EMRFD Message Archive 5521

Message Date From Subject
5521 2010-12-09 17:04:24 klopfensteinrex "First Receiver"
I am finishing up building my "first transmitter" and my interest is peaked. I am now looking at building a receiver. I am interested in a direct conversion receiver. I have been reading information on "A Modular Direct Conversion Receiver" on pages 8.13 thru 8.15 (also the original article on CD) of EMRFD. Has anybody built this receiver? How does it perform?

Rex Klopfenstein
5524 2010-12-14 08:27:07 Tim Re: "First Receiver"
I haven't built that exact receiver but look at it and note the similarities between it and the mini-R2 or a R2Pro. I'm very happy with both the mini-R2 and the R2Pro I built, I can't tell you how satisfying it is to hear so clearly with them.

If you build the one you mention, you might want to leave enough room to later add a second channel and the audio phase shift networks that would let you turn it into (effectively) a mini-R2 with LNA. You'll also go back and put phase shift networks into your VFO.

The "Modular direct conversion receiver" like the R2Pro and mini-R2 uses some standard many-mH inductors etc. for diplexer and audio filtering but you might not have them
5527 2010-12-15 04:14:35 drmail377 Re: "First Receiver"
Hi Rex,

Congratulations on completing your transmitter. Here are some suggestions on the receiver build:

1. As for a first receiver take a look at the Juma-RX1 design at this link:


The Juma-RX1 is a clean little DC receiver design with AGC (well... ALC really). You can buy the kit, but I would build from the ground up attempting to improve it along the way ;-)

2. One option for a DC receiver VFO is the DDS VFO from N3ZI. Look here:


There's a Yahoo Group for this VFO here:


The latest generation of the N3ZI DDS VFO seems to be working very well from what I've read. That's a big plus in my opinion, and the price is right. The thing I don't like about the N3ZI VFO is that the source code is closed. But from what I've read, there are many ways to customize the VFO operation by programming commands via the serial port.

N3ZI also has a "General Coverage" receiver kit for sale too. It's pretty much general coverage except for a small gap around 11MHz where the IF wraps (it is not direct conversion). The N3ZI receiver uses NE602 chips. Personally I avoid radios using NE602 type chips because they tend to overload easily. But many are just fine with the NE602 radios - YMMV.

3. There's a relatively new DDS VFO kit available from W8DIZ here:


The firmware for the W8DIZ DDS VFO seems to be fairly mature these days but still evolving. I believe the firmware is open.

While you're at the Kits & Parts site take a good look at the RFtoolkits available from "Diz". You can build a nice DC or even a superhet receiver with the little modules available there. The modules are very reasonably priced. But where I run into costs is when adding the little "interconnect" kits between the modules, they're kind of pricy given how many you can use. Personally I would hook the modules up with my own cabling.

The likes of the W8DIZ DDS VFO and his RFtoolkit modules are discussed in the Kits & Parts Forum here:


4. Last but certainly not least, there is a very affordable VFO kit from K5BCQ & K5JHF that uses the Si570 clock generator from Silicon Labs (www.silabs.com). See here:


Some have said this is the best option there is for a VFO. The Si570 is as stable as a good crystal oscillator, have very good phase noise performance, and none of the (minor but still present) spurs that come with a DDS VFO. I'm finding the documentati
5528 2010-12-17 14:07:17 g0kla Re: "First Receiver"

I built the R2 (by KK7B) as it is described in the 2009/2010 ARRL Handbooks. I think it is known as the microR2. There is a very similar version in EMRFD. It is a single signal direct conversion RX using the phasing method. It's more parts than the other suggestions, but it was actually easier to get going than the First Transmitter.

It is a superb receiver. An absolute joy to listen to.

I built it ugly style on three small pieces of copper clad board. One for the VFO, one for the RF and one for the audio board. I can supply more details if it helps.


5529 2010-12-18 06:54:51 kb1gmx Re: "First Receiver"
There is a near parallel group "R2Pro" here in yahoo groups
that cover the R2 family of radios and related subjects.

Yes the microR2 is a good RX, I've also built and use the MiniR2
and a variati
5530 2010-12-18 22:25:20 Ashhar Farhan Re: "First Receiver"

i would also advice you to start with the classic roy lewallen's dc receiver
(it is a part of his now classic "optimised transceiver" design). it has a
simpler circuit. once you get that going, you can easily upgrade to R2Pro by
adding the diplexers.

here is my build of that classic:

<http://phonestack.com/farhan/dc40.html>- farhan

5531 2010-12-19 08:32:00 Bob Re: "First Receiver"
Farhan -

Nice story, enjoyable narrative! Makes me want to plug in the iron!

Best Wishes,
Bob, K3NHI

5534 2010-12-21 17:00:28 Rex Klopfenstein Re: "First Receiver"
I have finished my "First Transmitter" and all seems OK. Now to play with my
Spectrum Analyzer and see what I have. I have also built low pass filter
described in EMRFD. I can check out my newly installed Tracking Generator. The
only problems I had was a bad transistor in the buffer amplifier and a miss
marked resistor in the sidetone generator.

I have decided to build the "Modular Direct Conversion Receiver" and do some
playing. Maybe in the future I'll migrate to the R2Pro.

Rex Klopfenstein