We are using Ettus N210s in the Virginia Tech Ground Station, similar problem in needing a few tens of watts out for 100mW or less in (We also use B210s for prototyping). Keep in mind that though the ettus datasheet may say 200 mW output for the B210, it is a frequency dependent parameter. So their sales brochure will quote the highest value achieved, which doesn't necessarily mean at 2m or 70cm you will achieve the same output power. Also, generally with these products you'll want to back off the tx gain parameter to avoid signal distortion that may occur at higher gains (and thus closer to the final output power). In my experience 50mW-100mW is a reasonable guess for a decent power level that can be achieved without significant signal distortion (lower is better if you can afford it).

I looked into the Toshiba Module solution mentioned, and it is a pretty decent solution, but my problem with it was filtering. Those modules are great but have pretty bad third harmonic and spur rejection. This means that final stage filtering will be required to stay within FCC limits (I think -60 dBc is the requirement, can't remember off the top of my head). The W6PQL reference is fantastic and is closer to a good solution because he has the filtering problem solved in his designs (you may have to get the filter board separate for the 70cm design, I think he includes a filter in the 80W 2m Amp design). For the budget conscious, this is the path I would recommend. I would probably look into using the Toshiba modules with lower output power (single digit Watts) as a driver for something like a Mirage Amp (that I think has the final stage filtering built in).

For our final design at the VT ground station, we settled on Kuhne amplifiers. A lot pricier than the Toshiba Module solution (though on the same order as say a Mirage amp), but they have good filtering and require around 50-100 mW to achieve full drive (60W out) and no intermediate amps required. (We want lots of TX power for command and control reasons to have plenty of margin on the uplink, for normal operations we'll be way down in the single digit Watts output power area)/

Search these model numbers on the kuhne website (http://www.kuhne-electronic.de/en/home.html) for the product pages: 2m Model: MKU PA 2M-60W HY 70cm Model : MKU PA 70CM-60W HY 23cm Model: MKU PA 23CM-100W A

(Note, the 23cm Module requires 500mW drive for full 100W out, I'll be looking into getting some minicircuits amps to provide a gain stage between the USRP and the Kuhne Module. We will primarily be using this for EME work though where we want the full drive. For sat work we will be way down from 100W output power so we don't blast any foxes out of orbit, Hi Hi :-) )

I can't tell you if this is a good plan or not yet because we are in the processes of assembling the amplifier decks this semester. A HUGE part of that process will be testing the amplifiers with the Ettus USRPs to characterize final power levels, signal distortion, and making sure we meet FCC requirements, etc. Also this semester we hope to get our website up and running where we will then post this kind of performance data, so stay tuned for that.

Hope this helps, Zach, KJ4QLP

Research Associate Ted & Karyn Hume Center for National Security & Technology Virginia Polytechnic Institute & State University Work Phone: 540-231-4174 Cell Phone: 540-808-6305

On 1/25/2016 1:03 PM, Edward R Cole wrote:

Juan,

You are probably going to have to build an amplifier, but many RF modules only require 40mw drive. I am building 80w 2m amplifiers using the Toshiba S-VA36: http://www.kl7uw.com/kits.htm

Other modules in that line such as S-VA10H outputs up to 14w. They all require pretty much the same pc board. I am using the board made by W6PQL which costs $17.50 without parts. Parts for the 80w amp are listed on Mouser as a special project which is linked from: http://www.w6pql.com/2_meter_80w_all_mode_amplifier.htm

If you did not want 80w output one could substitute the 10, 25, or 50w RF modules: https://www.rfparts.com/module/rfpower-mosfet.html

Not sure what you mean by "pass through" unless you mean an amp that bypasses for Receive. The W6PQL does that and has ckt for RF sensed keying in transmit or external PTT. I've enhanced the design with addition of power output metering and temp-controlled cooling fan.

But building in limited quantities means the parts are not cheap.

73, Ed - KL7UW

Date: Mon, 25 Jan 2016 10:38:32 +0100 From: Juan Sanchez jsdenis@gmail.com To: amsat-bb@amsat.org Subject: [amsat-bb] Ettus B210 Message-ID: CAD9R3jOYs1VDjxUntU1XQYi_NDvZJoY1UtbBXQ69qmb_0fEXFQ@mail.gmail.com Content-Type: text/plain; charset=UTF-8

I'm looking for some information about using some ettus SDR for sat work. I have a B210. What kind of amplifier can I use able to be driven with the 200 mW of the Tx/RX output, better if it's pass trought. My google search was unable to find some ham who has made somethin similar Is ther some similar work with another SDR? I would appreciate any kind of help... I'm a newbie... Thanks a lot. 73 Juan EB2FVT

73, Ed - KL7UW http://www.kl7uw.com "Kits made by KL7UW" Dubus Mag business: dubususa@gmail.com

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