|
New to Ham Radio?
My Profile
Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question
Operating
Contesting
DX Cluster Spots
Propagation
Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers
Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net
|
| Reviews Summary for Ramsey Electronics QAMP-20 Linear Amp |
|
Reviews: 16
|
Average rating: 2.0/5
|
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
|
|
Email Subscription
You are not subscribed to this review.
Subscribe!
My Subscriptions
Subscriptions Help
|
You can
write your own review of the Ramsey Electronics QAMP-20 Linear Amp.
|
W4DNQ
|
Rating: 0/5
|
Mar 11, 2012 16:53
|
Send this review to a friend
|
|
HE Amp
|
Time owned: 0 to 3 months
|
I have purchased many Ramsey kits before and this one is all junk. Just like the rest.
|
|
K9HTL
|
Rating: 4/5
|
Feb 7, 2012 12:34
|
Send this review to a friend
|
|
Apprehensive at first but satisfied
|
Time owned: 0 to 3 months
|
After reading the reviews I was apprehensive about ordering the QAMP20. But following some of the suggested mods while building it resulted in an amp that works well. I have had success on PSK31, SSB and SSTV using a FT817 to drive it.
Mods performed:
1. Installed small 2 inch fan on lid to blow directly down on heat sinks. Drilled vent holes in front panel in line with heatsink fins.
2. Added ferrite beads to gates.
3. Added 33 mfd cap across C10 to increase TX/RX time delay.
4, Adjusted bias to 0.2 when cold.
5. Added heatsink grease to MOSFETS
I had to rewind T1 and T2 due to turns shorted to the 2 hole ferrite cores....pulled turns too tight!!
The circuit board is evidently of higher quality than earlier versions. No hint of traces lifting.
Power out is a solid 20 Watts with 13.8 VDC as measured at the amp power plug and the 817 set at 2.5 Watts. The 817 sees an SWR of about 1.6.
So far, so good!!
|
|
KB1NLW
|
Rating: 4/5
|
Jun 8, 2009 20:39
|
Send this review to a friend
|
|
Must add a Fan
|
Time owned: 0 to 3 months
|
I built a 20 meter version and it is working fine on PSK (a continuous high power mode, ALMOST 20W peak and 15w average). However the kit should be considered a starting point needing a few modifications.
A must is the addition of a cooling fan. Without a fan the heating of the output FETs causes their bias current to increase, causing further heating, increasing the bias
Also take care with the potentiometer, make sure you start with the taper at the R3 end check with a VOM before powering up. I believe this probably the biggest problem with the kit, so be sure to add a fan. I added a 1.0 square 12 v 0.09 amp DC fan under a 1.0 round hole the top cover and vent holes behind the heat sinks. The tiny fan fits over the heat sinks without a problem.
The manual recommends setting the bias for at 0.25 amp input. I recommend not more than 0.2 amp. Note that there is a steady rise in current as the FETs warm up.
Based on other posts, I also added 10 ohm resistors in series with the FET gates by bending up the FET gate leads and using the PC board holes for one end of resistors and tying the other resistor end to the gate. I also changed R8 & R9 270 ohm resistors to 220 ohm 1w.
One last change was to change to BNC connectors in place of the cheap RCA connectors.
It does appears to work well in combination with my Small Wonder Labs PSK-31 20m. PSK reporter showed reception of signals all over Europe.
(I would not build this without the mods becaue it probably would self distruct)
|
|
W7RJR
|
Rating: 2/5
|
Apr 9, 2007 18:00
|
Send this review to a friend
|
|
Followup
|
Time owned: 0 to 3 months
|
The MOSFETs provided by Ramsey in this kit were incorrect resulting in multiple component failures/smoke during initial testing.
I replaced the semi-conductors with common ones found at Radio Shack. The IRF-510 MOSFETs at $1.99 each worked like a charm. This amplifier now works. Better quality control will assure a better experience for the end user.
|
|
W7RJR
|
Rating: 0/5
|
Apr 7, 2007 15:20
|
Send this review to a friend
|
|
Caveat Emptor
|
Time owned: 0 to 3 months
|
Obviously some folks have been able to get this to work! That is to their credit. Despite being an experienced kit builder, I have not.
After hours of troubleshooting, lifting components to test with a multimeter, double-checking for cold solder joints, solder bridges, mistakes, etc., this device will not work! The only schematic you can get is the one that comes with the instructions, which is faded and missing some critical traces.The schematic only provides voltage references for TP1 making troubleshooting that much more difficult. The schematic shows the primary and secondary windings of the matching transformers in reverse. A call to Ramsey Electronics netted a brief conversation with a fellow that wasn't all that familiar with it. He stated that he heard that some incorrect semiconductors had been ordered and perhaps my kit contained some of them.
The PC board is cheap looking but despite a lot of pulling parts to test them none of the pads or traces have lifted yet. I fear that will happen soon.
I will replace all of the semiconductors in this thing (which won't amount to a lot) and see if it plays. If not, it will occupy a proud position in my trash can.
|
|
NJ3C
|
Rating: 4/5
|
Dec 13, 2006 18:49
|
Send this review to a friend
|
|
Works fine with mods
|
Time owned: 3 to 6 months
|
Despite the poor reviews here I bought it, knowing that I would have to make some modifications to get it to work. Here are my mods:
add 1/2W 10 Ohm R's in series with MOSFET gates
repl C's in low pass filter (C4-C7) w/ silver mica
repl R8, R9 with 1/2W 270 Ohm R's
add 1/2W 270 Ohm R across primary of T2
use #28 magnet wire in T2 instead of #24
use heat grease under MOSFET's
Without the 10 Ohm resistors in series with the gates, my QAMP went into self oscillation when I tried to bias it. I decided to use better, 500V caps in the low pass filter because I did not trust the ones supplied with the kit. Using higher rated feddback resistors for R8/9 keeps them from burning up. The 270 Ohm resistor across the primay of T2 was used it to keep the input SWR down. Wrapping T2 with #28 wire gives you a bit more room and reduces your chances of a short. Finally, the heat grease helps keep the FET's cool.
I have used my QAMP20 in the field now fairly often and have not been disappointed. The FET's get hot but do not overheat when operating CW. I have made a lot of contacts with this amp that I would have never made barefoot with my 2W Wilderness SST. Overall well worth the $50.
|
|
AD5JN
|
Rating: 0/5
|
Dec 1, 2005 05:44
|
Send this review to a friend
|
|
Junk
|
Time owned: more than 12 months
|
Don't buy it! Pure junk. The thing blew up after powering up. PC traces are cheaply done. I did the required mods but still not working. I put it in the same MFJ junk pile. This was the first and last time I buy anything from by Ramsey. BTW Support from them is zero %!
AD5JN
|
|
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.
|
|
If you have any questions, problems, or suggestions about Reviews,
please email your Reviews Manager.
|
|
|
|
|
