SWR meter kaput?
 

Recently started to renew my interest in ham radio and so pulled out
some old equipment.

I set up a temporary antenna yesterday and connected it to my rig,
including an MFJ Versa Tuner II (Model MFJ-949D), purchased about 15
years ago.

Setting the transmitter (Icom-725) to low output power (about 10W) I
closed the CW key and the tuner indicated about 15W of forward power,
and no reflected power. That is, it "indicated" a SWR of 1:1.
Unlikely, to say the least.

The reflected power meter just doesn't move at all. Regardless of band.
Thus, I am convinced that something is wrong with it (it has been
moved twice since purchase). I did open the case and nothing looks out
of order. Touching the reflected meter terminals with an ohm meter
causes the reflected meter needle to jump, so it appears that the meter
itself is working.

The antenna seems to work very well for receiving. And I am able to
"get out", as it were. I can hear myself on a little SW radio I have at
14.2 MHz in AM.

Questions:

Any thoughts as to where to look for the "problem" with the tuner?

Is there another way to determined SWR with just the meters on the
transmitter (RF power out) and the forward power meter on the tuner?

Thanks in advance.

73s,

Thomas

I set up a temporary antenna yesterday and connected it to my rig,
including an MFJ Versa Tuner II (Model MFJ-949D), purchased about 15
years ago.

Setting the transmitter (Icom-725) to low output power (about 10W) I
closed the CW key and the tuner indicated about 15W of forward power,
and no reflected power. That is, it "indicated" a SWR of 1:1.
Unlikely, to say the least.

The reflected power meter just doesn't move at all. Regardless of band.
Thus, I am convinced that something is wrong with it (it has been
moved twice since purchase). I did open the case and nothing looks out
of order. Touching the reflected meter terminals with an ohm meter
causes the reflected meter needle to jump, so it appears that the meter
itself is working.

The antenna seems to work very well for receiving. And I am able to
"get out", as it were. I can hear myself on a little SW radio I have at
14.2 MHz in AM.

Questions:

Any thoughts as to where to look for the "problem" with the tuner?

Is there another way to determined SWR with just the meters on the
transmitter (RF power out) and the forward power meter on the tuner?

You can look at the power and then interchange the input and output of the
meter to see what the swr actually is when you are not using the switches in
the tuner position but in the bypass position.
Thank I would look at the diode first to see if it good. Being a MFJ you
may need to see if any of the connections are loose. I have one similar to
that tuner and the first thing I did was open it up and tighten up all the
loose screws. Bought It new at a hamfest from a dealer and when I got it
home I noticed it making a noise when moving it around. Found a loose nut
and washer inside it.

"Thomas" wrote in message
...
Recently started to renew my interest in ham radio and so pulled out
some old equipment.



If you were getting Forward power on the meter, then the meter
movement is obviously good.

If the meter was working when stored, that
might likely rule out the most
likely failure--a bad diode in the coupler. It could be
a bad diode, but less likely. My first suspicion
would be a dirty switch contact on the Forward/Reverse switch
at this point.

Now, there is no way you are going to determine lowest
SWR with the meter the way it is. You could install the
meter "backwards", antenna to equipment side of meter,
vica versa, and that would let the meter show minimum
SWR if you had to.

Pete

Put a resistor on one of the unused coax connectors on the 949D, 100 or 25 ohms should give you a 2:1 swr.
I put a 25 ohm on my 949D and for 10 watts in read 1 watt reflected. It could also just need recalibrated, I
borrowed a friend's Bird and calibrated both the HI and LOW settings. Works better now.

73
Richard WB8KRN


Any thoughts as to where to look for the "problem" with the tuner?

73s,

Thomas

Thomas wrote:
Any thoughts as to where to look for the "problem" with the tuner?

Using low power, hook up the antenna tuner backwards so the
reflected power reading is actually indicating forward power
and vice versa. If the reflected power meter needle doesn't
move, you've got a hardware problem.
--
73, Cecil http://www.qsl.net/w5dxp



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"Thomas" wrote in message
...
Recently started to renew my interest in ham radio and so pulled out
some old equipment.

I set up a temporary antenna yesterday and connected it to my rig,
including an MFJ Versa Tuner II (Model MFJ-949D), purchased about 15
years ago.

Setting the transmitter (Icom-725) to low output power (about 10W) I
closed the CW key and the tuner indicated about 15W of forward power,
and no reflected power. That is, it "indicated" a SWR of 1:1.
Unlikely, to say the least.

The reflected power meter just doesn't move at all. Regardless of band.
Thus, I am convinced that something is wrong with it (it has been
moved twice since purchase). I did open the case and nothing looks out
of order. Touching the reflected meter terminals with an ohm meter
causes the reflected meter needle to jump, so it appears that the meter
itself is working.

The antenna seems to work very well for receiving. And I am able to
"get out", as it were. I can hear myself on a little SW radio I have at
14.2 MHz in AM.

Questions:

Any thoughts as to where to look for the "problem" with the tuner?

Is there another way to determined SWR with just the meters on the
transmitter (RF power out) and the forward power meter on the tuner?

Thanks in advance.

73s,

Thomas

Proly a bad switch or pot. Try a little switch juice.