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Author Topic: Station Test Equipment for QRP different?  (Read 735 times)
KB0KOQ
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Posts: 31




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« on: July 17, 2002, 09:05:54 AM »

  Does QRP equipment require the same test equipment as stations operating with more than 5 watts?  What about the SWR meters, Grid Drop meters, frequency counters etc?  
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WB2WIK
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Posts: 20545




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« Reply #1 on: July 17, 2002, 11:10:17 AM »

Most equipment should be exactly the same.  Frequency counters don't work by "power," they only need "voltage" to record, and usually 1Vpk is plenty.  Grid dip meters are usually used to check resonance of a passive tuned circuit that has no current flowing through it at all, thus no power present.

SWR meters and Wattmeters, obviously, need to be able to indicate with only 5W (or less) applied, and many do, so just choose those which have a low-power range.  Even my Autek WM-1, which has a 2000W forward power scale, indicates power and SWR accurately when used with 1 Watt.  Bird "Thruline" wattmeters, and many similar designs, use replaceable detector elements which have specified power and frequency ranges, and are available in 5W full scale, and lower, ranges.

WB2WIK/6
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WB6BYU
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Posts: 13028




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« Reply #2 on: September 04, 2002, 04:24:51 PM »

Many of the inexpensive SWR meters (especially those designed
for CB use) are frequency sensitive.  They work well for QRP on
the higher bands, but you may not be able to drive them to full
scale on the lower frequencies.  For example, I have a couple that
require about 10 watts full scale on 40m (still usable) and 25 watts
for full scale on 80m (with little indication at 5 watts output.)  On
the other hand, I can drive them to full scale with my HP608
signal generator on 2m, with something like 10 milliwatts.

The meters that are calibrated in watts usually use a toroid core for
the transmission line coupling, and these will give a relatively
constant indication with frequency.  The frequency sensitive ones
use conductors running in parallel with the transmission line.  If
you take the case off of the meter you can usually tell the
difference.

The other difference between QRP and regular stations is that the
power supplies don't have to be as big for QRP.
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KU4QD
Member

Posts: 59




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« Reply #3 on: October 14, 2002, 01:19:51 PM »

Mostly, as others have already said, the same accessories and test equipment should work at any power level.

One exception is a wattmeter.  You either want 5W Bird slugs if you have a Bird, or, if not... I highly recommend the OHR WM-2 wattmeter for Oak Hills Research.  It's a kit, but can be bought built and tested as well.  It accurately reads ouput power and has three scales:  10W, 1W, and 100mW.  I have several Mizuho QRPp rigs with 200-300mW of output power and this wattmeter can measure their output accurately.

72/73,
Caity
KU4QD
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