DFD4A for bench top test equipment.

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DFD4 has a built-in prescaler good to more than 2 GHz.

(shown connected to my rubidium frequency reference)

DFD4 has 4 operation modes.

The mode is displayed for a moment whenever it is changed.

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How to order? Click here

DFD4A has the TCXO Reference Oscillator option built in.

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kit ($49.95) it is not calibrated and you need to calibrate it by zero beating to 20MHz WWV or against your own frequency reference.



DFD4A is configured as a bench top frequency counter usable from 0 Hz to more than 2 GHz.

(note: 15 turn trimpots shown are not used on the DFD4A)

All thats needed is 3 switches, two resistors and two RF connectors from Radio Shack

Controls Kit add $5.00 includes SPST ON/OFF switch, SPDT FAST/SLOW switch, DPDT HF/UHF switch and two BNC connectors a 10K and 20K resistor. Everything needed to implement the counter shown above..

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A NON-BACKLIT version of the biggy display is available for the DFD4A.  Add $10 to the cost of kit or the assembled kit.

Non-backlit is ideal for bench top test equipment usage.  Of course it will not fit the enclosure example or assembled unit shown below.

Example assembly in a Radio Shack instrument case

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3" X 4" X 1 1/2"

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I made a front panel out of single sided copper clad PCB material.  It is important that one side be insulated so the display module connector wiring will not be shorted.  Otherwise you will have to be sure to space the display module far enough to clear the connector wires.

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I then made a front panel using a graphics program and printed it on self sticking Avery label stock which you can print out 3.8" X 2.7" (Click to enlarge to maximum resolution)

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Stuck it to the panel and cutout the holes.

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Then I mounted the switches, connectors and display module.  The display module self-threads with #4-40 screws.

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This is what it looks like from the front.  The display module frame protrudes through the cutout in the panel.

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Then assemble the PCB.

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and plug it into the display module.

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Add the wiring per the instructions shown above.

Connect a 9 Volt battery and install the system in the instrument case.

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The completed counter.

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Here it is connected to my Rubidum frequency standard.


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Here's how one customer packaged his in a radio shack instrument case. 

He comments also:

Building the DFD4 as a bench counter requires two resistors such as 10k and
20k, or 10k and 5k, or whatever as long as one is 1/2 the value of the
second... well, what I did since I didn't have any 20k resistors, or 5k for
that matter was to use three identical 10k resistors that tested very
closely in value.  I put two in parallel to get the 1/2 value.  Mentioning
this might make assembly simpler for those that don't think of it and can't
buy two values (one half the value of the other) at Radio Shack.  :-)

Thanks again!
- Brice

And another customers fine example

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Dear Neil,

This is to inform you that the DFD4 you sent me is up and running perfectly! I calibrated it against the AADE frequency standard at 10 MHz, and I must say it has excellent temperature stability! Far better than a commercial unit I have, which costs 2 times as much!
I am sending a photo of my finished project (JPG file). Please accept my thanks and congratulations!

73, Tasos


Hi, Neil.
I have finished casing-up my counter; I thought you might like the attached photo.
I’ve also attached the panel artwork if it’s of any use to you or others. I do panels in Publisher, laser-print on ordinary paper (light yellow in this case) and cover with self-adhesive laminating film; the one I get is cheap, it’s made by Marbig and is called Quick Laminate. I glue the paper to the panel with an ordinary office glue-stick which doesn’t “bleed” into the paper; a good quality one is required, I use UHU-stic.
I have a 12V outlet panel on my bench so didn’t use the battery; you can see the DC lead in the photo.
The case is a die-cast box painted grey (looks blue in the photo).
The counter works up to at least 2.4 GHz (the limit of my equipment); I was pleasantly surprised as it only uses point-to-point wiring, not microwave-style.
I used PCB for the panel. The bezel you supply was a little awkward to fit as it is designed for a thicker panel so I made one from plastic (I have a mini-lathe and a mini-mill).
Thanks for a great little unit; it won’t replace my HP 5345/5355/5356 combination (to 26 GHz) but it is worthy to sit on the same shelf!
Regards, Kerry .
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LED Backlit Display module also available. (Don't use for battery operation, too much current)

This module is the same size as the non-backlit module and replaces it directly. You will have to supply a dropping resistor to set the current from your primary power source. The forward voltage drop of the LEDs is 4V and the maximum current is 200ma. The unit lites up pretty good with 30ma. At this setting it can be powered continuously from the on-board 5V regulator through a 33ohm 1/4 watt resistor. From 12V you need an 80ohm/2W resistor for 100ma, or a 160ohm/1W resistor for 50ma.

For LED backlit module instead of regular module add $7.50

BIGGY lcd display module option

  View DFD4 Instruction Manual
Disregard references to offset capablility.

How to Order

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By Phone with Visa/MasterCard

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By Mail   Almost All Digital Electronics, 1412 Elm St. S.E., Auburn, WA 98092

E-Mail neil@aade.com

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DFD3 multi use user programmable unit (auto-programs itself for many radios)

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