Batboard

It's a bad idea. You know it, I know it, and the American people know it. Real men hang mobiles off of remotes, not portables. Now I've gotta convince somebody of it.

Aren't portables prohibited from use as fixed stations under Part 90? I haven't been able to locate anything specific, but I recall hearing this from way back.

Thanks for any pointers.

...something other than the side of the argument, that it's stupid? Conversion loss on power supplies, low power output, duty cycle of the units, poor cooling potential, jury-rigging required...etc...

Go to the FCC Part 90. There is an exhaustive, detailed, numerical section index at the start of the document so if there is such a prohibition it can't be that hard to find. Here is the location:

http://www.access.gpo.gov/nara/cfr/wais ... 90_06.html

Look at frequency stability, the portable may not have the required stability to be used as a base station. In the UHF "T" band the GM300 and the CDM's cannot be base stations or repeaters unless they have the high stability option

MassFD wrote:Look at frequency stability, the portable may not have the required stability to be used as a base station. In the UHF "T" band the GM300 and the CDM's cannot be base stations or repeaters unless they have the high stability option

Ah, it just clicked in my head why Motorola canceled the high split CDM original model numbers and went with new ones that don't match their typical nomenclature. I'm guessing the threshold is 1.5ppm?

[quoteby MassFD » Mon Nov 07, 2011 11:08 pm

Look at frequency stability, the portable may not have the required stability to be used as a base station. In the UHF "T" band the GM300 and the CDM's cannot be base stations or repeaters unless they have the high stability option][/quote]

Wow, that is obscure... Forget gm300 as it is not current production, the CDM in the high power model is 1.5ppm compliant for 12.5 khz operation. Remember, specifically in the t-band there is a difference betweem and base station, mobile unit, and control station. If I recall, 30 watts was the magic number that dictates frequency stability, but is someone really going to complain about using a low power cdm as a control station in the T Band. I hope not, because alot of local FD's here would be in big trouble. I am certain that this is an antiquated rule from the day of crystal and tube controlled radios were around when radios would walk all over the place. The newer mobile radios usually stay on channel. Just my two cents.

FMROB wrote:I am certain that this is an antiquated rule from the day of crystal and tube controlled radios were around when radios would walk all over the place. The newer mobile radios usually stay on channel. Just my two cents.

It's not that old, around 5 or 6 years ago you had to have the HS option on a CDM to use them as a base or repeater. I think you could apply the mobile stability rule to a control station.

You are right that the recent CDM's in R2 (450-512) are all 1.5ppm stability, just brought up the stability issue as the OP was talking about the reason for not using a portable as a base station. I could see someone thinking it was a good idea to use a portable and backing it up with a 50W amp. I would not want to be their neighbor.

That's basically it. I mean, we all have a technical background with enough practical experience that I wasn't even concerning myself with regulations. But, this guy's bosses saw salesman at a trade show with their portables connected to their demonstration consoles, so OF COURSE that's what they asked neighboring jurisdictions to supply for their interop plan.

Or I could just wait until the portables start melting down and say "I told ya so".

Kev, Its a good point. I never honestly thought of that aspect until you mentioned it. There has to be hundreds of cdms installed in our area as base stations not meeting that requirement. Oh well, hope they stay on channel. LOL

That's interesting I was planing on using a VHF Astro for my 225 watt Micor station to make it narrow band compliant. Inject 1/2 watt at 150 mhz and you get 225 watts out at 477 mhz.

RADIOMAN2002 wrote:That's interesting I was planing on using a VHF Astro for my 225 watt Micor station to make it narrow band compliant. Inject 1/2 watt at 150 mhz and you get 225 watts out at 477 mhz.