Homebrew

Receive BPF

Having added the trimmer caps to the BPF I still had issues, the filter was off band and I couldn’t quite work out why, I fiddled a bit, replaced one of the variable caps which wasn’t measuring correctly, and then decided to model the filter in LTSpice to reproduce my VNA findings.

First of all I reproduced the schematic (with a 50 Ohm load). C3 and C6 represent the variable capacitors, adjusting them to 35pF brings the filter on band.

Filter as designed, C3 and C6 are the variable capacitors

I managed to reproduce my problem by changing the 150pF capacitors (C2 and C5 below) to about 190pF, however I was fairly confident in those components, so I played with the inductor values and managed to reproduce my VNA findings almost exactly by adjusting the values from 0.4µ to 0.5µ.

A closer examination of my filter and it became clear that the issue was the windings on the inductors which were too closely placed, once I spaced them out further I was able to get the filter on band.

Start On The VFO/BFO

After a period of procrastination I’ve been forced to take a short pause on the IF board whilst waiting for some enamelled copper wire of the right SWG to arrive for the toroids, so thought I’d make a start on the VFO/BFO module.

When I originally prepared the board I didn’t test the breaks in the traces for continuity, so before placing the components I checked them and there were a number of breaks which had continuity. After sorting the continuity I placed the power regulator first (and tested it), I then started to place the rest of the components.

I’m not all that happy with some of the soldering on this but I think its good enough and shouldn’t need redoing.

IF Board Relays

I’ve made a little progress on the IF board and started wiring up the relays, I also confirmed that they switch as expected with 12v. For the wiring, other than the 12v line, I used offcuts from components, however I’m not convinced that was the best move as it was somewhat tricky soldering them on to the relay and I’m concerned that I don’t have the best connections. I’ll take another look and if I don’t think they are good enough I’ll give them another go.

IF Board Power Regulation

I’ve made a slow start on the IF board now, just the power regulation, decoupling capacitors and RF chokes. I was planning on connecting up and testing the relays too, but I got a bit confused on how to hook them up, I’m using DPDT relays hooked up in ‘SPDT mode’ so am holding off until I can get some assistance from the ScratchQRP group.

IF Board Layout

So far when doing Manhattan construction I’ve tended to have a general idea of where everything will go (much simplified thanks to the build documents on this project), I then start in one place and stick and solder as I go. This method has had the advantage of ensuring that in general pads are no closer/further apart than they should be and leads to a very neat layout assuming I don’t get the board size wrong.

For this module with it being larger and more complicated than the previous ones the “stick and go” method didn’t really seen viable, particularly as I couldn’t really start at one point and build across from there. This being the case using the layout and photos from the build document I’ve pre-stuck all the Manhattan pads and the relays and soldered the IC sockets into place. Next step will be to finally start the build!

Board Prep for the VFO/BFO

I’ve made no more progress on the IF board although I’ve ordered some QRPme MePads for mounting the ICs, once I have those I put the manhatten pads, relays and IC sockets in place. In the meantime I’ve started the board for the VFO/BFO module, I am using stripboard for this as it doesn’t lend itself well to manhatten style and G0FUW produced a layout for stripboard.

I cut the board to size, pencilled in the breaks and then used a small (3mm) drill bit to make the breaks in the strip. I need to test for continuity but am happy with how it’s turned out, I just need to solder the components on now!

A Tentative Start to the IF Board

I’ve made a very tentative start to the IF board for the sudden transceiver project, it’s the largest and most complicated module (well it’s really a set of modules) so I’m taking stock as I try to figure the best way to attack it, however I’ve made a start by cutting the board, marking it out and attaching the crystals. I’ve used a few extra of the Manhattan squares to attach the crystals as one block.