I know this was gone over before, but.....
What is the BEST Motorola antenna to use on the HT750 VHF radio? What's the number?
HT750 antenna
Moderator: Queue Moderator
Motorola finaly admitted to me, just last Monday, there is a very bad problem with the receiver in the line.
SRN 1290 addresses this by changing some parts in the antenna matching circuit and "reflashing" the radio. On further investigation, it has be found that a capacitor change in the antenna matching circuit, and replacing the antenna is all that is needed for the radio. It states that only the VHF radios are affected, I do not belive this as I have worked on many deaf UHF radios too. I am trying to get a copy of this SRN and others on this subject.
I am still waiting for Motorola to provide the correct antenna numbers, as most if not ALL the tapered antennas were poor to bad peformers.
SRN 1290 addresses this by changing some parts in the antenna matching circuit and "reflashing" the radio. On further investigation, it has be found that a capacitor change in the antenna matching circuit, and replacing the antenna is all that is needed for the radio. It states that only the VHF radios are affected, I do not belive this as I have worked on many deaf UHF radios too. I am trying to get a copy of this SRN and others on this subject.
I am still waiting for Motorola to provide the correct antenna numbers, as most if not ALL the tapered antennas were poor to bad peformers.
I actually had better receieve on the bench with a test lead clipped on for the antenna!
I remember quite a while back, somebody used (I think) either an HT1000 or Antenex and reported great results compared to the tapered piece of crap from the factory.
I'd like to hear "M"s explanation as to why they released all of these radios like this?
I bet it's the same answer to the same question, but for the Minitor III.
I remember quite a while back, somebody used (I think) either an HT1000 or Antenex and reported great results compared to the tapered piece of crap from the factory.
I'd like to hear "M"s explanation as to why they released all of these radios like this?
I bet it's the same answer to the same question, but for the Minitor III.
Last edited by Nand on Sun Jan 18, 2004 10:32 am, edited 1 time in total.
I replaced the antenna on my vhf ht1250 (same problem as the ht750) with the vhf antenna from the MT1000, and got a dramatic increase in receive sensitivity. I'd like a nice wideband (144-172 MHz) antenna for better rx on ham channels, but since I mostly use this radio for work, the antennas listed below work great.
8505816K22
Heliflex Molded, 136-150.8 MHz, 6.5"
8505816K21
Heliflex Molded, 150.8-162 MHz, 6"
8505816K23
Heliflex Molded, 162-174 MHz, 6"
8505816K22
Heliflex Molded, 136-150.8 MHz, 6.5"
8505816K21
Heliflex Molded, 150.8-162 MHz, 6"
8505816K23
Heliflex Molded, 162-174 MHz, 6"
According to Motorola today, I just got the NEW part number for 150 to 170 of NAD6579A.
Motorola is sending me some replacement antennas, and I will let you know how they work. The important thing is the componet(s) changes in the radio.
I also reported some time ago that the Antenex broadband for 136 to 162 is DEXW136MX and for 148 to 174 DEXW148MX and are 8 1/2" long work rather well. I also have used them on P200, GP300, and HT1000 in K9 search and rescue work.
Motorola is sending me some replacement antennas, and I will let you know how they work. The important thing is the componet(s) changes in the radio.
I also reported some time ago that the Antenex broadband for 136 to 162 is DEXW136MX and for 148 to 174 DEXW148MX and are 8 1/2" long work rather well. I also have used them on P200, GP300, and HT1000 in K9 search and rescue work.
I recently bought seven HT-750 VHF radios, and I specified the PMAD4023 helical antenna over the standard wideband antenna, simply because I believe that an antenna that is specific to a particular band segment will always outperform a wideband antenna. Of the 17 HT-750 radios I have in service, none have ever given me problems with performance or receive sensitivity. Maybe I'm just lucky...
The wide band antenna from motorola arrived today and it is 7 3/8" long, taller than the radio. Seems to work just fine and I am going to test it against the Antenex, and GP300 antennas in the lab. I'll let everyone know how it makes out.
Thr SRN just arrived too, I'l post it as soon as I unpack/read it.
<font size=-1>[ This Message was edited by: Will on 2002-03-28 20:11 ]</font>
Thr SRN just arrived too, I'l post it as soon as I unpack/read it.
<font size=-1>[ This Message was edited by: Will on 2002-03-28 20:11 ]</font>
Subject: HT750/HT1250 VHF (136 -174MHz) Range Limitation
Symptoms:
1. Radio will not receive or carrier is noisy when receiving a radiated signal in a location that is within the usual coverage
area.
2. Radio transmitted signal will not always cover proper range or is noisy when operating within the usual coverage area. Please note that this is radiated receiver sensitivity and radiated transmitter power effect. It cannot be tested using the conducted receiver sensitivity or conducted transmitter power measurement procedure.
Potential Problem Radios:
Models Affected:
AAH25KDC9AA2AN, AAH25KDC9AA3AN,
AAH25KDG9AA4AN, AAH25KDF9AA5AN,
AAH25KDH9AA6AN
Serial Numbers: 672TYWxxxx through 672TZRxxxx
749TYWxxxx through 749TZRxxxx
Cause:
The radio is exhibiting excessive processor noise. The antenna matching circuit needed to be optimized.
Corrective Action:
Two radio design improvements have occurred.
1. Improve the radio code to decrease processor noise.
2. Improve the antenna matching circuit to provide a better power transfer from the antenna to the harmonic filter. HT750/HT1250 VHF radios with the serial numbers above may exhibit poor range symptoms. This depends on the range of operation. HT750/HT1250 radios that exhibit poor range must be sent to the Radio Support Center for repair.
Radios that have been repaired are marked with a information label reading "R02.00.01R". Radios shipped after the above serial number dates reads "Firmware Ver R02.00.01" and should have the mods.
Symptoms:
1. Radio will not receive or carrier is noisy when receiving a radiated signal in a location that is within the usual coverage
area.
2. Radio transmitted signal will not always cover proper range or is noisy when operating within the usual coverage area. Please note that this is radiated receiver sensitivity and radiated transmitter power effect. It cannot be tested using the conducted receiver sensitivity or conducted transmitter power measurement procedure.
Potential Problem Radios:
Models Affected:
AAH25KDC9AA2AN, AAH25KDC9AA3AN,
AAH25KDG9AA4AN, AAH25KDF9AA5AN,
AAH25KDH9AA6AN
Serial Numbers: 672TYWxxxx through 672TZRxxxx
749TYWxxxx through 749TZRxxxx
Cause:
The radio is exhibiting excessive processor noise. The antenna matching circuit needed to be optimized.
Corrective Action:
Two radio design improvements have occurred.
1. Improve the radio code to decrease processor noise.
2. Improve the antenna matching circuit to provide a better power transfer from the antenna to the harmonic filter. HT750/HT1250 VHF radios with the serial numbers above may exhibit poor range symptoms. This depends on the range of operation. HT750/HT1250 radios that exhibit poor range must be sent to the Radio Support Center for repair.
Radios that have been repaired are marked with a information label reading "R02.00.01R". Radios shipped after the above serial number dates reads "Firmware Ver R02.00.01" and should have the mods.