Dual Filter Board for DigiLite 5.9 by Dave Kenward G8AJN
Download the entire BATC CQTV article as a pdf file here

This page is intended to show extra items arising from the CQTV article and some ideas and suggestions and tips.

CONNECTORS:

For a simple 6 way header and receptacle you could consider the MOLEX 22-03-2061 header (Farnell: 9731113) and SAMTEC CES-106-01-T-S (Farnell: 1667512).

If a right-angle receptacle is preffered try SSW-106-02-G-S-RA (Farnell: 1668357).

INDUCTORS: The inductors supplied in the STORE page are all 5% tolerance, markings are 5R7J (=5.7uH), 6R8J(=6.8uH), 150J (=15uH) etc.

CAPACITORS: The capacitors supplied in the STORE page are all 5% tolerance.

Here is a table of the different values needed if using a SINGLE PCB for each symbol rate.

Here is a table for DUAL 4Ms/s and 2Ms/s on the same board.

The pin spacing on the 6 way header JP4 is the usual 2.54mm (0.1”) and ideally it should be a shrouded or polarised type to ensure correct fitting, but suitable pairs are hard to find. The 'plug' on the filter board can be a right-angle type to allow the board to lay flat over the DigiLite board, or a straight plug to let the filter board sit up vertically. As it is only 18mm tall it should not present a space problem in most builds.

As with all my articles I have had some professionally manufactured PCBs produced and they are available from my website, along with a number of more hard-to-find components. However the layout is not critical and veroboard or home-etched boards should work fine. Keep any wires to panel switches as short as possible .

If you have already made the DigiLite 5.9 and have fitted the inductors and capacitors onto the main pcb they will need to be removed if you wish to use the plug-in filter board. The SMD inductors should be re-useable on the filter board, always assuming you do not destroy them in the removal process!

As the values are fixed there is no set-up needed but do use the best quality lowest tolerance capacitors possible, 5% or better is good, never mix types, the balance of I and Q could be upset and affect the digital modulation waveform.

CONSTRUCTION NOTES:

The 6 way connector JP1 should be selected carefully to fit the type of header(socket) JP4 on the DigiLite main board. It can be fitted to either side of the filter board, note that pin 1 is the square solder pad.

The I and Q links can also be mounted on either side of the filter board as desired, depending mainly on the orientation of the JP1/PL4 connector. Take a careful look at which side the links will be best before soldering up. All vias are through-hole plated so they can be soldered on only one side satisfactorily.

If you are intending to use the optional LED make sure that the JP1 connector is fitted before the LED as it may be difficult to fit JP1 flat afterwards.

It would also be possible to permanently mount the filter board using hard-wired links to the main DigiLite board instead of connectors.

BILL OF MATERIALS:

There may be other suppliers but these are the ones I have found and used for initial tests. Some of the inductors are becoming difficult to find except in large quantities.

I plan to hold a small stock of inductors and perhaps a kit of inductors for 4Ms/s and 2Ms/s. See my website STORE page for details.



F = Farnell R = RS Components M = Mouser CPC = CPC.Farnell.com

Check for any mods and updates on this website before commencing construction .