I would also like to have a headphone jack and an internal speaker. How do I wire this?

Bob

On Wed, Feb 28, 2018 at 07:23 am, Jerry Gaffke wrote:

The uBitx surface mount R's and C's are all in the 1206 package.
The surface mount 2n3904's are are mmbt3904's.
The audio amp is the TDA2822M variant (M says it's in the 8 pin DIP package).


On Wed, Feb 28, 2018 at 05:54 am, Walter wrote:

What value SMD's do you think these are? I see 0603,0805, 1206.?

Outstanding.? I have them ordered thanks for the help
?
--
73, W9KJO
Walter

开云体育

Hi Allard,
No, I had not tried that yet. I didn't connect this problem with a possible alignment issue. I will do that (hopefully this weekend and hopefully with help from my more technically-adept friend who was listening to me) and see if it helps.
Vy tnx & 73,
Rich

The threads are M3 × 0.5.? The standoffs I have are 11 mm long with a 6 mm male threaded part.? Lots of kits on ebay.

There's a band-pass filter at L1, L2, L3, it is used during both transmit and receive.
You require a fairly broad passband,? but I suspect it will work fine across your 500khz.
As designed, it has input and output impedances of 50 ohms (though it likely sees a load of around 200 ohms at Q1).
I suggest you either simulate that filter in LTSpice or find some other software to model such filters,
and find new values for the inductors and capacitors such that it has a passband from 8.222 to 8.746 mhz.
Or you could just make all the capacitors smaller until you bring it to your operating frequency.
For initial testing (not when transmitting into an antenna) you could probably just short across this entire filter
with a wire, but you will now be receiving an image frequency and the transmitter may have extra outputs
at unexpected frequencies..

The low pass filter at L6, L7? allows through our 7.2mhz signal from the transmitter and blocks all harmonics
(at 14.4 mhz, 21.6 mhz, etc).? Again, would be best to obtain correct values for your operating frequency,
though simply decreasing the value of the the capacitors will probably be sufficient.
If this is not done correctly, you may wind up transmitting at frequencies other than what you intended.
This low pass filter is only used when transmitting, not when receiving.

Crystal filter should be fine, leave it at 12mhz.??
If that is not clear, then you need to read up about superhetrodyne receivers before proceeding with
your hacks to the Bitx40, perhaps in one of the excellent amateur radio publications such as
the ARRL Handbook, RSGB Handbook,? or Experimental Methods in RF Design.
There is likely something similar available in most other major languages.

Up to date firmware for the Bitx40 can be found here:
? ??
either "bitx40" (simpler hardware mods)? or "bitx40-raduino-v2" (allows the bfo to be varied)
Adjusting the tuning range in that software should be a matter of changing a few numbers,
folks in this forum could probably help if you get stumped by this.
You will also need to download the Arduino IDE to a host computer, use that to load
your new firmware into the Nano processor embedded in the Bitx40.

Should be a fun and educational project!
Hope that helps.

Jerry, KE7ER

Will do! Stop by 3930 some afternoon. We rag chew from about 2pm till the net starts at 5. Looks like I'll be running the net on Tuesdays.

Vince.

--
Michigan VHF Corp.

This Group is mighty nice.? I have enjoyed it tremendously for a while now and have learned from others here.? I have a question now.? I have installed my xbitx in an old junked Repeater Case, no testing yet, but I would like to have better choices with the standoffs for the board and display.? The display is a little too far in for my total liking.? Maybe you can see with pics.? Not finished yet.? What are the threads per inch (maybe 4-40) and so on?? I ordered some from Mouser but were surely not what I wanted and expected.? Any help is surely and greatly appreciated.

Ron
KJ4FFG

Check paypal in case you just didn't get the notice.

Vince.

--
Michigan VHF Corp.

What was your order date?

Lovely, DHL's tracking is down.

Vince.

--
Michigan VHF Corp.

Remove PA-PWR from the rig so the IRF510's won't be working, then try sending CW.
Does the sidetone come through the speaker?? If not, you have a very simple?
path from CW-TONE to the speaker to debug.? Perhaps wire a speaker between?
the junction of R250,R251 and ground, should hear the sidetone there if it's coming?
out of the Nano properly.?
?
If not, triple check connections at the volume pot and out to the speaker.


Many here have reported a blown TDA2822M, apparently due to shorting the speaker line to ground.
Probably best to add a series resistance of 4 to 8 ohms at the output of the TDA2822M and/or
reducing the supply voltage to the TDA2822M:? ? ??/g/BITX20/message/42723

If you suspect a blown TDA2822M, you could of course swap that chip out.
Hard to get as NXP has discontinued manufacture, perhaps now cloned in China?
An alternative is to google for "lm386 kit", and wire that into the volume control pot.
Perhaps permanently.

If you hear the sidetone when transmitting CW but no receiver audio, try soldering a wire
across nodes M1,M2 in case the relay at K2 is not working properly.? Does that fix receiver audio?

Can you hear a pop when stroking C50 with a screwdriver?

Beyond that, perhaps try the tricks shown in this video on receiver debug.
The wire he uses is just 3 or 4 feet of hookup wire, nothing on the other end,
it is acting as an antenna to pickup up random noise.
??


Be sure to restore the hacks I suggested (PA-PWR removed and M1,M2 short) before
trying to operate the rig.

Jerry, KE7ER

John,

Good job!

tim ab0wr

On Tue, 27 Feb 2018 20:42:11 -0800
"John" <passionfruit88@...> wrote:

After trying a few schemes I have settled on a MAX9814 circuit for
the AGC.

I used the Adafruit board but there are a few variations on eBay with
some probably requiring less hacking than the Adafruit design. I had
to solder a wire on a SMD component to access the CT (time constant
capacitor) pin of the MAX IC, and remove the Electret capsule.

I have attached the schematic and a few pictures of the AGC circuit
as I now have in the rig. The 5VDC is taken from the Raduino board.??

Performance wise I took two sets of measures, one with the AGC turned
down low and one with the AGC turned one third of the way up.

A few notes on the tests. I used an A/B comparison with an FT-817,
with the pre-amp off, receiving??a carrier at 1,500Hz? from local
radio stations (with attenuation). The FT-817 S-Meter seem
notoriously non-constant in the steps between the S-units, but that
is all the reference I have where I am. The AGC voltage is taken from
the CT pin of the MAX9814.

The AGC voltage fluctuates quite a lot, so I tried to record the
average value.

At high signal strength, to determine if the saturation was coming
from the AGC circuit or the uBitx upstream, I would bypass the AGC
and keep the volume down to prevent the audio circuit past the volume
pot from saturating. If the harmonics of the audio disappeared, the
AGC alone was producing distortion, otherwise it appeared at least
before the AGC, and possibly in as well.

Here are the results:

1. "Medium" AGC: input pot turned to about 30% of full scale.

FT817? ? ? ? ?AGC
S-Meter? ? ?voltage(mV)? ? ? ?Notes
S0? ? ? ? ? ? ? ? ? 0? ? ? ? ? ? ? ?
S1? ? ? ? ? ? ? ?300
S2? ? ? ? ? ? ? ?350
S3? ? ? ? ? ? ? ?400
S4? ? ? ? ? ? ? ?460
S5? ? ? ? ? ? ? ?510
S6? ? ? ? ? ? ? ?650
S7? ? ? ? ? ? ? ?750
S8? ? ? ? ? ? ?1,700? ? ? ? ?Large variation. FT-817 S-meter S8
plateau issue? S9? ? ? ? ? ? 2,200? ? ? ? ? Some saturation of AGC
noted (starts to appear in audio FFT, not noticeable) S9+10
?2,460? ? ? ? ? ?Saturation of AGC audible, but not unplesant. S9+20
? ?2,460? ? ? ? ? ?Audible saturation of both uBitx and AGC (harsh
sound).

The AGC kicks in early and keeps the volume pretty constant until
saturation occurs. Saturation of AGC does limits the dynamic range of
receiver.

1. "Low" AGC: input pot turned to about 7-10% of full scale.

FT817? ? ? ? ? AGC
S-Meter? ? ? voltage (mV)? ? ? ?Notes
S0 -S4? ? ? ? ? ? ? ?0? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??
S5? ? ? ? ? ? ? ? 50-200? ? ? ? ? ? (100mv avg)
S6? ? ? ? ? ? ? ? ? 200
S7? ? ? ? ? ? ? ? ? 360
S8? ? ? ? ? ? ? ? ? 500
S9? ? ? ? ? ? ? ? 1,260
S9+10? ? ? ? ?1,800
S9+20? ? ? ? ?2,300? ? ? ? ? ? ? ? ?Saturation of both uBitx and AGC
(visible in audio FFT, but not really audible) S9+30? ? ? ? ?2,400
? ? ? ? ? ? ?Audible saturation of uBitx and mostly of AGC.

This is the most "FT-817 AGC" like, from my perspective, and is what
I have settled for.? I want to use the AGC voltage as an s-meter
input and this setting does produce a gap at the bottom end, but this
is not critical IMO.

In both cases I noted some small "clicks" when the AGC kicked in on
strong sudden signals.?

The maximum gain of the MAX9814 as set in the schematic attached is
of 50dB and requires screened cables in the audio circuit. I
originally had the input and output of the circuit fed to a two core
"stereo" screened cable and I would get feedback. I had to use two
single screened audio cables.

73, John (VK2ETA)

I got payment confirmation on January 4 and still waiting for my second one to be shipped.

Thank you for your reply..

There is no requirement for the modulation itself, I think SSB is good enough and suitable for my project. Did one RF-Front End circuit work for both transmit and receive system?

What about the Crystal Filter Circuit, should I make change on the circuit? Did the Crystal Circuit aim is for keeping the IF Frequency fixed tuning in 12 MHz??

Thank you

?

Michael,

I like your layout. I am considering putting the on/off switch on the
back as well in order to keep it close to the power connector.

I have a bit larger case than yours. I have a four pin mic connector
that will mate with most of my older ham and cb microphones (mic +
ptt) so it probably needs to go up front. The cw key can easily be on
the back panel, that's a good idea.

Thanks,

tim ab0wr

On Tue, 27 Feb 2018 17:37:32 -0800
"Michael Babineau" <mbabineau.ve3wmb@...> wrote:

Tim :?

I did something similar with the BITX40.

If you tune with your left hand and don't put the tuning Knob on
the?left that you will likely find that you obscure the display when
you are tuning. I use a Computer headset with my?Bitx40 and it has
long leads so I opted to put mic/phones/ptt and key jack all on the
back panel. IMHO the front panel is?already busy enough with the
display, tuning and volume etc. Attached is a photo of my BITX40
front panel. I intend to do something similar with my uBITX when I
get around to it.

Cheers

Michael VE3WMB

I ordered Dec 23. Arrived Feb 22 in USA. Paypal had DHL tracking entered on Feb 19.? I never received notice of it being shipped. Also, there were no duties or taxes.

--
Jason Schlager
KM6AUS

The uBitx surface mount R's and C's are all in the 1206 package.
The surface mount 2n3904's are are mmbt3904's.
The audio amp is the TDA2822M variant (M says it's in the 8 pin DIP package).

So "didn't have power on SSB" means you didn't see power into a wattmeter (with dummy load) when attempting to transmit?
Have you tried transmitting CW with a hand key?
Is that scope good to 10mhz or so?

Inspect the entire board carefully under good light and with magnification for damage somewhere in shipping.
Often the torroids have trouble with broken or shorted wires, or enamel left on the wire, or an otherwise
poor solder job.? However, if the receiver worked, all torroids except those between Q90 and the IRF510's
are probably ok, and the mixers and local oscillators are fine.
The TX side of the BiDi amps is probably ok since they are simple and auto-stuffed and seldom have trouble.

Switch to one of the low bands like 80m or 40m, hopefully within range of the scope
Remove power (PA-PWR) from the IRF510's so you don't have to worry about dummy loads and such
while debugging the transmitter, when things are working you should see a couple volts of RF at the
gates of the IRF510's.

When pressing PTT with no input to the microphone, all those 2n3904's at Q90,911,912,92,93,96,97?
should have around 0.6 volts dc between base and emitter, and the emitter should be a little bit above ground.?
You can check this with a DVM.? Do they all look ok?

When speaking into the mike or using the hand key, I believe the base of Q90 will have something on the
order of 50mv rms of RF on it at the operating frequency, can you see that with the scope?

If Q90 is getting RF, then?follow that on through the other stages, should see a volt or two rms
of RF at the gates of the IRF510's.? The gates of the IRF510's should be biased by RV2 and RV3 to
around 3 or 4 volts (but DON'T twiddle RV2 and RV3 unless monitoring quiescent drain current at PA-PWR).?

If you do see RF at the IRF510 gates, then it's time to attach a dummy load and restore PA-PWR,
see if the dummy load gets signifcant power when attempting to transmit.
If not, do the drains of the IRF510's get 12v dc when ptt is pressed?
Does PA-PWR current go up to 200ma or so (100ma of quiescent drain current per IRF510) when pressing ptt
with no audio into the mike, demonstrating that the IRF510's are probably working fine?

Jerry, KE7ER

Should we add Carl's case to the ubitx.net enclosures section.

I purchased one of these, by the way, and the quality is excellent!!

--Neil, W2NDG