On Mon, Aug 19, 2019 at 10:44 AM, Ashhar Farhan wrote:

My IP address is blocked on the forum. I can't seem to get through.

Try a web proxy?
?
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Hi,

Was the spur problem of the previous versions, reliably fixed on v5?? I seem to remember the solution sometimes causing issues with low output on 40m.

73,


Mark.

Thank-you Jack.? As usual always helpful.

73
Evan
AC9TU

Relays are working properly..before the filter at tp7 the signal on the scope is reduced, so must be first few components of the 40 meter filter are wrong to drag it down that much.? I will poke around some more there. I was hoping there would be some history on this (thanks). I want to get 40 working so I can check out signal reports with ssb and the ssm2167 chip integrated..works great on 80.
73 Brad

开云体育

dgclifford,

I would look into a buck boost supply that can supply 3 amps.? This would work with both power supply options.? The potential disadvantage is the possible HF interference from the switching nature of the device(s).? I had read here that some included an LC filter after the supply to overcome this disadvantage.

The buck boost would allow a constant 12 vdc to the rig.? Though the finals are not that fussy (could run the 19.5 vdc direct from the laptop supply) the main board is.? It really should stay around 12 volts unless you start adding heat dissipation to the Raduino regulator.? I found that higher than 12.5 volts the regulator got very hot.? I am supplying 13.5 volts, I added a heat sink to the regulator, AND dropped the voltage to the main board? through 2 1n4001 diodes.? The diodes are not in the circuit to the finals.??

If you run higher voltage to the finals, you will need to beef up the heat dissipation.? Most have just added a fan to run when transmitting to conserve power.? Not needed if you feed the rig with 12 vdc as designed.? You could wire the circuit to run the fans when on the laptop supply and not when running from battery to conserve power.

There are quite a few buck boost supplies on the web.? A lot of bear bones with adjustable voltage are available for under $2 each in small quantities (2-8).? The devices with built in displays run more.

The above are my recommendations, and may be in error.? I would verify and test.

73
Evan
AC9TU

why not just use your shack power supply with a fuse?
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So far I don't think anyone has written code for that display.

You can use lots of different displays but you will have write your code/sketch.

Raj

hello i am preparing for the arrival of my ubitx? and whilst i have a 35 amp power supply for my shack i think it would be best to have a lower rated supply for the bitx. i have a few ex laptop supplies, should i modify one of these? . if? use the bitx away from the shack i plan to use 11.1 v lipo batteries, but i? need something slightly less powerful? for shack. use any ideas would be great??? dave c? gw0nvf.

The short answer is yes, if you add the screen features you want to the Arduino firmware.? I am not aware of any such firmware available.? There is also a shortage of I/O in the stock Raduino.?

I would suggest that you first look at the Nextion display work that can be found here:??

Dr. Lee has written software and screen designs to work with the Nano that came with the uBitx.? With all the added features, there is very little room for more modifications in the Nano code.? You do need to purchase a Nextion display with touch screen capability.?? Be sure to verify the screen size and the enhanced version with touch capabilities to work with the KD8CEC software.? I used both the 2.4 and 3.2 inch enhanced versions.? Available from multiple vendors.

There is the also JackAl add on board that did change the processor to one with more memory and speed.? That is available here:?? This has higher capabilities, at a higher price.? Be sure to note that the listed price for the board does not include every thing that you need to make it work.

You can go the route of converting the Nano code to a larger/more powerful processor like the Teensy on the JackAL board or other newer Arduino based system.? Regardless, that will be a significant effort.? Would be curious to see any results that you come up with.

73
Evan
AC9TU

Dries,

Here's what I hope is a helpful answer to your questions about the Bitx20

Yes, you could use FT-37-43 cores on the transformers.
Just duplicate the transformers used on the Bitx40, 10 turns trifilar:
? ??

Carrier suppression on transmit mostly depends on T3 and the two nearby diodes
being wired correctly, also the nearby 100 ohm pot must be adjusted for best suppression.
The crystal filter will then improve on this somewhat, assuming the BFO is adjusted correctly.

Curt's suggestion to check the BFO placement is a good one.
Have you tried adjusting the 22pF trimmer in parallel with L3?
There's a whole paragraph about tuning in the BFO on? ?
? ??
starting with the words "On amateur bands above ..."

Here's a technique for debugging a receiver that might prove useful:
??
Farhan uses a short piece of wire as an antenna, perhaps 1 meter long.
It picks up houshold QRM, and he injects that into various parts of the radio,
listening to the result out of the speaker.? Perhaps this will help.

Once the receiver mostly works,?you might verify the crystal filter shape.
To do this, measure the audio coming out to the speaker using a scope
while tuning through a strong carrier in one of the bands.??
Ideally, you would start hearing it around 300 hz on one side of the carrier,?
it shouldould quickly rise up to full volume and stay there till around 2500 hz,
at which point the volume should rapidly fall into oblivion again.

I am not quite sure what to say about all of the "mixing frequency products"
that you hear in the receiver.? I don't know how clean this radio was,
but they should not get in the way of casually tuning in stations across the band.
It could be just a matter of a wiring error or bad part.
Or it could depend on how the parts were placed on the board.

When building the crystal filter, it is best to choose a set of?
four 10mhz crystals that match in frequency within perhaps 100hz
when plugged into an oscillator, using a frequency counter.? ?
It may be necessary to do this if the above test of the filter shape looks wrong.

We can worry about Q14 and the 2n2218 JBOT power amp
after you get the receiver working properly.
?
If you get stuck, you can certainly ask questions here.
But best would be to find a local club of radio amateurs who know
about working on radios and have appropriate test equipment.
Perhaps someone there would like to help.

Best Regards,
Jerry Gaffke, KE7ER

Brad,

In the past every time that issue has been seen it was the 40 low pass filter having
wrong components installed at assembly.? Other wise the issue would be evident
on other bands.

Generally the power goes down as one goes up from 80 through to 10M.
Nominally 40m should be less than 80 and more than 20.? This is assignable
to the power amp.?

If 40 is much lower than 20 then low pass filter or switching is broken.

Allison