[TenTec] Power supply types

[Ken Brown]

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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