[Amps] Time for New Power Meter

Jim Thomson jim.thom at telus.net
Tue Apr 28 06:29:51 EDT 2015

Date: Mon, 27 Apr 2015 07:28:00 -0500
From: Steve Lott <lottsphoto at gmail.com>
To: Jim Garland <4cx250b at miamioh.edu>
Cc: amps at contesting.com
Subject: Re: [Amps] Time for New Power Meter

I have and highly recommend the LP-100A


##  I have two of the array solutions couplers..and four
of their displays.   Each pair of displays is bolted together
which can then be rack mounted.   One pair can go in the
shop, and the 2nd pair goes into the shack.   You can easily
parallel two identical power master displays, they both always read
identical info.   I did it that way so I can read the power input into an
amplifier, and also on the output of the amplifier.   A couple of the hb
amps  are too noisy for the shack, so reside in the shop. The remote
pair of displays allows for tuning in the shop.   A simple footswitch 
and  variable negative dcv on the alc buss back to the xcvr, allows
varying the power of the xcvr...while tuning in the shop next door. 

##  what ever wattmeter you end up with, make sure it has provisions for 
high swr shut down.   I looked at the alpha wattmeter years ago, and at the time,
it did not have high swr shut down.   On the array solutions power master couplers
and mating displays, you can shut things down three different ways..due to high swr.
A- open off key line to amp.   B- apply a few volts..negative, to the ALC buss on the xcvr,
and C- apply an inhibit condition, usually either a grnd or 13 vdc onto the xcvrs TX inhibit lead.
The high swr alarm can be set to 1.5:1   or  2:1   or  2.5:1   or  3:1...or OFF. 

##  with two displays in parallel, I can use any two of the 3 schemes described.   There is also
other features, like low or high power alarms.  It has enough smarts so that it doesn’t see a low
power alarm when the vox drops out, and u are on rx.  Switch amp to stand by, trip vox, and it will  trip the
low  power alarm.   Drive the amp too hard, and you can have it  trip the high power alarm. 

## With 1 watt display resolution on the numerical display, when above 100w ...and  .1 watt  resolution
when below 100 watts, its plenty good enough.    The auto ranging bar graph works superb. Makes tuning
any GG amp up real easy, just peak for max bars.  Same  bar graph can be used  in SWR mode.  
This makes tweaking ant tuner a snap.  Just tweak until bar graph  dips, and minimum bars displayed. 
Plug the powermaster  displays into a pc, and now you can read the gain of the amp, since you know 
the drive applied and also the power output.   You can also read rvs watts. 

##  heres what you cant do,.,,, at least on the older ones I have.  You cant read average power, only pep on
ssb / cw .... or cxr power on FM and AM..and pep AM., when modulating an AM .   IE:  switch on the
processor on ssb mode, and you cant see the increase in average power..meanwhile pep stays the same. 

##  they are  calibrated to nist standards.  Each coupler has a label with the correct 
forward and rvs  calibrations on it.  Each coupler is individually calibrated.   The frwd and rvs calibrations 
can be tweaked in 1% increments, from –15%...to +15%.      They provide for two sets of calibrations, one for
160-10m...and the other is for 6M  band.   The 10kw coupler doesn’t cost much more than the 3 kw coupler,
and both cover 160-6m.    You can get couplers with any connector you want.   I use SO-239 on the 3 kw
couplers....and  7-16 DIN on the 10 kw couplers. 

##  My bird and coaxial dynamics meters  are used very little these days.   Good to haul to top of tower to
take a power reading, and also to read average power, that’s about it.  

later.... Jim  VE7RF   

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