Hello Jerry Gaffke,
Thank you for your details troubleshooting tips.
Details of my uBitx is at /g/BITX20/message/73904

I dont have a battery. So I kept my PSU connected.

I use a metal box. Still I wrapped using kitchen aluminum foil.

Following your steps, I observed that the moment I connect my antenna cable, I start getting the local broadcast.?
So is it concluded that I need High pass filter?

Could you please suggest any DIY High pass Filter ?

73
vu3onx

This case is available.

Christopher

On Sun, Dec 22, 2019 at 5:42 PM Sheldon Howard <drsheldonhoward@...> wrote:

If the case is still available, I would?like to purchase it.?

On Sun, Dec 22, 2019, 3:59 PM Ken Hansen <ken@...> wrote:

Hello all,

After selling my unbuilt uBitx & Bitx40 (thanks again to all that expressed interest), I just uncovered a Carl Beck (SK) 3D-printed uBitx case & knob kit, new and unused.

This kit was made for the uBitx specifically, with all appropriate holes and openings as needed. This case is suitable for a recent version of the uBitx, NOT the V6 model with the touchscreen.

I repeat, this is NOT suitable for the current V6 uBitx.

More information can be found here:?

If interested, I’d like $45 shipped, but I’ll entertain offers.

This case is no longer available, this may be one of the last examples of his work available, ready to contain your uBitx V5 or earlier..

Thanks,

Ken, N2VIP

Just crush the transistors with a set of small diagonal wire cutters and wipe the legs off the pads with a low watt soldering pencil.? Save the $16 plus shipping on the chipquik.

?

From: [email protected] [mailto:[email protected]] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Sunday, December 22, 2019 11:49 AM
To: [email protected]
Subject: Re: [BITX20] TOPIC OF THE v3 v4 L5 L7 Mod GOT ME WONDERING

?

On v5 (and v6), the changes Farhan made to reduce the 45mhz-DialFreq spur are as follows:
? ?v5 has a new low pass filter at L31,L32,C205 to block the 90mhz harmonic of the 45mhz IF
? ?R26 is now 220 ohms, to increase current (and reduce distortion on large signals)
? ?Transistors Q20,21,22 are now BFR93W for lower distortion (less harmonics) at 45mhz

I have listed those in what I consider to be their order of importance.
Changing out the transistors is the most difficult, and the other two changes may well be
sufficient to reduce the spur enough to meet FCC regs.?

I suggest using a low temperature alloy such as ChipQuik if removing those transistors:
? ??
You first wick away most of the old solder using solder braid and flux, then add a bit
of the ChipQuik as if it were normal solder.? If that ChipQuik is more than luke warm
(via either a soldering iron or a $20 hot air embossing gun) it will be molten, making
it easy to pluck the transistor off with tweezers.

ChipQuik will also be useful when removing the old relays, if replacing them with Axicom relays.
You must either replace those relays or use an external filter appropriate for each band
to prevent harmonics from going out on the air with a v3 or v4 rig.

Here's the discussion in the forum where Farhan developed those changes:?
? ? ?/g/BITX20/message/61645
Note that there are 70 messages in that thread, and there are other such threads.
That particular message doesn't mention the transistors, but the 2n3904's simply don't have
sufficient Gain-Bandwidth-Product to work well at 45mhz, and so distortion occurs?
which produces that 90mhz second harmonic.? But if the filter of L31,L32,C205 is successful
in preventing the harmonic from reaching the first mixer, that's most of the fix.

For better performance during receive, you might also want to change out Q10,11,12?
to the BFR93W's.??

How swapping out L5,L7 for shielded parts would reduce this particular spur
is a bit of a mystery to me, but could well be the case.? Shielded coils
would prevent high magnetic fields in the nearby final amp from getting back into
the IF amp, so worth doing if you have them on hand.? There were other?
problematic spurs beyond the 45mhz-DialFreq spur that this could cure.

There were a bunch of other changes around the audio amp for v5.??

If you have an LM386 or a non-DX branded TDA2822 working in the audio amp, that should be fine.
The discrete transistors of v4 worked well enough for many, but if you have trouble with distortion
or insufficient power it should be easy enough to patch in an LM386 or TDA2822.
That new 2n7000 is there in front of the audio power amp on v5 to reduce annoying PTT pops
in your received audio when keying the mike, but is not essential.

Lots of changes to the final power amp for transmitting, these bring up the transmit power?
on the higher frequencies.? Without these mods you may only get a watt or two at 30mhz,
while getting perhaps 10 watts on 3.5mhz.? But these mods are hardly worth the trouble.
I would just use an external linear such as the 10W linear from QRP-Labs if you need more power,
though you will need an appropriate attenuator between the uBitx and that amp.

Be careful of increasing mike gain beyond what's available in the design as shipped from hfsignals.
Increasing mike gain to compensate for loss of gain in the transmit power amp at higher frequencies means
larger signals in the IF amps, and thus more distortion in those amps and in the mixers,
and thus far far worse trouble with spurs which you won't be aware of unless you look it over good
with a spectrum analyzer.? The rig can sound fine on the air, and still be putting out significant
out-of-band spurs if the mike gain is too high.

Jerry, KE7ER



On Sat, Dec 21, 2019 at 08:17 PM, Jerry Gaffke wrote:

Raj found that using a particular brand of shielded inductor fix at L5 and L7 would cure that spur.
Some report it didn't work for them.
Farhan found he could tame the spur on his rig by adding a filter between the 45mhz IF
and the first mixer that prevented the 2'd harmonic of 45mhz from getting into that mixer.
Again, this is a kind of tricky fix.? ? When I search for "spur" in the forum I get 757 hits, mostly
discussions about the above two possible ways to fix this spur.
On v5 and v6, Farhan changed a number of components to reduce the harmonic content
of the signal from the 45mhz IF, this fix is working very well.