Bendix King upgrade to narrowband ability

[Flatlander]

Perhaps this has been covered - if so, my apologies.

What makes the older BK portable radios wide band only? Their programming is synthesized, so I don't understand why some can do narrow and others can't.

I've got a bunch of MPH portables (LPH with metal case) that now can't be used by my crews. Does anyone know if it's possible to do some kind of retro fit programming to get these to do narrow band? I hate to have to junk all of my radios.

[ksengb]

It has to do with how much bandwidth is used when it transmits on a given frequency, and that is a factor of the internal circuitry. Newer equipment was designed to be able to do either. Some radios (maybe all, I'm not sure) that can do either narrow or wide actually use separate internal circuitry for each mode. It's theoretically possible someone with some real radio tech skills could exchange components and make them work, but realistically no one is doing that and manufacturers are more than happy to make old ones obsolete and have you buy all new equipment, so they're not generally making retrofits available...long story short, join the club. Just disposed of thousands of dollars worth of perfectly good, but no longer legal, radios. A shame to see them go to waste.

[FIREWATER]

FYI The new Forest Service water tender/engine contracts reads P25 radios in 2014. So from wide band to narrow band and now going to digital. No retro kit for that?

[ajohansson]

We aint going digital anytime soon. Its so sad they are requiring things like this just like the federal and state grants do. Look how long it took us to narrow band!

[Flatlander]

...long story short, join the club. Just disposed of thousands of dollars worth of perfectly good, but no longer legal, radios. A shame to see them go to waste.

I was afraid this would be the answer. I was hoping some jumper or shot or anybody had figured out how to tweak the old ones.

[Com20]

The LPHs and MPHs will not program on many of the new splinter frequencies so there are some frequencies that may be assigned or recently added by some agencies that the radios will not operate on.

[smokeybehr]

The recommended BK radios are the GPH and DPH. Some of the EPH radios will do narrowband, but may not do the 7.5 kHz "splinter" channels. There is a TSB from BK denoting the serial number range of the EPH radios that will do the 7.5 kHz channels.

edit: The TSB is for wide/narrowband, what they call "flex-mode". http://www.relmservice.com/Bulletins/BK/BKSB-1006.pdf

[Flatlander]

The recommended BK radios are the GPH and DPH. Some of the EPH radios will do narrowband, but may not do the 7.5 kHz "splinter" channels. There is a TSB from BK denoting the serial number range of the EPH radios that will do the 7.5 kHz channels.

edit: The TSB is for wide/narrowband, what they call "flex-mode". http://www.relmservice.com/Bulletins/BK/BKSB-1006.pdf

Good info, but not where I was going. Yes - wide band is now illegal and NIFC has a short list of supported radios. But there are lots of us who poke around inside our radios. I'm no radio tech. I know enough to be able to open up my radio and re-solder stuff. I was hoping that somebody somewhere figured out how to modify wide band only BK portables to do narrow.

[NVJims]

Any radio that you modify will no longer be Type Accepted by the FCC and hence no longer be legal to use in the commercial and government frequency bands. Yes, the bandwidth can be changed by replacing parts, but you still will not be able to use some of the newer interstitial frequencies which are showing up in the repeater pairs and tacs issued by NIFC. That is controlled by the microprocessor chip and the frequency synthesis circuits. Duck tape a couple of them together and use them as wheel chocks, drill a couple of holes in one and bolt it to the outhouse door as a pull handle, or use a bunch of them to anchor your fishin' boat and get some real usage out of those old radios. (Ham radio operators can modify them to work only in the ham band and still use them on those frequencies.)

[firescout]

We (my dept.) usually figure the average lifespan of a fire service portable two-way radio to be 10-12 years. Generationally speaking, the L-series BK radios are ancient. The E-series is very old, and the first G-series units are getting close to the end of their lifespan. Agencies and contractors need to work this into their long-range radio replacement budgets so they aren't surprised by new equipment requirements (= forced purchases) 8-10 years down the road.

To further elaborate on the narrowband/splinter freq capability: It is mainly dependent on the stability and tolerance of the radio's main crystal oscillator. Today's radios have oscillators (and some other circuitry) with much tighter tolerances and more stability than older units. This enables them to function in today's narrowband/interstitial channel environment.