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Author Topic: Recomended SWR meter (and tuner) for QRPp  (Read 9654 times)
KE7FD
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« on: May 17, 2014, 10:09:56 PM »

I have a Rockmite 40 (<1 watt) that works well but I'm finding that I need a way to check then tune the portable wire antenna I'm using.  I have one of the usual over the counter SWR meters but it is intended to see a bit higher wattage and does not reflect enough for me to see what is going on with the antenna.  I'd like to also have a built in tuner to eek out as much power to the antenna as possible.  I'm sure there are a few $$ units out there but I'd like to build one considering how simple these ought to be.  I could modify my existing CB type of SWR meter too.

Winder what you guys are using?

Glen - KE7FD
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OH6I
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« Reply #1 on: May 17, 2014, 11:44:10 PM »

Glen, maybe this is what you looking for:
http://www.4sqrp.com/QRPometer.php

Jari
OH6I
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K0OD
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« Reply #2 on: May 18, 2014, 12:07:32 AM »

My trusty Autek WM1 seems to measure power and SWR accurately down to a watt or a little less  (and up to 1500 watts). The product was recently discontinued after a run of many years.
http://www.eham.net/reviews/detail/139

I guess the meter to have for true QRP and QRPp fans is the Oak Hills WM2 kit (at $110)."The unit operates from 300 KHz to 54 MHz. It will measure forward and reflected power at QRP levels down to 5mW."
http://www.eham.net/reviews/detail/171

I'm interested in this thread because I'm tempted to try a CQWW CW at 100mW.

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WB0FDJ
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« Reply #3 on: May 18, 2014, 07:49:28 AM »

FWIW in the shack I use a Diamond SX-200 which has three ranges, 5 W, 20 W and 200 W. It seems reasonably accurate. If one wants to measure accurately below one watt I think you would want one of the two meter mentioned above.

Doc WB0FDJ
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N7DMA
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« Reply #4 on: May 18, 2014, 09:33:07 AM »

I use this a lot when I am portable:

http://www.qrpkits.com/sota.html

Works well with my R4020, and the Tayloe SWR led even lights brightly with my RM-20. Easy to build, and inexpensive.

The mfj-971 is also another option. I think you get some useful indication at QRPp levels, but I don't really recall. Benn a while.

Karl
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WB8YYY
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« Reply #5 on: May 22, 2014, 06:14:31 PM »

I agree also that your real need is for an antenna tuner with a sensitive swr indicator.  I use 2 different tuners with this kind of led indicator, one being a zm2 and the other a similar tuner inside a pfr3.  If you don't have a deep junkbox the sota tuner does look interesting.  Or if you run into a small tuner at a hamfest you can homebrew an led swr indicator.  The sota tuner may have enough info or I can help you by finding an earlier article.  Long term a nice qrp power meter is a good investment but not necessary to merely hook a rockmite to a wire.  Yes a tuner and sensor is whats needed.  Also qrpp power can be measured with a simple diode circuit and dvm as described by w7zoi.  I have one of these also in my stash even though I have a qrp power meter.  73  Curt
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KF4LXB
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« Reply #6 on: May 24, 2014, 12:31:56 PM »

I'll second the OH6I's recommendation of the QRPometer from 4 States QRP Group. I purchased one about a year ago. It is affordable and took about 3 hours to build. Being designed specifically for QRP power levels I think is a plus. It also acts as a dummy load.
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Christian
Albemarle, NC
EM95
http://kf4lxb.blogspot.com
AD6KA
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« Reply #7 on: May 28, 2014, 10:26:53 AM »

I have a Rockmite 40 (<1 watt)
  I'd like to also have a built in tuner to eek out as much power to the antenna as possible.
Glen - KE7FD
When using QRP or QRPp power, I'd skip the tuner and
design and build a resonant (or close to it as possible) antenna for
that band.
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W1JKA
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« Reply #8 on: May 28, 2014, 11:09:34 AM »

Re: AD6KA

I'm glad someone finally sad it. Wink
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KC2UGV
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« Reply #9 on: May 29, 2014, 06:38:58 AM »

I have a Rockmite 40 (<1 watt)
  I'd like to also have a built in tuner to eek out as much power to the antenna as possible.
Glen - KE7FD
When using QRP or QRPp power, I'd skip the tuner and
design and build a resonant (or close to it as possible) antenna for
that band.

I mostly agree with this, however, those doing backpacking with their qrpp rigs tend to look to tuners, rather than an antenna for each band Smiley
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W4FID
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« Reply #10 on: June 01, 2014, 07:00:59 AM »

I like the small MFJ that matches their 94xx series. Has a cross needle and tunes a pretty wide range. It's small and light enough.
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KE7FD
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« Reply #11 on: June 06, 2014, 07:52:15 PM »

I have a Rockmite 40 (<1 watt)
  I'd like to also have a built in tuner to eek out as much power to the antenna as possible.
Glen - KE7FD
When using QRP or QRPp power, I'd skip the tuner and
design and build a resonant (or close to it as possible) antenna for
that band.

WRT to this comment, well of course and that's what I'll do.  The wild card is that when backpacking one has to use whatever the environment provides for supports (trees, cactus, slow-moving low-altitude comets) and changing the layout of an antenna will alter its resonant frequency up or down, making the use of some kind of tuner a requirement rather than a luxury.  Even if the operator makes the effort to fine-tune the antenna out in the field he's got to lug something along like a meter so why not couple the meter with a tuner?  Many things are possible I suppose and based on the low power present coming up with a tuner should be fairly easy.  The biggest challenge I've encountered is finding a meter movement in the 50-100ua range.  Most to the CB type and above use 100-200ua movements.  If anyone has a lead on one of these, a meter would be easier to read than LED's, IF at all possible (and it may not be). 

I have a handful of small air tuning caps that would be ideal for this sort of thing and a few toroid cores that I can wind, so I'm almost there.

g
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W1JKA
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« Reply #12 on: June 07, 2014, 03:45:17 AM »

  Another QRP portable antenna without a tuner perspective: Our small group has one thing in common, we all use resonate dipoles without tuners and as some of our more than day stay locations the open space for more than one antenna set up is severely limited. Due to this I made up a Dipole feed point with 3 isolated radiator connections (about 1 in. apart to accommodate 3 bands, usually 20/30/40 meters and fed by 3 separate rg 8x feed lines. With this set up three of us can each operate on one of the three bands with our own Cubs or SWL rigs at the same time from one suspended feed point. We can experiment with each set of radiators in various configurations i.e. one horiz., one inverted Vee and one inverted L. either in plane or offset from each other to get the best results on each band.

  Bottom line is that we all have our fair share of contacts and QSOs when operating at the same time and to answer the question of what one or three SWR/tuner(s) would indicate in this situation I quite frankly tell you we don't want to know as we figure the SWR (interaction etc.) would be off the charts even with 2-4 watts output.

 
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ZENKI
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« Reply #13 on: June 07, 2014, 05:26:10 AM »

http://www.qsl.net/k/k5bcq/Kits/Kits.html

His QRP wattmeter  is one of the best around. The SWR/wattmeter has special calibration routines in it that makes it a very accurate.

Its a neat little wattmeter/SWR meter that is very accurate.
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KE7FD
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Posts: 169


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« Reply #14 on: June 07, 2014, 06:41:31 PM »

http://www.qsl.net/k/k5bcq/Kits/Kits.html

His QRP wattmeter  is one of the best around. The SWR/wattmeter has special calibration routines in it that makes it a very accurate.

Its a neat little wattmeter/SWR meter that is very accurate.

Wow, yes. Those are nifty gadgets. Might have to find my wallet..

g
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