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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | Ramsey Electronics QAMP-20 Linear Amp Help


Reviews Summary for Ramsey Electronics QAMP-20 Linear Amp
Ramsey Electronics QAMP-20 Linear Amp Reviews: 19 Average rating: 1.9/5 MSRP: $49.95
Description: 20W Linear Amp to give a modest QRO boost to QRP SSB/CW rigs. Available for 80/40/30/20M. Enclosure also available.
Product is in production.
More info: http://www.ramseyelectronics.com
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K6RXL Rating: 0/5 Oct 21, 2005 07:59 Send this review to a friend
stinks!!  Time owned: 0 to 3 months
Don't buy this kit! I'm an experienced kit builder having built a K1, K2, LDG tuner and many Heath's, and should have read the other reviews posted here. The total design is inferior. The components are of sub-standard quaity and were not rated or "derated" properly. The resistors should be 1/2W and the caps voltage value is also too low. The circuit board is of the poorest quality so be very careful while soldering cuz you're bound to lift pads. This is the poorest excuse for a kit I've ever seen and I will never, ever buy another product from Ramsey!
 
K5MGB Rating: 0/5 Nov 16, 2002 21:02 Send this review to a friend
Bad News  Time owned: 0 to 3 months
Upon turn on, the unit went up in smoke. Triple checked component placement and soldering. No problems there. Still not working after hours spent on it.

I have put together several other kits with no problems. Ramsey tech help was no help.
 
5R8GQ Rating: 4/5 Aug 7, 2001 00:55 Send this review to a friend
Works Well *After Modifications*  Time owned: 6 to 12 months
I bought this amp to use as a boost to my PSK-20 when conditions are marginal. I too had the well known problems listed in other reviews, but since being fixed it has performed very well for the last 10 months. I get the full 20 watts out of my unit and use it several times a week in the demanding PSK-31 mode. The mods I used were: 100 ohm 2-watt flameproof resistors for R8&9, 1000 pf silver mica capacitors for C11&12, as well as replacing all others capacitor in the unit with ones of better quality and/or higher voltage rating. I don't have any problems with the carrier operated relay circuit. For heat sinks I made a "sandwich" of three different TO-220 type sinks for each MOSFET,including one on top of each MOSFET. The PSK-20 and Q-Amp fit nicely into a Radio Shack 6"x8"x3" metal enclosure (about $12), but you have to overlap the boards by using different length stand-offs. With the right heat sinks and enclosure, I don't think you really need a fan, but it is a nice touch. And yes, I do have long QSO's with no problems.
In conclusion, the amp will not play from the box, but with a few cheap parts it makes an excellent little booster for the PSK-20. Using this combo I have worked South Africa, Latin America, New Zealand and W. Europe from my California QTH.
 
KT4HT Rating: 4/5 Jul 31, 2001 22:20 Send this review to a friend
Worked fine first try!  Time owned: 0 to 3 months
Given the poor reviews, I was pleasantly surprised that my amp worked fine the first try. I did replace R8 & R9 with 270 Ohm 1/2 watt ones before cranking the amp up. Getting great reports on SSB & CW.
 
K3SUI Rating: 1/5 Jun 25, 2001 17:22 Send this review to a friend
Looser  Time owned: 3 to 6 months
I bought one of these, but it and it immediately blew up upon power on. No problems with construction, just a lousy design. After reworking almost everything unit is now usable. It's a shame it would never work out of the box !!
 
N4WFS Rating: 2/5 Dec 2, 2000 23:23 Send this review to a friend
Kit a starting place to make Boots for PSK20  Time owned: 0 to 3 months
Stock design has major problems.

1. Very high input impedence with large reactive component causing the PSK 20 to face a SWR >3.
2. Only a single Bias adjustment for both MOSFETS. Ok if they are well matched. Mine were not.
3.Feed back resistors are inadequate wattage and promptly burn up.
4.Heat sinks are totally inadequate.
5. Case plastic and too small for adequate heat sinks.
6. Phono conductors for input and output..
7. Case needs to be grounded to computer to keep sound card happy.

Here is what I did to make it work.
1.Put in in a 270-253a ventilated metal case from Radioshack and installed real RF connectors.
2. R2--4.7k ( allows higher bias )
R8,R9 150 2W ( Depending on MOSFET match may range from 100 to 270)
C1 3,300 uf Stock may be ok
C9 .0047uf less loss of Rx performance
D2 1N34A germanium
C10 1uf
R10& L4--Remove and replace with bundle of 5 270 ohm 1W resistors in center of 1/2" 8 turn coil
T1 Make center tapped primary of insulated 22G phone wire.
T2 Make center tapped primary of 22G phone wire, and reduce secondary to 4 turns
Q1 Q2 Cheap IFR 510 from radio shack
CPU Heat sink with plastic fan. turned on side, drilled and tapped to attach MOSFET and anchor to PCB. Air directed out vent holes in side of top.


 
W3DP Rating: 2/5 Oct 16, 2000 16:03 Send this review to a friend
A nice kit for the money. Easy to build.  Time owned: 0 to 3 months
I recently completed and tested the Ramsey QRP 20Watt Amp. I included the mods of ferrite bead in the gate of the finals and a 220 uf electrolytic across the relay for semi QSK on CW. I still need to add a resistor pad to reduce the output from my OHR-100A from 5W to about 1.8W to drive the amp. One problem noticed is that when first keying, the power output is low until the finals warm up. The power then rises to full output after sending for a short period. Any suggestions on how to fix this? Initially I had a short to the core on the big transformer. The #22 enameled wire is a bit large to fit on the core. I rewound with #24 which seems to work OK. Still need some on the air experience with it to completely evaluate. 73, Dick W3DP
 
W1EZ Rating: 2/5 Sep 24, 2000 14:24 Send this review to a friend
Good amp but needs a few mods  Time owned: 3 to 6 months
I am also using a QAMP-20 with a Small Wonder Labs PSK20, but it's certainly not a plug and play amp. The amp has serious shortcomings and requires modification for PSK20 duty. Once modified, however, it makes a nice afterburner for the PSK20.

Here's what I had to do to make it work:

1. Replace the 100 ohm R8 and R9 resistors with 270 ohm as shown in the schematic. The 100 ohm resistors supplied literally burn up.

2, Add a 10 ohm, 1/2 watt resistor in series with the gate of each power transistor to stop oscillations. Until I did this, I had some serious parasitic oscillations on the output. This can be done by lifting the gate leg of each transistor and wiring the resistor between the lifted leg and the original hole in the pc board.

3. Change C10 from 0.1 uF to 1.0 uF to prevent the rf sensing relay (nice feature) from chattering when running PSK31.

4. Replace the heatsinks supplied with larger heat sinks and provide plenty of ventilation. I already burned up one set of power transistors using the heatsinks supplied and the Ramsey enclosure without holes. Even with the top off the enclosure, the heat sinks supplied are too hot to touch when running PSK31.

With the changes mentioned above, this amp makes a nice addition to any 20 meter qrp rig, and is especially nice with the PSK20. Good luck getting yours to work.

 
N9VV Rating: 3/5 Sep 24, 2000 08:55 Send this review to a friend
modest QRO for QRP rigs  Time owned: 0 to 3 months
Travis K5AVH and others have been enjoying the Ramsey QAMP-20 as an added bit of punch for their PSK-20 kits. Read all about it at
http://home.uchicago.edu/~khopper/k5avh.html

Building the QAMP has not gone all that smoothly for some builders. Check out the tips and tricks to give it a new heatsink, better cooling, and xfrms that don't short out. They seem to be working reliably after these mods.

I wish to thank Travis for his generous contribution of pictures, text, and editing for this webpage. It was my pleasure to meet him on PSK31 Saturday and to learn about the QAMP-20.

dit dit
de Ken N9VV (solder melter and webpage hacker)
http://www.qsl.net/n9vv/
 
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