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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | Ramsey Qamp 40 Help

Reviews Summary for Ramsey Qamp 40
Ramsey Qamp 40 Reviews: 13 Average rating: 3.5/5 MSRP: $$49.95
Description: 40 meter linear amp
Product is in production.
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KA4DQJ Rating: 4/5 Feb 7, 2016 06:53 Send this review to a friend
Still ticking  Time owned: more than 12 months
After 5 or 6 years, my 40-meter version is still working even though I've had to change the finals twice. The good news is that the MOSFET final amp pair are dirt cheap, so I bought a small bag of them for the occasion. Interestingly, my finals never failed in use, but only upon accidental keydowns when the amp was on and I was out of the shack (once was the cat kicking the key lever). The bottom of the case is warped from the keydown heat, and I think I had to replace a couple of heated resistors too, but it's turned out to have been an excellent purchase. Just remember to keep spare final amps around. :)
W7SHA Rating: 4/5 Feb 6, 2015 19:30 Send this review to a friend
Works good after tweaks  Time owned: 0 to 3 months
I read all the reviews and decided for $40 what the heck. Well T2 was no fun. I finally wound it with some 24 guage hookup wire I had. Added the gate resistors everyone seems to be using. Set the bias at 3 volts, not sure of the current. And away it went. Right now I am only doing JT65-HF, so I set the output of the radio to one watt and tried it. I got 12 watts out and made 2 contacts before the finals went. Man those things got HOT. I read where someone had used IRF530's and I just happened to have a pair. So I replaced the originals and tried again. Same bias all the same parts. Same drive 15 watts output. Oh and I did replace the filter caps with 500v mica's. And I am going to do some of the other mods. But it is working great right now. Does not get hot, loafs along at 15 watts. It will do 30 watts if I want. And this is on 12volts. If you don't mind messing with it a little I do not think you can go wrong.
NG9D Rating: 5/5 Jan 19, 2014 08:25 Send this review to a friend
If it ain't broke, don't fix it  Time owned: 0 to 3 months
I was somewhat skeptical - with the precision of electronic component manufacturing, how could folks have such widely different experiences with this kit?

I read all the many useful hints and suggestions. When the kit arrived, I noticed that it is designed to work with an input power level from about one to two Watts. So it seemed that no mods were needed for my application, and I decided to build it according to the manufacturer's instructions.

The only small difference to the manufacturer's instructions: since no #24 gage enamel wire was included in my kit (it had been opened) I used #26 enamel wire for the secondary transformer, and #22 enamel wire for the primary transformer and the toroids.

By the way, if you go to Radio Shack to get enamel wire, DO NOT use the RS part number listed in the Ramsey instruction book, since that RS part number is for un-insulated #24 gage wire! The RS part number for the enamel wire I used is shown in the link below.

Now my little QRP rig, based on Doug DeMaw's tuna-tin circuit, is putting out 10W! I took a series of slides to show how it went together and how it is working. You can see them here:

I suppose time will tell how this amp holds up. If I learn any more, or if it melts down, I will report at

K1EAR Rating: 4/5 Dec 4, 2013 13:01 Send this review to a friend
works, but watch drive  Time owned: more than 12 months
I built one about ten years ago and use it now and again. Had some problems at first driving it with my TenTec PM3 which puts out nearly 4 watts on 40 M. Reports of bad sound (one RST 592!), but when I backed off the drive to 2 watts the reports were OK. So other than the clattery relay, I am satisfied with device.
2 years ago found one at a Hamfest for $5; someone had conveerted it to 11 meters. I tore out the tank circuit and put in a simple pi-net for 30 Meters and now use it with my TenTec 1330.
WB5MTR Rating: 4/5 Jan 21, 2012 11:01 Send this review to a friend
Great project and it works  Time owned: 0 to 3 months
I purchased the unit after reading the eHam reviews and added the extra MOSFET Heat Tabs , cooling fan and a 7 amp pico fuse. With no other modification at this point the unit worked out of the box as assembled. It will me nessessary to ad the diode and cap to stop the chatter in the TR relay, but other wise I can now use my Yaseu FT-817 moble or base station even on a marginal day for HF.
I chose 4 out of five because of having to add the mods, but am very satisfied.
KA4DQJ Rating: 4/5 Jan 1, 2012 12:50 Send this review to a friend
It's Alive!  Time owned: 6 to 12 months
After reading these reviews, I suppose I got lucky! I built the QAMP-40 to use with my SW-40 transceiver and didn't have the first construction or operational problem. I built the RF Amp about a year ago, and on several occasions have really put it through the paces. Two-watts in fetches 20w out. The thing gets hot, but never runs away.

To me it's clear that more substantial heatsinking would keep the thing cooler, but I've had it about as hot as it can get without problems. The only gripe I have is the "insta-on/off" relay which follows each dot and dash without a milli-second of delay. Well, full-QSK ain't so bad, but this relay is LOUD! The PC board makes a perfect sounding board, and the thin plastic case does nothing to insulate the clicks. At times the clicking relay competes with the sidetone during send! I also have no doubt that such excessive make-break of the contacts will eventually result in wear of the contacts.

I've been wanting to figure out a way to introduce a bit of delay into the relay. If that doesn't work, I'll have to add a manual switch to keep the relay energized during send.

One other thing which would have been very useful is a power light to show when the thing is on, and I don't recall a voltage reverse-protection diode in the power input.

But for $50 I can't really complain too loudly.
WA6MCL Rating: 4/5 Jul 4, 2011 09:19 Send this review to a friend
Qamp QRP amps  Time owned: 0 to 3 months
Well, I read all the reviews and was a bit concerned on building one. I built one for 40 meters and right away it worked as stated. No problems, overheating, etc. The RF sensing TR switch is clicky but does not seem to affect performance much. I did not expect much for about $50.00 and was surprised.

Yes, it is a bit crude, and many guys are critical, but fot the money...... I am driving it with 5 watts and see almost 25W out on 13.8 VDC. Time will tell but for now, it was easy to build and priced right.

Some immediate design considerations I did were; added a 2 amp inline fuse, added a reverse polarity protection diode across the input jack, and a biased LED so you can tell when it is powered. The light easily shines throught he front panel holes with no modifications.

N9MS Rating: 4/5 Jul 1, 2011 19:12 Send this review to a friend
Works great with Ramsey replacement parts  Time owned: 0 to 3 months
My first pair of MOSFETs shorted out. I called Ramsey and they said that the newer MOSFETs are lead-free and have more gain which causes them to heat up and short out. They sent me a new pair of MOSFETs and replacements for R8 and R9 originally 270 ohm resistors. The replacements are 180 ohms which reduces the gain.

I added a fan over the heat sinks and used a generous amount of heat sink compound. It's been running on CW and PSK31 for a week now and is working great! It draws about 4A from my Alinco Power supply at 13.8 volts and puts out around 20 watts.

N9MS Rating: 1/5 Jun 20, 2011 06:14 Send this review to a friend
During first QSO unit died  Time owned: 0 to 3 months
While initial testing showed that the amp was working right out of the box, upon making my first CW QSO, the two P16NF06 Power MOSFETs over heated and shorted out.

During my first QSO, I was getting 20 watts out and received a great signal report! During my second transmission, the unit suddenly died. I opened it up and Jumper JMP1 had melted open and both final MOSFETs had shorted out. I used heatsink compound to help dissipate the heat but apparently that is not enough protection. Perhaps 2 new MOSFETs and a fan will help?

I did make one modification prior to my first QSO: During testing I noted that the antenna relay followed every dit and dah which was very annoying so I added a female RCA connector connected to the relay to manually switch it from transmit to receive. I changed the SPST transmit/receive switch on the SoftRock to a DPST and had the second set of contacts key the amplifier relay which worked great.

That one modification, and adding heat sink compound to the finals were the only changes I made to the unit.
N9MS Rating: 4/5 Jun 16, 2011 08:38 Send this review to a friend
Worked first time out of the box.  Time owned: 0 to 3 months
I built the kit, followed the initial tests and everything seemed to go smoothly. I adjusted the current to 250ma which took the voltage at TP1 to 3.9 volts. I wasn't sure which was better 3.5volts or 250ma so I decided to go with 250ma.

I plugged in my SoftRock 40m Xcvr and power output went from 1 watt to 20+ watts. The only problem was that the relay followed every dit and dah on CW which is very annoying. I'll try upping C10 to a higher value to see if that holds the relay for a second or two otherwise I'll just add another jack and control it manually with the Softrock Xmt/Rcv switch.

I was surprised that the kit didn't include a small tube of silicone grease but I think I'll add some to help dissipate any heat.

This was my first time winding toroids and it worked the first time! I'm a happy camper.
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