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Author Topic: Amplifier for QRP Rigs  (Read 1616 times)

RadioRay

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Amplifier for QRP Rigs
« on: April 19, 2013, 08:49:05 PM »
By definition, in CW (Morse code) , hams refer to running 5 Watts or less as 'operating QRP'.  I love running low power and Gil and I have a regular sked from Virginia to Florida.  He has run as low as .100 Watt (100 milliWatts), but usually runs 3.5 to ten Watts, depending upon what rig he decides to use that day.

However, there ARE times when it's handy to have a station running some power, like when the fellow you have a sked with , lives in a city, possibly in an apartment, and local electrical noise is high, so it HELPS him if he can have a more powerful signal to receive through the noise.  The great thing though is tht you do NOT need to buy a BIG rig for power and then use your great QRP rigs onyl when it's easy.  I just built a 140 Watt amplifier, from kitted components bought from Communications Concepts Inc.  This is not a kit, in that you do not have detailed instructions.  There is a quick 'cheat sheet' and the manufacturers' application notes to build it by.  However, I just fired it up on ONLY 20 meters tonight and yes -  it is absolutely working! Listening on internet web receiver, I gain roughly two to 2  1/2 S-units on a distant receiver.  That makes a huge difference when there is noise.  I plan to make the other output filter modules for other bands and then put it all into a metal box for easy use.  However, this means that my QRP rigs, with their fine receivers and etc. now become my 'Big Rig'!  It's THRIFTY too!


>de RadioRay ..._ ._
« Last Edit: April 20, 2013, 02:22:49 AM by RadioRay »
"When we cannot do the good we would, we must be ready to do the good we can."  ~ Matthew Henry

cockpitbob

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Re: Amplifier for QRP Rigs
« Reply #1 on: April 19, 2013, 10:05:17 PM »
I've considered going the route of QRP with an amp when needed.  It makes a lot of sense and can be cheap. Ramsey sells 20W single band amp kits for $45.  Granted 20W isn't much but when you are working with 1W Rockmite it is a 20X (13dB) increase.  Reviews say the heatsinks are too small, but other than that they work.
 
The 35W HF Packer-amp seems close to ideal for semi-QRP operations.  It does all bands and has low standby current.  But at $260 for the kit, it isn't cheap.
 
Lots of options and not enought time to play with them all  ;D 
« Last Edit: April 19, 2013, 10:14:27 PM by cockpitbob »

Joe

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Re: Amplifier for QRP Rigs
« Reply #2 on: April 19, 2013, 10:12:17 PM »
Have been running the idea of a amp for QRP around for a few days since I ordered the Rockmite kit. Once I get the rig and accessories built. That will be my next project. I am looking at the Ramsey that cockpitbob sugested. But may just build one complete myself.

RadioRay

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Re: Amplifier for QRP Rigs
« Reply #3 on: April 20, 2013, 01:15:47 PM »
Hey Joe -

You might take a look at the reviews of the Ramsey amplifier first.  There are some good and many bad.  You mileage may vary.  The basic design is soud, but many people have found that they needed to redesign the input stages for stability.


>>>  BTW - I have a GREAT contact with Gil (from this form) from his campsite in Florida today, using my QRP rig and this home brew amplifier.  IT's not in a box, spread all over the table top and looks like a total mess - yet Gil reported that I had a 'Big Signal'.



>de RadioRay ..._ ._

Ps. Now to install it into a case.  Likely a Pelican case for protected portability.
"When we cannot do the good we would, we must be ready to do the good we can."  ~ Matthew Henry

Joe

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Re: Amplifier for QRP Rigs
« Reply #4 on: April 20, 2013, 08:54:04 PM »
Thanks RadioRay

I am not set on anything, and after looking closer at the Ramsey I think the money would be better spent building one. I have been looking at Communication Concepts web site, looking at what all they have. It will be about two months before I get around to the amp build. I have holsters to make and guns to fix for some friends, so spare time is kind of short.

I will post what I have come up with to get feed back, To make sure I am on the right path. The wife gets mad when a smoke test doesn't work out to well and I stink up the house.

73 Joe

RadioRay

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Re: Amplifier for QRP Rigs
« Reply #5 on: April 20, 2013, 09:40:12 PM »
Hey Joe,

Please do let us know.  The idea of the QRP rig for portable and the amplifier for when you can afford more power consumption, is a good one and adds a lot to your radio.  It's also a great way to build-up a station in modules: transceiver kit, amplifier kit and etc.  The Ramsay kit is attractive for that price.  I don't know that I could buy the parts for it at the price they sell them.  Just about any QRP kit with that 20 Watt amp would be a good combination with a simple, dipole antenna in the trees.


>Ray
"When we cannot do the good we would, we must be ready to do the good we can."  ~ Matthew Henry

KC9TNH

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Re: Amplifier for QRP Rigs
« Reply #6 on: April 20, 2013, 10:48:13 PM »
>>>  BTW - I have a GREAT contact with Gil (from this form) from his campsite in Florida today, using my QRP rig and this home brew amplifier.  IT's not in a box, spread all over the table top and looks like a total mess - yet Gil reported that I had a 'Big Signal'.
+1 - sounded good. Easy copy.

gil

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Re: Amplifier for QRP Rigs
« Reply #7 on: April 23, 2013, 10:49:10 AM »
Ray, you sounded very good on 20m. Too bad I didn't have an S-meter. On 40m, your tone sounded like an alarm clock buzzer... Weird... I'm sure you'll figure that one out  :)

Gil.

RadioRay

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Re: Amplifier for QRP Rigs
« Reply #8 on: April 23, 2013, 11:51:19 AM »
On forty, I was using the 746PRO from the county.  I found the antenna switch on the 20m HalfSquare antenna, so it was probably a severe antenna mismatch that the 'tuner' took care of as far as SWR, but not stray RF.


Glad to know that the home brew amp works well!


>Ray
"When we cannot do the good we would, we must be ready to do the good we can."  ~ Matthew Henry

cockpitbob

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Re: Amplifier for QRP Rigs
« Reply #9 on: August 13, 2014, 11:02:58 AM »
It's been a year.  Anyone doing anything with amps?

I keep going back-n-forth on this.  I want a QRP to QRO amp, but I think it's just because "I want one".  I find myself in one of 2 situations:  either I have to carry it, in which case I'm not bringing enough batteries to do QRO, or I don't have to carry it in which case I've probably got AC power and will use my 100W rig.

Still, this little 45W unit really has my eye. It's just the right size, features, and power.  It would give my KX1 a 2 S-unit boost, which is nothing to sneeze at.

gil

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Re: Amplifier for QRP Rigs
« Reply #10 on: August 13, 2014, 11:58:07 AM »
Hello,

I have noticed that when Ray uses his amp, or his Icom with 50W out, it can be the difference between having to listen through earphones or the speaker. When there is some fading (QSB) it helps to not miss a few letters or words sometimes. Contact is still possible with low power but takes more time when the conditions are bad because we need to repeat ourselves occasionally. An amp helps with that... 50W CW is like 1kW SSB!

Gil.