Hello: It is bad engineering to accept bad efficency and compensate with
cooling. Regarding the SB 220 switches, HEATH may have changed later from
the original yaxley receiving type ones - I do not know. I am worried about
the current capability of those tiny paralellt receiving type switch
contacts. Definitely no more than a few amperes I am sure.
Prosit de Hans
----------
>Från: measures <2@vc.net>
>Till: "Phil Clements" <philk5pc@tyler.net>, "AMPS" <amps@contesting.com>,
"Larry Molitor" <w7iuv@nis4u.com>
>Ämne: Re: [AMPS] Coil heating
>Datum: sön 25 jun 2000 21.21
>
>
>>
>>> The curious part of this whole business was the location of the heating.
>>> With turns on BOTH sides of the tap involved, I have to wonder what,
>>> exactly, was going on there. In the past, when I've melted down tank coils,
>>> the heating (and deformation) was confined to the center of the active area
>>> of the coil. Has anyone else seen this effect?
>>>
>>IMO, the heating was at the tap point, spreading out each way. Chances are
>>the "black" area would have spread with time.
>>
>>There has been mention on the reflector of directing cooling air on a coil
>>to prevent "melt down." This does nothing about the losses due to under-
>>engineering. RF is being converted into heat and does not reach the antenna.
>>Heat can be eliminated by selecting the proper components for the job to
>>be done.
>
>Copper has a positive temp. coefficient. The hotter it gets, the more
>resistance. Cooling air is helpful.
>
>> Hans and I are in agreement....there is a limit to how small you can
>>make an RF deck.
>>
>>The same is true about band switches. One must take into consideration not
>>only the voltage and current rating, but also the distance between contacts
>>when selecting the proper component.
>>
>? Measuring the actual withstanding voltage is not a bad idea.
>
>cheers, Phil
>>
>>
>>--
>>FAQ on WWW: http://www.contesting.com/FAQ/amps
>>Submissions: amps@contesting.com
>>Administrative requests: amps-REQUEST@contesting.com
>>Problems: owner-amps@contesting.com
>>
>>
>
>
>- Rich..., 805.386.3734, www.vcnet.com/measures.
>end
>
>
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>Problems: owner-amps@contesting.com
>
>
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