Date: Thu, 2 Oct 2025 07:55:33 -0700
From: Steve Harrison <k0xp@k0xp.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Feedline (choke) question
>Decades ago, I designed and helped produce a rack-mounted
>1-kilowatt-minimum-output solid state transmitter for a government
>agency operating from 400 - 450 MHz.
>During acceptance tests, while looking for hot spots throughout the
>transmitter during key-down time periods as long as six continuous hours
>of 1-kilowatt output power using a VERY expensive thermal IR camera and
>other thermocouple probes, I found that among the hottest spots were the
>type N plugs screwed into the female chassis connectors of the power
>combiners; they would approach 300-degrees F after just ten minutes and
>slowly climb higher as the rack's internal ambient temperature also
>climbed.
If it's hitting 300 deg F..... I would say you are using the wrong
connector !
300F is nuts. That much heat is also going into the inside of the
gear..and if going into any type of TR relay, filter output etc, that too
will be cooked.
Did you use type N on all the connectors that were used, like between
TX and ant ? They would all be cooking.
What are ham folks using for coax and connectors if using 1.5 kw data mode
on the 70 cm band ?
A 7-16 DIN has identical power ratings on all freqs vs a 7/8" EIA
flange connector. I wonder how those would get ? BTW, you can put 5 x
as much torque on a 7-16 Din vs a type-N connector.
The type N uses that stupid BNC pin..which is way too small.
Are type N connectors even rated for 1 kw CCS CXR on 70 cm band ?
Jim VE7RF
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