[AMPS] Alpha

paul apollo_six@btinternet.com
Wed, 3 Jan 2001 17:23:58 +0000


In this case it's much more likely to be a mismatch causing a high
voltage arc.

Did something similar to my ATU last week drawing a 2 inch arc, no marks
on the switch however - it was a real ceramic switch not the Mickey
Mouse (sorry Mickey) types fitted to some amateur equipment.



Paul


In message <030801c0758e$5d146f40$6401a8c0@neptune>, Michael Tope
<W4EF@dellroy.com> writes
>
>I have an old Ten-Tec 4229 tuner that is on its second ceramic wafer switch 
>(this is 
>the switch used to change the L-network configuration from Hi-Z step down to Lo-
>Z
>step up). I destroyed the original switch using an SB-220 and a center-fed zepp 
>that
>must have had a particulary high input impedance. The SB-220 suffered no damage,
>so it is my belief that the damage was caused by arcing of the switch contacts 
>that
>resulted from the excessive RF voltage associated with the Hi-Z of the antenna. 
>
>That is not to say that parasitics aren't in the realm of possibilities. Based 
>upon my
>limited experience, I don't know enough about the impedance characteristics of 
>HF tank components in the VHF range to really say with any certainty. What is 
>clear
>to me, is that load mismatches (wrong antenna, improper tuning, etc) can 
>generate
>RF voltages at the operating frequency which are well in excess of nominal 
>operating 
>levels. This seems to me to be a more likely explanation for switch failure. 
>
>73 de Mike, W4EF.............. 
>
>----- Original Message ----- 
>From: "measures" <2@vc.net>
>To: <Wt8r@aol.com>; "Tom Rauch" <W8JI@contesting.com>; "AMPS" 
><Amps@contesting.com>
>Sent: Monday, January 01, 2001 9:14 AM
>Subject: Re: [AMPS] Alpha
>
>
>> 
>> >
>> >In a message dated 12/29/00 12:37:26 PM Eastern Standard Time, 
>> >w8ji@contesting.com writes:
>> >
>> >> Hi Bob,
>> >>  
>> >>  > I don't intend to start a war, however based on my observations over the
>> >>  > last 2 decades (at least) in going to rallies (what Americans call
>> >>  > hamfests) and my observations of some of the questions which crop up on
>> >>  > the ham radio newsgroups the average ham is too lazy to do anything.
>> >>  
>> >>  I don't intend to start a fight, but from my viewpoint the average 
>> >>  ham is too quick to condemn everyone else. 
>> >>  
>> >>  > Some of the comments which appear on Rich Measures web site about
>> >>  > commercial equipment are well justified, rigs with so called fast break 
>> >in
>> >>  > using standard power relays to switch linears, no soft start for power
>> >>  > supplies, short circuiting HT lines as a safety measure, band switches
>> >>  > that arc because there is inherent in the design of an amplifier a cause
>> >>  > for VHF parasitic. 
>> >>  
>> >>  I hate to tell you this, but if you think a VHF parasitic can arc a 
>> >>  bandswitch you need a course in electronics 101.
>> >>  
>> >>  Perhaps you should look at the voltages and currents required to 
>> >>  do that, instead of being critical of other for not knowing what is 
>> >>  going on.
>> >>  
>> >>  Obviously you haven't researched the problem.
>> >>  
>> >>  73, Tom W8JI
>> >>  w8ji@contesting.com
>> >>  ========================================================
>> >
>> >Tom,
>> >
>> >Since you are not the average ham, what, in your humble opinion, is the 
>> >cause of bandswitch arcing ????????
>> >
>> >You seem to have eliminated all the things that DON'T cause arcs, what is 
>> >the real cause?
>> >
>> ? according to Mr. Rauch, he has not completed Electronics 101.  
>> >
>> cheers, Dave.
>> 
>> -  Rich..., 805.386.3734, www.vcnet.com/measures.  
>> end
>> 
>> 
>> --
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>> 
>
>
>
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>

-- 

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