I have been having a great time with my Maxlog M-8900, especially on 12 meters and ten meters. Very good reception reports and some of my contacts said it sounds like one of the big three HAM rigs! As for receive the signals on my end were pretty good and the S meter is fairly accurate.
Only items I did not like are the audio on strong signals was 'buzzy' sounding and the radio becomes very warm in both receive and transmit. The audio 'over load' was solved by reducing the RF gain a tad. When I did reduce the gain it sounded nice and smooth on SSB. Signals that were not too strong were received well with no 'buzz'. The rig has 'good ears'!
Important that a proper antenna be used on the respective bands. My 10 meter works well on 11 meters but is not good on 12 meters, I used a Jetstream on 12 for this.
For the heat problem I plan to use a small fan mounted on the heat sink. It seemed to me that most of the high temperatures came from the pass transistor mounted on the side of the radio. This is a TIP 36 PNP plastic case (TO3P). This is a common transistor used in mainly audio and current circuits and it is used with the TIP35 as a push pull audio pair. In the Maxlog it passes the current mainly to the MOSFET finals and transmitting it has to deliver a lot! Reducing the power level helps, but.....
I opened the rig up and noticed the TIP 36 is mounted to the side of the radio with the use of what appeared to be a ceramic insulator ans no heat sink compound. I removed the transistor to correct this and the insulator was in three pieces! I carefully remounted the transistor with a bit of compound.
Next to the TIP 36 is mounted the audio amp and an eight volt regulator, so heat produced is sort of concentrated on this side. Most of the heat is produced when transmitting by the TIP 36 pass transistor. This could be as the MOSFET finals are consuming a lot of power. I plan to monitor this with an amp meter and maybe reduce the current consumption of the finals.
It also appears that the MOSFETs and heat sink do not have heat sink compound used! The finals do appear to use ceramic insulators. In my book, too much heat means a short life!
73 mechanic
Only items I did not like are the audio on strong signals was 'buzzy' sounding and the radio becomes very warm in both receive and transmit. The audio 'over load' was solved by reducing the RF gain a tad. When I did reduce the gain it sounded nice and smooth on SSB. Signals that were not too strong were received well with no 'buzz'. The rig has 'good ears'!
Important that a proper antenna be used on the respective bands. My 10 meter works well on 11 meters but is not good on 12 meters, I used a Jetstream on 12 for this.
For the heat problem I plan to use a small fan mounted on the heat sink. It seemed to me that most of the high temperatures came from the pass transistor mounted on the side of the radio. This is a TIP 36 PNP plastic case (TO3P). This is a common transistor used in mainly audio and current circuits and it is used with the TIP35 as a push pull audio pair. In the Maxlog it passes the current mainly to the MOSFET finals and transmitting it has to deliver a lot! Reducing the power level helps, but.....
I opened the rig up and noticed the TIP 36 is mounted to the side of the radio with the use of what appeared to be a ceramic insulator ans no heat sink compound. I removed the transistor to correct this and the insulator was in three pieces! I carefully remounted the transistor with a bit of compound.
Next to the TIP 36 is mounted the audio amp and an eight volt regulator, so heat produced is sort of concentrated on this side. Most of the heat is produced when transmitting by the TIP 36 pass transistor. This could be as the MOSFET finals are consuming a lot of power. I plan to monitor this with an amp meter and maybe reduce the current consumption of the finals.
It also appears that the MOSFETs and heat sink do not have heat sink compound used! The finals do appear to use ceramic insulators. In my book, too much heat means a short life!
73 mechanic
