DIY rack-mount headless HF transceiver based on the HL2

[Vince Conroy]

Hi, I'm new to this group and a fairly new Ham, but long-time electronics/software tinkerer. I'm considering building a "headless", 1U or 2U high 19"-rack-mountable HF transceiver based on the HL2 board, an HF power amp board (maybe based on this), filter board and controller for band-switch control etc. Think "poor-man's Flex radio" :). 

I would install the transceiver in a rack where my network, server and home automation gear is located. This is also where I have easy access to run coax outside to antenna(s) and my rack has a beefy UPS for power outages. As I am more of an IT guy than a Ham the idea of running it all headless and accessing the radio remotely from my laptop or a large screen is really appealing :). 

Not to get too far off of the core HL2 focus of this group, one question:

Any reason that a high-quality (low-noise or filtered) PC-type switching power supply would not be ok for the 12V power to the HL2 and amp? 

If anyone has any other thoughts or "gotchas" about this idea, would love to hear. So great to find this group and all of the expert knowledge I am sure to tap into as I explore this more. 

 

Vince - KN6ZRM

[Clifford Heath]

Please consider lightning protection for your networked equipment before wiring external antennas to it.

In addition to the unavoidable exposure to the above-ground power grid, my house has an aerial cable Internet connection. I have the radio and my cable modem isolated from the rest of the network by an optic fibre.

Clifford Heath 

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[Alan Hopper]

Hi Vince,

I often run my HL2 from a pc psu with no problems.  I have no experience of of using one with an amp.

73 Alan M0NNB

[John Burch]

I have been trying to work through this very thing, not to rack mount it with my servers but just to use a set of rack mount rails on a desk to rack it there for saving desktop space. I think the biggest issue is more about the amperage needed to run both the amp and the radio. I have been looking at something like this 48volt 12.5 amp power supply and then running it through an adjustable buck converter to adjust it down to 13.8 (seems to be a good voltage) which if my math is right should give around 40 amps of current to play with.. They other thing I would/am worried about is rf shielding between the supply and the amp as well as between the amp and the radio.

John - KC0ZOD

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Remember its all fun and games until someone loses an eye. Then it is fun and games with out depth perception

[Heath Petty]

I would not down convert from a 48v PS to 12v. Finding high quality, high amperage buck converters would cost as much as just buying a good switching PS or even a linear PS for 12v. I have a setup similar to what you describe, it sits in the corner of my garage. I use an astron 35m PS. I got it in a trade, and it was a good deal. Keep your eyes open, then come up used often. I have so much RFI at my QTH (from both my home, and from my neighbors homes), so even if a PS does put out noise, its not likely i'd even be able to tell it apart from all the other noise. With a computer rack and servers, I think you may see quite a bit of RFI from them.

To give you some data, my HL2 and PA-100D running at full tilt pulls about 22A. I don't usually run it that high, my shack at home is for very casual operation, digital modes, and testing stuff for eventually being used in the field (POTA SOTA etc).

-Heath

[Clifford Heath]

You can get server power supplies that directly produce 40A at 12V. I even have an HP one here that produces 240A (3kW) but what kind of PA could use that much power at 12V?

Clifford Heath 

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[Max]

It's very common to use server rack power supplies (48v tweaked up to 50v) with the higher powered LDMOS amplifiers. I've got HL2 running on a standard 12 volt 2 Amp "wall wart" PSU (switcher but carefully picked to be RF quiet) and the HL2 directly drives my 600W LDMOS linear.

The linear is power by server PSU Eltek Flatpack2 3000W @ 50v which was recommended to me by more than one linear builder/seller as being (1) RF quiet (2) plenty powerful enough and (3) commonly available at low cost (it was very cheap on eBay but beware some "chancers" wanting much larger money, especially on the online ham markets). It all coasts along with no drama and no RF noise that has ever caused me any bother on HF. Assume there are 12v PSUs of similar pedigree readily available at low cost on eBay.

73

Max