[CW] My low pass filter works

[Hans Brakob]

Back in the day (40 years ago?) they only came in one version.

On Tue, Jul 30, 2013 at 12:08 AM, D.J.J. Ring, Jr. <n1ea at arrl.net> wrote:

> My low pass is a 54 MHz cutoff.  You could have purchased the 34 MHz
> version as 50 MHz cutoff does nothing for you.
> When you took it out did it work?
> David
> On Jul 30, 2013 12:41 AM, "Hans Brakob" <kzerohb at gmail.com> wrote:
>> Did you ever have one of those days that you thought maybe you ought to
>> check to see if your Novice license was still valid?
>>
>>
>>
>>
>> Couple years ago K0CKB gifted me a modern Yaesu FTdx-5000 radio which
>> includes all those new WARC bands, and even 6 meters.
>>
>>
>>
>>
>> Well I finally got curious to see what lay behind that "50" band-button,
>> and having no antenna, I cut and bent and soldered up a bunch of copper
>> water pipe into a reasonable facsimile of a 6-meter J-Pole last week.
>>
>>
>>
>>
>> Put it up in the air, ran some fresh coax to the shack, and hooked it to a
>> vacant connector on my antenna switch box.
>>
>>
>>
>>
>> Mashed in the "50" button on the rig, tuned around, and the band seemed
>> empty.  Checked the SWR at 50.010 --- infinity.  Checked SWR at the top
>> of the band and spots between --- infinity at all those spots too!  Checked
>> all my construction dimensions, ohmed out the new coax, tried several
>> adjustments to the J-pole feed point looking for a match.  NOTHING.
>>
>>
>>
>>
>> So this evening I borrowed an antenna analyzer from N0AT.
>>
>>
>>
>>
>> Unhooked the coax from the switch box, attached the analyzer, fired it up,
>> and found a nice 1:1 match at 52.873 mHz, and under 2.5:1 across the band.
>>
>>
>>
>>
>> WTF!?!?
>>
>>
>>
>>
>> Hooked the coax back to the switch box and checked the SWR at the radio.  Infinite
>> mismatch across the band.
>>
>>
>>
>>
>> WTF!?!?
>>
>>
>>
>>
>> Clambering around under the desk looking for a bad patch cord (or
>> something), I came face to face with......
>>
>>
>>
>>
>> .....the low pass filter (50 mHz cutoff) that I installed way-back-when to
>> protect TV channel 2 in the neighborhood.  On the input line to my
>> antenna switch box!
>>
>>
>>
>>
>> Sunnuvagun!  See the subject line.
>>
>>
>>
>>
>> de Hans, K(n)0HB
>>
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>> =30=
>>
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