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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | LINEAR amp UK Gemini HF-1K Help


Reviews Summary for LINEAR amp UK Gemini HF-1K
LINEAR amp UK Gemini HF-1K Reviews: 9 Average rating: 4.6/5 MSRP: $2500 GBP
Description: New solid state HF and 6 metre linear amplifier capable of 1 kiloWatt with low distortion.
Product is in production.
More info: http://https://www.thedxshop.com/
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GW0ETF Rating: 5/5 Dec 2, 2018 19:23 Send this review to a friend
Very happy - plug and forget..!  Time owned: 0 to 3 months
I wanted to wait until after a couple of contests before writing a review and CQWW CW in November was one obvious opportunity to do that. I operated 42 hours in All Band so the new amp had a good test and along with a couple of other recent contests and rag chew sessions has fulfilled my hopes and expectations completely.

The only other amp Iíve owned is the Acom 1000 which is a great amp - 10 years and still going strong. Naturally Iíd read the dimensions of the Gemini before taking delivery but even so was slightly surprised at the size and weight; in some ways it feels a bigger beast than the Acom. But to me that suggests nothing has been scrimped in the power supply or heatsink department which is reassuring but would think twice if I was after a portable amplifier. I wanted the Gemini as a base amp for the automatic band and antenna switching (plus instant on) and Iím delighted to find this kit being produced on my doorstep. I have a garden shack and like to fit those computer type security fittings on all my expensive gear. Roger personally assured me one of these wouldnít affect the warranty and even went further to say if I ever wanted to sell it on in the future they could replace the rear panel if the buyer didnít like the fitting on the back!

The app is excellent and allows me to see whatís happening on screen without having to look over at the amp. I have OmniRig running which connects to my K3 via Lp-Bridge; itís seamless and just needs Lp-Bridge and the Gemini app started for everything to connect and the amp to follow band changes on the radio. I like this because if I want to quickly check another band the antenna selection will follow immediately - no need to hit the key for a shot of rf and the panadapter shows correct signal levels at all times.

The QSK is so good that your sidetone in cw can sound just like a signal in the receiver. There was one weird moment in CQWW brought on no doubt by tiredness when someone replied to my CQ on exactly the same frequency/tone and caused me to imagine it was a long echo from my own transmission. For a high power amp the QSK is remarkable and totally silent except for a barely perceptible faint ticking in time with the keying(?). I have the 10w version and I disable the PA in the K3 so the power is limited to 12 watts; that way I will hopefully avoid any overdriving accidents, something that could easily happen in the last hours of a long contest.

In normal use the amp is super quiet and unnoticeable. Iíve used it in one ssb contest lasting an hour and the temperature never showed any sign of going past about 37 degrees as I recall; the fan sound was very quiet. However when operating cw in either a busy contest or long rag chew the higher duty cycle often causes the temperature to rise up the point when the fan noise is quite loud. That point is around 49 degrees and Iím not sure if this is a separate heavy duty fan that kicks in but it has so far prevented the temperature going any higher than 52 or 53 degrees. At that point itís significantly noisier than the Acom but normally isnít an issue for me as I routinely use headphones anyway. Maybe Iím overcautious but Iíve raised the feet up onto small blocks of wood 45mm by 45mm and 20mm thick to give more space underneath which may help in my tiny not so well ventilated shack. The system is clearly efficient because any hiatus in keying of more than a few seconds results in the temperature dropping quickly and the loud fan going silent.

The above paragraph is more an observation in contrast to what some others have written but I do have one complaint - it doesnít keep my garden shack as warm as the Acom in the winterÖ.;-)
 
WB4KTF Rating: 5/5 Nov 1, 2018 00:52 Send this review to a friend
Works like a charm and very quiet  Time owned: 0 to 3 months
I received my HF-1K 2 weeks ago. I had one problem that I fixed (had to add a RF choke (6 turns or coax between the IC-7610 and the amp). My set up is an Icom IC-7610 connected to the HF-1K then to my Palstar HF-Auto. The amp replaces my Collins 30L-1, yes I have moved up several decades. This setup works extremely well with my G5RV antenna. The amp is so quiet that I need to look at it to make sure it is even on. During a longer conversation I do hear the fans come on and speed up as the temperature climbs on the huge heat sink. This amp appears to be well designed, it weighs 19 kg, they did not skimp on this boy. The displays are simple and easy to read (RF Out, Current and VSWR), it has 1-input and 3 outputs (I use 2 of them, one to the HF-Auto and the other to a 1.5KW dummy load), a RCA pin plug for amp keying (I have this directly connected to my Icom IC-7610), an ethernet port and a 0db port. The manual is just 12 pages long, so this amp is easy to setup and use.
 
LB1RH Rating: 5/5 Sep 6, 2018 07:41 Send this review to a friend
Great!  Time owned: 0 to 3 months
I was initially planning to go for Acom 1200S, however first reviews were not very positive, so I decided to look for alternatives. Gemini HF-1K does have few advantages over Acom: multiple antenna ports, 2x LDMOS for clean signal vs 1 in Acom, predistortion output, controllable via LAN network, full QSK. And it's cheaper.

I bought 10W drive version, which means I can use the PA with my KX2. I tested my Gemini HF-1K at this years fielday and it was a blast. I operated for about 20 hours, had pileups that lasted many hours. Multiple times people commented how strong and clean my audio was. PA temperature never rose above 41C (we were in a tent, outside temperature was about 10C) and the amplifier was very quiet. Couple of times I chose a wrong antenna port, which, as expected, triggered high VSWR protection.

One small annoyance I can mention is that LCD viewing angles are not the best.

All in all, so far I'm very happy with this purchase.
 
M0VMX Rating: 5/5 Aug 28, 2018 20:20 Send this review to a friend
Outstanding !  Time owned: 0 to 3 months
I was hunting around for an auto amplifier for quite a while a friend Howard G3YZY said come around and have a look at mine so I did and I am so glad I did! I put my order in straight away with Roger and 3 weeks later it arrived.
I have only had my Gemini 1K for 5 days and all I can say is WOW what a superb perfect amplifier
Its so quiet you donít even know its there also I donít ever need to keep looking at it as I use the network control software so all the information is right on my screen in front of me.
I have only using the Gemini on 7mhz and 14mhz so far and its outstanding, my signal is clean and a perfect 3K wide with no distortion its also is just ticking over at the UK legal limit, if you are looking for a solid state amplifier this is the one to buy and its UK built. My next order will be a Gemini 4 for 70mhz Thank you very much Roger for all your hard work you have designed a perfect amplifier.
 
G3XJE Rating: 5/5 Aug 25, 2018 16:11 Send this review to a friend
Superb   Time owned: 0 to 3 months
I have had my HF-1K now for more than a week. It has worked flawlessly. I have had excellent reports of the audio quality on the air. It is very quiet and very easy to use.
 
GW0GEI Rating: 5/5 Aug 15, 2018 13:04 Send this review to a friend
Superb silent performance  Time owned: 0 to 3 months
I have owned several old and modern amps including alphas, expert, om power, and Acom 1000. Apart from the Acom 1000 all were noisy to some extent.

Having owned recent lin amp vhf amps on 4/6m and my current Gemini 1.2kw 2m amp I waited with interest on the development of the new solid state Gemini hf/6m as I wanted an amp that will switch bands quickly and can be operated remotely.

I picked up my Gemini hf/6 last week and it took me 15mins to hook it up, download the remote app software, and throw an 80m dipole up at my new qth. The amp tripped on a vswr alarm when I applied a couple of watts drive from my Anan 7000 sdr. Sure enough I had a problem on my old dipole centre peice. I replaced it with a new 1:1 balun designs centre peice with n sockets (also bought from Roger at The Dx Shop. Problem solved, and the amp went on to put out the uk legal limit of 400w with just 4w of drive (I had specified the 10w max drive option when ordering as it allows me to also use my ft817nd radio on hf and 6m and still get legal uk limit out of the amp).

I am amazed how quiet this new amp is, even compared to my 2m one. It's quieter than the two Acom 1000 amps I previously owned and much much quieter than the om3500 or spe expert 2kw amps I also had.

The amp switches quickly to another band without any cable, and I have never had any amp that does qsk cw so effortlessly and quietly. Cw ops who like qsk at high speed are going to love this amp.

The remote app to control and amp is very easy to set up and use. The amp is connected to my lan, as is my Anan 7000 sdr radio and 4o3a 2x8 port remote antenna switch. I have the remote app running on my hd tv monitor in a small window, alongside my Anan openhpsdrmrxps software and dx lab logging software or N1mm contesting programme. I can switch antennas, or put the amp into run or standby with the click of a mouse, and I can see the power out, current level, vswr, and the amp internal temperature all on my screen. The amp currently sits on my temporary shack desk, but I don't look at it, and it will eventually move to a remote shack in the garden next to the planned antennas and towers, along with the sdr radio and the so2r remote antenna switch. All will be controlled remotely from the house shack/study via the cat 6 cable connecting it all up to my house lan.

I haven't yet tried the amp on 6m but the revised firmware has sorted out the false alarm bug that I was informed about at the time of purchase last week.

This morning I joined a uk dx net on 80m which I usually frequent in the winter months, and was delighted to work my first Zl1 of the new season with 400w to a simple dipole at just 35ft agl.

Only a week so far, but getting excellent audio reports with the new amp, and a friend who also runs openhpsdr confirmed that the already clean tx from the Anan 7000 is equally clean with the full legal limit running from the Gemini. I have "pure signal" pre distortion feedback cable connected from the 0db sampler in the Gemini back to the aux external sampler socket on the rear of the Anan radio, which ensures that my tx signal is as clean as it can be. I always run with pre distortion feedback switch on, even in contests when it might be better to be wider.

I will post a later review on the new amp in a few months after I have run it in a few multi band ssb and cw contests with a larger selection of antennas. So far I am a very happy bunny, and if it's as reliable as my other vhf Gemini amps have been I doubt that I will be needing the two year eu warranty that comes with the amp. Already one of my ham friends has decided to replace his Acom 1000 with one of these amps, as he does a lot of qsk cw and needs a small footprint quiet amp for his very small radio shack. I expect Roger will be kept busy building lots more of these amps, and I might be back for a second one once I have my new contest station sorted and need a second amp for so2r contesting.
73
Steve gw0gei /GW9J in major contests io72ve
 
G0GSR Rating: 1/5 Jul 24, 2018 19:11 Send this review to a friend
Too many problems  Time owned: 0 to 3 months
I am sorry to have to report that I have given up on the HF-1k and sent it back for a refund.

The amp was first returned to DX shop with several faults reported and was returned with modified firmware.
This solved the problem of an "out of band" trip when attempting a 2 tone test to look at suspected non-linearity.
However the auto band switching from 50-3.5MHz was still not working resulting in a VSWR trip every time.
Roger informed me that he had tested my amp with his Elekraft K3 and the band switching worked just fine, however with my IC-7300 (probably the most common radio in the world), I had a problem.

The band switching problem was fixed almost immediately with a further firmware update. Fantastic!
However, after this, I still noticed that during a transmission, the band selection relays were spuriously trying to switch.

The major problem for me was that I could hear noticeable distortion whilst monitoring my signal on a remote Web SDR.
Also, two stations, without prompting reported my signal as being distorted. My audio sounded rough, like an amp with incorrect bias but the two tone envelope viewed on my oscilloscope looked perfect.
Roger AT DX Shop was extremely helpful and assured me that the amp was 100% but I and others could still hear the distortion which wasn't present whilst using my Acom 1000 amp at exactly the same power level.
RF feedback was not the problem, I eliminated that possibility.

Maybe I had a bad one but I had totally lost confidence in the design by this time.
To say I am disappointed is a gross understatement. I have been waiting since June 2016 for this amp.

Obviously, I can only speak about my own experiences with my amp. I genuinely wanted to keep this amp but it was a big investment for me and I was just not happy with the design.

Frank
 
G4ELI Rating: 5/5 Jul 20, 2018 05:08 Send this review to a friend
Superb  Time owned: months
I am a beta tester, I have had one of the first units for several months. This is an excellent amplifier, important is that it's quiet and very simple to use. I drive it with 10 watts from a FTDX-3000.

Output is clean and quiet on HF and on 6m.

I am also the author of the Windows remote control software (free for the HF-1K owners).

Previously I tried the ACOM 1200s which was returned after a week. The HF-1k is the amplifier to keep.
 
G3YZY Rating: 5/5 Jul 19, 2018 14:34 Send this review to a friend
The Gemini is absolutely superb and loafs at full UK power.  Time owned: 0 to 3 months
I have owned this amplifier for just over a couple of weeks and used it on most HF bands including 6 metres. My previous amplifier was an Elecraft KPA 500 which I was very pleased with. The Gemini is absolutely superb and loafs at full UK power. I have had excellent signal reports and the signal looks very clean into web SDR sites I have tried. With the Elecraft I had to have the fan running at the second up setting which made some noticeable noise in the shack. The Gemini is virtually silent most of the time even under long SSB overs with moderate compression. When the fans eventually come on they are very quiet which is important to me. I have evaluated the Acom 1200S which had some problems with fan noise. As a retired antenna and RF consultant to UK MoD and industry I believe overall that the Gemini is a much superior amp and design (IMHO). The amp is very simple to set up and operate and with my station is completely transparent yielding a 1 kiloWatt capable transceiver (see my QRZ page). Highly recommended!
 


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