MFJ849 meter

clucas6308

Newbie
Joined
Jun 21, 2015
Messages
3
Hello all,

I have been struggling with high SWR readings. While ohming out cables I found continuity between the center and the outer threads on the bare meter. no continuity on the VHF side. Also I had continuity on the center and outer shield to the antenna, Maco 5/8v. Do I need to set the meter to higher resistance?

Thank you.
 

clucas6308

Newbie
Joined
Jun 21, 2015
Messages
3
Update, the Maco 5/8V has continuity between the center and outer threads of the SO connector. Should it be like this?
 

WA0CBW

Member
Joined
Dec 8, 2011
Messages
1,355
Location
Shawnee Kansas (Kansas City)
Set the meter for continuity (lowest range). The 5/8v may have a matching network (loading coil at the bottom) which would show continuity from center conductor to shield.
 

majoco

Member
Joined
Dec 25, 2008
Messages
3,609
Location
New Zealand
A loading coil is in series with the antenna - it should show open circuit. A 5/8 wave antenna has a matching coil ( and maybe a small capacitor) with a tap for the feeder, the bottom end to ground and the top to the whip. Go to your antenna and disconnect it - disconnect the VSWR meter too. From the bottom measure the resistance from shield to the centre conductor - it should be open circuit, high resistance or whatever your meter shows for open circuit. Now go back up to the antenna and short the shield to the centre with a clip lead or something. Now go back down to the bottom and check for zero or very low resistance, hopefully less than 10 ohms - NOT the characteristic impedance of the cable. If you're going to transmit then you should have a 50 ohm load suitable for VHF or higher depending on your use - connect that to the top, measure it's resistance from the bottom - should be 50 ohms plus the cable resistance. Reconnect the VSWR meter and transmit into the dummy load to check the VSWR - it should read very low, less than say 1.2:1. Don't exceed the power rating of the dummy load. Reconnect your antenna and read the VSWR - if it's not very low then we now know that it's the antenna that's suspect - not the cable or the VSWR meter.
 
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