[TenTec] Power supply types

Bob McGraw - K4TAX RMcGraw at Blomand.net
Mon Jan 20 23:56:28 EST 2014 

As a pilot we at taught and trained and practiced to deal with emergencies. 
So as a ham are we prepared to deal with an emergency, although not of life 
or death magnitude,  where a product does not perform as expected or needed? 
It is largely related to ones expected level of performance.

You mean that you would take a new power supply, linear or switcher, to a 
remote location and not know if it will perform as expected?   Would you 
take a new radio to a remote location and expect it to work?   If that is 
really your expected performance level, somehow you must be assured the 
electric company won't drop the mains or the storm won't drop a tree across 
the primary some 5 miles away.  In this case, best you take a pair of fully 
charged batteries and do check to see that they are fully charged and not 
rely on the power company or the power supply of your choice.

Remember in today's world of manufacturing, new only guaranteed new......not 
necessarily good.  Today all companies work with a number defined as AQL. 
That says they expect a certain number out of 1000 pieces to fail or be 
inoperative out of the box.  Just today our new $600 Maytag dishwasher, now 
only 6 days, old has failed and must be replaced.  I can also tell you of a 
twin engine airplane that I was piloting with two new factory engines with 
less than 20 hrs each where one locked up at MTO power during take-off.  I 
did maintain control of the aircraft and put it on the runway with no damage 
to the aircraft or passengers on board.  And yes I did a complete ground 
check and proper engine run-up before take-off.  The fault was diagnosed as 
failure of lubrication on a main crankshaft bearing.  {I won't comment on my 
nerves or the condition of my pants after the event as the pucker factor 
likely went off of the chart.}

If I required the radio and power supply to perform to 100% of expectations, 
you bet your boots that I would assemble it as a system, operate it and give 
the system a "burn in" of several hours to assure a high degree of 
reliability.  Should any part of the system fail or not perform to 
expectations the it would be replaced.

To check a power supply, power the radio from a battery, then using a DC 
blocking T connected to the receiver input and put the power supply under 
load. Then tune the bands listening for noise.  This test is very reliable, 
very easy and you'll hear anything that comes out of the supply.  Of course 
don't be alarmed when you hear something,  for likely it will be a good bit 
below atmospheric noise at the quietest of locations.

Yes, I do think my airplane comparison is quite reasonable.

73
Bob, K4TAX











----- Original Message ----- 
From: "Ken Brown" <ken.d.brown at hawaiiantel.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Monday, January 20, 2014 9:49 PM
Subject: Re: [TenTec] Power supply types


> Hi Bob,
>
> I don't find the airplane comparison to be reasonable. In my example the 
> penalty for choosing the wrong power supply from a very limited choice, 
> with little information about the performance of the available choices, is 
> a week at the cabin without being able to hear weak signals on your radio. 
> In your example the penalty of piloting an unsafe aircraft could be death.
>
> I devised a hypothetical situation in which a person has limited time, 
> information and resources to select a power supply. I think anyone in this 
> situation who is experienced with HF radio and DC power supplies of both 
> the linear  and switched mode varieties would chose the linear mode 
> supply. Even those of us who know that "properly engineered" switched mode 
> power supplies do exist, are aware that the chances of getting RF noise 
> from a switched mode power supply are much greater than from a linear mode 
> one.
>
> DE N6KB
>
>
>
>
> On 1/20/2014 5:21 PM, Bob McGraw - K4TAX wrote:
>> I would never pilot an airplane unless I performed a proper and complete 
>> ground inspection while using a check-list.
>>
>> I would never buy a power supply unless I perfromed a proper evaluation 
>> but first knowing the needed power requirements.
>>
>> 73
>> Bob, K4TAX
>>
>>
>>
>>
>> ----- Original Message ----- From: "Ken Brown" 
>> <ken.d.brown at hawaiiantel.net>
>> To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
>> Sent: Monday, January 20, 2014 8:19 PM
>> Subject: Re: [TenTec] Power supply types
>>
>>
>>> They are both commonly available and they can both be used to power 
>>> typical HF transceivers. I think it is a reasonable comparison to make.
>>>
>>> Here is another question: What kind of power supply did you first see 
>>> reviews in QST in which the subject of RF noise generation was even 
>>> mentioned?
>>>
>>> Yes, switched mode power supplies CAN be made that do not generate (and 
>>> radiate) RF noise. And switched mode power supplies are generally more 
>>> energy efficient.:
>>>
>>> How about we state the question this way:
>>>
>>> Suppose you're on vacation and you brought your mobile rig along with 
>>> you, which runs on 12 VDC. You planned on only operating from your 
>>> vehicle, so you did not bring a power supply for use from 120 VAC. You 
>>> are offered an opportunity to stay for free in a nice vacation rental 
>>> cabin for a week. The cabin has all the conveniences, including grid 
>>> power. There are tall trees and you have a spool of skinny copper wire 
>>> and an antenna tuner in your vehicle. You think it will be a great 
>>> opportunity to get on the air from a remote location, with hopefully not 
>>> a lot of RF noise. Before you head up into the mountains to the go to 
>>> the cabin you see a store which sells two kinds of power supplies that 
>>> have the right voltage and current rating to power your rig. One of the 
>>> power supplies is very lightweight and the label say it is super 
>>> efficient and uses switching mode technology. The other power supply is 
>>> heavier, and you can see it has a laminated iron core transformer and a 
>>> big electrolytic capacitor in it. The prices of the two power supplies 
>>> are identical and they both appear to be well constructed. You cannot 
>>> find any other data about these power supplies. The drive to the cabin 
>>> is long, and you don't intend to drive back to town until you have 
>>> finished your stay at the cabin. If you buy both power supplies, you 
>>> won't have enough money left to buy the wrist rocket slingshot you 
>>> intend to use to send the skinny wire up into the tall trees.
>>>
>>> Which power supply would you buy?
>>>
>>> DE N6KB
>>>
>>> On 1/20/2014 3:41 PM, Kim Elmore wrote:
>>>> This is an apples vs pecans question.
>>>>
>>>> Better-stated questions:
>>>>
>>>> What's the probability that a properly-designed and engineered linear 
>>>> power supply will radiate  RF noise of sufficient amplitude to be 
>>>> bothersome?
>>>>
>>>> What's the probability that a properly-designed and engineered 
>>>> switching power supply will radiate  RF noise of sufficient amplitude 
>>>> to be bothersome?
>>>>
>>>> Answer: unknown. likely small but equal.
>>>>
>>>> Kim N5OP
>>>>
>>>>
>>>> On 1/20/2014 7:13 PM, Ken Brown wrote:
>>>>> What is the probability that a transformer/rectifier/capacitor 
>>>>> filter/linear regulated power supply will generate and radiate 
>>>>> (through AC power input or DC power output leads) RF noise of 
>>>>> sufficient amplitude to be bothersome? That probability may not be 
>>>>> zero.
>>>>>
>>>>> What is that probability that a switched mode regulated power supply 
>>>>> will be not "properly engineered" and generate and radiate RF noise of 
>>>>> sufficient amplitude to be bothersome?
>>>>>
>>>>> How do those two probabilities compare?
>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>
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