02-03-2012, 11:05 AM
Hello Al, thanks for the reply, this is the only data sheet I can find:
http://www.minicircuits.com/pdfs/SBL-1-1+.pdf
I remember experimenting with one of these years ago in a homebrew direct conversion receiver but that receiver was a solid state job, it was a long time ago and to be honest I can't remember what was what only to say that it worked and worked quite well.
I am wondering if the SBL1 (or similar type) can be grafted into a valve direct conversion receiver. I could not find the port impedances on the data sheet but I am pretty sure that they would be designed to match a nominal 50 ohms. I am thinking that the A/F output impedance from the device could be stepped up to feed a valve A/F stage by what ever means and that a VFO feed could be arranged via a suitable winding or lower end tap on the VFO coil.
So far as the R/F in is concerned then an L/C matching network between the aerial and input port would probably do but I would like to build a valve R/F preselection stage if it is possible, I am guessing that the anode circuit of that would have to be broadly tuned if I was to step down the anode impedance down to 50 ohm for the input port of the SBL1, the grid circuit would be standard parallel tuned with an aerial coupling winding to give the old time 400 ohm (approx) aerial input impedance. I realize that there might be a few small mismatches along the way but this homebrew job would be for Rx only not Rx/Tx (as in QRP) Any thoughts would be appreciated bearing in mind I'm not an R/F designer.
Thanks.
Lawrence.
http://www.minicircuits.com/pdfs/SBL-1-1+.pdf
I remember experimenting with one of these years ago in a homebrew direct conversion receiver but that receiver was a solid state job, it was a long time ago and to be honest I can't remember what was what only to say that it worked and worked quite well.
I am wondering if the SBL1 (or similar type) can be grafted into a valve direct conversion receiver. I could not find the port impedances on the data sheet but I am pretty sure that they would be designed to match a nominal 50 ohms. I am thinking that the A/F output impedance from the device could be stepped up to feed a valve A/F stage by what ever means and that a VFO feed could be arranged via a suitable winding or lower end tap on the VFO coil.
So far as the R/F in is concerned then an L/C matching network between the aerial and input port would probably do but I would like to build a valve R/F preselection stage if it is possible, I am guessing that the anode circuit of that would have to be broadly tuned if I was to step down the anode impedance down to 50 ohm for the input port of the SBL1, the grid circuit would be standard parallel tuned with an aerial coupling winding to give the old time 400 ohm (approx) aerial input impedance. I realize that there might be a few small mismatches along the way but this homebrew job would be for Rx only not Rx/Tx (as in QRP) Any thoughts would be appreciated bearing in mind I'm not an R/F designer.
Thanks.
Lawrence.
