[HBQRP] Cross post of some interesting links for builders

Fri Aug 6 11:53:24 EDT 2010

HI  HBQRP groupies!
I found this on another list, and thought that it might be of interest to some of the people on this list.  It seems like there has not been a lot of activity on this list this summer, so I don't see it as 'clogging up' the forum.. :)
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Sources and Info on Xtals, DDS etc for BITX builders.
    Posted by: "g3oth" g3oth at mypostoffice.co.uk g3oth
    Date: Fri Aug 6, 2010 6:16 am ((PDT))

Hi
I came across this msg today on the Yahoo emrfd group, which I thought would be of interest to some BITX members here.

QUOTE:

Hi Dave,

Long reply, but hopefully it contains something of use to you...

A. Crystal Filters

* I don't have specific part numbers for Digikey or Mouser crystals. But for comparison purposes for what follows, typically decent crystals run around $0.25 USD/100 or so (see Mouser P/N 815-ABL-8.192-B2, 8.192MHz, +/-20ppm).

I would buy a bag of 100 pcs or more. You can match the crystals up into sets and toss the outliers. When buying this many pieces, unit price becomes an important factor.

* I once bought a bag of 100 11.0592MHz crystals (a magic frequency, see below for more on this) from AllElectronics dirt cheap, less than a dime a piece including shipping. They worked as good as one can expect for a ladder filter at that frequency.

Deals like these come and go at AllElectronics. As of writing time the deal I got is gone. But today for example they have 9.8304MHz HC49/U (HC18/U) crystals for $0.15 USD each in 100 pcs and up; five for a buck otherwise (CAT# CRY-9830).

www.allelectronics.com

* I have heard of good results when buying crystals by the bag-full off ebaY. Here's an example:

Item no. 110469507346 (Buy-it-now), 100 pcs 8.192MHz HC49, $7.99 + $2.99 shipping by USPS. Comes to $0.11 each.

* Generally, lower frequency IF crystal filters perform better, but there are often advantages to higher frequency IF's (life's a trade-off).

* Choose crystal frequencies that are commonly manufactured. They are typically cheaper and the manufacturing batches are larger so you have a better chance at getting closer-matching parts. Because of RS-232 UART timing reasons, clock crystal "magic" frequencies that are commonly manufactured are often multiples of 300 or divisible by some factor of 2 at common RS-232 baud rates. Frequencies that are a multiple of 2 are quite common too.

4.9152, 5.5296, 6.1440, 7.3728, 8.192 (factor of 2), 9.8304, and 11.0592MHz are some of these magic frequencies. For more on this subject see the section "Oscillator & Magic Quartz Crystal Values" here:

http://en.wikibooks.org/wiki/Serial_Programming/Typical_RS232_Hardware_Configuration

Same link here:

http://bit.ly/aKJdDS

* Diz's KitsandParts site has a crystal filter "RFtoolkits" PCB for $4 USD. He sells pre-matched (+/-10Hz) sets of crystals at 5.0688 or 4.9152 MHz (there are those magic frequencies again) for $1 USD per crystal. You need to supply the the caps for his board. Vary the cap values to change the filter bandwidth.

http://www.kitsandparts.com/xtalfilter.php

For that matter, Diz's RFtoolkits may have all the board kits you need to prototype your whole radio if it is of the stand-alone type. He recently added a DDS VFO Development Kit to the line-up (more on that below with a link).

Look at the Erector RX project by ak2b in the KitsandParts user forum. That project at one point used the Hycas IF board too.

http://www.kitsandparts.com/fluxbb/viewtopic.php?id=16

* Dig around on Jack Smith's (K8ZOA) site for good articles on building a crystal measurement jig and actually measuring crystal motional parameters. Once you know the motional parameters you can simulate your filter easily in LTSpice which is free from Linear technologies. Look at the files area in the LTSpice Yahoo Group for examples of simulated crystal ladder filters. If memory serves Jack has some nice papers on designing ladder filters on his site too.

www.cliftonlaboratories.com

www.linear.com

http://tech.groups.yahoo.com/group/LTspice/

B. Starting points for a DDS or Si570 VFO. Here are some suggestions:

* K5JHF and K5BCQ have an Si570-based Si570 controller kit with shaft encoder and LCD. It is relatively inexpensive. Off-hand I don't know if the firmware is open or closed. It do remember the micro-controller is neither an AVR or a PIC though, but I suspect you should be able to get a copy of the source. If you are fixed on using an Si570 and want a tuning knob and LCD, this may be the best jumping off point. But (and a very big but) I'm not sure if the "Slow-tuning algorithm" is used on this VFO (see more on this below). You may want to enquire about this. If it isn't, then you may want to port Fred's (PE0FKO) code over from the ATtiny Si570 USB controller used with the Softrock radios.

http://www.qsl.net/k5bcq/Kits/Kits.html

Jack Smith reviewed an early version of the KB5BDC/K5JHF Si570 here:

http://www.cliftonlaboratories.com/si570_kit_from_k5bcq.htm

* WA7UFQ has a universal VFO controller with a shaft encoder and LCD that controls both DDS's and the Si570. Off-hand I don't know if the firmware is open or closed.

http://home.roadrunner.com/~wa6ufq/universal_vfo_controller.html

* Look at Diz's above mentioned DDS Development Kit RFtoolkit on the KitsandParts Web site. The firmware is open-source.

http://www.kitsandparts.com/DDS-Dev-Kit.php

There's an active area on the KitsandParts User Forum dedicated to the DDS Development Kit.

http://www.kitsandparts.com/fluxbb/viewforum.php?id=7

* Richard N8YSK sells the DDSV4. This is a "high-end" DDS VFO in my opinion as it is pre-built, uses an AD9859 and has a shaft encoder and LCD. The icing on the cake is that the firware is open-source and the processor is an ATMEL AVR (if memory serves). The firmware is written in BASIC using the BASCOM-AVR compiler; but it is too big to fit into the free version of the compiler. Fortunately the BASCOM-AVR compiler is affordable. Richard's firmware might be a great starting point for adding a shaft encoder and LCD to a DDS using a lower cost AD9834 for-example. You know all there is to know about building DDS boards, I'm sure.

http://www.rmt-tech.com/

* N3ZI sells a nice relatively low cost DDS VFO with shaft encoder and LCD. Alas, the firmware is not open source (I've asked). The kit uses an AD9834:

http://www.pongrance.com/

* Tom KM5H sells single Si570's and the QRP2000 Si570 USB controller (more on this below), see this page:

http://km5h.com/default.aspx

* If you are going to use a PC to control the Si570, you're almost there with your previous work on the Si570 breakout board and the UHF/SDR. All you need to do is add the USB/i2c micro-controller bridge with appropriate firmware.

I would consider using the circuit from the current Softrock Ensemble radios. The Si570 circuit is isolated from USB inexpensively and Fred's (PE0FKO) ATtiny firmware is up-to-date and stable (more on Fred's firmware below). The schematic for the current Softrock Ensemble kits can be found on this site:

http://www.wb5rvz.com

The Softrock Yahoo Group is here:

http://groups.yahoo.com/group/softrock40/

* The QRP2000 USB Si570 controller is available from SDR-Kits. Remember, this controller has no shaft encoder or LCD, it is intended to be used with a PC. The SDR-Kits site has a small application for Windows that will allow you to tune this board or any Si570 controlled with the same protocol (such as a Softrock SDR kit with Fred PE0FKO's ATtiny AVR firmware). This kit does not isolate the Si570 i2c control from USB, so ground loops may occur.

http://www.sdr-kits.net/

* If you are going to use an Si570, no matter how you control it you will likely want to employ the "smooth-tuning algorithm". This prevents the Si570 from starting and stopping as you tune it. But it only works relatively close-in to the current frequency you are tuned to (the latest Si570 data sheet has more on this). Use Fred's (PE0FKO) AVR ATtiny Si570 firmware as an example of how to do this. The source code is open.

http://home.ict.nl/~fredkrom/pe0fko/SR-V9-Si570/

That's all I have. Please share your project with us. Like with your previous projects, I'm sure this will be very interesting. I see this new project is not posted on your Web page or on the dds-controller Yahoo Group.

Best 73's, David WB4ONA

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So there you have it!!!
OH,   also, whats up for the next meeting?   (I have to work that weekend but I hope to stop by for a short while)
73 - Arnie KA0NCR
EN11SK14wt

P.S.   found this neat mapping thing, it will give your grid square down to 10 characters if you hunt it down on map web site by zooming in and clicking on your house..
http://no.nonsense.ee/qthmap/