--part1_e.f83f519.288040ba_boundary
Content-Type: text/plain; charset="US-ASCII"
Content-Transfer-Encoding: 7bit
Jim, I ran into a similar problem with a Dentron DTR-2000L linear amplifier.
The DTR-2000L does not have a tuned-input circuit and was causing excessively
high SWR when driven by my solid-state transceiver (Yaesu FT-840) . I built a
small external pi-network tuned-input circuit using a double-pole rotary
switch to switch in different value toroid inductors and fixed mica
capacitors for each band in addition to 365pf air-variables permanently wired
across the input and output sides of the circuit for fine-tuning. I used #2
mix (red) toroids about 1" O.D. size and #18 magnet wire for each toroid.
These will easily handle 100-150 watts of RF at the relatively low impedance
levels for a tuned input circuit. The whole circuit is mounted inside a small
aluminum mini-box and connected to the amplifier input thru a 1 ft length of
RG-213 coax. The values for the toroids were fine-tuned after basing their
values on a handbook article using the 8877 tube. This arrangement keeps both
the exciter and amplifier happy. I recommend always keeping an SWR meter in
line between the exciter and amplifier at all times to monitor the condition
of match between the two, as well as a second SWR meter to monitor the output
match to the amplifier. Hope this may help. 73 Todd Roberts WD4NGG .
--part1_e.f83f519.288040ba_boundary
Content-Type: message/rfc822
Content-Disposition: inline
Return-Path: <owner-amps@contesting.com>
Received: from rly-yh03.mx.aol.com (rly-yh03.mail.aol.com [172.18.147.35]) by
air-yh02.mail.aol.com (v78_r3.8) with ESMTP; Mon, 09 Jul 2001 13:10:07 -0400
Received: from contesting.com (dayton.akorn.net [216.1.128.73]) by
rly-yh03.mx.aol.com (v79.20) with ESMTP id MAILRELAYINYH32-0709130941; Mon, 09
Jul 2001 13:09:41 -0400
Received: from dayton.akorn.net (dayton.akorn.net [216.1.128.73])
by contesting.com (8.11.2/8.11.2) with SMTP id f69H9dW12110;
Mon, 9 Jul 2001 13:09:39 -0400
Received: by dayton.akorn.net (TLB v0.10a (1.23 tibbs 1997/01/09 00:29:32));
Mon, 09 Jul 2001 13:09:28 -0400 (EDT)
To: <amps@contesting.com>
Date: Mon, 09 Jul 2001 13:09:16 EDT
From: Km8i@aol.com
Subject: [AMPS] Tuned input
To: <amps@contesting.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
X-Mailer: Unknown (No Version)
Message-ID: <16.f033544.287b3f3c@aol.com>
Sender: owner-amps@contesting.com
Precedence: bulk
X-Sponsor: W4AN, KM3T, N5KO & AD1C
A friend of mine recently purchased a Dentron MLA-2500. In the archives I
noticed some one had asked about this amp before, but I could not find the
answer to this question. Since the MLA-2500 does not have a tuned input what
percautions are necessary to use it with a solid state rig.
As you can probaly guess I am not very familiar with amplifiers or their
construction, but am planning to rectify that with some studying on the subject.
TNX & 73,
Jim KM8I
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
--part1_e.f83f519.288040ba_boundary--
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|