Re: Increasing the range of varicaps, tips and tricks needed
So you are right on the money there. I doubt if you can do much better than that.
I used two BB112 which go from 440pF to 35pf with an input of 0 to +10 volts.
Frequency was 497Khz at 0v, 500 Khz at +5v and 503 Khz at +10v.
Amazingly linear, and the frequencies were within a few tens of Hz.
So my capacitance range is around 35pF to 440pF (about 12.6 to 1) per varicap, and I used two in series across a two terminal 500 Khz resonator.
Likewise, my restriction to VHF and above was lifted when the compulsary Morse test was dropped in the UK. Living in a deep and sparsely populated valley, even a few Km is considered a good range at VHF/UHF and there are no other operators or repeaters in range. HF opened up new posibilities and I now have an IC756 to play with although I have never used it for transmitting CW. I can read Morse but not at high speed, I used to be anble to do about 15 wpm but my brain has shrunk a bit since then! Using it as a broadcast receiver, I listened in to a show from a local station in Alice Springs a while ago, phoned in and got interviewed on-air!
Suggestion for that schematic: move the 100nF cap from the TOP of the volume control to the junction of the 10K and 22nF capacitor, that will remove the DC from the filter switch. You can then replace the 100nF in series with the switch with a parallel LC filter so you get an audio peak for reading CW instead of just HF cut.
Brian.
You mean something like this?
Just a note, this regen stage already has an audio peak on near 2.5KHz, which is a bit high of course.
Nice transceiver you've got there! I could only afford an IC728, but It has an oven and 250Hz filter installed.
Remember last time we chatted about it? I had not got an antenna or a PSU. Now I have both and made SSB contacts through out Europe (Russia weak). One contact came from Canada one day, and I just use a 10-12m sloper wire without any ground!
The closest to UK was Belgium and I was 5-9, so I believe UK won't be a problem during good conditions. I would be really happy if we could talk on air, it will be a challenge, but also fun as well! If you like too, we could schedule such a QSO. Of course, the invitation goes also to anyone from here interested!
I dream the day I will find some people to talk for technical issues on HF. Most not interested in this aspect.
That is why I have made this program http://5.55.76.118/schematix/ to exchange schematics over radio. But I find no one to test it on air!
Thats exactly what I meant. It wouldn't give as sharp a peak as an active filter but it would be better than just reducing higher tones.
I'm happy to try a HF QSO and send/receive using Schematix. My antenna isn't very good, just a long wire running NE/SW and ATU so it isn't even 'aiming' at you but it's worth a try. I use MultiPSK running under Linux which seems to work very well. There might be a problem with RF feedback into my codec box but even if I can't transmit data back to you I should still be able to receive it. I did some tests using FreeDV (narrow band voice) a few months back which worked fine when receiving but everything in the shack lit up and rattled when I hit TX!
Brian.
Ok Brian, that's nice. My antenna is randomly placed and it seems it works whole Europe, but not too well Russia and not at all Turkey. The funny thing is that in Greece, I can barely be heard and in 10Km from home I can also barely heard, where I can be heard in Canada! But in your direction it does well anyway.
Ok I only have to build an audio and ptt cable to connect the transceiver to the PC, I will let you know when this happens, probably next few days.
Please email me, so that we can arrange this more directly. My email is found at the end of my website www.qrp.gr
About the filter, Although more complex, it might worth the effort to build something like the one used in this receiver http://www.ke3ij.com/JFETrgn.htm It could provide some preamplification (which I need) and better filtering response due to the active devices used.
I know, the simplicity of the single shunt capacitor is of no match and the beauty of regens is that they are kept simple. But I want to see if a nice, mostly single signal, receiver can be built even if it is a bit more complex than bare bones, but not too complex though, like a phasing direct conversion or a superhet.