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June 2000 QST - PSK31 Transceiver

Jun 1st 2015, 21:54

W7PEA

Joined: Jun 8th 2011, 17:36
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Total Posts: 0
Small Wonder Labs is no longer around and I want to build the project outlined in this June 2000 QST project.

JUNE 2000 - QST (PG. 31)
A Panoramic Transceiving System for PSK31
Author: Benson, Dave, NN1G
Article: QST Archive in PDF format http://p1k.arrl.org/pubs_archive/99041


I am having some problems finding replacements or identifying a few of these parts, can anyone help me out with comparable part numbers.

Part Description in QST
L1 4.7 uH, 5% tolerance RF Choke (Mouser 43LS Series)
L2 1.2 uH 5% tolerance RF Choke (mouser 43LS Series)
L4 10uH 5% tolerance RF Choke (Mouser 43LS Series)
L7 6.8uH 5% tolerance RF Choke (Mouser 43LS Series)

I've pinged Mouser about these ones too. That 43LS seems to reference a XICON product they no longer carry and Xicon isn't online (closed?). I'm not precisely sure where I can vary the part against the original. I can find fixed inductors that match the uH and Tolerance, but then there are a variety of Q, Resonant Freq, and other parameters and I'm not sure which are important.

Part Description in QST
L3, L8, L9 1uH, Toko TK1411 (DigiKey TK1411)

Toko says they no longer make variable inductors and they can't ID that part number. I don't know enough to guess what all the proper specs would be for a replacement and the article doesn't supply more than that information and the schematic representation that L3, L8, L9 are adjustable inductors.

I'll share more as I go, but right now I'm stuck on sourcing the parts.

Thanks,
W7PEA \ Patrick
Jun 2nd 2015, 01:45

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
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Substituting RF parts is tricky because the measurement frequency used by the manufacturer often isn't the same as the one used by the builder--so the effective inductance or capacitance can be quite a bit different than what the part is marked.

The best way to get around this is to build and test filters with the substitute parts and adjust as necessary to get the desired performance. The same goes with impedance matching circuits.

Zack Lau W1VT
Jun 2nd 2015, 05:02

W7PEA

Joined: Jun 8th 2011, 17:36
Total Topics: 0
Total Posts: 0
Hmmm, that could be bad news. I assumed if I could find components with the same specs that I'd be fine but that is proving hard. For instance the author says about resistors. "Unless otherwise specified, resistors are 4-1/4 W, 5% tolerance carbon-composition or metal-film units. All small-value capacitors are NPO/COG types; do not substitute." And it seems to me as if 4.25W rated resistors are about as common as Sasquatch. I assumed I could pop-up to 5W, but maybe not.

He does also state after that sentence, "Unless otherwise noted, equivalent parts can be substituted." Problem is without many of the specs for the original parts its hard to match them.

I'll keep plodding a long... more may become obvious once I get deeper into this.

Thanks for that information though!
W7PEA \ Patrick
Jun 2nd 2015, 13:43

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
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Hi Patrick,

The "4" is a scanning artifact--it should have been "are," not "ar4"
You can use quarter watt resistors.

Yes, the parts are hard to substitute, which is why he was able to give away the design and sell kits. Not an easy business--as parts changed he had to find substitutes and possibly re-design boards as necessary.

Zack W1VT
Jun 2nd 2015, 18:28

W7PEA

Joined: Jun 8th 2011, 17:36
Total Topics: 0
Total Posts: 0
Hi Zack, not sure I understand what you mean about the "ar4" and "are".

For context for everyone else. In the reprinted article it actually reads, "Unless otherwise specified, resistors ar4-1/4 W, 5% tolerance carbon-composition or metal-film units." Notice the ar4 part.

I assumed that just the "e" and SPACE were missing and the "4-" was valid. Are you saying that the "4-" is incorrect and they should just be 1/4W resistors.

Thanks,
W7PEA \ Patrick
Jun 2nd 2015, 19:09

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Those are just quarter watt resistors.
More than likely some computer software mistook the image of an "e" and substituted a "4" in its place. I think Google now has better image scanning technology, but it is not widely available.

Zack W1VT
Jun 2nd 2015, 19:26

W7PEA

Joined: Jun 8th 2011, 17:36
Total Topics: 0
Total Posts: 0
Wow, that is a very confusing "typo" it totally changes the meaning of what is being conveyed.

Thanks again Zack!

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