Digital Simplex Frequencies

[w6kjb]

It seems like a lot of folks with digital voice capable radios (Yaesu Fusion [C4FM], D-Star, DMR, NXDN, P25, etc) wonder what simplex frequency to use.
I realize some modes, like D-Star, already have some common frequencies, but still, I'd like to throw my hat in the ring and offer a researched answer after having reviewed many coordinating bodies' band plans. I think this list will satisfy most bodies in the US.

Primary 147.520 and 445.000 (1 MHz away from national FM calling frequency, already in use for digital)
Alternate 146.580 and 446.158 (second to last simplex freq within FM national calling simplex portion, already in use for digital voice)
Contingency 145.5625 and 441.1625 (6.25KHz step for digital, at edge of next lower simplex portion, already in use for digital voice)
Emergency 145.541 and 441.144 (easy to remember, same back/forward)

 

[nd5y]

Some of those frequencies are on tuning steps that can't be entered on most radios.

 

[w6kjb]

Good point, while all DV radios should be able to do 6.25KHz steps, not all can do 1KHz steps.

Here is a step safe (but dual band) list then:

Primary 147.52 (for 20KHz steps like Texas and Arizona but if you want to follow your local coordinating body, it might be 147.525 in places that use 15KHz step like the north east and California)
Alternate 445.000
Contingency 145.5625
Emergency 441.1625

Thanks @nd5y

 

[popnokick]

Wow- Those are WAAY different from what are listed in many of the northeast US states by various coordinating councils and band plans. Many of those fall into the "FM Voice Simplex" plans here in the Northeast, but not the "Digital Simplex" allocations. And I think "fly over country" (Midwest) uses even different ones. So advice to the ham traveling using digital voice modes: "When in Rome..." (consult the local freq coordinator).

 

[mmckenna]

For "emergency", why can't users just program them in as analog?
Do we really need a frequency set aside specifically for emergencies for digital users? Seems like that really narrows down the chances of getting help in an emergency. It's already hard enough to get help on the VHF/UHF bands with analog FM and repeaters everywhere.

 

[w6kjb]

@popnokick Not all coordinating bodies have digital simplex allocations. What got me started on this was that I was on a 1000 mile road trip and found the locally coordinated simplex frequency I was on had a repeater setup on it. I needed to change the whole group while on the move and didn't have a good plan for that. In this situation, consulting the coordinating body for every county along a 1000 mile stretch is not practical and I needed some reasonably sane frequencies to keep programmed.
@mmckenna PACE plans vary widely, I have a separate PACE plan for FM, you can choose do organize your PACE frequencies however you wish.

 

[jeepsandradios]

So....many formats on Digital. DMR, P25, Fusion, etc as you said. So why would you pick one frequency ? None of these formats can talk to the other and there is no reason to scan a "frequency" hoping the same mode as you gets used. Can you explain what purpose this is accomplishing ?

As @mmckenna said if its an emergency analog will be the best format to get someone to answer. If my radio is P25 and your in my yard screaming for help on DMR I'm never going to hear you. I'm confused.

 

[mmckenna]

@mmckenna PACE plans vary widely, I have a separate PACE plan for FM, you can choose do organize your PACE frequencies however you wish.

As long as you have pre-arranged to have someone listening, that'll work fine.

For general use, most hams will have better luck with analog FM. "Luck" is the key word, however.

 

[N4KVE]

You use whatever freq’s you, & your friends decide to use on simplex while at a ham fest, car race, car trip with multiple cars, or any other event. I always choose a freq where the chances of any one listening there are slim, to none. Depending on the event, I may use UHF, but more often it’s 900 MHz, as nobody’s there.

 

[KevinC]

I vote for 38 mHz. Sorry, I just couldn’t resist.

 

[AK9R]

Primary 147.520

I suggest 147.510 MHz instead of 147.520 MHz. The highest repeater output frequency in most 2m bandplans is 147.390 MHz. If you assume a step size of 15 kHz, counting up from 147.390 in 0.015 steps lands you on 147.510 MHz.

 

[mmckenna]

I vote for 38 mHz. Sorry, I just couldn’t resist.

Stop it. I already almost went there. If I resisted, so can you Mr. Super Moderator.

 

[k6cpo]

My feeling is that digital can be used on any frequency that is already designated as a simplex frequency, particularly if it's Fusion digital. The ability of Fusion to rapidly switch from analog to digital and back is a definite advantage. This is what my club does. We have a designated simplex frequency and we hold a weekly analog simplex net on it. Once a month we hold a digital (Fusion) net, rotating between our two repeaters and simplex.

 

[AK9R]

The ability of Fusion to rapidly switch from analog to digital and back is a definite advantage.

Except that automatic mode switching has to be enabled on everybody's receiver for this to work. We can suggest that people with Yaesu radios enable AMS, but we can't mandate it.

 

[K6GBW]

There really should be at least one frequency per band that is designated digital simplex. Otherwise we'll keep getting that incredibly annoying digital buzz over 146.520. As much as I love that sound I see how it can annoy others.

Oh....38 MHz...YES PLEASE! Then I can use my PRC-77!!

 

[K5MPH]

When on a road trip I take Analog and put Digital in the back seat.......

 

[vagrant]

Analog is king and having a nincompoop using digital on 520 is ridiculous. The suggestion of 147.510 MHz seems like a fine choice for shared digital simplex. Okay, now what about 70 cm?

438.5625
438.500
438.450
433.080
Something else like 441.000?

 

[Project25_MASTR]

Seems more like a proposed solution looking for a problem. Except for select few digital radios...everything can go analog regardless of the digital mode and is the reason Homeland Security's NIFOG clearly outlines analog interop frequencies for everything except 700 MHz.

 

[hill]

Going forward for contacting random hams or being used in an emergency analog is the best.

I see digital simplex only being used between hams that know each other with a known frequency and mode.

We used to hams running simplex Fusion on Friday evenings on the same frequency they use for analog. It sounded great and I really don't like or use Fusion anytime. It was one the 147 simplex frequencies in the upper part of the band.

I have a few simplex DMR frequencies on 2M and 70 CM programmed in the radios from some list I saw a few years ago. Never heard anyone on them, but did play around with a few my radios to test them.

I did ask about P25 simplex with some know hams that use this mode at a hamfest, but really didn't get a good answer on it.

 

[KB2GOM]

Color me "clueless in upstate NY," but what's the deal with 38 MHz?