Re: 7277 Bitx >Bitx Today 12/2/18
I had a couple of QSOs on 7.177mhz looking for QRP. None of them was. On 7.277 there were only strong AM stations at least here in the Euro side. To be on the safe side a General should call at 7.178.
Il 05/dic/2018 04:16, "d balfour" < davesters@...> ha scritto: I will listen to 7180 but find it crowded on Sunday afternoon at times. 40 can be bad with AM Carriers. 7.285 is a fairly recognized qrp frequency. I had a 20m qso last Sunday on 14.285 They were in Florida about 1000 miles away.? 20 of course is not friendly to those with Bitx40s.
Although technically US Generals can go as low as 7175. On LSB that will put one in violation of the rules.
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Re: Great Results with Mic Preamp
I suspect that RF is getting into the base emitter junction and causing problems.? The preamp was designed to be located inside of the microphone with nearly zero lead length between the mic cartridge and the input.? Adding a mic cable with considerable? length that couples directly to the emitter changes the situation quite dramatically as you have placed an antenna on the emitter of the 2N3904.? You are also inside the same enclosure in closer proximity to the RF output stage.
As I mentioned, the preamp circuit was a minimal design meant to fit inside of the diecast mic body so no RF bypass capacitors or ferrites were needed or included in my application.? Some measures I might suggest to mitigate are adding 1000pF bypass capacitors to the base and collector leads of the 2N3904.? If more help is needed, ferrite beads can be added in series with the collector and emitter leads.? Finally, if the issue persists, shielding may be needed to attenuate RF energy that is radiated directly into the device.? Also make sure your internal preamp grounding in low impedance at RF.
73 - Paul - K8PD
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As for older boards that need relay replacement I have to say they were all but an easy swap. Using just a solder iron, copper braid and a pump I could not remove any of them. They were useful but not enough. I had to use a rework SMD station (and a screwdriver for leverage to pull them out) , something I was discouraged here using it, but it worked well. And no other component fell or burn. Using the recommended Axicom I have seen the 3rd harmonics further down by something like 15db. I can only measure it using an sdr receiver, so not a real spectrum analyzer. Having said this what is lacking is a real aftermarket shop for the mods required depending on the version of various boards. Even some Drake rtx were not perfect and kits have greatly improved their performance, becoming legendary in some cases. This 'absurd' situation is just a business opportunity for others.
Il 05/dic/2018 04:25, "Jerry Gaffke via Groups.Io" <jgaffke= [email protected]> ha scritto: Between Raj and Farhan, we have some nice minimalist solutions for spurs.
A number of fixes for the harmonics have been proposed,
I like swapping out the relays if that works well enough.?
If inductors are involved, a specific ready made and easily obtained part would be ideal.?
But the toroids Farhan used in his filters would be acceptable.
Would be nice to resolve this to a recommended set of fixes.
Fully described? ?
List of exactly what parts to buy.
Schematics and photos.?
> It cleans up the act only on the higher bands.?
I guess that means it cleans up the spur we have trouble with on 15m, 12m and 10m.
This spur is at? ?45mhz - DialFreq.
At 17m and bands below that, the spur is sufficiently above the transmit frequency
that the transmit low pass filters take care of it.
Farhan also had a fix for the 12mhz spur that's due to crosstalk from clk0? into? clk2 at the si5351.
One issue was that his fix knocked out 30m, which may not be an issue on a a mostly SSB rig.
Another issue is that the part values he gave would resonate closer to 10mhz that 12mhz,
though there may be a reason for that.
A third issue is that Jerry Gaffke kind of thinks a HPF on clk2 with a corner at 30mhz or so?
might be a better, less finicky solution. But he's not to be trusted on this stuff.
Jerry Gaffke
On Tue, Dec 4, 2018 at 06:50 PM, Raj vu2zap wrote:
The 45MHz filter fix of mine and the LP filter of Farhans does the same thing. It
cleans up the act only on the higher bands. I tested it on a new board last
week.
Change to AXICOM relays is a must. Spurs are further reduced with change of
L5 and addition of 45MHz LP filter.
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Re: Is push pull hf amp has higher spectral purity
Brian,
So when operating between 7.1 and 7.3 mhz on the Bitx40 we have a transmit spur at 7.2mhz?
That would be weird, especially if the spur didn't move as we tuned across that range.
The receive birdie at 7.2mhz is due to the? 12mhz - 7.2mhz = 4.8mhz low side VFO
having a 5'th harmonic at 5*4.8=24mhz which beats with the second harmonic of the 12mhz BFO.
Anybody see any way that this might go out as a transmit spur?
Has anybody else seen this spur?
Jerry, KE7ER
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On Mon, Dec 3, 2018 at 01:23 PM, Brian wrote:
The stock Bitx40 has a problem with the 7.2MHz birdie not only on receive but also it produces a spur on transmit which does not meet fcc spec.
You could use it on 7.1MHz and below or change the vfo to high side and move the carrier oscillator to the other side of the filter (Allard's software). Whether you can do that depends on the xtal filter in your Bitx40. You may get lots of carrier and poor sideband rejection.
The Bitx is a good entry into homebrew. You might get away with using it barefoot but take care if you want to push to higher power.
73 Brian.
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Re: Documentation on uBitx help
Bret try ubitx calibration or zerobeat into search engine, that should take you to hfsignals page. My bfo setting was way off, I needed a clue on it to get it close enough to align.
If you happen to be using Sunil's case, check out ubitx.com for latest info.? its a different site than ubitx.net. assembly is a snipe hunt, so patiently work it.
Curt
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Re: Documentation on uBitx help
Bret,
you may start calibration here??
and wiring according to the enclosed sketch.
73 Axel
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Between Raj and Farhan, we have some nice minimalist solutions for spurs.
A number of fixes for the harmonics have been proposed,
I like swapping out the relays if that works well enough.?
If inductors are involved, a specific ready made and easily obtained part would be ideal.?
But the toroids Farhan used in his filters would be acceptable.
Would be nice to resolve this to a recommended set of fixes.
Fully described? ?
List of exactly what parts to buy.
Schematics and photos.?
> It cleans up the act only on the higher bands.?
I guess that means it cleans up the spur we have trouble with on 15m, 12m and 10m.
This spur is at? ?45mhz - DialFreq.
At 17m and bands below that, the spur is sufficiently above the transmit frequency
that the transmit low pass filters take care of it.
Farhan also had a fix for the 12mhz spur that's due to crosstalk from clk0? into? clk2 at the si5351.
One issue was that his fix knocked out 30m, which may not be an issue on a a mostly SSB rig.
Another issue is that the part values he gave would resonate closer to 10mhz that 12mhz,
though there may be a reason for that.
A third issue is that Jerry Gaffke kind of thinks a HPF on clk2 with a corner at 30mhz or so?
might be a better, less finicky solution. But he's not to be trusted on this stuff.
Jerry Gaffke
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On Tue, Dec 4, 2018 at 06:50 PM, Raj vu2zap wrote:
The 45MHz filter fix of mine and the LP filter of Farhans does the same thing. It
cleans up the act only on the higher bands. I tested it on a new board last
week.
Change to AXICOM relays is a must. Spurs are further reduced with change of
L5 and addition of 45MHz LP filter.
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Re: 7277 Bitx >Bitx Today 12/2/18
I will listen to 7180 but find it crowded on Sunday afternoon at times. 40 can be bad with AM Carriers. 7.285 is a fairly recognized qrp frequency. I had a 20m qso last Sunday on 14.285 They were in Florida about 1000 miles away. 20 of course is not friendly to those with Bitx40s.
Although technically US Generals can go as low as 7175. On LSB that will put one in violation of the rules.
|
Re: Documentation on uBitx help
Bret try ubitx calibration or zerobeat into search engine, that should take you to hfsignals page. My bfo setting was way off, I needed a clue on it to get it close enough to align.
If you happen to be using Sunil's case, check out ubitx.com for latest info.? its a different site than ubitx.net. assembly is a snipe hunt, so patiently work it.
Curt
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Documentation on uBitx help
Well after a year I have finally got my radio in the cabinet and now I'm ready to calibrate the zero beat and BFO and wouldn't you know it I can't find the calibration documention.?
I also have the TX/RX board installed but am not sure where to wire it up as I can't find instructions for that or a schamatic diagram that shows that part of the circuit.
So if someone can send me a link to these docs I would appreciate it very much.
I have looked through the MANY web pages but can't locate this information.?
So if you can help that would be great.
--
thanks and 73's
Bret
WX7Y
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The AXICOM relays mounted on sockets is as bad as the original.
They must be soldered direct on PCB. This I have confirmed on
two boards.
Raj
At 05/12/2018, you wrote:
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I concur there are multiple
remedies on the web.? However, at least one experimenter had
confirmed that the Axiom relays did not remedy the spurs.? I would
be careful prescribing this as the preferred fix - a separate bank of
relays will further reduce unwanted coupling.? On the 45 MHz
filtering, there seem to be several methods shown to work on at least one
unit.? Best to not jump to conclusions - forgive me if I have!?
Eventually we do expect to have 23 units tested with the separate relay
solution - if other techniques will sufficiently, repeatedly knock down
the spurs - okay.? But read and observe carefully.?
73 Curt
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Jerry,
The 45MHz filter fix of mine and the LP filter of Farhans does the same
thing. It
cleans up the act only on the higher bands. I tested it on a new board
last
week.
Change to AXICOM relays is a must. Spurs are further reduced with change
of
L5 and addition of 45MHz LP filter.
Raj
At 05/12/2018, you wrote:
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My point is, most readers of the
forum have no idea how to proceed.
Having three different vaguely described fixes is not quite putting this
to bed.
We should have a good simple recommeded fix, probably based on Farhan's
recommendations in your link:
???
/g/BITX20/topic/28088828#61869
Should describe exactly what parts are used and show exactly how to
install them.
Instructions that are complete enough that somebody having trouble
relating schematic to board can complete it.
And the fix should be verified by somebody with a spectrum
analyzer.
We have no idea with what mods a uBitx from HFSignals will currently
have.
Or how to tell a production board with good relays (if such exists) from
one with bad relays.
If this does not get nailed down, we will have thousands of posts here
from
somewhat clueless uBitx owners wondering if they will get thrown in jail
for operating their uBitx.
(Nobody has yet reported any such trouble.? And there are several
thousand unmodded uBitx's out there.)
I'd say it's fair enough to call the current situation
"absurd".
No way to run a railroad,
Jerry
Andy wrote:
>? Farhan has solved the spur problem twice, possibly three
times.?
>? As it appears to actually have been resolved, and as Farhan
has confirmed
>? that production is updated? as fixes are identified,
>? I'd have to see a board delivered without fixes to agree that
it's 'absurd'.
Andy, KG5RKP
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Re: Spectrum purity of uBITX and BIT40
The spur and harmonic trouble not reported with Bitx40. It is limited to just the ubitx. The boards continued to ship with the same relays as some have also reported no difference with the new relay. On the other hand, a new board layout with spur fix, allions suggested lpf layout and an lm386 af amp is in the mail. I will prototype it as soon as it arrives and share the results. - f
On Tue, 4 Dec 2018, 00:11 ajparent1/KB1GMX < kb1gmx@... wrote:
Seem to hear that self build, home brew is more relax under fcc laws than mass production factroy machine, to allow progress
in test, training, education, etc., in principle.? ?
NO.? The rules for factory and HB are the same.? They are not hard to meet but reasonable attempts to meet them are expected.
So far the relay is not the improved one.? Its not one its four and they are a pain to extract.??
Some people have built the uBitx as a ground up project using a self designed board or ugly (Manhattan, dead-bug style) on
a sheet of copper clad as a ground surface and the general result is much better.? Layout is everything.
Allison
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Re: spur & harmonics fix, v2
Evan, My fix was only for the spur, not for the harmonics. If you could try it out, it would help us all get on with it. - f
On November 12 Ashhar posted a fix and that his tests verified it corrected the spurs.? In that same post he advised to wait for others to verify.? Since then I have only seen discussions of theory and some information none specific to testing Ashhar's fix, or on just parts of the recommendations.? Though the discussion is very educational, I still would like to know if the proposal by Ashhar does correct the spurs and potential harmonics issue?? Has anyone with the testing capability verified the results?
I do have some test equipment, though lacking? the background in RF testing, I am less comfortable in doing the tests.? Do not really want to hack my board unless there is a good chance that it will fix the issues, as there is significant risk that I would botch something up.? I am new to surface mount systems, as back in the 70's all was leaded.
So my question is if anyone has implemented Ashhar's mods and have verified that they do solve the issues.
Thank-you in advanced for the feed back.
Evan
AC9TU
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Re: FS: SotaBeams Laserbeam DSP Variable Filter
Sorry gents should have made the link more obvious. I sold it this afternoon to a group member -- David
?N8DAH
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Is ubtx and btx40 good for digimode
Is the audio frequency narrow band spectral purity good? ?
I refer to unwanted signal, Hz to hundreds Hz from the audio carrier. Not RF purity, which is many MHz.
For example, Fldigi manual state psk31, 31 Hz up and down from carrier, should be 20dB lower
73 Simon
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Re: spur & harmonics fix, v2
On November 12 Ashhar posted a fix and that his tests verified it corrected the spurs.? In that same post he advised to wait for others to verify.? Since then I have only seen discussions of theory and some information none specific to testing Ashhar's fix, or on just parts of the recommendations.? Though the discussion is very educational, I still would like to know if the proposal by Ashhar does correct the spurs and potential harmonics issue?? Has anyone with the testing capability verified the results?
I do have some test equipment, though lacking? the background in RF testing, I am less comfortable in doing the tests.? Do not really want to hack my board unless there is a good chance that it will fix the issues, as there is significant risk that I would botch something up.? I am new to surface mount systems, as back in the 70's all was leaded.
So my question is if anyone has implemented Ashhar's mods and have verified that they do solve the issues.
Thank-you in advanced for the feed back.
Evan
AC9TU
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Specially with a msg title ¡°Ashhar Farhan¡±. ?Not terribly descriptive. ?I suggest ¡°Rant¡±.?
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On Dec 4, 2018, at 8:49 PM, Gordon Gibby < ggibby@...> wrote:
OK guys, I¡¯m getting ready to resign from this list if this keeps up. ?
Gordon?
On Dec 4, 2018, at 19:18, Laurence Oberman < oberman.l@...> wrote:
Pleaae dont use the words like "fake news" in our threads.
Its only "fake news" when its the truth certain people dont like.
I never said I was LOOKING for an alternative.? FAKE NEWS people keep adding it.?
--
Lee - N9LO? "I Void Warranties"
?
--
¡_. _._
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The BITX20 group has been great for info and support!? I hope we can keep it on topic.
73,
Woody? KZ4AK
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IMO it's past time for the moderator(s) to issue a lengthy time out to a bunch of people!
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On Dec 4, 2018, at 6:49 PM, Gordon Gibby < ggibby@...> wrote:
OK guys, I¡¯m getting ready to resign from this list if this keeps up. ?
Gordon?
On Dec 4, 2018, at 19:18, Laurence Oberman < oberman.l@...> wrote:
Pleaae dont use the words like "fake news" in our threads.
Its only "fake news" when its the truth certain people dont like.
I never said I was LOOKING for an alternative.? FAKE NEWS people keep adding it.?
--
Lee - N9LO? "I Void Warranties"
?
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_Dave_ AD0B
Raj vu2zap
N8DAH
MadRadioModder
Jim Sheldon