[RFI] DFing intermittent connection

[Stephanie WX3K]

DAS - Distributed Antenna systems used in major airport/commercial to redistribute cellular service

PIM - Passive Intermodulation, usually caused by the rusty(ferrous) connection that will cause IM products as a result. Usually found in poorly tightened/crimped connectors and can be caused by an external source outside the coaxial cables.

Your 2nd harmonic may in fact be caused by a rusty connection somewhere that is excited with higher power levels. Does it occur no matter what power levels ? Or just high power levels ?

Stephanie WX3K


> On Aug 8, 2021, at 3:34 PM, Pete Smith N4ZR <pete.n4zr at gmail.com> wrote:
> 
> 
> PIM?  Googled that one without success.  Ditto DAS.  I agree with your diagnostic approach, though
> 
> 73, Pete N4ZR
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> On 8/8/2021 3:28 PM, Stephanie WX3K via RFI wrote:
>> Difficult to use something that selective on HF.
>> 
>> I do a lot of PIM troubleshooting on DAS and the BEST method i find is tapping connections/hardware with a rubber mallet while the systems is active. You could remotely watch your secondary RX using remote desktop on your cell
>> 
>> Stephanie WX3K
>> 
>> 
>>> On Aug 8, 2021, at 3:19 PM, Steve London <n2icarrl at gmail.com> wrote:
>>> 
>>> This is a little off topic from the usual, but the expertise in DFing on
>>> this forum is outstanding.
>>> 
>>> I am a serious contester, and do lots of SO2R. That means I need to be able
>>> to listen on one band while transmitting on another band. With filters and
>>> stubs I have brought the harmonic and overload energy down to acceptable
>>> levels. However, I have recently developed a new problem. Something on the
>>> tower is intermittent and causing the level of the 2nd harmonic to vary
>>> many S-units as the wind blows or I turn the rotator on the 40 meter beam.
>>> When this happens it creates hash across the band. I have looked for the
>>> obvious, but no luck yet. Yes, it could be something loose on the 40 meter
>>> beam hardware, but before I take on the project of taking it down, I would
>>> like to pinpoint the source. I am a tower climber, so I can get close to
>>> everything on the tower. What are the options for something handheld, very
>>> directional, and not overloaded by the fundamental ?
>>> 
>>> 73,
>>> Steve, N2IC
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