[TowerTalk] RE: RS Digital HF Power Meter...

[Hsu, Aaron T.]

I first saw the meter at the ARRL SW Convention in 1995 (on the Queen
Mary).  I remember the Radio Shack booth and picking up info on the
meter and the "new" 2m mobile rig.  Looked interesting at the time and I
picked one up a few months later for $79.

I sent the following e-mail to someone last January.  I'm forwarding it
here due to interest in the meter...

  - Aaron

**************************

> Lawrence,
> 
> I picked one up a year ago and it's been collecting dust ever since.
> For the $$$, it's a pretty decent unit, but it does have a couple of
> problems...
> 
>   - Peak hold time is too short for CW or SSB.  It was obviously timed
> for constant carrier applications.  You'll get a reading, but you need
> to be quick to read it.  If you're doing 13+ WPM on CW, then it should
> hold long enough.
> 
>   - The connector for the remote sensor is NOT weatherproofed nor does
> it look like it was designed to be.  Just tape it up well or use lots
> of putty sealant or silicone.
> 
> There were also a couple of other "minor" problems, but I don't
> remember what they were.  On sale for $59, it's not really a bad
> deal...sorta like their DSP (had one of those too...until I tried
> transmitting at more than 10 watts HF... not very well shielded at
> all!  Got a Timewave instead).
> 
> A while back, one of the design engineers of the unit appeared on one
> of the HAM usenet or mail reflector groups.  He asked for opinions of
> the unit and I had a BUNCH of questions for him.  I wish I saved that
> mail, but I do have some of his responses.  I've included them below.
> Basically, I asked what the accuracy would be above HF (seems pretty
> good on 6M) and if there were any mods possible with the unit (to
> increase peak hold time).  Accuracy was based on freq and power levels
> and the firmware was masked on a custom ROM, no mods possible.  You
> might want to e-mail him and ask his opinion of the unit.
> 
> Try it for $59.  If you don't like it, return it on the 30-day return
> policy.  Couldn't hurt!
> 
> 73!
> 
>   - Aaron Hsu, KD6DAE
>     athsu@unistudios.com
>     dae@pacbell.net
> 
> 
> ps.  Below is e-mail from Doug, the engineer...
> 
> -----------------------
> 
> Actually, we did test this with SSB before code release.  We left it
> as RS
> OK'd it. Looking back it would have probably been a good idea to field
> test
> this with lots of hams to get more comments before we went to
> production.
>  Unfortunately, we never did this really for any product our group
> designed,
> RS always had really tight schedules to be able to meet catalog
> release.
> 
> Thanks for the feedback.  I am wondering what's on the addendum since
> it was
> obviously released after I left in December.
> 
> Regards,
> 
> Doug
> KA8CTL
> 
> --------------------------
> 
> ALL of the timing for the meter is done in software, so there is
> really no
> way to change to peak hold time.  I kept changing the timing until
> Radio
> Shack Engineering OK'd what they liked.  Unfortunately it beginning to
> look
> like quite a few hams don't like it.  I wish I could could offer a
> software
> fix, but the micro is a masked Samsung part and there are no
> one-time-programmables available.
> 
> I don't know what the power accuracy is at 2 or 6 M.  We only had
> equipment
> when I was at Tandy to check this over the HF bands.
> 
> Althought the power accuracy is spec'd at 10% of full scale this isn't
> really
> the best the meter can do.  The meter is calibrated at 1, 5, 10, 100,
> 500,
> and 1000 W in both the forward and reverse directions at the factory.
> This is
> stored in EEPROM and then used to interpolate the power reading during
> normal
> use.  What this means is that the accuracy is pretty much as good as
> the
> calibration (at those points).  If you were to calibrate using a 1%
> reference
> meter, you could probably get the overall accuracy at those points
> down to
> 3-5%.  The accuracy in between would be a little higher. Unfortunately
> getting that good of a reference meter is really difficult.  Just for
> reference, we looked at the $199 Daiwa meters and they were spec'd at
> 12%
> worst case.  I won't tell you how bad the other RS wattmeters really
> are over
> the HF bands.
> 
> Hope all this was helpful (or at least informative).
> 
> Doug
> KA8CTL
> 
> 

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