Date   
Re: W8TEE B40 real time clock connections #w8tee

kc1at
 

Hi Rob

Thanks for rolling up all that AA information. I'll read these over and try to digest them. I vaguely remember some of the conversations but I think I'm getting to max saturation. Got so many projects on the bench and being an Arduino programming newbie  doesn't help. I understand the programming architecture but I have to research just about every change that's recommended.... Its like drinking from a fire hose. 

On top of all that I ordered a uBitx this morning....Its a sickness. No cure.

Thanks again
73
Don KC1AT

Re: ubitx AGC?

Jerry Gaffke
 

No AGC on the production uBitx.

The original schematic for the uBitx here:  http://www.phonestack.com/farhan/ubitx/ubitx.html
shows the second half of the TDA2822 used as an AGC amp, attenuating the audio through the 2n7002 nfet.

Apparently Farhan found that he preferred using the rig without that particular AGC scheme.

As Henning/DK5LV has shown in the distant past, that npn audio pre-amp stage for rx is a dynamic range bottleneck.
if AGC is applied after it around the volume control as the above AGC scheme does.

I think something like the original uBitx AGC level detect could work, but we'd be better off if the attenuation occurred 
somewhere prior to the npn audio pre-amp:    https://groups.io/g/BITX20/topic/5913954

Jerry, KE7ER


On Sun, Dec 10, 2017 at 12:01 pm, <jettoblack@...> wrote:
Does the uBitx have AGC? It was discussed in some of the previous threads, but the website only has this comment: "The audio amplifier uses one section of the TDA2822 – a quieter device compared to the LM386. It has two audio channels, the second channel is kept free for use as an AGC audio amplifier."  I am not sure if that means an AGC can be added later, or is it already present?

Re: ubitx is available for $109, there are a3 catches

VE7BEE
 

Ordered ! Can hardly wait ....so went with the quick shipping !

Re: BITX QSO Night, Sunday, December 10, 7pm Local Time, 7277 kHz in North America, 7177 kHz elsewhere

John P
 

Was on at 3PM. Nothing heard! I'll try again at 7PM.

Meanwhile, my logging program lost all my data. If possible, could anyone I've worked in the past few months; particularly bitX to bitX send me the contact info, email WA2FZW at ARRL.net.
--
John - WA2FZW

Re: ubitx AGC?

Jerry Gaffke
 

Search for AGC in this forum and you will see lots and lots of schemes to implement it.
The thread I pointed to is just part of a discussion, I think somebody renamed the thread and 
we continued the conversation from there.
At some point, somebody pointed out that the multiple pin diodes form a pi network attenuator
that presents a more or less constant characteristic load impedance, which can be of critical importance.

Jerry


On Sun, Dec 10, 2017 at 12:33 pm, Jerry Gaffke wrote:
I think something like the original uBitx AGC level detect could work, but we'd be better off if the attenuation occurred 
somewhere prior to the npn audio pre-amp:    https://groups.io/g/BITX20/topic/5913954

Re: ubitx AGC?

giuseppe callipo
 

This is a good question, but I think that the answer is No at the moment, in the schematic description on hfsignals site i can read  some tipa :"AGC as audio" in second channel of tda2822 and an IF AGC as Improvements of a better designed IF section. The homebuilder will have some occasions to work on It. 
Best 73, IK8YFW, Giuseppe

Re: Shielding plastic boxes

giuseppe callipo
 

Re: Shielding plastic boxes

Thomas Sharka
 

Re: BITX QSO Night, Sunday, December 10, 7pm Local Time, 7277 kHz in North America, 7177 kHz elsewhere

philip yates
 

Lucky for those of us that do not have access above 7.200, 7.277 is wiped out by a broadcast station.

Back to 7.177, just monitoring as the rest here have had an early night.

Phil - G7BZD

On Sun, Dec 10, 2017 at 8:41 PM, John P <j.m.price@...> wrote:
Was on at 3PM. Nothing heard! I'll try again at 7PM.

Meanwhile, my logging program lost all my data. If possible, could anyone I've worked in the past few months; particularly bitX to bitX send me the contact info, email WA2FZW at ARRL.net.
--
John - WA2FZW


Re: Reverse polarity diode circuit

Karl Heinz Kremer, K5KHK
 

They are $0.18 at Tayda: https://www.taydaelectronics.com/circuit-protection/polyswitch-devices/poly-switch-resettable-rxef-series-72v-3a.html

Of course the problem is that you need to get more than $5 worth of stuff in your shopping cart before you can check out. But that is usually not a problem for me ;)


Karl Heinz - K5KHK


Re: Shielding plastic boxes

giuseppe callipo
 

Great Cooper foil, Can It solder ? 

Re: Shielding plastic boxes

Thomas Sharka
 

Yes. if you're careful of the plastic underneath.
 


Sent from Yahoo Mail. Get the app


On Sunday, December 10, 2017 5:02 PM, giuseppe callipo <ik8yfw@...> wrote:


Great Cooper foil, Can It solder ? 


Re: ubitx is available for $109, there are a3 catches

K9HZ <bill@...>
 

Yeah BIG warning on this scheme.  Elecraft uses this in the K3… for the “ON” switch by controlling the gate.  I had mine SHORT in the CLOSED/ON position.  Doesn’t do much good when the diode shorts…

 

 

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

Like us on Facebook! facebook icon

 

 

email:  bill@...

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Arv Evans
Sent: Sunday, December 10, 2017 11:59 AM
To: BITX20@groups.io
Subject: Re: [BITX20] ubitx is available for $109, there are a3 catches

 

Colin

The MOSFET solution looks good.  I will try that.  Power MOSFETs are not very expensive.

Should be interesting to smoke-test the protection circuit.  8-)

Arv
_._

 

On Sun, Dec 10, 2017 at 10:48 AM, Colin Hemming <cphemming@...> wrote:

This is the best solution for reverse polarity protection. Lower voltage drop than a series Schottky (if you pick the right FET with a low rdson). Safer than a reverse bias diode across the supply terminals and very easy to implement.

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: 10 December 2017 17:16
To: BITX20@groups.io
Subject: Re: [BITX20] ubitx is available for $109, there are a3 catches

 

A Schottky diode in series with power to the rig should work fine for reverse power supply protection.
The lower forward voltage drop of 0.3v (vs around 0.6v or more for standard silicon diodes like a 1n4007)
means the rig sees something closer to the 12v coming from your battery.
It also means the diode does not get so hot,  with 2 Amps at 0.3v that Schottky is dissipating 0.6 Watts.

I'd recommend separating out the main rig supply and the supply to the IRF510's.
For higher power, you may want to give the IRF510's more than 12v.
Also, it allows any fusing and reverse supply protection to be more effective.

The main rig can live fine with somewhat less than 12v, and only needs 150ma or so.
Could use your series diode (schottky or 1n4007), or the hfsignals scheme of a reverse shunt diode plus fuse,
or in my case an LM2940CT-12 regulator (which unlike an LM7812 provides reverse voltage protection).
In any case, this should be protected by a fast blow fuse of maybe 0.5 Amp.

The IRF510's only need a 3 Amp fuse to protect them.  The intrinsic diodes in the IRF510's will conduct
if a reverse supply is applied, blowing the fuse.  Fuse will also go if you set the gate bias voltage too high.
If you don't include a fuse, it will be the traces of the board that blow when current goes beyond 3 Amps
as many Bitx40 owners have found out.  

Perhaps next rev of the uBitx board could have very thick traces for that IRF510 drain current
except for a short moderately thin trace, a plated hole drilled at each end of that thin trace.  
The thin trace is your first fuse, once that is blown you replace it with either something like
28 gauge magnet wire or an honest-to-gosh fuse.

Could also do something similar for the main 12v supply to the rig, but with a skinnier trace.
Then the only explicit reverse protection device required is the main rig reverse protection diode,
probably series is best though shunt should work.  I'd be a bit suspicious of a 1n4007 shunt diode,
since with a high surge current the forward voltage drop across it will rise above a volt,
might be enough to blow some IC's.

Would also be nice to have some way to monitor heat at the IRF510's.  
Occasionally putting your finger on the heatsinks to check how hot they are might be good enough.
Or sprinkle them with something that starts to stink at 60C or so.
A more elaborate scheme would sense the temperature and yank down on the IRF510 gate bias voltage if it gets too hot.
If giving the IRF510's more than 12v, I'd recommend going to a larger heatsink than supplied with the uBitx,
and also insulating the heatsink from the IRF510 devices.  

If you don't insulate the heatsinks, be sure to keep loose wires from hitting them as the heatsinks are at 12v.
A number of Bitx40 owners blew out their Raduino when a spare wire passed by the heatsink.

Jerry, KE7ER


On Sat, Dec 9, 2017 at 07:44 pm, Kevin Luxford wrote:

Is there any reason why not put a Schottky diode in series with the power supply?  Sufficient current carrying capacity and low forward resistance?

 

Re: W8TEE B40 real time clock connections #w8tee

Michael Monteith
 

Rob,
 Take a look at the QRP Labs QLG1 kit.  They use it in their DDS VFO kit to maintain accuracy in frequency.  But they also use it in their Clock kit to get date/time information from GPS satellites.   Most hardware based RTC seems to be inherently inaccurate.     Depends on what you need the RTC for I guess.   I wasn't sure of what you were trying to accomplish in the end.

73, Michael
KM4OLT

Re: ubitx is available for $109, there are a3 catches

Keith VE7GDH
 

VE7BEE wrote...

Ordered! Can hardly wait so went with the quick shipping!
The race is on... I went with the free shipping. The road
trip to your QTH should be about equal to the ferry time
for over here.

--
73 Keith VE7GDH

Re: W8TEE B40 real time clock connections #w8tee

Rob Cox (N4MN)
 

Haha!!! I ordered my uBitx last night too! 

Like I said, hopefully I'll have some time over the holiday to investigate this a little bit, but I, like you, seem to have too many projects. I think I need to commit to NO MORE PROJECTS until I finish what's on my bench. :)


On Sun, Dec 10, 2017 at 12:06 pm, kc1at wrote:
On top of all that I ordered a uBitx this morning....Its a sickness. No cure.

Re: ubitx is available for $109, there are a3 catches

Mansueto Grech
 

Hi Gordon,
The reverse polarity relay is very simple and works fine.
Basically the supply to you equipment goes to the normally closed contact.
You put a diode in series with the relay coil in reverse. ie conducts only when the polarity is reversed.  
So with correct polarity the relay is off and the supply is delivered to the equipment through the Normally Closed contacts.
If, however the polarity is  reversed the relay is energized and supply does not reach the equipment. 
One can add a buzzer on the Normally Open contacts as an audio indication the polarity is reversed.
With this system there is no extra drain on the supply during nornal operation.
Hope this was of some help
73's
Mans. 9H1GB

On 10 December 2017 at 02:02, Gordon Gibby <ggibby@...> wrote:
I guess you could wire it so the relay is in series and only provides current further down the line if the diode powers the relay indicating the current is of the correct polarity?

Then you simply never get any power at all when the polarity is wrong!   Time Constance is of no issue.   Relay simply refuses to provide you any power since you're current is the wrong way.   However, you would have to deal with the constant relay current then.

Sent from my iPhone

> On Dec 9, 2017, at 19:57, John Backo <jabac@...> wrote:
>
> This appears to be more or less standard practice in the schematics
> I have seen lately. I suppose it is to avoid the 0.7v voltage drop of the silicon
> diode. Sometimes that matters in portable rigs.
>
> What it is really doing is providing a path to ground for the positive voltage.
> The power supply is assumed to be fused so the ground path is short-lived.
> This is the principal protection to the rig. The time constant of the fuse blowing
> is much less than that of the relay engaging.
>
> I don''t think that a reverse voltage would not engage the relay...but I suppose it
> is possible in some instances.
>
> All-in-all, I prefer an in-line diode that positively blocks reverse voltage. That
> appears to me a better solution in spite of the somewhat greater power
> consumption (another consideration -- the search for less power consumption!).
> It is true polarity reversal protection...not one dependent on pieces outside of itself.
> The only real consideration is the reverse voltage of the diode. The 1N4001 has a
> reverse barrier of 100v, more than enough for our purpose.
>
> YRMV. To each his own solution, as long as it works. Hi.
>
> john
> AD5YE
>
>
>




Re: ubitx is available for $109, there are a3 catches

ojiisan@...
 

I ordered  the uBITX and I have a BITX40 that i never started to
assemble yet, I'll take
$35.00 for it shipped to a U.S. address if anyone is interested in it.
The BITX40 was opened to check the parts and that was it, I never
started to assemble
it and decided to go for the uBITX instead.
Bill W4OM

Re: ubitx is available for $109, there are a3 catches

Mansueto Grech
 

Hi Jerry,
I do not agree with you in that I had an experience with an FT290R whose polarity was reversed.
The diode, a high current one installed by Yaesu shorted and a 20A PSU fuse blown. 
It has to be a high current Diode of course.
As I wrote before the best system I found, and I have it on all my Portable xverters for microwaves work all have this relay system and so far never had any problems.
73's
Mans. 9H1GB


On 10 December 2017 at 02:19, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
Yup.
Not all power supplies have a fuse, and if it's 30A it wouldn't do much good here anyway.
Most 12v batteries do not have a fuse.

I think what I'll do is blow $1 on an LM2940CT-12 for the main board.
Provides reverse power protection (unlike an LM7812) and overvoltage protection (unlike that diode plus fuse).
At 150ma, dropout voltage is only 150mv or so, and quiescent currents are quite reasonable.

Probably just a fuse on the IRF510's. 
The IRF510's conduct through an intrinsic diode if drain voltage is less than source, so that's the reverse protection diode.
And have a bunch of spare IRF510's taped to the inside of the back panel.
 
Jerry, KE7ER


On Sat, Dec 9, 2017 at 04:53 pm, Arv Evans wrote:
I had the same concern.  That is why I added fuses to the back panel. 
I used some ugly old panel mount fuse holders because that is what was in my
junk box.

 


Re: W8TEE B40 real time clock connections #w8tee

Rob Cox (N4MN)
 

Thanks for that Michael, do you know if the QRP Labs DDS is AD8950 - or are they using the Si5351? According to some, the issue is with the AD8950 and its handling of data on the bus. I'll take a look.

I think the RTC in the W8TEE B40 was simply to display the time (hh:mm:ss) on the screen. I don't think it was used for any frequency accuracy or anything like that.

73,
-Rob (N4MN)


On Sun, Dec 10, 2017 at 02:53 pm, Michael Monteith wrote:

Take a look at the QRP Labs QLG1 kit.