Maratrac UHF Low Power
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Maratrac UHF Low Power
Have a UHF Maratrac with changing power. Shifts from 75watts to 20watts. Then will stay low until it cools down and then go back to 75watts and then back down to around 20watts or so. Any ideas?
One idea would be that maybe the freqs programmed are not within the tuning of the XMTR. Even though it may accept the freqs in the RSS, the radio may need to be retuned, if in fact it will accept the retuning. Had a Maratrac I attempted to put ham freqs into and it was spastic below about 448 mhz. Couldn't seem to get it to like anything in spite of the tricks found on this board.
I have two Maratrac high band VHFs that will accept the ham freqs in the RSS, but one does just what you describe with the variable power out syndrome unless you put in a freq that's above 148 mHz. The other seems to care less what the freq is as long as it's between 144 and 174. The one that doesn't like anything under 148 mHz has been retuned and it does seem to be stable at 144 mHz, but the power, while consistent, is down to about 70 watts at best. It is now back at about 110 watts out at 153-159 freqs where it will stay.
If your variable power experiences are happening across the radio's range, then the problem is not very likely the same as I've experienced.
I have two Maratrac high band VHFs that will accept the ham freqs in the RSS, but one does just what you describe with the variable power out syndrome unless you put in a freq that's above 148 mHz. The other seems to care less what the freq is as long as it's between 144 and 174. The one that doesn't like anything under 148 mHz has been retuned and it does seem to be stable at 144 mHz, but the power, while consistent, is down to about 70 watts at best. It is now back at about 110 watts out at 153-159 freqs where it will stay.
If your variable power experiences are happening across the radio's range, then the problem is not very likely the same as I've experienced.
curmudgeon.....and I like it.
I don't know if it is along this line, but here is an important note about maratracs and tx power.
Have you ever installed a new maratrac? It had warning tag on its green lead that stated it must be hooked up to wherever the red A+ lead went to. What was that all about? I want the radio to go off with the ignition, so I'll just hook it up in the fuse block somewhere. Hey! Works great!
Now drag out your schems and look at the tx power circuit. An ugly thing run by a comparator. Now here's the hitch. If there is a voltage difference between the red A+ lead and the green lead (with the green lead less volts), it will throw the comparator off, producing low or no tx power.
Why is the green lead voltage less? You tell me (funky fuse block,corroded fuse, those wierd 24 to 12 converters in buses).
My fix is to remove or dike the green fuse from the head. Now open top and bottom of chassis. Solder fuse holder with short leads from A+ terminal on P-1 (is that pin 17? I forget) to pin # 4. Now there is no voltage diff between red and green leads.
Oh you want ignition sense? Hook orange lead to switched power, open control head and nuke JU-1003. Whup, ther it is....
Have you ever installed a new maratrac? It had warning tag on its green lead that stated it must be hooked up to wherever the red A+ lead went to. What was that all about? I want the radio to go off with the ignition, so I'll just hook it up in the fuse block somewhere. Hey! Works great!
Now drag out your schems and look at the tx power circuit. An ugly thing run by a comparator. Now here's the hitch. If there is a voltage difference between the red A+ lead and the green lead (with the green lead less volts), it will throw the comparator off, producing low or no tx power.
Why is the green lead voltage less? You tell me (funky fuse block,corroded fuse, those wierd 24 to 12 converters in buses).
My fix is to remove or dike the green fuse from the head. Now open top and bottom of chassis. Solder fuse holder with short leads from A+ terminal on P-1 (is that pin 17? I forget) to pin # 4. Now there is no voltage diff between red and green leads.
Oh you want ignition sense? Hook orange lead to switched power, open control head and nuke JU-1003. Whup, ther it is....