EMRFD Message Archive 14807

Message Date From Subject
14807 2018-05-14 21:46:43 bwbangerter PC board for Hayward-Kopski TIA.

Does anyone know of the availability of a circuit board for the Hayward-Kopski termination-insensitive amplifier, which uses through-hole components?  I have several of the “QRP BITX TIA” board by Janoc from OshPark.  It is for surface-mount parts, is the size of a posrage stamp, and too demanding for my visual and manual dexterity after my 76 trips around the sun.  Any help will be appreciated.

73 - Ben, K0IKR

14811 2018-05-17 13:05:11 Mark Schoonover Re: PC board for Hayward-Kopski TIA.

I can build that for you. Take a look at my work on my website under on the bench menu. Send me the board and all the parts plus a little extra to cover shipping.  Address good on QRZ. 

14821 2018-05-19 05:33:21 Rahul Srivastava Re: PC board for Hayward-Kopski TIA.

I designed one based on Bitx variant. Will gladly make one for the original. Just let me know single sided or double sided board and 1/4 or 1/8 W resistors. 


Rahul VU3WJM
14822 2018-05-19 10:11:44 kb1gmx Re: PC board for Hayward-Kopski TIA.
Dead bug it and use what you have.  it will work.

If you want a PC board I'd go two sided with one side (Top) as
ground plane and all the "wiring " on the bottom but that may 
be overkill.

There is a lot of depends what you ant to do and what frequency range.

Generally for experiments and testing I dead bug it (manhattan or whatever)
and get to testing.  Its efficient and with care it can be very rugged and allow 
things like shielding.  That a bias on my part.

14826 2018-05-20 10:41:19 iq_rx Re: PC board for Hayward-Kopski TIA.
Amen on dead bug.  Wes and I nearly always do early/experimental prototypes without a pc board, and long ago I absorbed his wisdom on the subject: "when there is a performance advantage it is in favor of ugly construction."  Look at the photograph at the top of this web page, and you'll see many lead lengths shorter and more direct than you could get with a thru-hole pc board, and a superior ground underneath.  I started my home brewing career at 144 MHz, and the lore back then was that if you could see the leads on the components, they were too long.

Some folks seem to think that pc boards have a more "professional appearance," but my background in scientific instrumentation, where pc boards are the hallmark of mass-produced gear, has left me with the expectation that behind the front panel of anything cutting edge or interesting I'm likely to find custom-designed dead-bug circuitry.

The steps from working high-performance dead-bug circuitry to a clean pc layout with equal performance are serious and non-trivial.  It takes me about 4 pc layout spins from hardware that works well in dead-bug to a KK7B board layout that I'm willing to have  duplicated and included in a kit.  For good pc performance at 50 MHz and above, I must use some surface mount parts.  Even in designs at 7 MHz, I've been surprised when thru-hole pc board traces and a 2N3904 combined for a parasitic oscillation near 300 MHz.

Unless you are specifically designing something to be easily reproduced, I strongly recommend "ugly," "dead-bug," or "NASA lab" construction--whichever term you find most appealing.  My friend Jim K8RZ builds experimental prototype circuits that are works of art.

Study the examples in EMRFD, and enjoy the dead-bug experiments,

Rick KK7B
14835 2018-05-22 08:51:03 bwbangerter Re: PC board for Hayward-Kopski TIA.
I greatly appreciate the responses to my question about the availability of a pcb for the Hayward-Kopski TIA that uses through-hole components.

Mark, thank you for your kind offer of assistance.  I await receipt of some of the smd parts, and think I may take a crack at assembling one of the boards myself before throwing in the towel in defeat.  The surface-mount constructions you show on your web site are truly beautiful.
Rahul,  thank you for your offer as well, and for downloading your designs to the files section.  Have you had boards fabricated, and they available?

Allison and Rick, and Wes, who commented in the HyCas IF Amplifer kit thread, your points about the benefits of “ugly” construction are well taken.  The benefits of short interconnections, an uninterrupted ground plane, and ease of circuit modification, are undeniable.  This is surely the way to proceed when developing a new circuit.  As for the TIA, this is a well engineered and characterized design, and I would not making any changes.  Hundreds, perhaps thousands, of this amplifier have been built and are in daily use (how many ubitx transceivers have been produced?).  It has effectively become a “component.”  The benefit of short lead lengths and compactness from the use of smd components is what prompted my interest in the Janoc/OshPark board, aside from the practicality of me actually assembling it myself.  That board measures ~15mm x 28mm, slightly more compact than the footprint of the TIA on the ubitx board.

My intended use of the TIA is in a dual conversion HF superhet receiver of conventional design that may evolve into a transceiver, with a first IF of 45 MHz.  This will be highly modular, and serve as a platform for my experimentation.  I have built little ham radio equipment in the 60 years I have been licensed, and am plunging in in my retirement.  So far I have built a few standard pieces of test equipment:  DDS signal generator, AD8307-based rf power meter, return-loss bridge, etc.  In my working life, I designed and constructed a spectrometer and various accessories for nuclear magnetic resonance spectroscopy, used in academic chemical and biochemical research. This equipment used frequencies in the 30-500 MHz range.  No ugly construction here, lots of interconnected modules, circuit boards laid out, etched and assembled in house, GaAs FET and MMIC amplifiers, ssb modulators and image-reject mixers...  The point is, I have some experience in rf design and construction, though not in the ham radio realm!

73,  Ben - K0IKR