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Midland 400

borderpolman

Newbie
Joined
Jun 30, 2017
Messages
5
Location
Grand Bend, Ontario
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

I ♥ Ø
Joined
Jul 27, 2005
Messages
12,178
Location
SNCZCA01DS0
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

Member
Joined
Feb 17, 2003
Messages
1,323
Location
Nashua, NH
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

Newbie
Joined
Jun 30, 2017
Messages
5
Location
Grand Bend, Ontario
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

Member
Premium Subscriber
Joined
Jan 5, 2020
Messages
251
Location
Sacramento, CA
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

Member
Premium Subscriber
Joined
Jan 5, 2020
Messages
251
Location
Sacramento, CA
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..
 
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