Tag: N8DAH

Posted on

Digital interface kit for your uBITx

David N8DAH is now producing a very handy digital interface kit.  This is a Gordon Gibby KX4Z design, and it features:

  • On board 5v regulator that you can power from 12-13.8v or you can leave it off for direct 5v input.
  • Built in VOX PTT via reed relay
  • PTT LED
  • Input and Output gain control
  • Audio Isolation transformers 600:600ohm

The kits are available for:

US$15 unassembled or US$20 assembled

https://shop.kit-projects.com/index.php?route=product/product&path=59&product_id=120

Reference
Posted on

CW Zero Beat Kit

David  N8DAH has been working on a few projects.    The first of these is a CW Zero Beat

https://www.youtube.com/watch?v=tSUGd2Igfic&feature=youtu.be

If anybody is interested in a CW Zero Beat addition to their µBITx, then he  has nine in kit form and one built for testing available.   The kits are US$13 shipped inside the US.  Add actual shipping costs outside Continental USA. He can build them for you for $2 extra or only solder the surface mount and allow you to build your own.

J1- Power in 9-12V

RV1- Audio in adjustment

J2- Audio in

RV2- Center Freq Adjustment

Questions please e-mail David direct

David is also working on a new digital controlled audio level project (AGC) and hope to have more info soon but this is still only in the prototype stage.

David’s website is:  Kit-Projects.com

Reference
Posted on

MAX9812 Mic Pre-Amp conclusions

David N8DAH has been testing the MAX9812L Mic Pre-amp module on his BITx40.  In theory this should improve the gain and signal quality.

David says “So far its working ok at best I sound a bit robotish.”

“I am TXing at around 20w with my amp. I took the audio out through a 10uf dc blocking cap to the bitx40 mic in.  I powered the board from a 9v just for testing.  R136 is about 1/4. If you use a pre-amp you should adjust this lower or you will cause one heck of a noise on tx.  I am not yelling or shouting to get audio out now but not sure I like the audio in any case.

This is without the pre-amp … with the audio files from Michigan to Milford PA websdr

This is with the pre-amp …

David has decided he “might just stick with the slight yell to get the audio out. I like the idea of not having to shout but do not like the audio from this version of preamp”.

Others may think differently.  Mike ZL1AXG thought his “more robot-like” voice was more intelligible because it was more “punchy”.

Jeff AD6RH says:

“I used another mic housing with a DPDT switch and wired it so voltage is supplied only when PTT is engaged. I am using a CR2032 3v button cell. It seems to work fine, but I have not compared the stock vs. preamp mic with anyone on the air yet. It definitely has more average power on the watt meter. I can hear some peaks come thru the speaker when transmitting. I may try installing a pot to dial back the gain.”

Reference
Posted on

BITx AGC kit

David N8DAH has assembled AGC kits for BITx transceivers.  These were designed for the BITx20 and BITx40, but should work fine in the uBITx.

The AGC design was posted on DuWayne KV4QB’s site found here and used with permission. All kits will come with:

  • PCB x 1
  • Parts placement layout x 1
  • 2N3904 x 1
  • 2N7000 x 1
  • 47uf x 2
  • 1N4148 x 1
  • 100R x 3
  • 100k x 3
  • 10k x 1 this is extra for the user to play with attack or input values.
  • 2k2 x 1
  • .1uf x 2 unmarked tan

Missing parts will be replaced.   

This is the 3rd run of the boards.  Many group members have this AGC already in use.

Cost and options:

#1 – Kits 13$ shipped

#2 – Pre-built OT service 15$ shipped and tested

Write to David if you want to reserve a kit.

Reference

NB these are sold out as of 29 January 2018.