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Midland 400

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borderpolman

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I have turned my Midland 400 into a base station. Its connected to a DC source that is good for 20 AMP draw. Everytime I key the mike the display says HI DC and shuts down the radio and restarts it. Anybody have this experience. The Midland FAQ page has nothing on this and no info on Google searches on this either. Any advice would be appreciated.
 

mmckenna

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Do you have a multimeter? Check the voltage on the output of the DC source, both when the radio is receiving and when it's transmitting. It should be around 13 to 14 volts, no more.
 

n1das

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Your antenna is outside, right, & not inside 2 feet from the radio/power supply?

What N4KVE said.

The power supply might be RF-susceptible and going out of regulation when hit with RF. Is the power supply a linear or switch mode type?

I learned this the hard way back in the late 1980s when I popped the VHF final in an Icom IC-32AT handheld when I powered it by a regulated 13.8V linear power supply and keyed PTT on the handheld. The power supply went out of regulation while PTT was keyed and gave the radio the full unregulated power supply voltage of around 23V. The VHF hybrid output module fried itself almost instantly. Nothing else in the radio was damaged. I ordered a replacement module from Icom and changed it myself. The lesson learned was to keep strong RF away from a power supply. And also harden the power supply up so that it is immune to RF.
 

borderpolman

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Thank you everyone for your responses. The antenna is outside and SWR is almost zero. The problem seems to be the power supply. When I connected the 400 to a 12 VDC marine battery it works just fine. The power supply is a Pyramid PS21-KX which seems to be the culprit. When tested it puts out 13.8 volts. Could well be that that the 3 foot power cord makes it too close to the 400 and it creates an RF issue. Will try to isolate it by extending the power cord to 10 feet.
 

russbrill

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Thank you everyone for your responses. The antenna is outside and SWR is almost zero. The problem seems to be the power supply. When I connected the 400 to a 12 VDC marine battery it works just fine. The power supply is a Pyramid PS21-KX which seems to be the culprit. When tested it puts out 13.8 volts. Could well be that that the 3 foot power cord makes it too close to the 400 and it creates an RF issue. Will try to isolate it by extending the power cord to 10 feet.

You can also try a Ferrite Choke just before the wiring is connected to the Supply...
 

russbrill

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Thank you everyone for your responses. The antenna is outside and SWR is almost zero. The problem seems to be the power supply. When I connected the 400 to a 12 VDC marine battery it works just fine. The power supply is a Pyramid PS21-KX which seems to be the culprit. When tested it puts out 13.8 volts. Could well be that that the 3 foot power cord makes it too close to the 400 and it creates an RF issue. Will try to isolate it by extending the power cord to 10 feet.

And a second thought, You could have a bad supply... See if you can return it and get your money back. Try a Astron SS-18..
 

borderpolman

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Follow up. I have now experienced the same problem again. I think its the firmware that is the culprit. The CPU is somehow confused when the mic is keyed on 15 to 22 and shuts down and restarts the unit. Its frustrating as it is turning out to be a brick not a radio!
 

WB9YBM

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I have turned my Midland 400 into a base station. Its connected to a DC source that is good for 20 AMP draw. Everytime I key the mike the display says HI DC and shuts down the radio and restarts it. Anybody have this experience. The Midland FAQ page has nothing on this and no info on Google searches on this either. Any advice would be appreciated.

I've had some power supplies go wonky when there's a high level of RF around, especially under load. One manufacturer that's not shown problems is Astron; they come in various ratings and have typically been sourced through amateur ("ham") radio dealers. I've been using Astron supplies for about 45 years with no problems.
 

borderpolman

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Problem solved!! The issue was fixed by installing a power supply that has 30 amps continuous output. The MXT400 takes a great deal of juice when you key it and 20 amps just was not enough. It works like a charm now.
 

mmckenna

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Problem solved!! The issue was fixed by installing a power supply that has 30 amps continuous output. The MXT400 takes a great deal of juice when you key it and 20 amps just was not enough. It works like a charm now.

That would indicate an issue with the radio or power supply. No way a 40 watt radio should be pulling more than 20 amps.
 

borderpolman

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That would indicate an issue with the radio or power supply. No way a 40 watt radio should be pulling more than 20 amps.
Could be the Pyramid PS21-KX is defective even though I tested it. However the Pyramid PSV-300 does the work perfectly. Lined to a stealthy Sinclair post antenna just 15 feet off the ground gives me a good 12 mile range.
 

mmckenna

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Could be the Pyramid PS21-KX is defective even though I tested it. However the Pyramid PSV-300 does the work perfectly. Lined to a stealthy Sinclair post antenna just 15 feet off the ground gives me a good 12 mile range.

Sounds good. Yeah, I suspect your old power supply has an issue. If it cannot run a 40 watt UHF radio, there's something wrong.
 

O-B-1

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Buying a DBR1 programming cable and downloaded the software to program my Midland MXT400.
You CAN program it into wideband operation, you CAN program it for split CTSS/DCS codes.

I have seen a lot of posts everywhere saying it is impossible to do so. I also found that none of the repeater operators in my locale bothered with split PL codes.
 

borderpolman

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Buying a DBR1 programming cable and downloaded the software to program my Midland MXT400.
You CAN program it into wideband operation, you CAN program it for split CTSS/DCS codes.

I have seen a lot of posts everywhere saying it is impossible to do so. I also found that none of the repeater operators in my locale bothered with split PL codes.
What is the advantage of wideband operation this band?
 

N4KVE

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What is the advantage of wideband operation this band?
Narrow band is not required for GMRS, so people still use wide band. They can still use commercial radios that are practically free that can not be used in most commercial services. When narrow band became law, many 2-way shops had dumpsters full of perfectly good Maxtrac, or Spectra radios that would be fine for GMRS.
 
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