Internal SWR meters......accurate or not?

I noticed that the internal SWR meter in my CRT-SS9900 was giving consistently low readings so I decided to test it against my antenna analyser. I took SWR readings on channels 1, 20 and 40 on low-band, mid-band and high band with the internal meter and then repeated the tests using my analyser. These are the results:

                                 INTERNAL SWR METER         ANALYSER
LOW BAND:  Ch. 1                1:1.0                             1:1.3          
LOW BAND:  Ch. 20              1:1.0                             1:1.3
LOW BAND:  Ch. 40              1:1.0                             1:1.3
 
MID BAND:   Ch. 1                1:1.0                             1:1.3
MID BAND:   Ch. 20              1:1.0                             1:1.4
MID BAND:   Ch. 40              1:1.1                             1:1.5

HIGH BAND:  Ch.  1               1:1.1                            1:1.5             
HIGH BAND:  Ch.  20             1:1.2                            1:1.7
HIGH BAND:  Ch.  40             1:1.3                            1:1.8

The readings from the internal meter were all taken in FM mode with 15 watts power input. The analyser is a RigExpert AA-30 and readings were taken at the radio end of the feeder (approx. 5 metres of Mini 8 coax). The antenna is a half-wave Double Bazooka (horizontal). As you can see there is a difference in the results, some of them quite significant. Has anyone else tried this test and if so, what results did you get?

Hi Phil,

I'm not at all surprised with your results and seeing differences like you have, you'll also see differences if you tried an external SWR meter too.

If you tested the rigs SWR readings and the analyser with a 50 ohm dummy load you'll probably get results similar to each other but again not guaranteed.

My own HF rig has a built in SWR meter and even when calibrated will give readings slightly different from an external SWR meter. I don't tend to worry about it using it more as an indicator than anything. If I have a SWR of less than 2 I know everything is good, start worrying & checking if the SWR starts hitting 3 and won't transmit if over 3. Luckily the rig winds down output if a big SWR is present.


I personally wouldn't overtly worry about it and neither should anyone else really, it can all become a bit compulsive, (like the elusive perfect 1:1 SWR )

For my own preference I rate my SWR accuracy as Rig - lowest, SWR meter - more accurate, MFJ Antenna Analyser - most accurate.


There's an old guitar joke that comes to mind....

(Question) How do you keep two guitarists in tune & time with each other?
(Answer)    Shoot one of them!

It's only when we start comparing that we actually notice these things.


All the best,
Victor

I would go with the RigExpert every time over the inbuilt jobby.
And as Victor say's anything under2 is ok but i know everybody wants that 1to1 but it's hard to get(but doable lol).

Yes, well said swr of 2.1 or under, enjoy the radio and relax and chat away the day.

When my antenna analyser arrived and I started using it I noticed the exact same thing but I recalled the topic being discussed on here previously in regard to a linear I think it was and the fact that everybody had experienced the very same thing left me feeling very reassured that everything was quite normal.
The important thing is the SWR protection has kicked in when required on a couple of occasions giving me an instant warning that all was not well, allowing me to search for the fault and rectify it before trying to transmit for an extended period.
Like yourself, I found the analyser far more sensitive than either my external SWR meter or the ones in my radios, and they are tiny increments it is understandable that there would be a little variance between meters I feel.
It looks like your double bazooka has good bandwidth no trouble getting down to the lower bands with that.

Alan - Mirror Man wrote:

It looks like your double bazooka has good bandwidth no trouble getting down to the lower bands with that.

Yes....I did an SWR scan of the analyser's whole frequency coverage and the SWR stayed below 1:2.0 all the way from 24.963 mhz to 27.931 mhz !! The internal meter gives much higher readings at these extremes so I'm wondering if they're only designed to be accurate on the "official" CB frequencies.

I think the answer is they just arent quite as accurate but they seem to give a good enough guideline and let you know when all is not well which is the main thing.

Victor wrote:

Hi Phil,

I'm not at all surprised with your results and seeing differences like you have, you'll also see differences if you tried an external SWR meter too.

For years I used an inline LED SWR meter in the field using VHF. 160(ish) MHz
Tuning a simple tripod vertical until the LED went out.

Accuracy wasn't exactly great and better at night as you could see the LED dim to almost black.

Checking it against a meter in ideal conditions, it was usually between 1.5 and 2. If it wasn't pouring with rain.
PaulGray

Love those little LED SWR indicators Paul and they're usually good enough for a quick check.

Somewhere I have a little three LED unit, SO259 either side and handy as heck for a quick field test. So small and handy I can't find the damn thing!

I did build it though so suppose I could ways construct another, but you can bet I'll find it the moment I build another!!!

Funny you should say that, I couldn't find mine after I thought of adding a picture of it in my post.
Happy Days. At least I haven't lost my soldering iron!

For me in built SWR meter is just useful for telling if you have a problem.  If it's reading very high then it's obvious something is wrong.   But I wouldn't rely on it for tuning my antenna.

Mine seems pretty accurate compared with my external meter but who’s to say that one is accurate?

26uk81 wrote:

For me in built SWR meter is just useful for telling if you have a problem.  If it's reading very high then it's obvious something is wrong.   But I wouldn't rely on it for tuning my antenna.

I agree with Chris.

When out mobile/portable, I use the internal meter as a guide.

If the SWR reading goes high, check the antenna, plugs & cables