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Reviews For: QRO HF-3KDX

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

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Review Summary For : QRO HF-3KDX
Reviews: 6MSRP: $4,595.00
Description:
THE HF-3KDX COMBINES SUPERIOR QUALITY AND EXCEPTIONAL
PERFORMANCE WITH THE POWERFUL, RUGGED, AND ECONOMICAL Taylor
8877/3CX1500 CERAMIC TRIODE
Product is in production
More Info: http://www.qrotec.com/
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0064.5
W1XYZ Rating: 2020-11-10
Very Good Amp and super rugged Time Owned: more than 12 months.
I have one of the older 4CX1600b versions of this amp, and when I got it, I realized those tubes were scarce, so I picked up two extras. I haven't had to use them, just tested them and put away in case they are ever needed. Talk about an under rated tube: These things were very powerful and it is too bad they are no longer in production. A more suitable name might have been 4CX3000b!

What can I say about this amp that has not already been said? It is very well made, with larger than average components, heavy iron, and designed for simple easy operation with broad tuning on most bands. So far, over nearly a decade, there have been no problems at all. The power output on some bands with this tube have >3dB available over the limit, and the amplifier simply loafs along. The fan is somewhat noisy, considering the little heat this beast creates as it leisurely pumps RF.

The design is easy to understand, and, I presume, easy to repair, should something go wrong. Though a little more costly than its presumed peers, I believe it has no peer, based on my experience with other expensive amplifiers made by vaunted manufacturers.

I have had one problem with this amp: At first I thought I had a noisy fan, and the buzz got worse over time. Then I thought there was something wrong with the plate transformer until I discovered that the Dahl plate transformer was not bolted down tightly enough. This fixed 99% of the buzz.

I also have found that relatively inexpensive Russian GU-91bs are pretty much a direct drop in replacement tube for the bigger 4CX1600b which is hard but not impossible to find. They are a little smaller diameter so I just made a teflon plate to keep the airflow through the anode fins. Power and tune up were the same. It is wise to let the filaments run for a day or more before applying the HV on these tubes, as this scavenges gas and reduces the chance of a flashover.
W9BHI Rating: 2019-03-10
It would work better if it was built correctly Time Owned: 0 to 3 months.
I bought one of these used a few months ago.
The first problem I noticed was the hum on the carrier when using it on AM ( you would never see the problem on SSB).
After looking at the unit and comparing it to the schematic,
I noticed that the bypass caps on the cold end of the filament choke that were shown on the schematic were missing from the unit.
They were never installed.
Also, the RF feed to the cathode and filament was connected to the side of the filament that was not common to the cathode.
If you look at the build pictures on the QRO site, it clearly shows the missing caps and the incorrect RF connection to the pins of the 8877.
The hum on the carrier was being caused by the cathode bias being connected to the center tap of the filament transformer.
Fine for a directly heated tube but not for one with a seperate cathode.
Tracing out the side of the filament choke that goes to the cathode and reconnecting the bias circuit to that side of the filament transformer eliminated the hum on the carrier.
Ater making the necessary repairs, the amp performs very well.
This amp suffers from the same problems that my HF-2500DX
had, poor design and lack of quality control (see my review of the HF-2500DX)
Also, don't expect an answer to any emails or calls to Ray.
I never got any after numerous tries.

K5WG Rating: 2015-11-23
Fantastic Amp! Time Owned: more than 12 months.
I have owned lots of amps over the years, including Kenwood, Drake, Collins and Alpha. I bought this amp based on recommendations from knowledgeable hams that I know and trust. I have had this amp for two years and love it. It's quiet, dependable, and easy to tune. Outstanding design and beefy construction. Look inside of one and you will be impressed. Heavy-duty components throughout. I use it on a daily basis for ragchewing, DX chasing and contests. It's a definite pileup buster! Absolutely the best amp I have ever owned!
Bill, K5WG
K5ZG Rating: 2013-06-13
FANTSTIC Time Owned: more than 12 months.
WOW, is all I can say, WOW. I got this amp based on previous experience with QRO for both quality and the back up given by Ray...I have owned several of the QRO amps over the yrs and still do. I even got to beta test a pair of 4CX1600's for Ray yrs ago.
This amp is so nice. Tuning is easy and very broad banded. It will put out 3K (into a dummy load of course). I have battered it at 1500 watts out in CW, Fone and RTTY contests without a glitch or burp. It does heat the shack.
Looking back at over 50 yrs of ham radio and all the amps Ive had, Kenwood, Swan, Collins big and little, Heath, Henry big and little, home brew 8877 this is by far the finest amp .Ive ever had. As Pee Wee Herman would say "Im the luckiest boy in the world". Compare the quality and company reputation and Rays backup to all the other amps and then look at the prices.....call Ray with an order.
If anyone knows me and amps I can say this is "HUD PROOF". See you in the piles...of course you will be behind me.
W5RIM Rating: 2013-04-08
FABULOUS Time Owned: 6 to 12 months.
Owned lots of amps, this one is a beast. Lots of voltage on the 8877 tube. Runs legal limit plus with ease. Ray is great to deal with. Liked this amp sooo much i bought a hf2500 also. These amps are built like a tank,very heavy duty components. I love it. Buy one you will not be dissappointed.GREAT CONTEST AMP.
73,
Julius w5rim
W7GO Rating: 2012-11-30
Powerhouse Time Owned: 0 to 3 months.
Wanna bust pileups? This amp will do it.
Very nice construction and easy to tune.
Powerhouse amp and great QSK operation.
Very pleased with this amp so far.