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Hi all.

I have a Heathkit HW-7, and would like to upgrade the RX, with a barebones SI5351 module, without display, without modifying the front panel and case, using the existing analogue slow motion dial.

Is there any such thing? Or, someone can develop?

Pr Rr.

HW-7 oldie and good.? Problem is the mechanical encoding of the dial to the?
microprocessor.? Not easy and mechanically, maybe harder.? ?Reason is the
5351 needs a complex set of commands to make it "tune" and a microprocessor
to send them.

Having the display is hard to avoid.

Allison

I do have a huff puff, from Cumbria, UK, still unbuilt!

I want to replace the rx completely, making use of the antenna input tuned circuit, and use a simple Softrock receiver, as monaural audio output. The local oscillator variable capacitor, will need to be replaced by the SI5351 shaft encoder, and the only difficult part is to match the tuning rate to that of the analogue dial!


Paul
9H1FQ

You should get in in touch with Gordon Gibby. You can find him on the BitX20 email list and he might be on this one. He’s done a lot with integrating Heathkit products and Arduino based technology.?

73,
Guy N7BIR?

You will need a way to convert pulses from the encoder into frequency
changes. You will have to determine, probably by experiment, how large
the frequency change needs to be for each pulse. A further
complication is that the function is probably not a constant. The
original tuning capacitor is not linear, and they cope with that by
adjusting the marking of the tuning scale accordingly. But that could
be dealt with in software if it turns out to be necessary. (I don't
know how non-linear the HW-7's tuning is.)

Another problem is that if you tune past the point where the physical
dial stops changing, the encoder will still generate pulses but the
tuning indication won't change. That will cause the synthesizer
software and the needle to get out of sync with each other. You could
deal with that by having a calibrate function; you tune to, say, 7.050
and then push a button that moves the synthesizer to that frequency.
Or you could get fancier by installing a few microswitches that would
be activated by the tuning needle and adjust the synthesizer when they
turn on.

Sounds like an interesting project. Though it's certain to horrify any
preservationist purists who are reading.

Replace the variable capacitor with a pot connected to provide a variable voltage to an arduino. Then create a table indicating what voltage matches the dial calibrations and then use a lookup table to set the SI5351 frequency.

Hi all,

All interesting stuff, worth considering. It’s more of practical work than theoretical I guess!

Another dream I dreamt, was that of reviving the good old G2DAF receiver, which for those who are not familiar, used a front end crystal controlled converter, then, making the IF stage, as the main variable tuning. The Progrock could provide the three xtals for the front end converter, and the vfo for the IF tuning!

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