[TowerTalk] Tuner SWR won't stay down
billaycock at mediacombb.net
Thu Jan 1 19:56:58 EST 2015
I'm puzzled that no one has mentioned the FIRST and most helpful trouble
shooting test-- substituting a dummy load for the antenna.
From: Charles Farr
Sent: Thursday, January 01, 2015 5:50 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Tuner SWR won't stay down
An inexpensive remote reading thermometer, like the one from Harbor
Freight would be a less invasive, and less likely to result in an RF
burn. Sounds like capacitor to me.
> Even at low power, large currents can flow in certain components. This
> sounds like something is heating up and changing value. A giveaway would
> be if the match drifts faster at high power than at low power. Assuming
> that's the case, can you get inside and, while running low power, feel
> around for anything getting warm?
> Kim N5OP
> "People that make music together cannot be enemies, at least as long as
> the music lasts." -- Paul Hindemith
>> On Jan 1, 2015, at 14:09, Tom Osborne <w7why at frontier.com> wrote:
>> I picked up an MFJ-989C tuner that has a problem (don't want to hear
>> about 'mitey fine junk).
>> The problem is that the SWR goes down and then slowly creeps back up.
>> I got a new roller inductor and installed it and the SWR still doesn't
>> stay low, even at low power.
>> I took the roller inductor out and put in a switch/coil combo to
>> eliminate the coil problem. SWR still climbs up.
>> Bypassed the SWR circuitry and ran the input from the antenna directly to
>> the capacitor. Still won't stay low.
>> I thought it might be the SWR circuitry but I put another tuner in front
>> of this one and when I tune the SWR down with the other tuner, it stays
>> down, so don't think it should be the SWR circuit.
>> This really has me puzzled. Can't see anything left to check. Any
>> ideas? Thanks and 73
>> Tom W7WHY
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