searching for compatible radios that will operate on the "splinter" fxs.
The radios must have the proper "IF" filters on rec. for NB.
I have heard that the Motorola CM300 "May" be usable for NB use.
I have a few Mot ASTRO Spectra mobile trunk mount radios. I have read that if they are labeled "2.5 kc" they may be usable.
I have not checked the Astro Spectra radios yet. (FCC id #)
Any ideas of compatible radios for me to tell our radio club about? (So they can utilize the rpt...LOL)
I appreciate any guidance or transceiver advice.
Tim
AE7TH
Vashon Is. Wa.
 

146.6875 out / 146.0875
?
Actually,taking a closer look.
146.6875 / .0125 = 11735.0
146.0875 / .0125 = 11687.0
?
Are even integers, so a 12.5 KHz? (and 6.25 or 2.5 KHz) radio will do it. Still some older Part 90 VHF radios may not. But if the model/brand was used on Federal VHF, it may work.
?
?
?
On Mon, Mar 17, 2025 at 08:12 AM, n3ltq wrote:
As you are no doubt finding out, the average ham radio has 25kHz IF
filtering and +/- 5kHz (or more) TX deviation with little or no
modulation limiting.

Your choices for equipment that can resolve to 2.5kHz channel steps
will be limited.




Quoting "TIM HARDY via groups.io" <w7trh@...>:

Hi folks,
I'm in Wa. state and WWARA has authorized me a NB rpt. pair 146.6875
out / 146.0875 in. (2.5 kc / 12.5 kc ch. spacing)
My rpt. is a Motorola Quanter.
I now am searching for compatible radios that will operate on the
"splinter" fxs.
The radios must have the proper "IF" filters on rec. for NB.
I have heard that the Motorola CM300 "May" be usable for NB use.
I have a few Mot ASTRO Spectra mobile trunk mount radios. I have
read that if they are labeled "2.5 kc" they may be usable.
I have not checked the Astro Spectra radios yet. (FCC id #)
Any ideas of compatible radios for me to tell our radio club about?
(So they can utilize the rpt...LOL)
I appreciate any guidance or transceiver advice.
Tim
AE7TH
Vashon Is. Wa.





?
--
The Real RFI-EMI-GUY
 

That's not gonna cause problems at all...<eye roll>

146.6875 out / 146.0875

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