Re: #ubitx More reliable CW keying
#ubitx
Hi Art,
You gotta build it yourself, but the circuit is really simple - see the attached schematic to my original post.?
Jim
|
Re: ?Bitx initial current measurement high
#ubitx
Unless there's a smoking crater in your board somewhere,
it's most likely going into the IRF510's.
I suggest you disconnect the power lead into the IRF510's?
and then measure the current to the rest of the rig.
toggle quoted message
Show quoted text
On Sat, Dec 23, 2017 at 08:57 am, Jerry Gaffke wrote:
3 amps at 12v is 36 watts, more than my soldering iron
Any idea what's getting hot?
|
Re: uBITX working, question about power, PTT pop, LOUD headphone output
#ubitx
Hi all,
I've been working on a pop mute solution which also deals with the loud CW sidetone issue that some of the earlier units may have experienced.
Firstly some credit, this comes straight from the Hans Summers QRP Labs QCX transceiver which has a TX mute circuit that mutes the receive just before the last audio stages. Interestingly the sidetone is injected before the mute but because their is enough leakage for the sidetone to get through.
So I had heard that some of the early uBitx units had 1K for R250 which made for a very loud sidetone. R250K was 220K on my uBitx so when I put the mute circuit in, the sidetone was barely audible with a dummy load connected. So I swapped out the 220K for a 1K and sidetone volume is at a comfortable hearing level.
The pop on the transition from receive to transmit is completely gone and on the transition from transmit to receive there is a small low frequency thump with headphones on.? With the speaker the thump was not noticeable. An added benefit for me was that due to the lack of pop on the receive to transmit transition, the timing on my CW keying was not thrown out, something which occurred a bit when I was keying with the pop present.
The circuit has four parts; 2n7000 mosfet, 120K resistor, 220n cap (I started out with 100n and increased to 200n) and 1n4148 diode.
Drain to wiper of vol pot, source to ground (I soldered it point to point on the pot terminals). The other three components all connect to the gate and the other ends as follows: Cap from gate to ground (again on the pot terminals), resistor to the T/R line (via a wire, I used a DuPont cable and put the female end on the protruding pin of the nano that controls the T/R line). Diode goes in parallel with the resistor with cathode at the mosfet end.
73
Simon VK3ELH
|
A silicon diode feeding a cap to ground like Jack has will create a DC voltage
that is 0.6v less than the peak RF voltage.
The RF is centered on ground, so this peak voltage is half of the peak-to-peak voltage.
We want a small load resistor on that cap so it does not just stay charged up when the RF goes away,
could use two resistors of 4.14k and 10k in series to ground so the junction scales to the rms voltage.
If you want the cap voltage to hold at voice peaks, maybe more like 414k and 1meg.
The voltage at the junction is 0.707 times the voltage on the cap to give us a DC representation of the rms voltage.
Could mount the dummy resistors plus diode, cap, and series r's to a scrap of pc board.?
Example:
With 1 watt of RF, rms voltage is exactly square_root(1w / 50ohms) = 7.07 volts,?
peak voltage from ground to positive tip of the sine wave is 7.07v * 1.414 = 10v.
The cap sees 10v - 0.6v = 9.4v DC due to the diode drop.
The scaling resistors bring that down to 10k * 9.4v / (4.14k + 10k) = 6.65v.
Using 6.65v as the rms voltage, we calculate 6.65v * 6.65v /50ohms = 0.884 Watts,
a little bit over 12% error due to the diode drop.
Can compensate for the diode drop by adding 0.6v/1.414 = 0.424v to the meter reading,
so rms voltage would be 6.65v+0.42v = 0.707v, and power is 0.707*0.707/50 = 1w.
That diode drop of 0.6v is a guess, and will be temperature dependent.? Might adjust the 0.424v
correction factor by comparing with an accurate wattmeter of some sort down at 1W or less.
With such compensation, should get reasonably accurate readings down to 10mw or so,
at which point the peak voltage is still 1v and enough to overcome the diode drop.
At 50w the meter reading will be up around 50v dc, diode current up around 3.5ma and thus
the diode voltage drop?greater than at 1w, but the percent error inconsequential.
Direct reading of Watts is cool and far less error prone.
Putting the resistors in an oil bath will greatly improve power handling in a small space.
But the above procedure might be enough to get you by till Jack's QST article comes out.
Paul Schmacher wrote:
>? I got a pack of 10 of the 100 watt 50 ohm dummy loads on ebay for about $1 each.
Those ebay dummy loads look even better?than the Xikon 3W metal film resistors on Mouser.
Jerry, KE7ER?
|
Re: ?Bitx initial current measurement high
#ubitx
3 amps at 12v is 36 watts, more than my soldering iron
Any idea what's getting hot?
toggle quoted message
Show quoted text
On Sat, Dec 23, 2017 at 07:42 am, Kerry wrote:
Hoping this makes sense to someone.? I've only finished the build as far as the DC connector.? ?According to the instructions, I should be getting a 90-110ma draw.? I'm getting over 3 amps when I connect my meter in series with + off the battery and the red wire of the plug.? I did a continuity test on the supply end of the red and black wires to the red, black and brown at the board connector before connecting it to the board or 12v battery.? I'm a huge noob at building kits but so far there hasn't been much to mess up.? Any idea why I'm getting such a large current reading?
|
|
|
Re: BITX QSO Night, Sunday, January 7, 7pm Local Time, 7277 kHz in North America, 7177 kHz elsewhere
I do wish someone would consider Saturdays rather than Sundays, some of us work Mondays for our sins.
Phil - G7BZD
On Sat, Dec 23, 2017 at 2:57 PM, John P <j.m.price@...> wrote: Greetings fellow BitXers! I'm thinking since this coming Sunday is Christmas Eve and next Sunday is New Year's Eve,? we won't get much of a turnout for our regular Sunday evening ritual of listening to noise on 40 meters! We should plan on resuming on Sunday evening January 7th at the usual times and frequencies.
Meanwhile I wish all of you a very Merry Christmas ad a great New Year!
--
John - WA2FZW
|
Yes Merry Christmas to all!
|
Re: Case Options for ubitx
Going for this one rather seems to have better height for options.
https://www.ebay.com/itm/2U-87-x-178-x-203-mm-DIY-Hi-Aluminum-Electronic-Enclosure-Project-Box-Case/122663827465?_trkparms=aid%3D777003%26algo%3DDISCL.MBE%26ao%3D2%26asc%3D41376%26meid%3D40e208c5bc50414eab00e73b1f3754c0%26pid%3D100012%26rk%3D3%26rkt%3D12%26sd%3D121967934560&_trksid=p2047675.c100012.m1985
|
Hello, I just finished the uBITX and I am getting distorted and low audio using the element that came with the kit, not sure why this is happening. Any help would be greatly appreciated.
K8MGB, MIKE
|
Re: Case Options for ubitx
they are not the same
Ubitx:6 inches by 5-1/2 inches
Bitx40:4-1/2 inches by 5 inches
|
Re: #ubitx More reliable CW keying
#ubitx
Jim
I would be interested
Art - N2AJO
Sent from my iPhone
toggle quoted message
Show quoted text
On Dec 23, 2017, at 10:59 AM, Jim Sheldon <w0eb@...> wrote:
I've worked up an FET switching circuit for more reliable CW keying using a hand key or bug with the uBITX. I added a couple of identical stages to handle the dot/dash inputs from paddles as well.
Due to the way the ADC was used for CW keying, contact resistance (varies with the key, length of connecting cable & how dirty the contacts are) was causing random dots & dashes even with a hand key and it was next to impossible to use my bug with it.
The 2N7000 switching stages I came up with give very reliable, low resistance closures to ground on the key line or the dot/dash paddle inputs (through the respective 2.2K and 10K resistors) which makes things work a lot better. I am actually able to key the uBITX at 25+ wpm with my bug and have it actually transmit what I send every time without introducing any garbage into the key stream.
I supply the schematic here for anyone wanting to see if the circuitry will help their CW operation. No PC board is available but the circuit is simple enough (2 resistors & two 2N7000 FET's per stage) that building it on a small piece of perfboard is easy enough to do.
Jim Sheldon, W0EB
<uBITX_CW_KeyingAdapter.bmp>
|
Re: ?Bitx initial current measurement high
#ubitx
Something shorted. ?
Begin taking things off the +12 line to detect where!!
Sent from my iPhone
On Dec 23, 2017, at 10:42, write2kerry via Groups.Io < write2kerry@...> wrote:
toggle quoted message
Show quoted text
Hoping this makes sense to someone.? I've only finished the build as far as the DC connector.? ?According to the instructions, I should be getting a 90-110ma draw.? I'm getting over 3 amps when I connect my meter in series with + off the battery and the
red wire of the plug.? I did a continuity test on the supply end of the red and black wires to the red, black and brown at the board connector before connecting it to the board or 12v battery.? I'm a huge noob at building kits but so far there hasn't been
much to mess up.? Any idea why I'm getting such a large current reading?
|
Re: Case Options for ubitx
I ordered one of these last week from an e-bay vendor sunilakhanly. They were sold as fitting the Bitx40 board. Is the uBitx board the same dimensions? It would be nice to have some pre-made options for cases.
Jeff KB7AIL
|
Re: Rugged Case Options?
#ubitx
I ordered a bud 3010a 6" x 10" x 3" x .04
So I could mount speaker forward. Very solid once cover is on. Light and $17. (Somehat
?Utiitarian) I used s smaller version with my bitx40 and cut the opening with a dremel.
Andy
|
Re: Case Options for ubitx
That looks like Sunil's handy work.
|
#ubitx More reliable CW keying
#ubitx
I've worked up an FET switching circuit for more reliable CW keying using a hand key or bug with the uBITX. I added a couple of identical stages to handle the dot/dash inputs from paddles as well.
Due to the way the ADC was used for CW keying, contact resistance (varies with the key, length of connecting cable & how dirty the contacts are) was causing random dots & dashes even with a hand key and it was next to impossible to use my bug with it.
The 2N7000 switching stages I came up with give very reliable, low resistance closures to ground on the key line or the dot/dash paddle inputs (through the respective 2.2K and 10K resistors) which makes things work a lot better. I am actually able to key the uBITX at 25+ wpm with my bug and have it actually transmit what I send every time without introducing any garbage into the key stream.
I supply the schematic here for anyone wanting to see if the circuitry will help their CW operation. No PC board is available but the circuit is simple enough (2 resistors & two 2N7000 FET's per stage) that building it on a small piece of perfboard is easy enough to do.
Jim Sheldon, W0EB
|
?Bitx initial current measurement high
#ubitx
Hoping this makes sense to someone.? I've only finished the build as far as the DC connector.? ?According to the instructions, I should be getting a 90-110ma draw.? I'm getting over 3 amps when I connect my meter in series with + off the battery and the red wire of the plug.? I did a continuity test on the supply end of the red and black wires to the red, black and brown at the board connector before connecting it to the board or 12v battery.? I'm a huge noob at building kits but so far there hasn't been much to mess up.? Any idea why I'm getting such a large current reading?
|
Are there any metal case options for he ubitx yet?
Like this particular design?
Sent from my iPhone
|
? ? ? ? ?Merry Christmas to everyone in the group and a great new year to everyone. FT73 from PY2PVT --
? 73 de Jorge PY2PVT
? Campinas SP
? GG67MD
|
Jim Sheldon
Arvo W0VRA
N8DAH
Michael Baker
