[TowerTalk] Tuner SWR won't stay down

[Tom Osborne]

I have 7 antennas here.  It will drift on every antenna.

There seems to be some confusion on my first posting.  This is what I asked:

"Hi

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 "

I would think the fact that I can tune the SWR down and it stays down 
with the other tuner would mean the jumpers and coax are all OK as the 2 
tuners are in series with each other.  There is definitely a problem 
with the bad tuner, but just can't figure it out.

But - I did put the output of the tuner into the dummy load and it still 
drifts at low power.  Maybe it's time to strip out the parts and build 
it into something else :-)

One last thing I'm gonna try is borrow one of those heat sensors from a 
friend of mine and shoot it at all the components and see what is 
heating up.  It has to be that what is causing the problem. 73 and 
appreciate all the suggestions.
Tom W7WHY


On 1/1/2015 10:10 PM, Jim Thomson wrote:
> Date: Thu, 1 Jan 2015 18:56:58 -0600
> From: "Bill Aycock" <billaycock at mediacombb.net>
> To: "Charles Farr" <cefarr at hughes.net>, <towertalk at contesting.com>
> Subject: Re: [TowerTalk] Tuner SWR won't stay down
>
> I'm puzzled that no one has mentioned the FIRST and most helpful trouble
> shooting test-- substituting a dummy load for the antenna.
> Bill—W4BSG
>
> ##  agreed !   We don’t even know what ant he is using.  Is it a yagi, or
> an OCF dipole, or is it a dipole fed with open wire line, OR coax.
> What band or bandS  does it drift on. Do you have some kind of
> defective balun at the feedpoint of the ant ??
>
> ##  Since it drifts, even with low power, you gotta real problem.
>
> ##  Run ONE good coax, directly from the output of the tuner.... to a dummy load.
> Don’t even mess with a wattmeter, or anything else between output of tuner
> and input of dummy load.
>
> ##  Then try and.... match the dummy load..and do it on every band, IF it doesn’t
> drift, your tuner is not the issue.
>
> ##If it does still drift, the tuner is the problem.
>
> Jim  VE7RF
>     
>
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