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Good morning (In the States) Hans!

I used a little 'Burt' force, and by alternating screws from each side and opposing corners i got it together with a good fit.? Thanks, I was afraid to put too much pressure on it.? So far so good!? Just checked the receiver on 20 and it was receiving as strong as my FT-DX10.? Very excited!? Bands appear a bit dead so far today for 20.? Working through the configuration steps next and then the xmit!? A fun and challenging build and oh that wonderful feeling of completion!

Thanks,
Burt K4SRQ

I have had it happen before with other extruded aluminum boxes where the fit between the two halves is not perfect. I use a pair of smooth-jawed pliers to give a very (slight) bend in or outwards on one of the edges so the grooves would line up.

The two halves are made in the same facility but not as pairs. Usually the production line is good enough that a production worker could grab and upper and a lower out of the two big bins and package them together.

I use flat jawed pliers to keep from marring up the anodizing. You could also use a pair of pliers with heat-shrink or a couple of layers or tape over the jaws so the serrations do not scratch through the anodization.

--
Tisha, AA4HA

Got through the build, added the firmware, booted up the rig.? Now to fit the case on!? This has turned into the most difficult part of the build.? The tongue and grove are off by a very small fraction.? I at first thought it must be the boards, so I took them out and verified that nothing was sticking up or out, the nuts were aligned etc.? Then I went back to the case and the empty case would not fit together.? Maybe a 64th of an inch or some miniscule amount but it is not a fit.? Anyone else have this fit issue?? The case was not stressed in any way and removed just prior to install.

Thanks,
Burt
K4SRQ

Generally...

video/RF amplifiers are measured the same.

Power output (undistorted and t 1db comprssion)?
Power gain (also votlage gain)
Distortion IMD, IP3, harmonics
Noise, noise figure of the amplifier.

You can use voltage gain or power gain so long as the input and output load
impedance are known.? For power the common use standard is 50 ohms and
DBW? or DBM.? Votage gain is sometimes used as well and if the load
impedance is know the conversion is easy math.??

That is an opamp amplifier so gain is the ratio of the feedback plus or minus 1.
The latter parts sign reflects if the amplifier is inverting or noninverting.

The series output resistors are for stability as most opamps are rather fussy
about reactive loads.? Fussy translated to they become unstable or can oscillate.

--
Allison
------------------
Post online only,?
direct email will go to a bit bucket.

In testing per the video cited (scrunching L4 and L10's turns closer together), I was able to get the output up to 2-1/2 watts but that only made me more convinced -- as you said -- that the BPF is the major factor in this situation.

Yes, I did.? Perhaps my surmise above was incorrect. As I said before, I'm reluctant to butcher the radio when it operates perfectly well on 20m through 12m so far as power out is concerned -- and I am fine with 2W on 10m for the moment. I have a Low Band QDX coming and I will be more circumspect about winding L12 and the LPF coils on that.?

Dunno.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."

William,

I count 20 turns on both of the toroid pictures.? The difference is on the 14th turn.? I count 15 turns to what should be the 14th turn and then only 2 turns between 17 and 20 on the second picture.

L12 will not impact the QDX output.? For 10 meters on a high band QDX, that is L4 and L10.? Have you tried squeezing or expanding those toroid windings?

73
Evan
AC9TU

Evan,

Thank you for your reply. I went back to carefully review my work as well as LY2H's video covering this subject..



After carefully inspecting L12, I believe it is one turn short between "17t" and "End (20t)". I am not sure that is apparent from the pictures I posted below but using magnifying eye glasses and a harsh light, it goes to the last turn being omitted. In testing per the video cited (scrunching L4 and L10's turns closer together), I was able to get the output up to 2-1/2 watts but that only made me more convinced -- as you said -- that the BPF is the major factor in this situation.

Interestingly, I will have to "work up the courage" to extract L12, rewind, and replace it. The other bands -- 20m through 12m -- put out a robust 4-6 watts* and I am loathe to turn the whole built rig into lunch meat for the sake of 10m. I may yet gain the nerve to do so, but my recent experience on 20m and 15m compels me to manufacture a 12m and 17m vertical and see what can I see.

..all of that said, I marvel at the technology and research that went into designing the radio, how Hans has brought fire from the Gods like Prometheus of old, and how wonderfully abundant this group is with knowledgeable hams as yourself to provide support.

Thank you again.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."

*which will be throttled back to about 5 watts by lowering the input voltage.

Borrowed a tinySA Ultra and a 40dB attenuator from a friend today, and got good results using that and 10dB of attenuation inside the tinySA.? All harmonics in the radio's output are in compliance with the FCC limit.? I declared victory and buttoned the QMX into its case. Looking forward to warmer weather and taking it into the field.

73, everyone,
Eric

thanks will do! as twisted as it sounds,? I am looking forward to trouble shooting this as my trouble shooting abilities are not what they used to be.? It will be great to exercise them again after 40 years.

On Sat, Mar 2, 2024 at 04:07 PM, Da Amazin' man G0FTD wrote:

If you accidentally leave it it on then you'd exceed the input spec

Unless you have a specific reason to turn on the LNA, leave it off.? It will reduce the upper limit of the dynamic range of your instrument at the same time that it increases sensitivity.? Always turn it off if you are using external attenuation.? Only use it if your measurement is front-end noise limited.
This is a powerful instrument and as such it requires some thought and understanding to make good measurements with it.??
There is a lot of good information on spectrum analyzer use at Keysight, Rohde & Schwarz, Anritsu and other manufacturers.??
Here are a couple to get started.


73, Don N2VGU

On Fri, Mar 1, 2024 at 12:59 PM, Evan Hand wrote:

For best results, keep the input at the TinySA under -25DBm.?

That is approximately -25dBm total power into the tinySA mixer; and gain/loss before the mixer, whether internal or external, will need to be accounted for.? -25dBm is not a hard and fast number and will vary with instrument and measurement.
One way to check if the level is OK or too high is to add some more attenuation and see if the carrier to intermod/harmonic measurement changes.? If no change then the IM/harmonic is real and not internally-generated.? If it changes, add attenuation until it doesn't.??
The "sweet" spot between distortion and noise can be narrow; some commercial SAs have 1dB (or less) step attenuators for fine level control for this reason.? An external step attenuator can be handy, but watch its power rating.....

I suspect that the tinySA designer made the internal LNA design such that it will saturate before it damages the mixer; that is what I would do.? What you will get instead is a screen full of massive distortion products, and, I expect, a warning from the instrument; I've never driven mine hard enough to find out.??
73, Don N2VGU

On Thu, Feb 29, 2024 at 08:20 PM, Ronald Taylor wrote:

Chris, you technically don't meet the -43 dBc requirement

Yes he does.

You clearly didn't bother reading his non US callsign which is quite clearly
written at the end of his post.

HINT - next time try reading the UK regs instead, there are no requirements
other than making sure your tx doesn't cause undue intereference to others.

Technically speaking, he can have a harmonic greater than a fundamental,
and if it's not causing "undue intererence" then no rules are broken.

OK, so that's an extreme example, but true. Reality is diferent, and most ops
will take pride in suppressing unwanted emissions so that they don't cause problems.

However, the point here is that many of us get just a bit pissed off with posts that
assume the world has the same US rules.

Now leave the rest of us alone to enjoy OUR regs, not yours.

--
- 73 de Andy -

The Backlight only need '12v' power applied to come on.

Most of the set runs on 5v via a regulator - but not the final few Audio OP amps which will generate some hiss..

Perhaps you ruined the first CPU (the instructions are too brief !) but the current one should have been fine.? ? I would proceed as the troubleshooting guide
in?

and?

Do all the DC checks in the build manual but start with is the 5V power there and at 5V !

?

On Fri, Mar 1, 2024 at 05:08 PM, Eric W. Hansen wrote:

What isn't clear to me, from the tinySA Ultra specifications, is whether its "recommended input power below -25dBm" is before or after the SA's built-in attenuator.? How do you read it?

Tiny SA also has a 20db LNA.

If you accidentally leave it it on then you'd exceed the input spec, so -25dbm should be your final target
just in case.
?
--
- 73 de Andy -

Questions / statements on this design.

First one is how the? drafter of the schematic - not the original designer came to? his Av? results

For instance the? input transformer has a voltage gain of? 2 and? a power gain of slightly less than one.

so as a? log ratio surely the? voltage gain is? +3 dbB ? But he uses? 20 log? V2/ V1 type formula I guess and he's getting? 6 dB

THe reason this is intriguing? is I want to see where his? Av of? 13.4 for the first video op amp comes from.

I 'd say that? the way to analyse this is? to replace teh 180 R feed back resistor with two 90Rs and a? virtual tap to GND.? That's because
it is a fully balanced circuit.??

So Av would? be? 332 /90? ? +1, using the std form for an inverting in put? FB amplifier.? THis gives a voltage gain of 4.7

I we use the Incorrect formula of? ? 20 Log? 4.7? ?we get 13.4? as a the? Av as a logarithmic gain. This aligns with his table.

This query is more about? the correct way of analysing the? performance of the RF amp than picking holes in whatever formulation he?
used for the? logarithmic voltage gain.??

any comments. ?
The other comment which I wills save is those ballasting resistors on the output? - they seem to be required as per the TI? datasheet for this chip.

Hi William,

The RF sweeps combine the LPF and the BPF (L12 and one of the selected capacitors).? The most impact is from the BPF.? If the LPF is correctly built, it will be significantly above the operating frequency.? With that said, I do not use the RF sweeps to tune the LPF.? That is done by compressing or expanding the turns on the two toroid inductors in the filters.? Both can impact the output power, though, for me, the most impact was with the L2, L3, or L4 toroids.

Hans has a video on tuning a QCX LPF that can apply to the QDX.? The QCX has more toroids, but the principle is the same.


73
Evan
AC9TU

Thanks to Jeff, W1NC for the great job repairing my builds of both kits.? I didn't believe the quick turnaround and how reasonable the cost was.? He will even throw in a tactful appraisal of your kit building skills :-) along with his frequent detailed communications.?

73
Reed AA1RB

OK, there is more to this story.? This was a functioning QCX,? but it had firmware version 1.00g.? I in my infinite wisdom decided to upgrade the firmware my self rather than just buy the chip.......oops LOL
I get all the cables, down load the software plug it all in and press the button..... I believe I should have not been powering the radio when I pushed the button.....Anyway, afterwards,? the chip did not update and the screen,? while it lights up still displays nothing.? I have since ordered a new chip.? Which has been delivered and installed.? Alas, the same issue? is still present,? The display lights up (Backlight?) but nothing is displayed.? Regardless of the contrast adjustment. ?? When I plug in my earphones I do hear hiss,? so I think? it is receiving?? but I do not hear anything but hiss.? since I can not see to tune the radio I am not sure that it is actually receiving....Any suggestions?? I did check pin 3 and the pot does adjust the contrast between 0 and 5V.

Thoughts on where should I look?

Kevin - W5LNA