34 - Improvements to the Direct Conversion Receiver

[@edbeckerich3737]

That's the way I build, cut and paste different circuits... Love the video, and Merry Christmas from the states!!

[@M0NTVHomebrewing]

Thanks very much Ed. Happy Holidays! 73 Nick

[@alanmacdonald65]

Excellent as always mate. Have a great Christmas and I'll see you on the other side.

[@M0NTVHomebrewing]

Cheers mate! Wishing you both a very Happy Christmas and I think we'll need to sink a few more Forty-Niners in the New Year!

[@tdumnxy]

Great video as ever and full of interesting things to investigate. You are keeping fine company with the great and the good of amateur radio. Happy Christmas.

[@M0NTVHomebrewing]

Thanks very much Stephen. Have a great Christmas yourself. 73 Nick

[@southernexposure123]

Some transceivers are contained in a box less than12 inches (300mm) square and this one is spread over almost 10 ft (3 meters) length. lol The end performance of this one, however is almost as good as (as good as) some commercial receivers. I'm seeing the value of building in modules. Bravo and thank you for sharing your time, hard work, research and success with us.

[@M0NTVHomebrewing]

Thanks very much. 73, Nick

[@burnerphone7220]

The smoothness of that pto is awesome

[@M0NTVHomebrewing]

It's not bad at all ... for a glue stick!!! Merry Christmas. 73 Nick

[@mohinderkaur6671]

Great explanation of the audio diplexor! Thanks!

[@M0NTVHomebrewing]

You are welcome. Thanks for watching and commenting. 73, Nick

[@williamglew2851]

Merry Christmas and New Year enjoyed the last year building and look forward to the next.

[@M0NTVHomebrewing]

Thank you very much as always William. I appreciate your kindness. Look after yourself. 73 Nick

[@acestudioscouk-Ace-G0ACE]

Great to see the culmination and it all come to life! As a returner to the hobby, the discrete component, analogue design is more familiar to me as it's where I left off and this is a good primer to start over. Thanks for the great videos throughout the year and season's greetings to you and yours. 73 🎄

[@M0NTVHomebrewing]

Thanks very much indeed! 73 Nick

[@mikewhelan5992]

Interesting video Nick. Merry Christmas, EI6AU

[@M0NTVHomebrewing]

Thanks very much Mike! 73 Nick

[@technishn]

Great video. Yes, a diplexer certainly helps. Another important thing I think is a DC path for the IF port. At RF an attenuator could be used on the IF port. I did find some transformers 50 ohm to 1k which I have used. Maybe a 1k to k or 600 ohm transformer could be used for a DC path. Best wishes for the season from NZ

[@M0NTVHomebrewing]

Thanks very much. Interesting idea - there is always something else to think about isn't there. 73 Nick

[@fflynnful]

The 51 ohm termination was used in the W7EL "Optimized QRP" transceiver published in a 1980 QST magazine. The receiver was fairly "crush proof" with this diode ring mixer. I understand now that the 51 ohm termination had a lot to do with that. I have built a few different versions of that rig. Working all states using it was something I had planned to do. I had better get going on that. 73 de km1z.

[@M0NTVHomebrewing]

You are absolutely right. Thanks very much. 73 Nick

[@trevorwoods3367]

Nick. I wonder if you'd gone back to Pete's mixer after all those changes, especially the audio diplexer, how that would have performed. Would you have got the break through still. It all started with Bill contacting you. This video showed up when I did a Google search on preamplifiers to use with a direct conversion receiver, and I really enjoyed it. Thanks.

[@M0NTVHomebrewing]

Thanks very much Trevor. Doing a bit of digging revealed the fact that those dual gate MOSFET mixers just seem to be very prone to AM breakthrough. It's just one of the unfortunate characteristics of the design I fear. Depending on which band you were going to use it on though + where you live (i.e. not 40m or 20m in Europe which have close by AM Short Wave commercial bands) then you might get away with it! Thanks again. 73, Nick

[@Steve-GM0HUU]

👍Thanks for video.

[@M0NTVHomebrewing]

You are welcome Steve. 73, Nick

[@troyscott3104]

You've an awesome way about yourself in presenting concepts and ideas here. I do visit your shelf at the New Great Library of Alexandria (the internet) often. ..... Do forgive this trivial inquiry. Where oh where does a fellow find and purchase those stick/glue on pcb pads? I can't seem to search them out on A'zon. I'm sure it's just a matter of the correct key words and tricky phrases 🙂. Keep 'er going. Thanks T.

[@M0NTVHomebrewing]

Hi Troy, thanks very much. Just Google "manhattan pcb pads" and you'll be spoilt for choice. The originals come from Rex at QRPme.com 73, Nick

[@Esteban_Pascazzi_LU8ATK]

Great video ! Diplexer quit noise too? Thank you 73s LU8ATK Argentina

[@M0NTVHomebrewing]

Thanks very much. 73 Nick

[@yakovdavidovich7943]

EMRFD presents several diplexers in chapters 8 and 9. E.g., figure 8.22 on page 8.14 shows one with some slightly different values, and then on page 9.17 there are a couple; one of which is very similar to the one you referenced, and the other is a bandpass version for extra oomph.

[@M0NTVHomebrewing]

Thank you for referencing those EMRFD designs which I am familiar with. You are right that they are remarkably similar to what Roy came up with but I think he pre-dated EMRFD by many years. In fact I have a feeling that Wes, Rick and Bob included an electronic version of Roy's original design on the CD that comes with EMRFD. It is clearly something I should have paid attention to before now! Every day is a school day hey? Thanks again. Happy Christmas! 73 Nick

[@rosscammisola335]

Tip41 and Tip42 Transistor s used for Audio Amp in Class B mode can get hot might need Heatsinks and mica washers or equivalent. Traditionally class B push pull Audio Amps were used in portable Radio s as when there s no signal the Audio Amps draws less current eg in standby mode , however there might be a little distortion in sound quality but as it is be used for portable purposes these are pro s and cons of the circuit and more components are used instead of a single ic, TV Engineer Ross

[@M0NTVHomebrewing]

Cheers Ross. 73, Nick

[@cozycactus]

diode rings mixers have 50 ohm impedance on LO input, so they need much more current. on the other side fet mixer have high impedance gate so they need only voltage. the problem that when you increase the current through diodes their low frequency audio noise increases so this drops receiver sensitivity

[@M0NTVHomebrewing]

As the saying goes, 'There's no such thing as a free lunch'! I find that so much in electronics comes down to compromise - the only question is what kind of compromise can you live with? Thanks for watching and commenting. 73, Nick

[@cozycactus]

@@M0NTVHomebrewing thanks. have you tried antiparallel diodes (harmonic) mixer with direct conversion receiver? in childhood i built receiver with it based on RA3AAE schematic

[@M0NTVHomebrewing]

Hi, no I don't think so. I'll have to check it out. Thanks.

[@cthoadmin7458]

You can always rely on Pete Juliano for robust audio!

[@M0NTVHomebrewing]

You certainly can! 73 Nick

[@johnwest7993]

Since I've heard AM radio stations simply by hooking an antenna to an audio amplifier is there a chance that the audio amplifier was simply rectifying AM pickup, and that the inductor (L3) and bypass cap (C1) on the input to the audio amp cut out the AM RF that was being picked up, and the 51 Ohm matching wasn't really what was fixing the problem?

[@M0NTVHomebrewing]

Hi there! Interesting idea but I'm pretty sure it is the impedance match that makes the difference. I've swapped audio amps in and out and (without the W7EL Diplexer in circuit) I get AM breakthrough. I've swapped product detectors in and out too. I've also usually built an audio low pass filter on the AF(IF) port which looks very like Roy's diplexer but has no impedance matching - I still get AM breakthrough. The only solution I've found to date is a double balanced diode ring mixer (product detector) + W7EL Audio Diplexer. If you haven't already you might find it interesting to check out Bill Meara's (N2CQR) KZbin channel ('Soldersmoke') where he tackles this same issue recently. Thanks very much for watching and commenting. Happy Christmas! 73 Nick

[@andye2005]

Very well done, Many thanks for an informative and interesting build. I've thoroughly enjoyed all your videos. I really want to have a go at a DC Rx, but like always I keep getting sidetracked - .I do have a large box of "bits" ready to work with so no excuse really! Have a really good Christmas and a Happy and prosperous new year. Looking forward the the adventures in 2023! Andy G0POY

[@M0NTVHomebrewing]

Thanks so much Andy. Have a great Christmas and Happy New Year yourself! 73 Nick