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Author Topic: Older MFJ-249 Frequency Counter Help Please!  (Read 2342 times)
NO4L
Member

Posts: 14




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« on: October 03, 2008, 02:20:17 PM »

I just acquired a MFJ-249 (the older model with the
frequency readout).  My question is specifically about the Frequency Counter (not the frequency readout during SWR tests).  

I have run a few tests using the frequency counter.
First, turn unit on, attach short wire or bnc duck antenna (Diamond RH77A).  Change input mode to 'B' for use of the frequency counter.  I put the unit close to a FT-1500 and transmit on simplex -- display on MFJ-249 doesn't do anything, and stays at 0.00000.  Then, releasing the ptt the MFJ-249 seems to be transmitting a tone as the FT1500 will now lock up on the same frequency
 146.445. Hmm, strange right.  

Now here's another rub:  if I switch the unit over to A mode for SWR readings the ~146.445 comes up on the counter.  BUT LET ME RESTATE, the frequency counter doesn't do squat in B mode.

Another test I did was to take a short wire, wrap it from the center of the bnc (frequency counter) jack to a coaxial cable connected to a scanner -- coiled it around the coax several times.  Tuned to NOAA 162.425, nothing, but the scanner starts picking up some signal from the MFJ-249 on the same frequency causing similar  issue as above.  During this test I did get a tiny bit of a reading on the display, but only .000500 or something close then back to all zeros.

Anyone with an older MFJ-249 or MFJ-259 that is an aficionado using the frequency counter part of this unit please let me know.  I'm willing to try some more testing.  I've read that the freq counter of these units are somewhat insensitive, could that be the case here?

Note: The SWR portion of this unit seems to do it's job well so far.

Thanks In Advance!
Rob
K4IXE
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KR4PC
Member

Posts: 2




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« Reply #1 on: September 01, 2013, 10:58:26 AM »

I was web searching on this same subject and found a manual for a MFJ 247 which interestingly enough says:

"If you want the use the counter to measure other than the 247's oscillator, attach a counter probe or a piece of wire to the BNC connector at the top right of the case.

NOTE: The sensitivity of the counter is about 600mV.  A "TIMES 1" probe must be used unless you are measuring a very large signal."



FWIW.  Probably has similar innards to the 249.

http://www.mfjenterprises.com/support/MFJ-247/MFJ-247.pdf
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K2OWK
Member

Posts: 1072




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« Reply #2 on: September 01, 2013, 02:28:23 PM »

Send me your E-Mail address and I will send you a copy of the page that covers this information.

73s
baracaro@bellsouth.net
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