[Elecraft] OT: For New Hams, How to Tell What an Amp Will Do For Your Signal

[David Gilbert]

I guess I wasn't particularly clear, or maybe I just didn't say it often 
enough.  If you are competing against other hams, such as calling CQ in 
a contest or calling DX from within a pileup, EVERY db counts no matter 
how good the propagation is.  An amplifier will often win the day for 
you even if you can hear the other guy while he's running QRP.

The same situation exists if it is noisy on the other end of the path, 
where as little as two db will make the difference between clear copy 
and no copy.  Check the files on my website if you don't agree.  The 
problem is ... the noise level on the other end may be significantly 
different than the noise level on your end.  Just because you can hear 
him doesn't mean he can hear you.

More importantly, propagation doesn't open up to the same path loss each 
day ... some days 5 watts gets the job done and some days even 1500 
won't cut it.  And just because you can hear F5XXX running 5 watts 
doesn't mean that you can hear PA3YYY unless he's running 1500 watts.

My point is that EVERYTHING is situational and generalizations don't do 
newcomers many favors.

Dave   AB7E




On 3/22/2013 8:34 PM, Ron D'Eau Claire wrote:
> Yes. An amp that takes you up 10:1 in power, e.g. 20 watts to 200 watts or
> 100 watts to 1,000 watts, makes a 10 dB difference in signal -- just a bit
> over one S-unit.
>
> I pointed out the beacon resource as a good example of how often that extra
> power is not needed on H.F., especially for narrow bandwidth modes.
> Otherwise we would not have QRP enthusiasts using simple verticals with DXCC
> awards.
>
> I liked the idea that new Hams can listen to the beacons themselves and
> decide whether the power difference is all that important.
>
> 73, Ron AC7AC
>
>
> -----Original Message-----
> That's a good resource but it doesn't tell the whole story.  An amplifier
> will give you around 10 db improvement in signal on the other end.  That's
> more than the difference between a dipole and a five element monobander.  As
> little as 3 or 4 db will make a significant difference when competing
> against others in a pileup, and of course as little as 2 db can make the
> difference between no copy and clear copy if your signal is right at the
> noise level.
>
> http://www.ab7e.com/weak_signal/mdd.html
>
> Hams have turned their noses up at amplifiers for decades, but the reality
> is that an amplifier and a decent vertical is often a more cost effective
> way to put out a good signal than is low power to a tower and big antenna
> ... especially if you live in a low noise area where you don't need lots of
> discrimination to hear DX (and even then there are compact receive loops
> that make possible alternatives).
>
> Dave   AB7En 3/22/2013 12:49 PM, Ron D'Eau Claire wrote:
>> For the newer hams, here's an interesting resource that will
>> demonstrate to you what a DX signal sounds like at 100 watts, 10
>> watts, 1 watt and 0.1 watt. All you have to do it tune into the beacon
>> frequency of 14.100, 18.110, 21.150, 24.930, 28.200 using CW mode and
>> listen. The beacon stations in 18 countries take turns sending call
>> signs and 4 dashes, each dash in descending power level. You might be
>> amazed at how often you can hear 10 watts or less clearly from half
>> way
> around the world when the band is open.
>> When the band is not open, a kilowatt doesn't get through.
>>
>> A complete list of the stations, locations and the transmission
>> sequence is
>> at:
>>
>> http://www.ncdxf.org/beacon/beaconSchedule.html
>>
>> IIRC, all of the stations use a simple 1/4 wave vertical antenna.
>>
>> I'm not saying that an amplifier isn't useful, but this helps put the
>> advantage of having one in perspective.
>>
>> 73, Ron AC7AC
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