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Reviews For: Linear Amp Gemini 2-500 144MHz 500W

Category: Amplifiers: RF Power - 6M/VHF/UHF+

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Review Summary For : Linear Amp Gemini 2-500 144MHz 500W
Reviews: 2MSRP: 1400 approx
Description:
Introduced in Spring 2017, the Gemini 2-500 is an uprated version
of the Gemini 2 300W unit. We have changed the LDMOS to a BLF184XR,
redesigned the RF and filter section and uprated the power supply.

The result is an amplifier that will put out >500W CW with a P1dB
of 480W. It still has the same built in protection for overdrive,
High SWR and Over Temperature.

By optimising the RF efficiency we have been able to build the
Gemini 2-500 into exactly the same outer chassis as the rest of the
300W range.

The 144MHz Gemini 2-500 incorporates the same, sequenced, front
panel switchable 13.8v preamplifier supply on receive. This can be
selected by the operator to be either an output voltage on the rear
panel or a bias tee feed as required.

The Gemini 2-500 is a complete turnkey solution incorporating a 50V
linear power supply so no external PSU is required.


500W output
Ampleon BLF184XR LDMOS
Integral 50V Linear Power supply
Drive requirements 4-25W (specified at purchase)
Advanced cooling for data mode operation
Full protection for overdrive/swr/temperature
Switchable preamp output voltage on RX with bias tee option
N Type connectors on input and output
All aluminium chassis
Compact dimensions - just 270w x 300d x 120h mm
Weight 11Kg
UK Manufactured on the Welsh Borders
Product is in production
More Info: http://www.linamp.co.uk
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0025
G8YTZ Rating: 2022-01-28
Superb Amp - Highly Recommended Time Owned: 0 to 3 months.
I ordered my Gemini 2-500 on 4th July 2021, and was delivered to schedule on 26th January 2022. The whole interaction with The Dx Shop could not have been better, true customer service. I can see why Roger Banks and his team have such a long lead-time for their products. If you want the best, you have to be patient, but the wait is worth it!

Pros:
- Compact unit, just a little larger than an IC-9700, but about the same height.
- Linear PSU with soft-start and toroidal transformer
- Quiet when in operation
- Super linear, performance exceeds specifications
- Good output filtering (confirmed on my HP-8060A)
- High quality components
- Large analogue meter and quality feel to the switches
- Choice of drive levels, I opted for 10W for compatibility with a future IC-705 purchase and for compatibility with DATV operation, but for most use cases with radios such as the IC-9700 the 20W drive option is the best option.

Cons:
- Lead time, the problem when you have a popular product!
- The “hate” mail you’ll get from other radio club members – only joking!
- Don’t try powering it into a Japanese co-linear if your house has a thatched roof :-)

In Use:
The amplifier performs comfortably in excess of the stated specification and is super-linear. Driving to the full 500W with my Icom IC-9700 (power set to 7% for SSB) it provided a clean and narrow-band output. I also tested it at 146.5MHz with Digital TV. Using DVB-S2 the shoulders were easily better than 40dB @150W (that’s superb BTW). Given the UK power limit is currently of just 50W ERP for the 146-147MHz (NoV) section of the 2m band, I doubt that linearity will ever be an issue, even if using the DVB-T modulation schema. For FM the output reaches saturation (>520W) with the IC-9700 output set to 10%.

Design:
Clearly when reading the handbook a lot of time has been put into the design of this amplifier. It’s really been thought through, from the attractive and high quality cabinet design, the quiet cooling system, how it interfaces with various transceivers and how it protects itself against misuse. What's most impressive is how this has all been achieved without resorting to overly complex technology, with its accompanying built-in obsolescence penalty. This is an amplifier that most competent amateurs will be able to maintain themselves for decades; in this throw-away world we live in that’s something I believe many amateurs will appreciate.

Performance:
My tests using TV and SSB have shown this amplifier to be very linear indeed. I also have quite a long coax run, so I need 500W at the Amplifier to achieve full UK legal (400W) at my [Dual PA144-432-14-1.5AP] antenna.

Protection:
The protection circuits have been carefully thought through, overdrive, over temperature and SWR protection are all built in.

My recommendations when ordering:
- Do add the 0dBm monitor point option, this is very useful if you want to see your spectrum output on (say) an SDR or Spectrum Analyser.
- I ordered the amplifier with the Black Anodised front panel, this makes a nice visual match with the IC-9700 and many modern radios.
- For the IC-9700, if you are also ordering 70cm and/or 23cm amplifiers then do consider ordering The Dx Shop’s PTT Multiplier, this will interface with the CIV port and send switching to the correct amplifier for the band in use. All the required leads are supplied with the unit and a high quality RCA “phono” cable is included with each amplifier.
- Consider the inter-connection cables that you’ll require and order some from The Dx Shop with the amplifier.

Finally, I have the 300W 70cm version on order which I expect to receive in the next couple of weeks.
G8RBW Rating: 2017-08-22
Very polished performance Time Owned: 0 to 3 months.
I was lucky enough to buy this linear second hand for a good price as an upgrade (I ran 180 watts for several years and then upgraded to over 300 watts and when this did not upset my close neighbours thought I'd go for the full UK limit of 400 watts).
So far it's been a very happy experience with no problems at all. I particularly like that it is possible to talk to the people who design and build these Gemini linears on the phone (and they are VERY knowledgeable!). The amp is quieter than I expected and not stressed when putting out 400 watts of SSB with long overs. Highly recommended!