[ICOM] Icom 706MKIIG vs Yaesu FT450

[marditti at dslextreme.com]

Switching  power supplies are space and weighgt savers, hower the spikes
can be a serious damaging problem.
My approach and practice when using swritchers is to always use an LC
filter between between the supply and radio. this includes the 706 in the
car and several hand held radios.  A good source for 'high current' low
cost inductors are computer power supplies.  These supplies are built
cheaply and they do fail. Inside, one can find a nice selection of
inudctors, some with multiple windings.  Remove these inductors from the
power supply, remove some of the windings and they work great.  Ome of
these inductors are rated for relatively high currents since the 3 and 5
VDC from these supplies is in the range of up to 20 Amp. Based on my
experience, most of the capacitors are only rated for 16 VDCW, which does
not have adequate safety derating to be used on 12 to 14 VDC.
I have taken apart many of these supplies and have never encountered a bad
inductor.

Good luck,

Mort, KB6BSN



Dave Shirk
> Jim,
>
> Thanks for the reply. Great points and I am aware of these. I used the
> rig on a diesel powered sail boat for years. It had a 'large iron'
> linear battery charger, and I never had a problem. After I removed the
> radio from the boat, I loaned it to someone who was interested in
> buying it for their RV. It was returned as 'it does not work'. My
> guess is, he had one of those spike ridden battery chargers on the RV,
> and that 'ate' the radio.
>
> I think I am close to getting all of the damage repaired. And thanks
> again for posting all of the tips.
>
> 73 - Dave - KI4KQ
>
> On May 18, 2008, at 10:39 AM, Jim Hargrave wrote:
>
>> Dave,
>>
>> You can eliminate a lot of the spikes, etc by running a heavy
>> battery cable
>> direct from the battery to the radio. The battery has a great leveling
>> effect on spikes and ignition noise. I never connect a transmitter
>> to any of
>> the accessory circuits for that reason. In my Motorhome, I have a #10
>> stranded wire pair going direct from the IC-735 to the coach
>> battery. Noise
>> and voltage spikes are almost non-existent in this setup. Another
>> trick is
>> to wrap several turns of the power wire around a large ferrite core
>> as close
>> to the radio as you can get.
>>
>> The only real noise source in most RV's is the battery charger that
>> operates
>> when the power unit is running or the RV is plugged into an external
>> AC
>> power source. This charger is a typical RV converter that furnishes
>> 12 Volt
>> to the lighting and charges the house battery. Most of them use a
>> pulser
>> circuit with SCR's. This problem can be solved by turning off the
>> charger
>> when operating the radio and using a normal linear charger. Most of
>> these
>> can be converted to a linear charger and it will eliminate this
>> source of
>> noise. All of the 12 volt runs make a great antenna and it sounds
>> like an
>> old spark gap transmitter across the entire HF spectrum. Now that is
>> a real
>> "noise floor" that is not the radio fault. Some of the high end
>> inverters
>> are now incorporating switching chargers that are a lot quieter.
>>
>>   * 73's Jim W5IFP *
>
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