1. The F connector has a peak rating of 1200 V RMS, but I totally agree I would
not be comfortable using it.
2. We had access to a way to test up to a 1000 Vdc. All of the rest of the
test equipment available worked at low voltages 😊
73,
Joe kk0sd
-----Original Message-----
From: TowerTalk <towertalk-bounces@contesting.com> On Behalf Of David Gilbert
Sent: Sunday, October 10, 2021 6:44 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Balun question
Two observations:
1. 1500 watts would be about 335 volts RMS into 75 ohms, but peak voltage is
about 475 volts. Presumably the F-connector specs have some margin built it,
but still ...
2. I don't think testing at DC is a particularly good indication of what it
can handle at RF, especially if you're talking about a dielectric. i don't
know why you would choose that for your test.
73,
Dave AB7E
On 10/10/2021 3:37 PM, Gary wrote:
> Carol,
>
> I believe I am one of the authors of the April 2021 QST article you
> referring too. I would have never thought to run high power through a type
> 'F' connector, and was a little surprised at what they are capable of when I
> read the specs available halfway down the page here:
> https://www.amphenolrf.com/connectors/f-type-connectors.html
>
> A back of the envelope calculation says legal limit Voltage in a 75 Ohm
> system would be around 335 Volts with a perfect match. Below the 400 Volt
> rating of the type F connector (I'm surprised), but that's cutting it close
> in my book.
>
> As for the baluns -- We tested all the ones we built at 1000 Volts DC and did
> not see any arcing, or measure any appreciable leakage. Dave (N0DL co-author)
> has access to a lot of neat test gear as part of his job. I would recommend
> you take special care to not kink or over-work the coax, and keep the passes
> through the core as spread out as possible.
>
> I hope this helps a little.
>
> 73,
> Joe kk0sd
>
>
> -----Original Message-----
> From: TowerTalk <towertalk-bounces@contesting.com> On Behalf Of CAROL
> RICHARDS
> Sent: Saturday, October 9, 2021 2:14 PM
> To: Towertalk@contesting.com
> Subject: [TowerTalk] Balun question
>
> Hello all,
>
> I have two questions which I hope someone will be able to answer...
>
>
> 1. I have acquired a large supply of 75 ohm ( aka RG 11) CATV hardline from
> the local CATV company. They were even kind enough to install the F-fittings
> for me. I have enough F-PL259 adapters to use with the cable. Will the CATV
> fittings handle 1kw on 80m and 40m inverted vee's?
>
> 2. I built several 1:1 Current Baluns from the April 2021 issue of QST and
> they work fine. The specs say they will handle legal limit. Both my 80m and
> 40m vees are cut for CW. When I want to go on SSB, I usually run the coax
> through a Palstar AT2K tuner. I never worried about this before since I
> always used coax chokes, but now I might have some concerns. Although the
> amplifier ( 1kw) is happy, SWR-wise, I realize that I might have some high
> voltage that might be going through the chokes and ultimately fry them. Any
> Thoughts out there?
>
>
> Carol
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