Receiver First IF Stage

By | 24th June 2017

I started the build of the receiver first IF stage today, etched the PCB, drilled it and started assembly – how quickly 5 hours goes.

The most time consuming part for me was the drilling, however this is an art I have mastered by using a magnified lamp and lots of patience.

Receiver First IF Stage PCB

Just need to order a few components to get this finished, hopefully I should have this on the bench for testing next weekend.

2 thoughts on “Receiver First IF Stage

  1. Andy

    Hi Rob, I am working on a homebrew transceiver project similar to yourself, I have been experimenting with different IF designs and built a 3 stage cascade module which works well, at the moment I am drafting a further IF board using the AD603 voltage controlled amplifier IC’s, the data sheet for these devices looks interesting and I like the way the amplifier gain stays fixed with a constant bias value to maintain linearity, the AGC then controls a precision resistor ladder network so controlling the gain through attenuation.

    On your cascading amp schematic the L-Match on the input of the 10.7MHz xtal filter looks to have an incorrect inductance value, whist the series cap at 36pF seems to be correct I calculated the inductance value to be 6uH and not 3u3 .

    Great to see your blog on this project and if you are interested in exchanging or discussing ideas please send me an email.

    1. Robert Mullen Post author

      Hey Andy thanks for the note, glad to hear you have a project on the go – I am interested in those AD603 devices you mentioned, I will grab the datasheet later and have a gander.
      As it happens I am currently debugging the 1st IF stage as I type this, it is sort of working but the losses in the Crystal filter (probably a poor match) seem excessive and the cascode stages do not appear to be amplifying very well as I am only seeing about 6dB gain per stage and the final stage is simply not working so got some debugging to do.

      Many thanks for pointing that error out in the L-Match, you are certainly correct that the L value is wrong – not sure how I got to that number (maybe computed with red wine)
      I will correct the schematic and re-publish it later this evening and, of course, change the inductor 🙂

      It would be great to collaborate on our projects Andy, I will drop you a note over the weekend.

      Cheers and 73



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