Albert, The Achillies heel of all low band portables is the lack of adaquet ground plane. At UHF the frame and circuit ground plane surfaces are satisfactory to provide the ground plane for the quarterwave radiator to work against. At VHF the ground plane surface area is reduced but is still of sufficient size to allow for reasonable performance. At low band however the ground plane surface area is a very small fraction of the wavelength resulting in miserable performance regardless of the antenna installed. Remember that at low band a quarterwave can vary in length from approximatly 8 ft in the 30 MHz range to slightly less than 5 ft at 50 MHz. Stick with the regular antenna cut for frequency. At one time there was an aftermarket antenna made by Centurion that used a base load coil and a tuning capacitor to resonate the antenna (tuned for max signal strength on Tx). These seemed to work OK for a single or narrow frequency range. Centurion was purchased by Laird (IIRC) and the availability of these antennas seems to have dried up. I tried to get some with a different connector several years ago and got brushed off.
My favorite low band performer was the MH-10 followed by the MT500. Both easily outperform the MT1000 any day but have the limitation of crystal control and limited frequency capacity, and now lack of parts availability. The entire Genisis line suffers from a design flaw regarding the connection of the antenna to the main circuit board. The bottom of the connector bends 90 degrees to solder to the circuit board. This joint or the bend itself will break due to the stresses placed on the antenna connector by the antenna. The bigger the antenna the quicker this joint will fail. The failure is easily seen by checking the solder connection at the top of the main circuit board. Sometimes it is necessary to use a magnifying lens to see the cracked solder joint but usually it will pe plainly visible. Resoldering the joint can fix many "no transmit" or "poor receive" complaints. Milt N3LTQ ----- Original Message ----- From: "Albert" <[email protected]> To: <[email protected]> Sent: Friday, July 10, 2009 3:55 PM 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 > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.10/2231 - Release Date: 07/11/09 05:57:00
