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Reviews For: Ramsey Qamp 40

Category: Amplifiers: RF Power - HF & HF+6M

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Review Summary For : Ramsey Qamp 40
Reviews: 10MSRP: $49.95
Description:
40 meter linear amp
Product is in production
More Info: http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=QAMP
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
00103.6
KA4DQJ Rating: 2016-02-07
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. :)

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Earlier 4-star review posted by KA4DQJ on 2012-01-01

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.
W7SHA Rating: 2015-02-06
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: 2014-01-19
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:

http://www.youtube.com/watch?v=lqV0v1Xk5OQ&feature=share&list=PLFiIJJI5T2wdmzU9Lu140Ebkz-a61nHCF

I suppose time will tell how this amp holds up. If I learn any more, or if it melts down, I will report at www.YouTube.com/NG9D

73,
Lynn
K1EAR Rating: 2013-12-04
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: 2012-01-21
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.
WA6MCL Rating: 2011-07-04
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: 2011-07-01
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.





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Earlier 1-star review posted by N9MS on 2011-06-20

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.
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Earlier 4-star review posted by N9MS on 2011-06-16

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.
IZ4KBS Rating: 2010-06-05
don't think it will ever work out of the box Time Owned: 0 to 3 months.
In spite of the many negative reviews I bought two of them, to make it worth the shipping from the US into Europe. So far I have only built the 40m unit, while the 20m one is still sitting in its package unbuilt. First of all, I did beforehand many of the mods suggested by others, namely:

* 10 ohm 1/2 watt resistors in series with the MOSFETs' gates.

* 100 ohm 2 watts resistor in parallel with the primary of T2, to make the rig see an acceptable VSWR level. Without this, the input VSWR was sky high.

* replaced D2 with a germanium diode 1N34A, and increased C10 to 470nF to prevent the RX/TX relay from chattering.

* added additional, larger heathsinks, and improved the thermal conductivity with some silicon grease.

While winding L2 I pressed too hard and I broke the T44-6 toroid core. Thanks to the invaluable "mini Ring Core Calculator" program, I was able to make a replacement L2 using a T50-2 core.

For those who don't know, the ferrite binocular cores of T1 and T2 are conductive! (their resistance is in the order of a few hundred ohms). When threading the supplied enameled wire through them, the chances that the bare wire gets exposed and touches the core, and possible in multiple places, are *very* high. Although I'm not a "first time coil winder", out of four attempts I got a short between the primary and the secondary windings 3 times! So I junked the enameled wire and used PVC insulated #26 AWG wire instead, and I recommend you do the same.

The I moved on to testing the unit, with the top cover removed, and it was pumping out about 12-13 watts at 12Vdc of power supply. After only a few minutes of keying with my NorCal 40A set at 1.8 watts, temperature on the heathsinks had increased to about 95-105 C°, so the heathsinks were *very* hot and could not be touched, but I didn't worry too much. I should have! After half an hour of testing, and in spite of the many preventive mods listed above, one of the MOSFETs shorted and went up in smoke, taking a couple of PCB traces with it because the original design has no fuses, and my DC power supply can deliver more than 30 amps before its short-circuit protection trips. I promptly cut the power, then replaced the two MOSFETs with a couple of cheap IRF-510, reworked the vaporized PCB traces, and added a 5A fuse in place of jumper JMP1. Then, because of the different MOSFETs, I also had to lower R2 to 2.2 Kohm to get the correct bias. Lastly, I added a 12V CPU cooling fan on top of the MOSFETs and provided pleny of ventilation by modifying the supplied plastic case a bit. The second test went fine, with the two MOSFEts that now get just about warm, also with the top cover applied, and after several QSOs the unit seems to work OK now.

In conclusion, not only this thing will most likely not work out of the box, but it may fail even if you do the suggeted mods, unless you also replace the stock MOSFETs and apply a cooling fan. The final result can be seen at this link: http://www.strozzi.it/users/carlo/hamradio/qamp-40/ .

In spite of all the troubles, and of the fact that as supplied the unit would deserve a rating of 0/5, with a bit of skillful patience it can be turned into something really useful, which I think has no competitors in its price range (including the cost of the mods). So in the end I'm giving it 3/5, because now it makes for an excellent QRP accessory, for those days where conditions are marginal and a bit of QRO can make the difference.

Another two mods that I did, which I think are quite important and that I forgot to list in my previous review, are: * used 1/2 watt resistors for R8 and R9. * replaced C4, C5, C6 and C7 with 500V mica capacitors.
WD6DBM Rating: 2008-11-28
Junk Time Owned: 0 to 3 months.
4 seconds after power up I got heavy smoke, then a cap exploded before I could pull the power. I checked my wiring and it was all correct. I can't get proper bias on the power transistors, and with the very inadequate instructions I'm not sure if I will waste more time on this project.

I have built many Heathkits, a KX1, RockMites, etc. The quality of the kit is poor.

I'll make a call to Ramsey to see if I can get help, but based on the other reviews I am not holding out hope.

The parts are pretty cheap
KSAVES2 Rating: 2006-02-04
QRP amplifier Time Owned: 0 to 3 months.
Am not a licensed ham yet but have been building some simple QRP radios for CW use. I have a 5 watt and 100 watt
dummy loads I use for bench work. Having built an SMT
Magnetic Anomaly Detection device for model rockets
(http://www.aeroconsystems.com/electronics/mad.htm)
I felt I had the skills to tackle a simple amplifier. And yes I am studying the ARRL manuals, learning code and I don't believe in unlicensed use of the airwaves.

I researched the net for some low powered QRP amps and found some plans but decided to order the Qamp 40 from Ramsey Electronics. I built a simple Tixie from a bare board from Far Circuits and I probably spent close to the cost of the QRP 40 acquiring the parts for it. Suffice it to say, I didn't want to have to track down parts for an amplifier project. Being new, I don't have a junk parts pile
yet! I also didn't read the prior review of the Qamp 20 here
before I ordered my unit. Most reviewers gave the Qamp 20 a poor quality review. They mentioned that the pc board was very inferior. The board I received with the Qamp 40 was of fine quality and soldered well. None of the pads lifted up.

The unit arrived adequately packed and the instructions were relatively clear. I was able to solder all the parts to the board except the three toroids and two large tapped ferrite beads in one evening. When I got to winding the toroids and beads, I found out I was short on the #24 enameled wire. Emailed Ramsey and I got replies within 24 hours. This was better than what others experienced with the Qamp 20 reviews. They sent me the needed wire and I was able to get the winding done and the parts soldered to the board.

Now it was time to set the thing up. I was very fearful here in that I saw some reviews that the Qamp 20 "just burned up" on powerup. I emailed Ramsey some questions about the alignment procedure and again they answered them within 24 hours. Only a DVM is needed to set the unit up. The positive probe goes to a test point on the board and the negative to ground. A jumper to the collector on Q3, 2N3904 transistor, needs to go to ground. Had to look up on the internet where the collector was on the TO-92 case. A bias pot is turned to the minimum setting to start.
The instructions talk about measuring the current draw but I was emailed back that one doesn't have to worry about this.
I was advised that one just has to make sure the voltage is between 3.2 and 3.5V. I adjusted the range of the pot to see if it changed the voltage at the test point. (It did) I then set the pot so it read 3.4 volts or thereabouts.
I connected up the Tixie which actually is running at 200 to 300mW output. The instructions say to use a transmitter 1/2 to two watts. I did it anyways. The relay froze close on the Qamp 40 and I cut the power. Hmmm, maybe too little driving power? I'll try my Peanut Whistle from
http://www.hamradiofun.com/peanut-whistle.htm.
Sure enough, the Qamp 40 worked. I had the setup running into a cheap Workman SWR-3P and my Oak Hills Research
100 watt dummy load. I then carefully turned down the bias
and the power output dropped through the meter. Again, I remembered the upper limit of the pot that gave a voltage of an acceptable level and connected up the Tixie and keyed it while adjusting the bias. That made the difference.
The relay no longer froze and the keyer was working fine.
I was getting a couple of watts with the Tixie into the dummy as opposed to roughly ten watts with the Peanut Whistle. Now my readings are relative as I have no doubt that my meter is likely inaccurate. I believe it was only adequate enough to show there was some amplification of
the input rf power. Also was monitoring the signal with
a Grundig S350 SW unit. Doubt if any rf got outside my basement!

I won't be able to review onair performance and that is why I rated the item as OK. The prior reviews of the Qamp20 commented upon "the poor quality parts" and "poor tech support". I didn't have those problems. There were the issues with the wire but they quickly fixed it.

It looks like the alignment procedure may need to be repeated when using a different transmitter/transceiver.
It would be easy enough to install a shorting switch from the collector of Q3 to ground and a jack to connect to a DVM from the test point. Only problem is that the bias pot sits in front of a mounting screw in the Ramsey case so one can't simply drill a hole for access. If I like the unit after I'm licensed and onair, I'll mount it in a different case with those changes. Disclaimer: I am in no way connected to the Ramsey company. I became interested in Ham Radio as I wanted to build homemade tracking transmitters into high powered model rockets. Want to be licensed so I can transmit my call with a K1EL keyer on 2 meters from 5,000 feet up! Then go track the downed model with a handheld
and Yagi.
Kurt Savegnago
ksaves2@sbcglobal.net