Do note that the "Typical Matching Range and Power Limits" as stated on
page 2 of the KAT500 manual. Pay particular attention to the power
handling and SWR range between 1.8 - 2.0 MHz. The SWR limits are to
5:1 Low impedance, and 10:1 High impedance.
In the 3 - 30 MHz range the power can be 1000 max but with only a 3:1
SWR or better.
Also note the Duty Cycle statement regarding power rating being ICAS,
thus being equal time on and off with a 5 min. limit max at full power.
If you aren't sure, then err on the conservative side so one won't let
the smoke out of the box.
73
Bob, K4TAX
Message: 2
Date: Sun, 11 Jul 2021 16:17:43 -0500
From: Jack Brindle<jackbrin...@me.com>
To: Elecraft Reflector<elecraft@mailman.qth.net>
Subject: Re: [Elecraft] Question about antenna matching
Message-ID:<7cc60665-e824-4132-bc62-014d695d7...@me.com>
Content-Type: text/plain; charset=utf-8
There is another big consideration in modern ATUs which use toroid cores for
the inductors. The cores will heat up during transmission, especially for bad
mismatches. Remember, the ATU still has to deal with the high reflected power
as it provides a good match for the radio. If the heating reaches a critical
level, the toroid will break, and the ATU will no longer be able to do its job.
ATUs are thus rated for the amount of reflected power (thus SWR) they can
handle with some margin for failure. An ATU like the KAT will handle higher
mismatches at low power, but when you start trying to push lots of power
through it, the heating margins drop, meaning that you should really watch the
match when trying to run a kilowatt through an ATU in order to avoid damaging
it. At 50 watts the KAT should handle a pretty bad mismatch, while at 500 a
lower maximum mismatch should be observed.
Also note that at higher power the connectors, adapters and coax cable will
also see lots of heating with big mismatches. These can fail also; in fact we
see that a lot. That?s why you see lots of admonitions to only use high quality
connectors and adapters. Right angle adapters are especially bad as the
conductor tends to migrate and short out at high power. Be sure that you use
coax that is rated for the power levels as well.
73,
Jack, W6FB
On 7/12/2021 10:24 AM, elecraft-requ...@mailman.qth.net wrote:
Message: 2
Date: Sun, 11 Jul 2021 16:17:43 -0500
From: Jack Brindle<jackbrin...@me.com>
To: Elecraft Reflector<elecraft@mailman.qth.net>
Subject: Re: [Elecraft] Question about antenna matching
Message-ID:<7cc60665-e824-4132-bc62-014d695d7...@me.com>
Content-Type: text/plain; charset=utf-8
There is another big consideration in modern ATUs which use toroid cores for
the inductors. The cores will heat up during transmission, especially for bad
mismatches. Remember, the ATU still has to deal with the high reflected power
as it provides a good match for the radio. If the heating reaches a critical
level, the toroid will break, and the ATU will no longer be able to do its job.
ATUs are thus rated for the amount of reflected power (thus SWR) they can
handle with some margin for failure. An ATU like the KAT will handle higher
mismatches at low power, but when you start trying to push lots of power
through it, the heating margins drop, meaning that you should really watch the
match when trying to run a kilowatt through an ATU in order to avoid damaging
it. At 50 watts the KAT should handle a pretty bad mismatch, while at 500 a
lower maximum mismatch should be observed.
Also note that at higher power the connectors, adapters and coax cable will
also see lots of heating with big mismatches. These can fail also; in fact we
see that a lot. That?s why you see lots of admonitions to only use high quality
connectors and adapters. Right angle adapters are especially bad as the
conductor tends to migrate and short out at high power. Be sure that you use
coax that is rated for the power levels as well.
73,
Jack, W6FB
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com
