Thursday, February 23, 2023

High School Direct Conversion receiver

After deviating from Bill's design I have come back to the fold and built the mixer as he described. Another insight is that I've come around to putting each functional stage on a board of its own rather than trying to build the whole project on one board. I don't have a 1k:8ohm audio transformer so I used a powered speaker purchased at the MRARC auction last week and that seems to hum for some reason when connected (I tried battery power on the radio).

My VFO drifts wildly but with care it can be made to work. Here's a bit of reception from 40m this morning.

Next I connected VK3HN's VFO up and see how that sounds.

Rock stable as expected but I get clicks as I tune. 


Bill Meara said...

Good work Peter! You are getting there!

-- We need to get you an AF transformer and some NP0 or silver mica caps. I can send them if you have no more local (!) sources. Please let me know.

-- It is good that you have put them on separate boards, but you need to nail it all down (perhaps on a wood board) and also move the boards closer together so that you don't need all those LONG wires linking the boards together. They are really kind of scary.

-- The video sounds good. If you just do the above the receiver will stabilize and you will be AMAZED. 73 Bill N2CQR

Peter Marks said...

Thanks again Bill.

All noted.

I've just visited "the big smoke" and obtained some suitable audio transformers.

Someone suggested grease on the tuning bolt. I have some NP0 caps on order, should be here in a few days.


Unknown said...

Clicks when you tune? I've never had that problem, so I suspect something has changed in the si5351 library you have installed. I can check the version I have if it helps.
Well done on the PTO DC Rx too.
Paul VK3HN.

Bill Meara said...

There are no clicks when you turn the brass screw in the PTO. (Sorry, couldn't resist.) How is the analog project coming along? 73 Bill N2CQR

Peter Marks said...

Chuckling here.
Some missing parts are due this week.