[TowerTalk] Balun question

[Ignacy Misztal]

 Regarding the power handling of the F connector...

I just unpacked 2m9x, the 9 element for 2m by M2. It has a phasing line (or
balun) made of RG6 (60% coverage) and flimsy looking crimp type F
connector. The beam is rated at 1.5 KW and has an excellent reputation.
Apparently both RG6 and the F connector can do pretty well at the legal
limit on 2m.

Ignacy NO9E

On Sun, Oct 10, 2021 at 7:45 PM David Gilbert <ab7echo at gmail.com> wrote:

>
>
> 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 at contesting.com> On Behalf Of CAROL
> RICHARDS
> > Sent: Saturday, October 9, 2021 2:14 PM
> > To: Towertalk at 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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