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Author Topic: Macaw DPM-1 SWR Meter  (Read 4996 times)
KD5HJF
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Posts: 1




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« on: August 13, 2007, 02:40:54 PM »

I have a flea market special DPM-1 SWR meter from MACAW.  It doesn't have a "set" position on any switch.  On the SWR switch it has two positions, FWD and REF.  I've been setting it on FWD then using the SENS (sensitivity?) control to set the meter needle to the far right "set" position.  Then I switch back to REF (reflected?) and measure the SWR. Does that sound correct?  The only other seitch is the power level switch which has settings for 20, 200, & 1000 watts.

Thanks for any help.

Steve KD5HJF
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K7KBN
Member

Posts: 2805




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« Reply #1 on: August 13, 2007, 02:52:05 PM »

That sounds right - you only use the right-hand meter for all of this - the "SWR SENS" knob adjusting shouldn't affect the power reading on the left-hand meter at all.
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73
Pat K7KBN
CWO4 USNR Ret.
KC8VWM
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Posts: 3119




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« Reply #2 on: August 13, 2007, 04:02:35 PM »

Correct.

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K8DFI
Member

Posts: 22




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« Reply #3 on: April 27, 2013, 07:35:13 PM »

My question on this meter is: Once you set the forward position, (1) Does this "set" position give you an accurate SWR reading in the  reflected position. (2) If your SWR is high, adjust the antenna to get it as good as possible, then when it is good , do you then just remove the meter and hook the antenna directly to the radio?
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David
K8DFI
WB6BYU
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Posts: 13281




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« Reply #4 on: April 27, 2013, 08:03:42 PM »

Quote from: K8DFI

My question on this meter is: Once you set the forward position, (1) Does this "set" position give you an accurate SWR reading in the  reflected position.



It should, as long as you don't change the band or power level.  (If you do, you have to
readjust the "set" control.)

That assumes the meter is properly working.  Many of the inexpensive SWR meters are quite
frequency sensitive:  I have one that takes 25W to reach full scale on 80m, but only about
20 milliwatts on 2m.  Unless the meter or the diodes have been burned out (certainly known
to happen when too much power is run in the low power position) then one or the other
setting might not be functional.

The meter might also not be adjusted correctly:  to check, measure the SWR then reverse
the meter connections.  Set the meter to REV, adjust the "set" control to full scale, switch
back to FWD, and see if you get the same SWR reading you did the other direction.

(That doesn't guarantee it is working, but should give about 90% confidence.)

Note that meters do have a frequency range outside of which they lose accuracy.  I've used
the cheap CB meters on 80m through 2m with reasonable results, but couldn't generate
enough power to get a useful reading on 160m unless the antenna was already matched,
and the readings were totally bogus on 440.



Quote

(2) If your SWR is high, adjust the antenna to get it as good as possible, then when it is good , do you then just remove the meter and hook the antenna directly to the radio?



You can take it out of the line if you want, but you don't have to.  On HF I usually leave a meter
in the line to monitor my SWR, especially when I am using a tuner.  On VHF I usually remove it,
as my antennas usually are more reliable.
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K8AXW
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Posts: 3860




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« Reply #5 on: April 27, 2013, 08:10:09 PM »

I always leave my SWR in the line to monitor SWR.  Never understood taking it out and having it just setting there.  The more stuff that is lit up and or moving, like needles, digital readouts, the better!   Grin
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