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Hi all, I am new here!

I would like to modify the rx of my Heathkit hw-7 , leaving the original front panel and case. I like to use a simple Quadrature switching mixer , thus, eliminating the common dc reciever hum, keeping the original analogue dial , feeding the existing af amplifier. Using a modern DDs or SI5351 or 570, replacing the existing variable tuning capacitor with a shaft encoder.
Any ideas please

Paul
9H1FQ

Hi,

An interesting concept, difficult part will be keeping the original dial if your intention is to maintain the original dial markings.
It would be much easier if you were to consider using a small 0.91 inch OLED for your display,? google 0.91 inch OLED Display.

There was a post earlier on her detailing how to derive quadrature outputs from the si5351 using an arduino.

This has appeared in may places...

it would be a royal pain to get a mechanical dial to encode to feed a DDS or 5351/570.

As other suggested a tiny oled display is a good way to go.

One I've seen was pretty slick but much more effort was to place a larger matrix
LCD (or oled) behind the existing slot and make a software moving dial display.
Takes a bit of programming to paint the dial (curved with dots and numbers)
and update it with a standard encoder.

To do that in the HW7 would be a lot of work.

Allison

Should be possible to use the old HW7 mechanical dial to program an Si5351..
I assume the rig has the usual variable cap in the VFO for tuning, 180 degrees of rotation.
One possibility would be to replace the variable cap with a high quality linear potentiometer,
watch the voltage from the pot with an ADC? ?Use that measured voltage to program an Si5351.
After mechanically installing the pot, use the ADC to measure the voltage at the bottom of the dial?
and at the top for each band, and associate those ADC values with the dial frequency
at those positions? All points in between are linear on both the dial and on the pot,
and so should map well enough.? A 10 bit ADC is just barely sufficient, 12 bits would be better.
If the dial is not quite linear, the software could perform piecewise linear interpolation.


The Bitx40 used a pot for tuning, read from an ADC, programming an Si5351..
So the code is pretty much already written.
I suggest you start with Allards codebase, he takes a number of measures to avoid?
noise from the pot which would otherwise cause small jumps in frequency.
? ??

Alternately, use an ADC and digital IO pins to measure the existing variable capacitor:
? ??/g/BITX20/message/52471

Jerry, KE7ER

And if you can find or fit one of appropriate size, replace 'in toto'. Could even give a 'dial pointer'.

Jack,

The thinking behind the small OLED is that it could easily be fitted? to the existing front panel without any change to the dial scale aperture.

Both display types use I2C so code to drive would be very similar but to fit the larger color TFT would probably require mechanical surgery of the front panel.

I recently bought a?couple of 0.9 inch I2C white 128x32 OLED displays for ?1.90 each from China, perhaps I have been buying badly
or looking at the wrong sources but the?cheapest color TFT display I have managed to buy was at least twice that amount.

73,

Bob GM4CID

Might get some ideas from what Pete has done with an HW-101.

http://n6qw.blogspot.com/2018/08/2018-year-of-ssb-transceivers.html

Jack,

Wearing my KISS hat!

73

Bob GM4CID