150KHz-30MHzReceiver Design, Revisited


Senior Member
On 15 May, 2007, kranenborg opened a thread discussing the design of a wideband superhet receiver. His goal is

My final, ideal goal is the following type of receiver:

- Double-Conversion Superhet
- Receiving range 150KHz - 30MHz (LW, MW, SW)
- Receiving modes AM, SSB, FM, DRM
- selectable IF bandwidths (PICAXE controlled)
- SA602A first mixer at 10.7MHz first IF
- TDA1572 (or TDA1072A) amplifier, second mixer + detector at 455KHz (single-chip AM circuit)
- PICAXE-controlled DDS circuit for receiver freq. oscillator
- PICAXE-tuned preselector stage
- PICAXE-controlled RF pre-amplifier (amplification control dependent of frequency and time!)
- Extreme user friendliness using PICAXE control circuit (fully automatic + full manual modes)
- Possibility to download and directly use SW broadcast schemes from internet
- Single PICAXE used (PICAXE-28X1)
(I'm going to address the following comments directly to Jurjen.)

Jurjen, I've been down that road a number of times over the years, to varying degrees. In every case, I've found that I'm no Wes Hayward or Ulrich Rohde. I've expended lots of time and effort, spent lots of money, only to wind up with something that fell far short of my goals, and didn't come close to matching the performance of a commercial receiver that I could purchase for much less money.

Unless you have the equivalent of a commercial laboratory's worth of RF test equipment and the knowledge and experience to use it, and a commercial fabrication facility in your garage, the homebrew superhet project isn't worth it for anything other than the knowledge and experience you'll gain (and perhaps the odd piece of RF test gear that you'll fabricate or acquire.)

However... and that's a big however...

The situation has changed. A man named Dan Tayloe, with a stroke of genius, has re-opened the door for the amateur to build a no-compromise, high-performance receiver with unparalleled performance, equivalent to anything that the commercial laboratories can turn out, using only the limited resources that we amateurs might have available to us in our home laboratories.

Tayloe has invented (or possibly re-invented) a commutating detector, placed immediately after the antenna jack. The detector provides all the tuning and selectivity that a superhet would gain from its RF amp, first mixer, IF strip, and filter(s). Lost in the process are all the dynamic range, intermodulation, image, spurs, noise, and compression problems caused by the RF amp, first mixer, IF strip, and filters. :)

The antenna connects directly to a 1:4 analog multiplex driven by a clock that's effectively four times the tuned frequency. The output of each mux channel feeds a capacitor that acts as an integrator. Each capacitor is switched in at 0, 90, 180, and 270 degrees at the tuned frequency. The RC time constant of these integrators determine the basic selectivity of the receiver, and the tuned frequency is determined solely by the rate at which the mux is clocked.

The outputs of those integrators are combined, producing an I and Q channel (90 degrees out of phase) that can be processed using a Weaver phasing network or fed to a sound card for downstream DSP detection and processing.

This is a pretty exciting concept. The front end is quite simple; just a few high-quality chips, some even available in through-hole packages. The most complex part of the receiver is the LO, which can be provided by a commercial or kit DDS generator. (Click the picture of the "IQPro".) Since there are no RF components prior to the detector, general coverage (broadband) performance is inherent in the design.

And the very same process works in reverse for transmission, greatly simplifying transceiver design.

I first heard of Tayloe's detector a number of years ago. I was excited, but decided to wait until a few receivers had been built to see if his concept provided the promised performance, or whether there was a fatal "gotcha" hiding within his design. Well, I'm embarrassed to admit that, in those years, I'd completely forgotten to keep tabs on its progress.

I recently stumbled across a link to a radio implemented using the Tayloe detector. The receiver showed promise, so I did some more searching and found a veritable flood of receivers and transceivers that implemented the Tayloe design. And the promise of high performance and inherent simplicity proved true. Here's a link to a relatively simple CW transceiver built using a Tayloe detector. This paper presents a detailed analysis of its performance, showing that the Tayloe detector, properly implemented, outperforms the best commercial superhet designs.

First, how does this pertain to the Picaxe, and second, what are the implications for us amateur scientists?

Full control of a Tayloe receiver is well within the capabilities of a Picaxe 28X1 or 40X1.

For us amateur experimenters, we can implement and experiment with Tayloe receivers without a king's ransom worth of test equipment, or access to a commercial fab factory. There's very little RF-type circuitry in the design. Most of the receiver is implemented with technology well within the capabilities of the amateur experimenter to understand, build, and measure.

Some further links:

Dan Tayloe's white paper that explains his design.

A stand-alone receiver implemented with a Tayloe detector.

A series of articles, "A Software-Defined Radio for the Masses." Scroll down the links; these four papers will be found about two-thirds down the page.

In addition to a good description of the Tayloe process, these papers are a very good primer on PC-based DSP processing, with lots of "how-to" information.

I haven't begun actively experimenting with Tayloe detectors yet, but I've been studying hard. I just ordered a DDS-60 kit, which incorporates an AD9851 DDS chip. This doesn't include a processor, so I'll experiment with a 28X1 for basic control.

The AD9851 isn't really suitable for a high performance receiver due to its 10-bit DAC. It's probably going to produce a receiver rampant with spurs. However, the kit is dirt cheap. I think it will provide a lot of useful knowledge and experience without costing an arm and leg.

(My budget for my initial experiments is in the vicinity of USD $150. Unfortunately, a good deal of that figure will be shipping costs. Grrrr!)

If it all comes together, and I find that I want to actually build a high quality receiver, I'll consider something that uses an AD9854 DDS chip. That chip contains a 12-bit DAC, and should provide substantially better spur suppression than the AD9851 chip.

So, Jurjen, if you're still pursuing your HF receiver design, I hope that the Tayloe detector will provide you another option. If your project has stalled, maybe this will get it back on track. For those who have never contemplated a homebrew HF receiver, Tayloe opens the door to performance that you can actually attain, at home, and for not very much money.

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Why not PM him Tom? May be quicker.

A helluva top project and majorly eduational too. I can see it taking a wee while and costing a few pennies. But serious Kudos if it works.

In the meantime I'll use my Grundig GUYB80 at £48.


Senior Member
Dippy, I'd actually started that post as a PM. But, as I was writing it, I realized that the topic could possibly be of interest to others rather than just Jurjen and yours truly. (Stan comes immediately to mind.) So I proofread it a bit more carefully and posted it for the betterment of one and all. :)

Know what you mean about the Grundig. About all I listen to these days is my little old portable Sony. (Which is sort of a crime, since I have a Drake R8B and a TenTec RX-320 gathering dust.)

Yes, it should be fun, and a good learning experience, exploring such an exciting concept. But, since I don't really need another high-performance HF receiver, I can't see pursuing this farther than the exploration stages. Which is why the tight budget.



New Member
That is very impressive. I remember switched capacitor filters coming along and changing audio processing, but this takes it to a whole new level by switching capacitors up at RF frequencies. I am still trying to get my head around it all.


Senior Member
Yep Tom - thanks! I've built various receivers and read articles in QEX and such and appreciate the references [I built the kit FCC-1 & FCC-2 DDS syntesiser last year from norcalqrp]. Somehow it all seems to be getting more comlicated rather than toward simpler designs... [I published an article in CQ about 45 years ago which was a receiver with xtal converter front end and regenerative detector - it also generated a back signal for real QRP - I think it had 4 transistors and worked amazingly well for cw - 'RXT-2']. 73...

BTW a way to clean up the DDS is to phase lock an oscillator to it with a longer time constant - unless you have need for very fast frequency changing spread spec and such...
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Senior Member
Howdy, Premelec,

I've been wracking my brains, wondering if there was even the tiniest chance that I might have read your CQ article. Lessee... I would have been about 15 back then. Although I was licensed and had a minimal CW station, at that point in my life I was more interested in sports and girls :) than ham radio, but you never know... In any case, congratuations! I've never had an article published in a ham radio magazine (although I did submit one to 73 magazine many years ago...)

Somehow it all seems to be getting more comlpicated rather than toward simpler designs...
That's the real beauty of the Tayloe detector. Other than the LO system, there just isn't much to the receiver section of one of these. Which is why the concept is so exciting. We hobbyists haven't had a chance of matching the performance of a commercial receiver since the vacuum tube days. In the intervening years, it's been largely pointless to attempt a homebrew HF superhet.

Suddenly, it's practical for us little people to once again experiment with HF receivers, with an excellent chance for success and winding up with a high-quality receiver for our efforts.

A field of electronic experimentation that's been largely closed to us for over 30 years is, once again, a practicality.

(And although I've only mentioned DDS frequency generation, that's surely not the only system that one might use for experimentation. For limited tuning ranges, a VCXO or permeability-tuned oscillator, consisting of a couple transistors, is more than practical. For coverage of an entire sub-band, or maybe even an entire shortwave band, something like a Huff-Puff-stabilized VFO might be in order. Lots of ways to skin a cat. Experimenters can build a minimal Tayloe receiver very simply and cheaply.)

BTW a way to clean up the DDS is to phase lock an oscillator to it with a longer time constant - unless you have need for very fast frequency changing spread spec and such...
Yep. Well aware of it. The problem is the 60:1 tuning ratio involved in a 0.5 - 30 MHz receiver. That would necessitate running the PLL at VHF, then mixing it down to the 2 - 120 MHz range.

I might have been able to build one of those back in the eighties or nineties. But I have no confidence that I could build such a system today. I'm just not geared up to work with sophisticated RF circuitry these days.

In any case, many thanks for your response.


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Senior Member
OK I don't think you want to design the VHF VCO - but they probably are available - In ham stuff I remember an article that loosely PLLd a standard boingy VFO every 100 Hz so it just popped 100Hz as you turned the knob... and my Yaesu FT817 sounds like that! Anyhow you might have to work with a bank of oscillators or one PICAXE controlled LC oscillator with a variable capacitor and roller inductor with 2 motor drives.... :) The question.... perhaps.... is whether to go for fun or precision!

There used to be some mechanically driven variable capacitors - wobbulator - to make FM signals - anyhow it's a lot of fun to do more with less which is presumably a reason we use PICAXEs! NorcalQrp has helped and having started out with 2 tube regenerative receivers I guess I'm impressed easily though it's nice to know that we can compete again with the Big Guys in engineering...

I noticed Wes' note on the Norcalqrp site saying some DDSs were much better than others - and more expensive likely - and getting into micro power. BTW I got the parts but never completely built the original 'Williams' DDS described in QST - he mentioned it would make a good IC - was working for TRW semiconductors at the time. Hams certainly have furthered the state of the art... anyhow it's likely with the great increase in RF devices the electric soup [QRM] will obviate the need for really good receivers - sorry - very sorry - about that... :-( There's still SETI...

Enough OT back to the digits... 73


Senior Member
In ham stuff I remember an article that loosely PLLd a standard boingy VFO every 100 Hz so it just popped 100Hz as you turned the knob...
Hams call that "Huff-Puff" stabilzation. It's a sort of frequency-locked loop arrangement. It's a nifty idea.

OK I don't think you want to design the VHF VCO - but they probably are available
Thanks! I did some searching, and found that Mini-Circuits sells a line of canned VCOs that might be suitable. Lessee... I have a couple extra SA612s in my junkbox left over from a QRP SSB transmitter IF strip project, and the filtering should be straightforward... just a low pass on the output of the mixer. And there are gazillions of PLL chips out there...

A "DDS cleaner" might be simpler than I thought!

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Senior Member
I found a freeware PC sound card demodulator for any receiver that provides I & Q (in-phase and quadrature) baseband audio outputs, such as the Tayloe detector does.

The program is called SDRadio, written primarily by Alberto, I2PHD.

It demodulates AM, AM-Synchronous Detection, USB, LSB, and FM. It provides drag-to-set filtering, AGC, and noise reduction. And did I mention that it's free?

The availability of such a program greatly simplifies the receiver design. (I just about had a heart attack when I priced the 1% capacitors needed for a Weaver phasing network. The sound card program saves many dollars worth of parts, and provides lots of bells and whistles that wouldn't be provided by the phasing network.)

So, at this time, the receiver will consist mainly of a 74CBT3532 1:4 analog mux, 74AC74 D flip flop, INA128 x 2 instrumentation amps, a DDS-60 DDS board, and a Picaxe 28X1. All but the 74CBT3532 are through-hole parts. The -3532 is a 16 pin SOIC chip, which isn't hard to handle, as SMD stuff goes.

Still waiting for the DDS-60 kit...


Instrumentation Amp

   TI INA128 - PDIP8

      Mouser P/N 595-INA128PAG4 - $5.80

      Digikey P/N INA128PA-ND - $5.80

   TI INA121 - PDIP8

      Mouser P/N 595-INA121PA - $5.00

      Digikey P/N INA121PA-ND - $5.00

Dual-D Flip Flop

   74AC74N - PDIP-14

      Mouser P/N 595-SN74AC74 - $0.40

      Digikey P/N 74AC74PC-ND - $0.55

Dual 1:4 Mux

   74CBT3253 - SOIC-16

      Digikey P/N 296-6432-5-ND - $0.72


Senior Member
Hi Tom (and others)

Time for me to give a reaction, albeit short. Very interesting concept, and I will seriously study the possibility. Thanks!