#DIFX_Transceiver #difx_transceiver


Arv Evans
 

DIFX Transceiver.  Does it compliment or compete with BITX.  The design sounds a lot
Might be interesting to see how the DIFX performs for spurs, harmonics, and IMD relative
to a BITX.

Arv  K7HKL
_._


ajparent1/KB1GMX <kb1gmx@...>
 

ITs a mix of bitx and the plessy BIDI from EMRFD.

I've used the plessy Bidi and its two transistors and works well at 9-17db (depends on how you
bypass the emitters) included is a picture of page 6.61 of EMRFD.

I built a 6M compact radio using that. With the devices selected it works to about 30mhz at 17db
and at 14db good to 50.  The voltage applied must not exceed 6-8V.

Its upside is good gain easily laid out, reproducable, and compact.  Downside not easily understood
unless standing on ones head for the other direction.  The TR lines must switch to voltages with no
drop.

Allison


MadRadioModder
 

Single band radio.  Easy to make work. 

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Arv Evans
Sent: Saturday, September 15, 2018 2:33 PM
To: BITX20@groups.io
Subject: [BITX20] #DIFX_Transceiver

 

DIFX Transceiver.  Does it compliment or compete with BITX.  The design sounds a lot

Might be interesting to see how the DIFX performs for spurs, harmonics, and IMD relative

to a BITX.

 

Arv  K7HKL

_._

 


Virus-free. www.avg.com

--

…_. _._


Tom, wb6b
 

Are the amplifiers used in the uBITX actually bidirectional? They just look like two independent amplifiers pointed in opposite directions and independently switched on so they don't create a big feedback loop.

Tom, wb6b


ajparent1/KB1GMX <kb1gmx@...>
 

Tom, 

Have you ever even looked at the schematic or the web site???
That called bi-directional.   Thats the general  ways its done.

The Plessy is exactly the same only one is upside down for fewer parts as they
share the same 1k bias and feedback resistor.  The right to left is the NPN amp
and the left to right is the PNP.

If you mean the same device for either way there is a good one using a fet and a
pound of diodes and chokes in EMRFD.  

Allison


Tom, wb6b
 

Yes, as a matter of fact I have looked at the schematic.


ajparent1/KB1GMX <kb1gmx@...>
 

MRM, 

Roger that.  Pete has been doing it for a while and differing ways.  Experimenter he is.
We talk/write from time to time.

Multi-band is not terribly hard but requires attention and filtering and 
maybe layout tricks.

I've considered doing the ubitx dead bug again only dumping the Bidi used for 
something that doesn't make a 3904 vendor rich for quantity.   That Plessy bidi
I've used before for a very compact 6M radio and has good return loss and 
scalable gain.  Take out the dozen 3904 and replace with 3904 and two 3906
dial back the 45mhz gain to 10-11db.  Maybe loose a few attenuators and use
SBL1 or MD108s.  That should fit in much less space and in a nice straight line.
that alone will minimize crud pick up.

Allison