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Author Topic: qrp vs. 100 watts  (Read 1154 times)
VK4TJF
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Posts: 100




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« on: January 07, 2013, 08:09:34 PM »

in a situation that is less then ideal here is the question
what is better 100 watts through a less then effective antenna ie.. gap antenna that is a vertical dipole that is only about
half the wave length than it should be
or say 10 watts through a proper vertical dipole that is actually 20 meters in height and is away from nearby dwellings?
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KB5ZSM
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Posts: 70




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« Reply #1 on: January 07, 2013, 10:03:02 PM »

I wish I had more info., but my choice would be 10 Watts to a properly resonant antenna as long as your feedline isn't really long ("is away from nearby dwellings").
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N4CR
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« Reply #2 on: January 07, 2013, 11:36:20 PM »

It's impossible to tell. Try both and see what the differences are.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
AC5UP
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Posts: 3955




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« Reply #3 on: January 08, 2013, 02:21:15 AM »

Everything works.

When you remember the difference between 10 and 100 watts is 10 dB, then recall that band conditions from one day to the next can vary by 20 dB or more, you realize power and antenna efficiency are only part of the consideration.

Then there's the concept of receive capability..........  If it was my choice I'd likely go with the full sized antenna if only for the ears.
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M6GOM
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« Reply #4 on: January 08, 2013, 07:07:23 AM »

The difference between a GAP and a full length dipole won't be 10dB. At best it'll be around 3-4dB. 100W over 10W is 10dB.

Now I know it is reciprocal with the antennas but a 3-4dB difference on receive at your end is around half a S point.
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KE3WD
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« Reply #5 on: January 08, 2013, 07:15:09 AM »

Mode of operation can also make a huge difference. 

For example, use of CW mode can often make a lot more contacts on the same day and hour where use of SSB voice might not work so good due to noise, propagation, etc. 

I love qrp CW, qrp phone, not so much.  Got better things to do with my time than yellin' at a mic and repeating my callsign over and over. 


73
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K6AER
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Posts: 3535




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« Reply #6 on: January 08, 2013, 11:41:44 AM »

There are a lot of variables going on. A good antenna up high will receive and transmit with a lower angle of radiation and the noise level will be much lower. I doubt you will pick up 10 dB (amplifier increase) on the transmit signal. If your signal is marginal the amplifier will greatly help the fella at the other end who generally has a high noise level if they live in the city or the burbs.

Running a 100 watts on a CQ will yield about 50% reply ratio. Turn on the amplifier and they are 4 deep on the call back. I am lucky and live in the country and have no noise to contend with.

If you are antenna space limited and have a lower noise level the amplifier will be the best way to go. With the amp there are other problems. AC power for the amp, RFI and upgraded components in the coax and antenna system.
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