Date   

Re: Reverse polarity diode circuit

Jerry Gaffke
 

If the diode were in series with the incoming power supply, it might serve as a fuse.
Unfortunately, that is not the case if implemented as shown here:  http://www.hfsignals.com/index.php/ubitx-wire-up/
with the diode placed as a reverse shunt across the power supply connector of the uBitx.

If you are lucky, the supply you happen to be using will be fused with something around 3 Amps, 
the 1n4007 will conduct if you reverse the power supply leads, and that will blow the fuse.
And the current through the 1n4007 will never be high enough that the 1n4007's V-forward
might blow an IC.

If you are unlucky, your supply might have a 30A fuse, or perhaps none at all.
The 1n4007 will quickly turn into a puff of smoke, and the full reversed supply will be fed to your precious *Bitx*.

Here's a couple posts in an older thread that I am reasonably happy with:
    https://groups.io/g/BITX20/message/35421
    https://groups.io/g/BITX20/message/35434

The entire thread is worth reading, there are plenty of ways to provide reverse protection.
A series Schottky diode would be more reliable than any of the relay based solutions.
Whatever you do, a fuse or polyswitch is highly recommended, maybe 0.5A to the main rig and 3A for the IRF510's.
    https://www.taydaelectronics.com/circuit-protection/polyswitch-devices.html

The PFET is often a good solution, particularly on a small battery powered QRP rig with a common 12v line
to everything including the finals where you don't want to lose the 0.3v  V-forward of a Schottky diode.
If that's what you plan to do with your *Bitx*, the PFET may be the way to go.

Jerry, KE7ER


On Tue, Dec 12, 2017 at 08:59 am, Ashhar Farhan wrote:
the diode is the fuse. it costs a few pennies. i have no fuses in my junk box, i have many diodes. if i blow one up, i can replace it with another diode.
 

Re: Reverse polarity diode circuit

Ashhar Farhan
 

one can make as complicated or simple a fix for this as possible. i know that several guys blew up their rigs by connecting the power in reverse. we needed a simple, cheap and easy to do fix.

the diode is the fuse. it costs a few pennies. i have no fuses in my junk box, i have many diodes. if i blow one up, i can replace it with another diode.
 
my target builder is actually not the kit builder, but someone who is building from her junkbox. so, i go by what a junkbox might have. 

btw, talking of the chinese suppliers, i have recently bought two linear 0-30v variable voltage, variable current supplies. each for about $100. they are used to test the uBITX and BITX boards. for my own work, i have a linear power supply made out of a 5 A battery charger transformer and a hefty 78H12. it has been around for more than a decade now.

- f

On Tue, Dec 12, 2017 at 10:02 PM, Mike Yancey <mikeyancey@...> wrote:

I also recommend a P-Mosfet in the positive line.

Acts like a diode, but with much, much lower voltage drop.

https://www.youtube.com/watch?v=IrB-FPcv1Dc

I use them in things to which *could* be reverse polarity could be applied.

Mike Y, KM5Z

Dallas, Texas


On Mon, Dec 11, 2017 at 08:17 am, Don Cantrell wrote:

Polyfuses are not difficult to find. Several manufacturers, even Littlefuse. I get mine from Jameco (P/N 199938) for 55 cents each (quan. 10).

Re: Seperate group for uBITX ?

Jerry Gaffke
 

If somebody among those who wish to fork to a uBitx-only group 
is willing to administer the new group, this might even happen.
At least we would lose all those posts from people who wish to start a new group.  ;-)

Me, I don't see enough difference between the Bitx40 and the uBitx
to make it worth the bother.  Most of the Bitx40 traffic here will apply to the uBitx, and vice-versa.
If I were worried about the volume of posts (I am not), I'd be more concerned with non *Bitx* traffic.
This forum has been in existence since 2004, and has successfully covered a large number of Bitx variants
The group is named after a variant that we now see little mention of.
    https://groups.io/g/BITX20/message/2

I expect to be staying put right here in groups.io/Bitx20.

Jerry, KE7ER


On Tue, Dec 12, 2017 at 08:20 am, <nphektor@...> wrote:
IMHO a subgroup would be the appropriate option. 

Re: Reverse polarity diode circuit

Mike Yancey
 

I also recommend a P-Mosfet in the positive line.

Acts like a diode, but with much, much lower voltage drop.

https://www.youtube.com/watch?v=IrB-FPcv1Dc

I use them in things to which *could* be reverse polarity could be applied.

Mike Y, KM5Z

Dallas, Texas


On Mon, Dec 11, 2017 at 08:17 am, Don Cantrell wrote:

Polyfuses are not difficult to find. Several manufacturers, even Littlefuse. I get mine from Jameco (P/N 199938) for 55 cents each (quan. 10).

Re: Seperate group for uBITX ?

nphektor@...
 

IMHO a subgroup would be the appropriate option. 


Just my 2 cents.

National Annual Convention of Amateur Radio Enthusiast in India Dec 16 - 17

zx97lite@...
 

Hi Farhan,

Will you be going to your National Convention in Kolkata this coming weekend.

Will you be giving a presentation on the uBITX?

Thanks!

Pete  WB9FLW

Re: BITX20 Ver3C SBL 1SV149 Orientation #bitx20help

Mvs Sarma
 

here is the datasheet for 1sv149. It would clarify all doubts with no interpretation.
all the best


regards
Sarma
 

On Tue, Dec 12, 2017 at 12:58 PM, Kevin Luxford <kbgluxford@...> wrote:

When I look at the photo of the BITX20 Ver 3C SBL-1 board in the construction instructions, it shows an MV209 varicap with its bevelled side facing the 22 pF trimmer near the board edge.  Now we are using the 1SV149  for which pin 1 is the anode, and should be connected to the ground plane.  (Varicaps are reverse biassed to obtainthe voltage dependent capacitance.)  If I have read the datasheet correctly, does this not mean that the bevelled side of the 1SV149 should be facing away from the 22 pF trimmer capacitor and opposite to what the photograph shows with the MV209?

Many thanks,

Kevin VK3DAP / ZL2DAP

BITX20 Ver3C SBL 1SV149 Orientation #bitx20help

Kevin Luxford
 

When I look at the photo of the BITX20 Ver 3C SBL-1 board in the construction instructions, it shows an MV209 varicap with its bevelled side facing the 22 pF trimmer near the board edge.  Now we are using the 1SV149  for which pin 1 is the anode, and should be connected to the ground plane.  (Varicaps are reverse biassed to obtainthe voltage dependent capacitance.)  If I have read the datasheet correctly, does this not mean that the bevelled side of the 1SV149 should be facing away from the 22 pF trimmer capacitor and opposite to what the photograph shows with the MV209?

Many thanks,

Kevin VK3DAP / ZL2DAP

Re: Ubitx only on preorder now

VK3HN
 

Hello John,

I did this for a scratch built SA612 receiver recently, have a look at the vid here:  https://vk3hn.wordpress.com/2017/08/28/an-ssb-receiver-from-an-arduinosi5351-vfobfo/  

The sketch allows you to shift the BFO just like it's the VFO to get best placement in the filter passband. This is by no means original, several others' sketches allow this.  

73 Paul VK3HN.  

Re: Got a uBIX on order - thinking about FT8

Ashhar Farhan
 

The documentation is quite clear that you can select the sideband, over-riding the auto selection. No need to recode

On 12 Dec 2017 1:39 am, "Chuck Kelly" <charleswkelly@...> wrote:
Thanks all for the swift and detailed replies. Gotta love the confluence of technologies in Ham Radio today :-) 

When I get a chance, I'll report back on what I've found in my quest. 

73!

Chuck

Re: Ubitx only on preorder now

Jerry Gaffke
 

I sure hope Allard has a uBitx coming his way.

Jerry, KE7ER

Re: Ubitx only on preorder now

 

Farhan,
KC1CCR can wait until the new year. Happy to give my place in the queue to anyone who needs it by Christmas 

73 de KC1CCR 
bammi

Re: uBITX power supply

Ashhar Farhan
 

Rx draws 150 ma on zero volume. It can go up to 200 ma on peaks.the tx draws south of 700ma without modulation, peaks to 2.5A on modulation.

On 12 Dec 2017 7:58 am, "Keith VE7GDH" <ve7gdh@...> wrote:
Ashhar VU2ESE wrote...

> You can always turn down the preset on the predriver
> stage to let the rig coast under 2 amps, or... remember
> to speak softly into the mic.

What are the TX and RX currents for the uBITX on 12V to 13.8V?

--
73 Keith VE7GDH



Re: Still need some parts #w8tee #parts

K9HZ
 

This on the uBITx...  would be a nice add...


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com


email:  bill@...

 


On Dec 11, 2017, at 6:46 PM, Vince Loschiavo <vince320@...> wrote:

So just getting around to start populating my board.   Thought I had everything but no  so now the wait is in again for some assorted resistors etc  all programmed  looking forward to fitting this in the 40  

thanks for the hard work
vince
N2AIE<image.jpg>

Re: uBITX power supply

Keith VE7GDH
 

Ashhar VU2ESE wrote...

You can always turn down the preset on the predriver
stage to let the rig coast under 2 amps, or... remember
to speak softly into the mic.
What are the TX and RX currents for the uBITX on 12V to 13.8V?

--
73 Keith VE7GDH

Re: VFO Instability Ver3B #bitx20help

Mvs Sarma
 

Imagine using a fet buffer for counter instead of present NPN transistor.
 The biasing mmethods change and we only need to have a 100k or so termination of gate.
 The dee cias could well be removed.

 try once and All the best
 regards
 sarma
 vu3zmv

 

regards
Sarma
 

On Tue, Dec 12, 2017 at 6:20 AM, <paulsmi55@...> wrote:
Well, I reduced the coupling out to the freq counter to around 20pf effective which was the lowest that would still feed adequate signal to the counter. But still I have the instability the moment I connect it up. The VFO is pulled down and sometime just runs at random frequencies. Wondering if there is something wrong with the buffer itself. I am going to try pick off a signal from the buffer stage Q6 output to the mixer and see if that perhaps works. Otherwise I may have to build another stage of buffering or maybe even try another counter. Really don't want to abandon my FLL-free VFO as it is very stable without the counter connected.

Re: Still need some parts #w8tee #parts

Rob Cox (N4MN)
 

Good luck! As Tom Petty says, "The waiting is the hardest part."

-Rob (N4MN)

Re: VFO Instability Ver3B #bitx20help

paulsmi55@...
 

Well, I reduced the coupling out to the freq counter to around 20pf effective which was the lowest that would still feed adequate signal to the counter. But still I have the instability the moment I connect it up. The VFO is pulled down and sometime just runs at random frequencies. Wondering if there is something wrong with the buffer itself. I am going to try pick off a signal from the buffer stage Q6 output to the mixer and see if that perhaps works. Otherwise I may have to build another stage of buffering or maybe even try another counter. Really don't want to abandon my FLL-free VFO as it is very stable without the counter connected.

Still need some parts #w8tee #parts

Vince Loschiavo
 

So just getting around to start populating my board.   Thought I had everything but no  so now the wait is in again for some assorted resistors etc  all programmed  looking forward to fitting this in the 40  

thanks for the hard work
vince
N2AIE

Re: uBITX power supply

Arv Evans
 

Doug

Take look at the average versus peak power draw by a sideband transmitter.
You might be okay by just adding some fairly large capacitors to the laptop
power supply.  Old PC power supplies usually have a pair of 2200 to 4700 mfd
caps. 

_._


On Mon, Dec 11, 2017 at 5:39 PM, Ashhar Farhan <farhanbox@...> wrote:
You can always turn down the preset on the predriver stage to let the rig coast under 2 amps, or... remember to speak softly into the mic.
- f

On 12 Dec 2017 5:46 am, "Doug W" <KD9CYF@...> wrote:
Any suggestions for a power supply for the uBITX?  I am using an old laptop supply for my BITX40 but it is only rated at 2.5 amps and it looks like Ashhar's latest masterpiece needs 3a.  I've been through my junk cache in my office and basement without luck.  I still have to rummage through my stashes in the garage and the barn but I might actually have to break down and buy something.  Of course buying a replacement for something I think I have is usually the easiest way to find it.