FWIW I have a 99-channel 42-50MHz MT1000 that I bought with the intention of using it for both 6m and 47 MHz Red Cross channels. The radio came with a 32-channel model number, but the radio took 99 channels just fine.
The radio is not in service yet as it needs to be modified from the 42-50 MHz range to 46-54 MHz. And I do not know if the radio front end (or the transmit VCO) will "reach" to both 47mhz and 52-53 MHz. If anybody has done any work in that direction I'd like to hear from you. If it does end up to be usable on both I know that I'm going to need to have two separate antennas - a shorter one for ham and a second, longer one, for Red Cross. Over the years I've learned that you should not expect any real transmit performance from a low band HT, especially an HT200 or an MT1000. Why? Two reasons... First: A 1/4 wave at 52 MHz is about 54 inches (about 4 1/2 feet). An antenna with a decent ground plane would have a 1/4 wave radiator and a 1/4 wave ground plane, for a total of just about 9 feet long. I can just see a 9 foot long coaxial antenna plugged into a 7 1/2 inch long radio. Second The MT1000 uses a hot-only antenna connector, with no ground (at least the GP68 got that part right). The only way to get a RF ground is to use a cheezy plastic adapter that uses an earphone plug to adapt the radio to a length of RG174 coax. (see the photos on <http://www.repeater-builder.com/motorola/genesis/genesis-index.html> and look above the photo of a hand holding a radio) FWIW I've seen a couple of the adapters converted to a BNC mounted into the top of the adapter. So without re-engineering the radio your choices are a footlong rubber duck that would make a good truncheon, or an external antenna. And the NAB6064B duck is about $24-$25 each. More and more I've been thinking that a crossband repeater from a Red Cross UHF frequency (locally there are several already coordinated, licensed and in use) to the particular 47 MHz frequency (locally we have at least three, one of which is the nationwide 47.42) might just be more practical. Mike WA6ILQ At 01:42 PM 07/10/09, you wrote: >Albert, > >In the 30-50 MHz band, the antennas for a portable radio must be cut for >proper operation, over a very narrow range of frequencies. The length of a >whip antenna must be changed by 1/4-3/8 inch for every 1 MHz. Motorola >still offers the NAB6064B "tunable" antenna for the MT1000 radio, which must >be cut to length for the specific frequency needed. In other words, there >is no such thing as a broadband antenna for low band, and the radio's PA >could be damaged by using an antenna that is not the right length. The >NAB6064B antenna costs about $23 from Motorola Parts. Call 800-422-4210 to >order. > >73, Eric Lemmon WB6FLY > > >-----Original Message----- >From: Repeater-Builder@yahoogroups.com >[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Albert >Sent: Friday, July 10, 2009 12:56 PM >To: Repeater-Builder@yahoogroups.com >Subject: [Repeater-Builder] Building HT antennas > > > >Hey guys, I posted this question over on the HT600e forum but didn't get >anything. I was wondering if anyone here could be of assistance. > >I recently acquired a low band MT1000 for use on the 6m band. It has a nice >new commercial antenna but I was wanting to do something a little better. No >one that I can find supplies or can supply me with a better antenna for this >radio. Even smiley antenna, my usual go to company for custom antennas for >the Genesis line can't help me. So I was thinking of building my own. > >My first thought, since the antenna connector on the MT1000 is basically a >1/4-32 hole, I could thread a piece of aluminum round stock to create a >base. Then I could just make a 1/4 wave whip from stainless rod. I know it >would be silly long but it is a start. If I do this, do you think I should >just use the standard 1/4 wave vertical formula? Would I need to compensate >for the HT's lack of a ground plane? > >Any thoughts would be appreciated. > >Thanks >Albert >KI4ORI
