On 10/2/2025 9:35 AM, Jim Brown wrote:
On 10/2/2025 7:55 AM, Steve Harrison wrote:
However, it is a fact that connectors of the 1/2"-size (which
includes UHF, type N, and even type C with their extra-thick center
pin) do heat up when a kilowatt or more is passed through them,
particularly at V/UHF.
Have you observed this issue with top quality connectors?
This was a commercial application, and our customer was a well-known
governmental agency; of course I used (and the company and power
combiner manufacturer paid for) the best available: silver-plated
Amphenol as well as some Suhners in several other places. And as I
mentioned, the agency's techs later showed me failed
formerly-silver-plated Amphenols (they burned up, so the silver-plating
was flaking off some of them). We did not, however, go as far as to spec
gold-plated: I don't know whether such was even available at the time,
unless you could specify space-qualified components.
That was not the issue: the real issue was the thermal expansion and
contraction of the connectors causing the connectors to loosen over
time. We are talking about connectors that passed a kilowatt at 450 MHz
heating up, then cooling off suddenly as they were near or within the
cool air-conditioned stream from the rack's environmental systems.
When I told my dad about the problem, he mentioned that at one time, TRW
was experiencing trouble with spurious radiation in satellites that was
eventually traced to some coaxial connectors in birds. As you know, most
commercially-available type SMA connectors are (or were, back then)
stainless steel. They had to quit using those and switch to
wholly-gold-plated coaxial connectors everywhere. That problem was due
to minute galvanic corrosion between dissimilar connector materials that
caused micro- diode junctions between connector interfaces, causing
microwatt-level spurious products even at very low transmit powers. The
present stories circulating about the spurious radiation from Starlink
birds that can be easily-heard on ground receivers makes me wonder
whether they made the same mistake. All over again 8-).
I have also heard of big multi-multis experiencing connector generation
of spurious products due to poor or loose coaxial connectors, which can
result from thermal expansion/contraction. Dissimilar-material coaxial
connectors can also cause problems; I remember reading of one in New
England that took the station operator SEVERAL YEARS before he
accidentally ran across (and cured) the real source of the spurious
products that had plagued his operators for years.
Steve, K0XP
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