BATC Forum

Hello all, from across the pond.

I want to let you know of an experimental pcb I made. This is a first version and will no doubt be upgraded later.

A wideband Rx Preamp and low power Tx PA for UHF, with T/R switch. This can be built for wide coverage or for a specific band.

I consider this an adjunct to the Langstone Project: https://wiki.microwavers.org.uk/Langsto ... sion_Forum This is my first of likely many iterations which will improve the utility of the ADALM Pluto.

From the Antenna, there is a simple mechanical Tx/Rx relay. On Rx, there is a low noise amplifier using a Qorvo SPF5189Z which is a rather good device. On Tx, there is a GALI-74+ which provides about +25db of gain. There is provision for another gain stage using a MOSFET AFT05M (there is a family). The low power device is in a SOT-89. The schematic is a direct copy from the AFT05M evaluation board.

My plan is to have a single BPF on the Antenna side, which will have 2 characteristics: low insertion loss (for NF) and deep stop bands to suppress TV stations. This filter will also serve to suppress the Tx harmonics. This filter is in the early stages of development. (as of summer 2020). Don't hold your breath waiting for it.

ALWAYS OPEN TO COMMENTS OR SUGGESTIONS! Look me up W0IY on QRZ

I've just received first boards and will be delayed several weeks by an important activity. If there is interest,I'll mail 2 pcb to the UK for anyone that will really put them to use. Share with a buddy. would prefer to make just 1 shipment.

That sounds really interesting. I was toying with the idea of making a band by band selection of these but that's on hold as I could not find suitable filters. I think others are working on this too. A common design would be great but it needs to meet spectral purity too so as well as the deep nulls for broadcast make sure there is good overall suppression of out of band on TX. This might be best achieved with a tight but more lossy bandpass filter somewhere in the TX chain and a LPF on the output. Bands up to 13cm are probably the most popular. 9cm is going away and 6cm is going to be difficult using common 50MHz-4 GHz parts like the SPF5189 that don't quite make it to the band.

Mike

Hello everybody,
I am in contact with a Spanish OM who is developing a similar, very concrete project.
RX: One LNA with filter per band. TX: a small broadband amplifier, then switch, per band filter and then everyone can build external amplifiers per band.

One RX / TX switch per band and you can cover all bands in the higher bands> 70cm with a parabolic mirror and a multi-band feed.

3400MHZ is still allowed in many countries. I recently called our agency. With point-to-point connections, there should be hardly any impairments. As long as there are no large-scale disturbances, it should remain allowed in DL.



73 Thomas DL5BCA

Hi Mike

9cm is going away

Interesting, not heard anything official or unofficially to support that. The PSSR a couple of years ago specifically retained 3400 - 3410MHz so it was not included in the recent auction and MoD is still PU who allows us to keep it warm for them

73
Noel

Noel - it's going away in the US....I was replying to someone in the US.

Mike

If anyone is interested, just let me know and I'll send you a blank PCB.
Details are available on github: https://github.com/w0iy