Antenna Analyzer vs SWR meter issue

[Dart]

I've been helping a buddy of mine set up a small base station. We put up a brand new (NOS) Shakespeare Big Stick and used new LMR-400 coax.

The two analyzers (MFJ-259b and the Sark100) both read the SWR at 2.2. The Vectroniks and PDC SWR meters both read the SWR at 1.2.

Four devices and its two against two. What would cause the analyzers to read higher? Bad ground? Reflect? Why wouldn't the SWR meters be able to "see" this problem?

Any advice or insight would be appreciated.

 

[sp5it]

Connect measurement devices via 180 degrees coax jumper or plug it just under antenna. Repeat measurement.
Also it is more than sure, that those SWR meters are crap. Connect 100ohm resistor instead of antenna and tell us what is SWR reading.
Mike

 

[vkrules]

Could be as simple as a bad patch cable, or CMC on the line causing the swr to change with the additional length of the patch cable. ( so you better check that ground).
What does the complex impedance look like? "J" value is pretty high I'm guessing.

I agree with Mike. Trust the two analyzers!.

 

[BBB]

Non-Calibration Certification. I would maybe trust the MFJ the most out of the 4?

This bad boy bird comes with an app:

http://birdrf.com/Products/Test and Measurement/Analyzers/Cable-Antenna-Analyzers.aspx

 

[vkrules]

Actually the sark is pretty good .Especially after you have done the multipoint calibration procedure as well as checked the frequency !

Of course it aint going to compare to the Bird.

 

[dennis4040]

Non-Calibration Certification. I would maybe trust the MFJ the most out of the 4?

This bad boy bird comes with an app:

http://birdrf.com/Products/Test and Measurement/Analyzers/Cable-Antenna-Analyzers.aspx

I use a Rig Expert 600 analyzer and a very accurate Lp-100A SWR/Power meter.
The Real RF readings with the meter are nearly always lower than the analyzer readings. Especially if the antenna is not very high off the ground. I have read that this is not so unusual but I really don't know the explanation for it. That being said your variance is a bit more than I usually see.

 

[StrangeBrew]

Are you using the same jumper between the meter and antenna as you are using with the analyzers?

 

[Mustang 131]

I've had 2 MFJ's go bad on me over the years. I only trust my bird for fine tuning.

 

[Dart]

Yes, same jumpers with nothing changed.

 

[HomerBB]

In simple terms use a 11.25' RG58 jumper, or a 15' LMR400 jumper with the analyzers, or multiples of those lengths, or else attach the analyzers directly to the antennas as has been suggested.

Unless attached directly to the antenna feed point you'll get your most accurate analyzer readings with electrical half wave jumpers.

Once you've done that trust the analyzers and make adjustments to the antenna to obtain a good match.

 

[sp5it]

...or get good measurement device capable to "exclude" any coax length from a measurement.
Mike

 

[bob85]

sounds like it could be a cmc issue,
the battery powered analyser has no path to ground,
when you hook the radio jumper & meter up you change the common mode impedance of the system,

try winding a choke in the coax to see if it effects vswr or add an extra jumper a few feet long with a barrel connector & see if that effects vswr,
if either changes vswr more than a fraction you have cmc on the braid.

 

[psycho]

Are you using the same jumper between the meter and antenna as you are using with the analyzers?

Analyzers don't need jumpers.

 

[Road Squawker]

Analyzers don't need jumpers.

???? then what am I supposed to hook up to the UHF connector on mine?

 

[Captain Kilowatt]

Analyzers don't need jumpers.

Only if you can connect them directly to the feedpoint which is the ideal place. Same thing applies for meters too actually. Question..... How would YOU connect an antenna analyzer to an antenna if it was not possible to reach the feedpoint? Answer......With a coaxial jumper.