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Re: AM antenna switch for 5kW ?
To: CRTech <crtech@crtech.org>
Subject: Re: AM antenna switch for 5kW ?
From: RADIO DOCTOR <lylehenry@fastmail.fm>
Date: Tue, 15 May 2018 20:09:29 -0700 (Pacific Daylight Time)
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In-reply-to: <ac193448-130b-4edf-5262-f529adc94e73@pari.edu>
References: <alpine.WNT.2.10.1805111649050.3300@Lyle-Dell-D630> <ac193448-130b-4edf-5262-f529adc94e73@pari.edu>
User-agent: Alpine 2.10 (WNT 1266 2009-07-14)
Thank you for your point by point analysis, Lamar. I'm sure Kintronic RF contactors will be fine, even if they were to end up in the open on the wall.

Yes, the 1/2" transmission line would seem marginal. It was installed back in about 1988 by former owners of the site. Fortunately it has always worked. If it burns up someday, we will replace with 7/8"

I'll use the larger line for the jumpers.

On Tue, 15 May 2018, Lamar Owen wrote:

On 05/11/2018 08:20 PM, RADIO DOCTOR wrote:
What remote control switches are being used for AM nowadays?
Shielded for y
 coax or open relay(s) on a panel/board?  Controllers? Automatic?

Kintronic's RF contactors have been the standard for years, both at the ATU/LTU and in phasors, and you've already gotten a pointer to those. Kintronics has a wide variety of controllers and can custom build pretty much anything related to AM antenna systems, including dummy loads.

 The transmission line is a 1/2" late 1980's version of the current 1/2"
 CableWave (RFS) LCF12-50J.

1/2 inch at 5kW?  Well, CableWave does rate the 2013 version of this cable for 38kW average at 1MHz and 38kW peak; with AM you have to take into account the peak, not average, power, which for 5kW at 100% positive modulation is 20kW (peak voltage at 100% 1kV; the cable is rated 1.95kV) .  Should be ok, although I have always recommended 7/8's for 5 and 10kW.

 What's best for jumpers?  Should I bother with connectors or just wire it
 up?  Transmitter will probably be 7/8" EIA output, but DIN connectors
 might be nice for hooking everything together.  Is there a 7/8" EIA to
 appropriate size DIN adapter.  I've never used DIN connectors anywhere.

At 5kW I'd use 7/8's flanges everywhere.  They're easy enough to work with, and it's just a few bolts to decouple when you need to do so.  In this case it's not the voltage but the current that becomes the primary concern; your connector needs to handle 10 amps with dead carrier and 20 amps at 100% modulation (and 1kV at 100% positive peaks).  This is hard to do with connectors smaller than 7/8's flanges, although the 7/16 DIN is a really good and rugged connector.

 Being an FM Guy, I've rarely dealt with real AM.  Always tried to keep AM
 at least 50 dB down :)

AM is a completely different beast in many ways.  You're solidly down in lumped constant territory, but distributed constant stuff keeps showing up.....  AM directionals are my favorite; love negative resistance towers..... :-)  You're also into real loudness-war territory, since with an AM your effective maximum listenable distance is directly related to positive modulation percentage.

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  Lyle Henry, CPBE  THE RADIO DOCTOR  K9DKW  Los Angeles, CA
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References: AM antenna switch for 5kW ?
(RADIO DOCTOR <lylehenry@fastmail.fm>, 12 May 2018 00:20:15 -0000)
Re: AM antenna switch for 5kW ?
(Lamar Owen <lowen@pari.edu>, 15 May 2018 04:45:46 -0000)
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