I think the PIN diodes are just fine for the job. but the reverse bias needs to be used, it think.

Mini circuits filter chips are really only designed for very very slow rolloffs- you cannot get miracles in a  1206 package

I'd recommend a 3 section helical filter from Temwell- off the shelf and about $12-$20. I use them in all my commercial equipment.. Or a BPF built with say T25 size toroids, 3 section would be enough ...

Just relax the filter you had in LT spice, so that the coupling caps come up to around 2-3 pF and then see what it all looks like.

The LNA/switches offered by most vendors are only characterised  800-2700  but may be worth while looking at 2m...

g

On 15/04/2015 4:37 AM, Shane Burrell wrote:
I'd suggest looking at newer parts for the TX/RX switch, LNA section as well as considering using parts that reduce the part count.  There are a lot of them on the board and generally parts back and front is really hard to assemble by hand.  Maybe a reduction in part count if you used minicircits filter modules?  Skyworks, Analog and others have low part LNA, TX/RX sections.  

On Mon, Apr 13, 2015 at 10:37 PM, Brady O'Brien <[email protected]> wrote:
Hi everybody,

I've been helping out with the development of VHF and up FreeDV and the minimalist VHF SDR. I've gotten to the point, on the analog side of things, that it seems appropriate to get a board made. What I've designed is a VHF frontend for further experimentation. It's based heavily on the VHF section of the DSP-10 transceiver, a DSP based radio described in the links below. Before I buy parts and send the board off for fabrication, I'd like someone with a little more radio design experience look over the schematic and maybe PCB layout. I'm using Kicad to design this. As this board is just a stepping stone, I'm going to keep it out of the Freetel SVN repo, at least for now.


Schematic for the front end: https://github.com/baobrien/vhf-radio/blob/master/exp-1/exp-1.pdf
Github repo: https://github.com/baobrien/vhf-radio

DSP-10 Part 1: http://www.arrl.org/files/file/Technology/tis/info/pdf/9909033.pdf
DSP-10 Part 2: http://www.arrl.org/files/file/Technology/tis/info/pdf/9910034.pdf
DSP-10 Part 3: http://www.arrl.org/files/file/Technology/tis/info/pdf/9911042.pdf

Thanks,

Brady O'Brien KC9TPA

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