FS: 400 to 800 MHz amplifier 2kW peak - Page 1
Forum section: electronics / general

author: alex.forencich
author_rank: Frequent Contributor
timestamp: September 03, 2014, 11:40:03 pm
content: A friend of mine is working with an electronics recycler to get rid of a whole bunch of retired Rohde and Schwarz TV broadcast amplifiers (VH602A2). Apparently they have around 600 of these things that came out of over 100 complete broadcast systems.I'm not sure if they are all the same part number, but they cover the 400 to 800 MHz range (approximately) and they can source up to around 2 kW. They are designed to be water cooled and to run off of a 408 volt 3 phase supply, about 8 amps. The guys at R&S say they should be able to run off of 220. Each amp has 16 BLF861A transistors for the main output stage, two more for the output stage driver, and then a preamp with four more assorted amplifiers. The preamp alone can source around 20 watts or so. All of the BLF861A transistors are soldered on to four thin circuit boards that sit on a large aluminum water block. The output and driver stage are built from amplifiers consisting of two BLF861A connected with baluns and hybrid couplers. The output stage consists of 8 of these modules interconnected with an 8 way splitter and combiner tree. The output is a giganic coaxial connector on the back. A gigantic switching power supply that provides 32 volts at around 165 amps is bolted to the other side of the block along with a blower for cooling everything that isn't directly connected to the block. The preamp also contains circuitry to monitor the power supply, blower, temperature, amplifier state, and input signal level, disabling itself if an issue is detected. The preamp also has a varactor diode phase shifter.These amplifiers are a bit of a pain to disassemble, so the recycler is interested in possibly reusing them for something else if it means they are worth more than scrap value and/or don't have to be disassembled. They could make excellent 70cm band transmitters.Is anyone here interested in such a beast? If this sounds interesting, I can post some pictures of the internals.Edit: more pictures are posted here:https://www.eevblog.com/forum/testgear/rohde-schwarz-400-to-800-mhz-2-kw-tv-broadcast-amplifiers/Also added plots of the frequency response of the preamp module and power stage driver. The preamp has four amplifiers inside for about 50 dB of gain. The final driver in the preamp is rated at 30 watts and 1 GHz. The driver stage has about 15 dB of gain and should be able to source maybe 200 watts.Edit: apparently the company has decided to try listing them on ebay here:http://www.ebay.com/itm/Rohde-Schwarz-Verstarker-Power-Amplifier-VH602A2-Liquid-Cooled-2082-9000-02-/321511774684?pt=LH_DefaultDomain_0&hash=item4adb9859dc. I believe the reserve price is set at 1k.

author: CM800
author_rank: Frequent Contributor
timestamp: September 04, 2014, 07:11:10 am
content: Gosh, i would love to see a few pictures of the insides of these. I would also love to get hold of them... but i have a feeling postage from america to uk would cost quite a bit, plus nasty import tax if the price is high enough

author: iampoor
author_rank: Frequent Contributor
timestamp: September 04, 2014, 08:31:49 am
content: Where in the US are you located?Pictures please!

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: September 04, 2014, 01:08:40 pm
content: I am a ham and would be interested also ?JohnKD0CAC

author: AllanMN
author_rank: Contributor
timestamp: September 04, 2014, 01:36:23 pm
content: I am a ham and would be interested as well....AllanWB0WHD

author: alex.forencich
author_rank: Frequent Contributor
timestamp: September 05, 2014, 01:50:21 am
content: Dang, somehow I did not get subscribed to this thread. Sigh.I posted this in the test equipment section as well to try to get some more visbility, and posted some pictures there:https://www.eevblog.com/forum/testgear/rohde-schwarz-400-to-800-mhz-2-kw-tv-broadcast-amplifiers/Basically, here's the deal: the company that has the amps right now needs to get rid of them. It costs them money to disassemble them. They would be very interested in any solution that does not cost them money, even more so if they can make some money. If we can come up with a reasonable price and enough interest and pitch it to them, then you guys could get your hands on some very nice amplifiers.Also, I am not a ham and so I cannot post about this on any forum that requires a callsign to sign up. If any of you ham operators want to spread the word on other sites, that would be amazing. It's not like there aren't enough of these things to go around.These units are located in southern california. They weigh about 80 pounds or so.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: September 05, 2014, 02:12:32 am
content: Same question different thread , the ebay add an example or the ones your talking about ?

author: alex.forencich
author_rank: Frequent Contributor
timestamp: September 05, 2014, 02:21:40 am
content: Quote from: KD0CAC John on September 05, 2014, 02:12:32 amThat's somebody else. They are the same amps, though (same part number). Those units are replacement units in road cases. These units are installed in complete transmission systems (loaded into racks with controllers, power combiners, piping, etc.).It may be possible to get these amps for significantly less. If we can get enough people together and figure out a reasonable price (I dunno, 1k each plus shipping perhaps?) then I can contact the recycler and see if they would be willing to sell them for that price. I'm sure there are a lot of hams out there that would be interested in one (or three?) so if we can get enough interest and a reasonable price, then we could make this happen.

author: alex.forencich
author_rank: Frequent Contributor
timestamp: September 05, 2014, 02:58:29 am
content: Looks like the circumstances have changed somewhat: the company has decided to list them on ebay as a trial run to see if there is much interest. Listing is here:http://www.ebay.com/itm/Rohde-Schwarz-Verstarker-Power-Amplifier-VH602A2-Liquid-Cooled-2082-9000-02-/321511774684?pt=LH_DefaultDomain_0&hash=item4adb9859dcI believe they have the reserve set at 1k.