Date   
Re: RD transistors, unobtanium?

Jerry Gaffke
 

IRF510 and IRF512 both have a Vds max of 100v.
According to these guys, at least, not many IRF512 datasheets out there:
    http://www.njsemi.com/datasheets/IRF510%20-%20IRF513.pdf
The IRF510 has a slightly lower forward on resistance, slightly higher max drain current.
So seems to be a win for the more common IRF510.

Though the IRF512 does have a slightly lower reverse voltage drop, I'll give it that.
Useful when using the FET as a freewheeling diode on a switching power supply,
but not of much interest to us until we reverse the PA-PWR supply leads.


BUZ20 has an input capacitance of 1500pf vs 180pf on the IRF510.
IRFZ10 has a gate capacitance of  300pf,  Vds max of 60, though can handle more drain current.

There are reasons the $0.50 IRF510 (in hundreds, Vishay, from Mouser) is so popular for HF amps.
Does seem to take something more than a few 2n3904's to drive it properly at 30mhz.

Jerry


On Thu, Mar 15, 2018 at 04:04 pm, John Backo wrote:
Actually, the closest available MOSET to the IRF510
is the IRF512, which is the same device, only it is rated
for a drain voltage of 100v. It goes by other numbers as well.

Re: 13.8 v power supplies safe for bitx?

Tim Gorman
 

Jerry,

I'm not sure everyone understands what foldback current limiting
is. Your message 40729 explains it well. In action it is like a fuse.
The power supply opens the power lead until the operator takes an
action.

It is not the same thing as current limiting.

I don't have any power supplies with foldback current limiting so for
me a fuse is the next best thing.

tim ab0wr

On Thu, 15 Mar 2018 16:46:37 -0700
"Jerry Gaffke via Groups.Io" <jgaffke=yahoo.com@groups.io> wrote:

True.  The standard current limiting supply I described is not
something to lean on to avoid driving the final too hard, that's not
what I was suggesting. If there's a current limit on the finals,
should be foldback current limiting:
https://groups.io/g/BITX20/message/40719

Re: Micro BitX No Audio TDA2822?

Jerry Gaffke
 

Regarding Joe's suggestion of using the Raduino's LM7805 to power the TDA2822:

One objection I would have is the extra wire, needs to be dealt with every time 
I unplug the Raduino.  Though not a big deal.
A spare LM7805 on the bottom of the main board is more convenient.

A 25 ohm 1/2 watt resistor in series with the 12v Vin lead of the Raduino's LM7805 
should solve the problem with extra heat.  And/or a heatsink on that LM7805.
Add caps to ground on both ends of the resistor to kill any tuning clicks.
I would think those caps could be fairly small, but some here report success using
electrolytic caps of several hundred uF's.  I haven't bothered, no clicks.

Adding that wire for a regulated 5v from the Raduino adds opportunities for
Nano clock noise to get into the receiver.  Keep it short, put a 0.01uF cap at each end.

Can't use the 78L05 that gives the IRF510's their gate bias,
because that regulator must be shut down during receive.

Jerry


On Thu, Mar 15, 2018 at 04:26 pm, Jerry Gaffke wrote:
Could work, first time this was suggested.
An extra wire, the Raduino regulator would get hotter.
 
On Thu, Mar 15, 2018 at 03:39 pm, Joe Puma wrote:
Jerry has the group discussed pulling 5v from somewhere else like use the 5v that powers the Raduino? Maybe temporarily until they can get a regulator and or new WX chip? 
 

Re: Micro BitX No Audio TDA2822?

Ashhar Farhan
 

One could use a voltage drop resistor. The higher the current draw, lower would be the voltage to the TDA2822

On 16 Mar 2018 4:56 am, "Jerry Gaffke via Groups.Io" <jgaffke=yahoo.com@groups.io> wrote:
Could work, first time this was suggested.
An extra wire, the Raduino regulator would get hotter.
 

On Thu, Mar 15, 2018 at 03:39 pm, Joe Puma wrote:
Jerry has the group discussed pulling 5v from somewhere else like use the 5v that powers the Raduino? Maybe temporarily until they can get a regulator and or new WX chip? 
 

Re: Micro BitX No Audio TDA2822?

Jerry Gaffke
 

Quiescent current into the TDA2822 is around 6ma, peaks can be 1 Amp.
Though 100ma might be sufficient for moderate speaker volumes.
You would need two resistors for a voltage divider, and maybe waste 500 ma through them
to keep the voltage moderately well regulated.

Good spot for an LM7805.


On Thu, Mar 15, 2018 at 07:10 pm, Ashhar Farhan wrote:
One could use a voltage drop resistor. The higher the current draw, lower would be the voltage to the TDA2822
 

Re: Micro BitX No Audio TDA2822?

Joe Puma
 

On Mar 15, 2018, at 10:22 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

LM7805

Re: Micro BitX No Audio TDA2822?

Jerry Gaffke
 

Some of these clones seem to blow for no particular reason.
I think we primarily must limit the supply voltage, not so much the current under load.

Though they are really good at dealing with variations in supply voltage.
The series resistor in the 12v supply could be a solution for a good (non WX) TDA2822
if you are worried about exceeding the max power dissipation spec at high volume
and low load impedance.


On Thu, Mar 15, 2018 at 07:22 pm, Jerry Gaffke wrote:
Quiescent current into the TDA2822 is around 6ma, peaks can be 1 Amp.
Though 100ma might be sufficient for moderate speaker volumes.
You would need two resistors for a voltage divider, and maybe waste 500 ma through them
to keep the voltage moderately well regulated.

Good spot for an LM7805.

Re: Soldering gun or iron

Dave Bottom <ars.kd6az@...>
 

Likewise somewhere I have my original Weller Soldering Gun from around 1958!  Yes, it still works  but I don't really have a use for it.  I do have a huge Weller soldering iron for replacing Can Electrolytic Capacitors.

While always having nice Hakko gear around work for soldering or SMD repair work many years ago, today there are many alternatives that should be OK.  

For my ham radio restoration work I bought one of the Radio Shack Soldering stations when it went on sale for half off ($60) in 2009.  I've used it almost daily for the past 9 years and other than the wand that gets wear and tear it's been very reliable.  When it needed a new wand I did the research and found it was made by Atten.  So I ordered a new identical Atten station and two new wands for less than the sale price from Radioshack.  I think they will last me for the rest of my life (I'm going on 70).

Like most outfits Atten makes entirely new more advanced products like the same soldering station in new packaging with automatic standby mode (when you forget and leave it on - hi hi). 

You can now get complete soldering and hot air workstations for less than $70 (Yikes Walmart has one!)  It's nearly identical to the Circuit Specialist one (that is just under $100) and includes 11 soldering tips.  I bought the Circuit Specialist one primarily because they have it private labelled for them and carry spare parts.  Considering I will have such poor vision or not be able to hold the soldering iron still enough when I'm 80, it should last me a while as well.  

Dave WI6R

On Thu, Mar 15, 2018 at 4:59 PM, KB1JPW <a.fairaizl@...> wrote:
It might be worth looking for some auctions as well. I've never understood how I did anything with solder before my metcal sp-200 iron I've had for 20 yrs now. It's way more iron than I need and bought it originally to do surface mount components.  It's near instant heat through high-frequency and will adjust based off of thermal demand.  

I did a quick search at my local "toy store" here in town but I'm not sure where you're located so it might be more trouble than it's worth.... They do ebay auctions from their physical location and have quite often had soldering irons roll through. I'm not affiliated with them but do give them business whenever I can  - https://www.ebay.com/itm/Metcal-SP-PW1-10-Soldering-Station-with-Iron-/352303950549 That's the same SP-200 model I have and they still have plenty of tips available on the market.  I'd definitely buy one again if the one I have dies.  Average used going price for them outright is around $100 USD. I can see if they'd let me test that one if you'd like since they're about 10 minutes from my house.

Look at the types of soldering you are going to do and match the capabilities of the iron to the work. The one above can go from SMTs to soldering a battery cable with the appropriate tips.  If you're just going to do the occasional soldering, get something with high ratings and enough power to handle what you'd anticipate if you pick up other projects.  

Drew - KB1JPW





--
73 Dave WI6R

Blew the irf510's up, substituted irfp260's in there place... #ubitx-help

Ghericoan
 

Well, pushing the limits on the irf510 mosfets, they caved on me. So, digging through my junk I found four irfp260's and soldered them in as an effort to get back on the air. So far, it seems to work, but I noticed the current draw is much lower and a bit more heat is created, however, I have pretty get distance on wspr and about the same reports on ft8.

Does anyone know if there are any changes that should be made to the ubitx to get it to work better (with more output) using these mosfets? The obvious answer is to order some more irf510's from jameco and put them in, and quit limping the radio along on these other mosfets...but..ya know, spare parts bin and all.
--
----------
N5WLF, Greggory (or my nickname, Ghericoan)
General Class, Digital Radio Hobbyist

Re: UBitX Transmit Problem Fixed

Guy N7BIR <sgbridge@...>
 

All I know is I wasn’t getting the correct voltages on Q90. It was 0 volts dc on all three pins. I was also losing the transmit dc in the vicinity of R84. So I replaced them both. Yeah, I know, kind of a shotgun approach but it brought it back. 

73,
Guy

Re: Soldering gun or iron

Christopher Miller
 

I find that holding my own hands sill enough to put a part the size of a couple grains of rice on a pcb without lifting a pad or tossing it on the floor is difficult for me even. Im 33! It looks to me like the Chinese rework stations have lots of tips available. Im really satisfied with it. it uses a microcontroller running a pid loop to control the temperature. for a few extra bucks you can get 3 in 1 including a power supply. If this person can afford it I believe its probably has way more uses than just an iron. Some smd parts cant be installed with an iron and I personally have had no luck with tight pitch ics with tons of pins yet but should work under hot air and flux. I tried twice.

I picked up a magnifying visor with a built in light for around 20$. Its true though, If they want to only build a ubitx and nothing else its probably not worth it. However I also suspect they will need to make repairs and possibly mod it. They may also want to build more kits.

Anyway, on a side note.. Amazon has kits to practice smd work for around 10$. 

You also will need a way to clean the tip. I have sponges and the metal tip cleaners. I have found the metal one picks up solder much better.

The last thing would be tweezers, wick, and solder. I use super fine leaded solder for smd work. Through Hole it really doesn't matter. The leaded solder works well for smd because it melts at a lower temp. However, it has less flux. I haven't needed flux yet as long as I am not trying the ics with pins really close together. 

Chris
Kf4ftr

Re: Soldering gun or iron

Christopher Miller
 

The images of what I needed minimum. It looks like the station is not available but there are ones with more features around 70$.

Chris

Re: Soldering gun or iron

Ashhar Farhan
 

I have learnt to live with just about any iron. What matters really is a nice clean tip. These days they are tips that don't pit. I like those. Keep a good sponge, wipe them often.
- f

On 16 Mar 2018 9:47 am, "Christopher Miller" <djmalak2k6@...> wrote:
The images of what I needed minimum. It looks like the station is not available but there are ones with more features around 70$.

Chris

Re: Blew the irf510's up, substituted irfp260's in there place... #ubitx-help

John Backo
 

These HEXFETS are rated for 200V and 50A. They will (sorta) work as you have shown.

But the gate input capacitance is 4000+ pF. That increases your standing wave in
the drive circuit and lowers your output considerably. You have 2 choices:
Either replace the finals with IRF510s (after you have figured out what blew them up),
or figure out how to lower the input capacitance to 180 pF. or so. You can also probably
safely use a drain voltage of 48v or so, but there would probably be oscillation which would
have to be accounted for. Incidentally, how do you know they are not oscillating now?
Since the potential drain amperage is so high, it is probably wise to provide a current limiter
if you have not already done so, especially using wspr or another more or less continuous
wave function.

It's better to replace the finals.

john
AD5YE

Popped Audio Chip #ubitx

Joe Holland
 

Greetings,


     I finally got my uBitx assembled and in the case of it's final destination.. I checked my wiring on everything, and nervously applied power..   Display came up and I was happy.. turned the VFO for a sec and watched the frequency changed.. pushed in to change function.. all at once.. I smelled the magic smoke smell and the audio chip went pop...  I happened to look in my parts bins and I have happened to have a few more.. it appears from a different manufacture, and these are the "M" flavor.  I replaced the audio chip.. but I have no audio, via headphone or speaker.. I turned it off.. wanted to check with the group.. 

73 de Joe KB5VJY k

Another uBitx Add-on PCB.

Nick VK4PP
 

Im loving the cheap and easy EasyEDA/JLPCB boards and simple web designer.
This time its a CW filter similar to the QCX and HiPerMite. I take no credit for the design, just copied it and added a switching relay.
I ordered 10 boards at $10 posted. love it!



73, Nick VK4PLN.

Re: Another uBitx Add-on PCB.

Kelly Jack
 

Nice.  Are you selling these boards?

Regards



Simon VK3ELH 

Re: Another uBitx Add-on PCB.

Nick VK4PP
 

Maybe, if they work ill put the extra ones up with my RadionoI2C boards....

Re: Another uBitx Add-on PCB.

Nick VK4PP
 

Just FYI:

Center Frequency: 700 Hz
Bandwidth: 200 Hz
DC Power: 5VDC
GAIN: Upto 20dB via R11 and R12 + trimpot.

Resistors 1206 SMD:
R1 33k
R2 33k
R3 1M
R4 47k
R5 47k
R6 36k
R7 36k
R8 10k
R9 750k
R10 10
R11 100K
R12 100K

Capacitors 1206 SMD:
C1  0.1u  104
C2  47n   473
C3  36n   363 (33n + 3n3 mount on side together)
C4  1n    102
C5  39n   393 (33n + 5n8 mount on side together)
C6  1n    102
C7  2n2   222
C8  2n2   222
C11 0.1u  104
C14 220u  Electrolytic

Other:
IC TLC274
Relay OMRON G6S-2-DC5
200K/100k trimpot

R11 and R12 are optional to parallel the 200k trimpot to make it a logarithmic 100k.
Or just use a linear 100k pot.

Use a switch connected to 5V to turn on the filter.
This powers the opamp and switches the relay feeding the audio into the circuit.
When off the relay just passes the audio straight through unfiltered

73

Re: RD transistors, unobtanium?

John Backo
 

Jerry:

I cite those only as examples. You are right -- the IRF510 was
chosen by WA2EBY both because it was the most workable
and one of the cheapest solutions. And now one can get good
devices made by Fairchild or Vishay.

There are others nowadays. One of the closest (besides the IRF512)
is probably the FQP9N08. It has a drain voltage of only 60V but a
Ciss of ~250 pF. Another one is the DPACK MTE300N2013S,
though I don't know about the cost of that one. The main disadvantages of
the smaller ones are lower drain voltage and lower power dissipation.
That must be accounted for...

There are many examples with Ciss in the range of 300 to 800 pF.
Even devices up to 3000 or 4000 pF. will work after a fashion.
These can be made to work with proper layout and some impedance
matching. Most are under $US1.00 each also. One can use another
power MOSFET if necessary, even the IRF520s or IRF530s,
though it is not recommended that they be used. Doug Demaw was
experimenting (and using) the MJE3055T, one of the earliest available
MOSFETS. It can be done. But they are rare now, alas.

john
AD5YE