[TowerTalk] ...and another coax adapter question

[David Gilbert]

We've been talking inferior UHF connectors here (especially angle ones) 
and it doesn't require voltage breakdown ... current alone can do it.

Assuming a KW on a 50 ohm line, a resistance of 0.1 ohm will dissipate 2 
watts, which is enough in that tiny spring to affect it and potentially 
cause an arc ... especially since any shift could easily cause 
additional resistance.  Maybe an insertion loss test sees something 27 
dB down ... maybe not.

Dave   AB7E


On 11/25/2023 11:51 AM, Scott Townley wrote:
> If that's the case, then wouldn't an insertion loss test reveal such 
> an issue?
>
> For example, I was deconstructing the power handling of a Charter 
> Engineering B5-series coaxial relay (N-female connectors).  If I map 
> "max insertion loss at x GHz" to the average power rating on their 
> published chart, at every point the dissipated power comes out to 11 
> watts.  That tells me that "good" N-connectors can dissipate 5 watts, 
> and for that mechanical form factor I should be able to derive a power 
> limit based on measured insertion loss.
>
> Or are the physics of power handling in "not-so-good" connectors 
> different from what would be revealed by an insertion loss 
> measurement?  Assuming of course that we are not in the realm of high 
> voltage breakdown of the dielectric (or maybe that's exactly the 
> difference?).
>
>
>
> On 24/11/2023 17:29, Jack Brindle wrote:
>> One of the big problems with off-brand connectors and adapters is 
>> their power handling capabilities. This is especially noted in the 
>> right-angle adapter. We see a lot of arcing when higher power is 
>> applied.
>> Higher power in this case is anything above just a few hundred watts. 
>> Whenever I see an amplifier log report with a lot of high reflected 
>> power or PA Dissipation faults, I immediately start looking at the
>> connectors and feed line for problems. These are usually found in one 
>> of several places - right angle adapters, and baluns that were meant 
>> for low power, but have been over-stressed with high
>> power.
>>
>> My advice? If the right-angle adapters aren’t Amphenol, throw them out.
>>
>> 73,
>> Jack, W6FB
>>
>>
>>> On Nov 24, 2023, at 12:59 PM, Scott Townley <scott at nx7u.net> wrote:
>>>
>>> Say I have a pile of coax adapters on my bench (we all do, right?).
>>>
>>> How do I separate the wheat from the chaff?  I have a fully equipped 
>>> bench...I would think the go-to would be a TDR measurement.  Any 
>>> better/additional suggestions?
>>>
>>> TIA,
>>>
>>> -- 
>>> Scott NX7U
>>>
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>