Comparing Meter Accuracy

[shortride]

Got a question about SWR meter accuracy.

I don't know if this is one of those, "you get what you pay for" situations or just the fact that there can be noticeable differences between meter accuracy. I've got a new Dosy 4002 PSW and a new Daiwa CN-801 meter. Comparing the 2 meters on SWR only, the Dosy indicates a 1.3:1 and the Daiwa CN-801 cross needle meter indicates just under a 1.1:1 reading. The needle barely moves. I realize .2 to .3 reflected power is not much difference as far as radio performance goes but I didn't think there would be that much difference between meters.

Which meter would you guys guess would be the closest to an accurate reading?

 

[rfradioconsult]

The Dosy meter appears to be aimed toward the CB market, as such it's accuracy on 2meters would be questionable.

 

[LtDoc]

Actually, accuracy isn't very important with SWR. If it's something on the order of a single decimal point difference, really, what difference is it going to make? I like 'cross-needle' meters, they tell you a lot with just a glance. If the reflected power is the lowest you can get it, that means it's the lowest SWR too. That's what people are after, right? No user calibrating mistakes, simple to read, etc, etc. SWR is the relationship between forward and reflected power. As long as the reflected power is as close to nothing as you can get it (no matter what it is), that's as good as it get's till you 'fix' the problem. An SWR meter can't tell you where/what the problem is, only that there is one, IF you know how to read and interpret the @#$ thing.
- 'Doc

 

[beachmark]

Guessing which is more accurate is close to a 50-50 bet. Both have detectors and couplers that will typically have their largest inaccuracies at low levels. The power at which you test can have an effect; low power will typically be less accurate. You would be better testing at higher powers if you are not already.

 

[dgmaley]

SWR Reading

Never check the performance of a SWR meter on an antenna. Check it on a known good dummy load with known good cables. The hardest thing for a meter to show is a perfect match. If you have a meter that can show power near full scale on forward and not even move on reflected when into a dummy load, you have a keeper.

Dave...

 

[shortride]

Thanks for the tips guys. I do have and use a dummy load. The only thing I had a question about was how much difference there was between the two SWR meters. My dummy load indicates a 1.0:1 and the Dawia meter is reading 1.1:1 SWR.