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Setting up a comprehensive station


Christopher Miller
 

I have purchased a 2 meter rig and it requires 13.8 volts. I plan on connecting it to the bench power supply in the photo and as long as I don’t transmit on Hf and 2 meters the only issue I see is that the bitx runs on 12 volts.

I looked in my parts box and I found some diodes to drop the voltage but I wanted to check my math before I mod the bitx.

I have 2 1N5400 rectifier diodes, they should drop the voltage by around 2 volts. I would like to know the following,

1) is the forward voltage drop correct?
2) where do I need to install them in series to protect the raduino?

Thank you, KF4FTR



Viktors Miske
 

Your 2 meter will run on 12 volts. Your ubitx will do 13.8. (and vice versa).
Not to mention you have a variable supply by the looks of it.


Christopher Miller
 

Ok, great

I asked once before and got the feeling I needed to mod the bitx. If I can just use nominal 12 volts I will and get more power. I have a heat sink so I may install that but I have zero desire to do any mods until I get both antennas tuned and up with the 2 meter rig ready to go for the emergency event Pima county has coming up. I’ll try it now and let you guys know if my raduino smokes.

Chris


David Nelson
 

You need to be careful with a 2meter radio close to your
bitx. I had a 2meter close to my bitx and when I transmitted 
with the 2meter it blew the transmit on my bitx. I had to replace
q90 in the bitx witch is not real easy. YMMV Dave  kc2ipx

On Wed, Apr 29, 2020 at 12:19 AM Viktors Miske <unclevic7@...> wrote:
Your 2 meter will run on 12 volts. Your ubitx will do 13.8. (and vice versa).
Not to mention you have a variable supply by the looks of it.


Gordon Gibby
 

There is a well described diode protection fix for Q 90. 

You might wonder why I know




On Apr 29, 2020, at 10:06, David Nelson <kc2ipx@...> wrote:


You need to be careful with a 2meter radio close to your
bitx. I had a 2meter close to my bitx and when I transmitted 
with the 2meter it blew the transmit on my bitx. I had to replace
q90 in the bitx witch is not real easy. YMMV Dave  kc2ipx

On Wed, Apr 29, 2020 at 12:19 AM Viktors Miske <unclevic7@...> wrote:
Your 2 meter will run on 12 volts. Your ubitx will do 13.8. (and vice versa).
Not to mention you have a variable supply by the looks of it.


Bill Cromwell
 

Hi,

I am voting with Viktors. I have been running "*12 volt*" gear on everything from 10 to 14 volts for 60 years. The sky did not fall and a piece of it did not hit me on the head. Yes that includes my uBitX and other cute QRP gear that is to be "powered by 12 volts only". You should 'worry' about real things like isolating the RF inputs and outputs of your radios from one another like David has suggested.

Have fun and...

73,

Bill KU8H

On 4/29/20 12:19 AM, Viktors Miske wrote:
Your 2 meter will run on 12 volts. Your ubitx will do 13.8. (and vice versa).
Not to mention you have a variable supply by the looks of it.
--
bark less - wag more


Arv Evans
 

As homebrew ham rigs become more commercialized it seems inevitable 
that there will be a lot of myth and mystique built up around how they 
operate and what one can do with them.  Some of this comes from hams 
not taking time or effort to understand the circuitry, and some from non-hams 
who use this equipment on other frequency allocations and for other 
purposes.  

I am with Bill KU8H...Sales information usually specifies the operating voltage
within a specific range.  Reading the user manuals will also tell you what the 
operating parameters are.  For the most part operating voltage is not all 
that critical.  A few percentage points deviation is usually allowable, unless 
the manufacturer says otherwise.  

Arv
_._


On Wed, Apr 29, 2020 at 8:36 AM Bill Cromwell <wrcromwell@...> wrote:
Hi,

I am voting with Viktors. I have been running "*12 volt*" gear on
everything from 10 to 14 volts for 60 years. The sky did not fall and a
piece of it did not hit me on the head. Yes that includes my uBitX and
other cute QRP gear that is to be "powered by 12 volts only". You should
'worry' about real things like isolating the RF inputs and outputs of
your radios from one another like David has suggested.

Have fun and...

73,

Bill  KU8H

On 4/29/20 12:19 AM, Viktors Miske wrote:
> Your 2 meter will run on 12 volts. Your ubitx will do 13.8. (and vice
> versa).
> Not to mention you have a variable supply by the looks of it.
>

--
bark less - wag more




Jack, W8TEE
 

You'd think that seeing a 12V voltage regulator on a board is a tip-off that the board might tolerate more than 12V. But then, I'm a software guy.

Jack, W8TEE

On Wednesday, April 29, 2020, 11:59:04 AM EDT, Arv Evans <arvid.evans@...> wrote:


As homebrew ham rigs become more commercialized it seems inevitable 
that there will be a lot of myth and mystique built up around how they 
operate and what one can do with them.  Some of this comes from hams 
not taking time or effort to understand the circuitry, and some from non-hams 
who use this equipment on other frequency allocations and for other 
purposes.  

I am with Bill KU8H...Sales information usually specifies the operating voltage
within a specific range.  Reading the user manuals will also tell you what the 
operating parameters are.  For the most part operating voltage is not all 
that critical.  A few percentage points deviation is usually allowable, unless 
the manufacturer says otherwise.  

Arv
_._


On Wed, Apr 29, 2020 at 8:36 AM Bill Cromwell <wrcromwell@...> wrote:
Hi,

I am voting with Viktors. I have been running "*12 volt*" gear on
everything from 10 to 14 volts for 60 years. The sky did not fall and a
piece of it did not hit me on the head. Yes that includes my uBitX and
other cute QRP gear that is to be "powered by 12 volts only". You should
'worry' about real things like isolating the RF inputs and outputs of
your radios from one another like David has suggested.

Have fun and...

73,

Bill  KU8H

On 4/29/20 12:19 AM, Viktors Miske wrote:
> Your 2 meter will run on 12 volts. Your ubitx will do 13.8. (and vice
> versa).
> Not to mention you have a variable supply by the looks of it.
>

--
bark less - wag more




--
Jack, W8TEE


Christopher Miller
 

Hello,

I spoke with another ham from the list a while back to try and run the bitx at 13.8 volts and was told not to. I’m also pretty poor so destroying an Hf rig I was gifted is not in my plans or budget. I think being careful is a good thing as I don’t have a lot of experience running multiple rigs.

I’m not a moron Jack, just trying to be careful not to be the guy asking for help after the fact.

Chris


Evan Hand
 

Gordon has a point.  Here is a link to one of the messages that describe a way to protect Q90: https://groups.io/g/BITX20/message/54362.  There was another I remember reading about that includes a miniature incandescent lamp in series with the receiver only path that added a little more protection.  I did not find the reference.  I will continue to look and post if I find it.

The alternative is to ensure that the uBITX antenna is disconnected or shorted before transmitting on the 2 meter rig.

73
Evan
AC9TU


Jack, W8TEE
 

Wasn't implying that you're a moron. What I am wondering is why you didn't look at the schematic to help you answer your question. I did a search on the input supply voltage and most agree that 15V is the max, which is also the max suggested for the 12V regulator.

Jack, W8TEE

On Wednesday, April 29, 2020, 12:56:48 PM EDT, Christopher Miller <djmalak2k6@...> wrote:


Hello,

I spoke with another ham from the list a while back to try and run the bitx at 13.8 volts and was told not to. I’m also pretty poor so destroying an Hf rig I was gifted is not in my plans or budget. I think being careful is a good thing as I don’t have a lot of experience running multiple rigs.

I’m not a moron Jack, just trying to be careful not to be the guy asking for help after the fact.

Chris

--
Jack, W8TEE


Evan Hand
 

Chris,

I have used my uBitx (3 of them) on 13.8 volts without any issues until I upped the display to a Nextion 2.4" or larger  That still did not have any problems, however, the 5 volt regulator got quite hot.  I then installed a single diode in series between the supplied 13.8 volts and the "red" mainboard power, leaving the PA direct connected (I wanted all the power I could get).  If you are concerned,  my first recommendation would be to install the 2 diodes between the PA and power in and the mainboard red power line.  I still think you are fine with the straight 13.8 volts to both.

In your case, it looks like a standard 16x2 display which has not had issues with the 13.8 volts.  If you really wanted to drop the voltage, I would only use 1 diode as the forward voltage drop is 1.2 volts at full load.  That would drop the voltage to 12.6 volts during transmit, slightly higher while receiving.

Do you know which version of uBITX that you have?

FWIW,
73
Evan
AC9TU


Bill Cromwell
 

Hi Chris,

It is your radio and if you are convinced that 12.000000001 volts will blow up your radio please be sure to run it at only 12.0000000 (or less) volts and get a good night's sleep every night. You radio will run perfectly well at that voltage and nobody at a distant receiver will ever notice the miniscule difference in your transmitter output. That difference will just not matter (is almost nonexistent).

For some of us, 13.8 or a little more is what we have so it is what we use. I am not using that voltage for any other 'benefit' than convenience. Sometimes it really is a little less (11.5?) and I use it anyway..for a little longer before recharge :)

Enjoy your radio and...

73,

Bill KU8H

On 4/29/20 12:56 PM, Christopher Miller wrote:
Hello,
I spoke with another ham from the list a while back to try and run the bitx at 13.8 volts and was told not to. I’m also pretty poor so destroying an Hf rig I was gifted is not in my plans or budget. I think being careful is a good thing as I don’t have a lot of experience running multiple rigs.
I’m not a moron Jack, just trying to be careful not to be the guy asking for help after the fact.
Chris
--
bark less - wag more


Christopher Miller
 

Thanks for that. Does the model of diode have to be what Allison quoted?

I will definitely do that mod as I would like both rigs up at the same time. And I don’t have much room.

Chris


Evan Hand
 

The short answer is that I would go with one of them if possible.  You also want it to be a small signal fast switching like the 1n914 or 1n4148.  Mouser has the 1n4148 in stock for $0.10 each.  Of course, the shipping will be more.

Do you have a part in mind?  We can look up the specs to verify.

73
Evan
AC9TU


Evan Hand
 

Here is the information on using a lamp to limit power to a receiver front end.
http://www.na0tc.org/lib/exe/fetch.php?media=technical:rx_protect.pdf

Here it states anything EXCEPT a PIN diode can be used.  Installing the lamp would take cutting a trace, and the protection is removed when transmitting.  I still believe that Allison's suggestion of back to back switching diodes (1n4148) on K1 Pin 14 is better.

Above are my opinions.  Yours can be different.
73
Evan
AC9TU


Evan Hand
 


Gordon Gibby
 

Elsewhere I have explained the likely actual mechanism, which involves charging up a capacitor in the circuit and blowing the base-emitter junction by reverse voltage due to its rectification.  a single diode backwards across that junction would prevent the charging of the capacitor and protect the system.   i used a simple 1N914.   I don't use that rig much right now, but I have many WINLINK gateway transmitters in my house that  can be in action at any time  and i never lost ANY bitx product.    

Gee, i think thishas been discussed 10 or 20 times now.

Gordon


On Thu, Apr 30, 2020 at 4:51 AM Evan Hand <elhandjr@...> wrote:
Here is the information on using a lamp to limit power to a receiver front end.
http://www.na0tc.org/lib/exe/fetch.php?media=technical:rx_protect.pdf

Here it states anything EXCEPT a PIN diode can be used.  Installing the lamp would take cutting a trace, and the protection is removed when transmitting.  I still believe that Allison's suggestion of back to back switching diodes (1n4148) on K1 Pin 14 is better.

Above are my opinions.  Yours can be different.
73
Evan
AC9TU


Evan Hand
 

Gordon,

Yes, it has.  The main issue that I have with Groups.io is poor search capability.  There is also a lack of new user introduction that might help as well.  Long time monitors like you and I spend a lot of time rehashing old topics because they are hard to find for a new member.

73
Evan
AC9TU


Curt
 

Chris

I do not see anything for measuring voltage. If you have a DVM or other instrument,  given your concern,  adjust that power supply to output between 12 and 12.5 volts.

While the rigs should be fine at 13.8 volts, the extra output power on transmit would not be noticed at the receive end. You need to double or quadruple output power for it to be noticed.

Lets hold off on running the ubitx PA at higher voltage. That requires 2 power supplies. For now, its barely worth the effort and risk to a new ham.

Great you are asking questions.

Curt