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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | SGC SG-500 Smart Power Cube Help

Reviews Summary for SGC SG-500 Smart Power Cube
SGC SG-500 Smart Power Cube Reviews: 36 Average rating: 4.3/5 MSRP: $1395.00
Description: Amplifier: One KW - Model SG-500 SmartPowerCube
Product is in production.
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N3ZH Rating: 3/5 Aug 18, 2009 10:18 Send this review to a friend
Won't function 22 to 30 Mhz  Time owned: 0 to 3 months
Well, as you all likely know, every product gets hardware and software changes over the years. The SGC500 from years ago is not exactly the same as what rolls off the assembly line today. This applies to radios, tuners, and all equipment.

I ordered my SGC500 from R&L - they were out of stock - had to wait a month or so. It is fresh off the assembly line.

There are some new changes which are not reflected in the owner's manual - and not even on the printing on the amplifier. The final band pass is now supposed to be 22.2 Mhz to 30.0 Mhz. There is no mod required to use this bandpass filter - it is supposed to come from the factory already enabled.

For Auto band pass filtering, one needs to remove the cover and move the "Export" jumper. That's all.

BTW, I highly recommend people buy the external power switch - because it is more than a power switch - it is also your band pass filter selection knob. One position of the knob is for auto-band pass filtering. You must remove a jumper visible from the outside of the amplifier before attaching one of the power switch's connectors to the radio.

I had to call SGC tech support for locating the export jumper, and the external jumper. SGC would get fewer calls if they had a nice "getting started" brochure with pictures and directions.

OK, I primarily use the amplifier for MARS work from 4 to 5 Mhz - and it works great - I am very pleased. The amplifier can go a little further past 500 watts, but I don't want to over-drive it - plus the MARS limit is 500 watts at these frequencies.

However, I also tested the amplifier on each Ham band. And this is where I was very disappointed. From exactly 22.0 Mhz through 30Mhz the SWR goes way way up both at the tuner and the radio and the amplifier quits operating to protect itself.

I have an Icom 746pro radio to SGC500 amplifier to Palstar AT-AUTO tuner. With the amplifier off, I can transmit 100 watts with a perfect 1.0 to 1.1 SWR. I turn my radio's power down to the minimum and turn on the amplifier and swr goes through the roof.

Everything works perfectly at 21,999,999 Hz with a perfect SWR. But, moving to 22,000,000 hz and high SWR occurs.

It sounds like something defective in the last band pass filter. But, no - the final band pass filter does not start until 22.2 Mhz according to SGC tech support!

I suspect that it is either the final band pass filter, or else it may be spewing large amounts of stray RF which may confuse the circuits in the Palstar AT Auto tuner. However I don't hear sounds that the tuner making any changes to L and C, so I suspect all the trouble is within the amplifier.

Tech support started asking me to look for cold solder joints on certain components, but I'm not going to stick a soldering iron into an expensive amplifier that is under warranty. So, after owning the SGC500 amplifier just a few weeks, I sent it back to the factory for warranty work.

I called the factory today - and was told a coil for the last band pass filter was not soldered properly. It was resoldered in place, and the amplifier is on its way back to me.

When I receive the amplifier, if all works well, I will raise my review rating.
K5JAX Rating: 5/5 Jun 11, 2009 10:10 Send this review to a friend
Works very well  Time owned: 0 to 3 months
I bought this in May 2009. They seem to build them as you order. It took about three weeks.
All test were for PEP and not key down conditions. It is ONLY used as a BASE STATION unit. It is shipped as a full bandwidth amplifier now. I did need to go inside to change a jumper to allow it to auto switch the band filters. I am pleased with the way it switches them automatically. I previously owned a TenTec Hercules II amp which worked great but was limited to having a smart interface for band switching.
I have tested it with a number of watt meters, different Bird loads with different coax cables and transceivers. There seems to be a slump around 20 meters as to power out versus input. I talked with their engineer and he confirmed that it is not absolutely flat.
It makes 500 watts PEP out on all bands. On 160M and 80M it can produce a little over 600 PEP.
Their engineer inquired as to what supply I was using and indicated it was designed to operate at it's best with an unregulated 14 VDC supply as labeled. All test were done with a 4 gauge power cable. I used welding cable. I had to modify some power connectors to allow them to fit into the terminal block on the amp. Don't skimp on the wire gauge to make standard terminals work. I also used a 4 farad GSI brand capacitor. This also has 4 gauge cables about 1 foot in lenght and connected directly at the amp power in terminals. This allowed even the Astron supply to produce impressive PEP outputs. I believe the cap is critical to the operation. The Astron got extremely hot as you would expect and was not going to be the operating supply.
I thought about the Optima battery route but they are quite expensive and still need a stiff battery charger.
I was told by the factory that a switching supply would not work due to RF contamination.
I still tested an "Intelli-power" model PD9280.
This has worked out very well because it is rated at 80 amps out. I tested it with a DC load and it can produce 83 amps. I also bought the little control that plugs into the power supply and with it you can switch between operating modes since it is a SMART supply.
It has a 13.8 power up normal mode and a charge boost mode which is 14.2 VDC and an automatic float mode. All of these are controlled by a processor. With the remote I can force it into the 14.2 volt mode after applying 120 VAC. This works very well because now I match the design voltage for the amplifier. I have been using it on the air with the Intelpower and the 4 farad cap and I have had very good reports. You can place the amp out of sight but still where you can reach the on/off switch.
I have added a 6" diameter DC fan to the unit and it keeps it really cool. I took pictures of the fan installation. I will post the article on my website 73's
N4NOO Rating: 5/5 Feb 23, 2009 09:57 Send this review to a friend
Very, very nice!  Time owned: 0 to 3 months
I use this with an Icom 7000 and a Hi-Q 6/160 RT/MC-3-H antenna in my Suburban and it makes a world of difference. The most common reply is "That's the best sounding mobile I have ever heard". If you want that extra bump, this is a great amp. It has been perfect from the first time on the air. No problems at all. Try it, you'll like it!
ZS1DDK Rating: 5/5 Sep 19, 2008 06:52 Send this review to a friend
Excellent Workhorse  Time owned: months
I have 2 Cubes installed in my shack and have used both for the past year. It is an excellent workhorse and operates flawlessly. The protection circuitry makes it absolutely IDIOT- proof !
My advise: Cut a polycarbonate sheet to fit over the bottom of the amp, install 2x12v fans side-by-side onto the polycarbonate sheet(Cut holes in this sheet the size of the fans obviously). Your fans are switched on by the thermal sencing of the amp ! Now you can run as many band pile-ups as you like - no problem!
9V1VV Rating: 2/5 Jul 7, 2008 22:41 Send this review to a friend
Overpriced  Time owned: more than 12 months
The design is very good but if you study the schematic you will see that a lot of expense is involved with the uP controlled protection circuitry for the bipolar finals.

The Ameritron and Motorola 4 x FET 600 watt designs are much simpler and cost much less becaue FETS are less prone to damage and do not need such elaborate protection.

The Ameritron equivalent includes the power supply for about the same price as the SG-500, which requires a separate 100 Amp PSU.

Also, the fan kit for SGC-500 is a ridiculous price. You can make your own for a few bucks.
W8NYY Rating: 4/5 Jul 7, 2008 10:02 Send this review to a friend
Great Amp for Mobile Operation  Time owned: 0 to 3 months
I had a bit of a rough start with the SG-500. Placed the order back in March and found I was going to have to wait 90+ days for it to arrive. Being an impatient sort, I decided to spend the time making sure my mobile install was done right. My mobile installation is a Honda Ridgeline truck and decided to install this under the back seat. Got a tremendous amount of help from Alan Applegate, K0BG, and the fact that he also drives a Honda Ridgeline made his help just more invaluable.
Bonding, more bonding, 4 AWG wire runs, Maxi fuses, an Optima Red Top Battery, a 1 farad stiffening capacitor and a whole bunch of ferrite beads and more ground straps and I was ready for the SG-500. About a week after Dayton the SG-500 finally came in. As I said, my initial experience was rough. Immediately started experiencing relay issues. The amp wouldn't return to receive. As recommended I manually played with the relays a bit and that problem went away. Then I immediately started having CURR faults. I checked and rechecked everything and then finally called Tech Support at SGC. Their advice was to ship it back saying it had to be an internal issue causing the variance of current to the amplifier modules. I shipped it back UPS ground insured (gulp!) and called them the day after they signed for it. Their immediate response was it would be 4-5 weeks before they could look at it. I explained (with passion) that I had yet to have a working SG-500 and after waiting 3-4 months for the shipment it was unrealistic for me to have to wait another 4-5 weeks before they would even look at it. After some mutters of "we'll see what we can do" I hung up and in desparation called AES in Cleveland, where I purchased it. I spoke to Ben, the manager of the Cleveland location. Ben listened to my story and said he'd call me back after he made a phone call. Ben called back in 15 minutes and said he'd have a new one shipped the same day, and I'd have it the next and explained he'd deal with SGC and the other unit.
AES may not be the cheapest guys on the block, but their service and support is A++. Thanks Ben.
As promised I got the new unit the next day and after making the simple 10 meter mod (they no longer make you connect the loose wire - only a jumper change now)I put it in place in the Ridgeline. I ran it through it's set up and tests and outside of having to install one more ground cable (engine header to frame) which eliminated a fuel injector issue when transmitting on 20 meters, the SG-500 has been working flawlessly ever since.
I was more than a bit concerned after my initial experience with the first unit but now I can say, I am very pleased with the SG-500 and consider it the crowning glory to my mobile set up. Only problem is I'll never be able to sell the Ridgeline but why would I want to do that anyway? It's just the way I want it.
I rated this a 4 because of the issues with the first unit otherwise it would have been a solid 5. Pictures of my install can be seen on Alan's site at
W9BR Rating: 5/5 May 16, 2008 07:50 Send this review to a friend
Terrific Amp - Gets you over 500 watt HF hurdle  Time owned: more than 12 months
I own two of these amps. They are both incredible ampliers. Actual SSB output as read on highly accurate peak reading meter is 600 to 650 wattas PEP. These amps are bullet proof. They have so much protection for SWR, current, voltage, etc. that you cannot ruin them. Those people that complain about this amp do not hook it up right, or do not have enough voltage at the B+ terminals. Use a 1 or 2 farad cap at the terminals. Easily availabe on E-Bay or Circuit City now as the kids use them mobile for thier boom boom amps. Remote controlling this amp is a breeze as they have a remote on/off/reset terminal available that also has LED indicator voltage. Cooling fan required for CW/AM. Easy to hook up your own fan!! 30-35 wattas drive is all you need for full output

KF6IKC Rating: 5/5 Feb 1, 2008 21:22 Send this review to a friend
Great amp!  Time owned: 0 to 3 months
Great amplifier. I use one for base operations powered from a Mean Well 100 amp 14vdc switching P/S. Makes for a very small setup. The power supply is 12"x 3.5" x 5" and only weighs 8 lbs. I do not use any of the "auto" functions so I can not comment on those. I have the remote unit and switch bands that way. And key the amp via the radio. I like the unit so much that I just bought another one for a back up. It seems there have been 3-4 "updates" in the history of these amps. From the auto function switches to final transistors used. One of the units I own has the Motorola MRF-454 and was built in 1996. The other unit uses MRF-458's and was built in 1998. I am told the newer units use Toshiba 2SC2290's. Motorola no longer makes transistors.
The unit with the 454's makes more output then the one with the 458's.
When driving the unit(s) per the up the drive to just before the attenuator kicks in yeilds about 800 watts PEP with the 454's. The 458 unit gives me just under 700 watts PEP.
I only drive them with about 40 watts and get 600+ watts out on just about all the bands.
Overall I am VERY happy with the SG-500. Easy to use. Lots of built in protection. Good output. And built VERY well.
K3GK Rating: 5/5 Sep 11, 2007 17:35 Send this review to a friend
Additional documentation  Time owned: 0 to 3 months
I'm very pleased with my purchase. If you purchase the domestic version and follow the test protocol be aware that both the RF sensing circuit and the auto band switching are disabled. I run mobile, with a 100 amp/hr battery and a solar panel to keep the battery near 14 volts, which is necessary to achieve 500 watts out. My Yaesu FT-857D uses the CAT port for an adequate PTT without an interface. Local field strength reports give 2 S units over my FT-857D running 100 watts. The antenna is a Tarheel 100 and that adds another S unit at least over a small screwdriver. Great for contests and mobile Dxing using one 20 watt solar panel. Well crafted and self protected, you will soon be very fond of the little amp. SGC customer service is formulated and self protecting as sometimes happens with a mature product line. I owned a Ten-Tec Hercules and this amp performs as well in a slightly smaller footprint. As for the customer service, as stated in other reviews I miss the southern hospitality, but the engineering competence of the product more than makes up for it.
George/ K3GK
EI6DP Rating: 5/5 Jul 24, 2007 06:52 Send this review to a friend
Great Service  Time owned: months
Hello Brethren,

My SG500 arrived today from R&L Electronics. I must say that in today's world of the "fast buck mentality" R&L are a rare company. Their service was exceptional, courteous and fast. The SG500 was very well packed and more importantly the price was right.

Regarding my opinion of the SG500, well, what can I say. It is a very solid block of top quality American engineering, built for the real world, as is all SGC equipment.

WELL DONE to all at R&L


Gerald EI6DP
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