Re: #ubitx SSM2167 mic compressor speaker feedback issue - resolved
#ubitx
Hello Kevin,
I will.
73, John (VK2ETA)
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Re: Harmonics measured by Warren. How bad?
Warren,
Not surprised.? Did that back in June to prove it for myself and have said it can be done since.
Didn't capture the screen, but you did, good.
The 15m however is a bit of a test, doable but less easy and you have to accept a bit more loss.
The real issue was and is how to switch it in and whos making up a board?
Allison
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Re: UBitx Crystal filter capacitor Q
The caps should have a high Q but there is a point of little return for ones effort to go better.
If you use quality caps its generally not an issue at 12mhz, bigger deal at 1296mhz.
?
So for this its more a matter of using the right value for that set of crystals.
Paralleling gets better Q but for this it allows you to exactly hit the desired value.
as capacitors in the 30 to 100pf range are generally standard values only.
For example your could put 56pf and 33pf to get 89pf, or 47and 47 for 94.
I believe the optimum value centers around 91pf but, 1% caps are scarce and far from cheap
especially AVX and other MLCC types.? So hand picking (with measurement) and paralleling
is the way to go.? For a given set of crystals as they also vary so the "correct" capacitors is
in the range of?82 to 100.
Of course one could extract the crystals measure them and then calculate the exact value.
That's a lot of work and a simple change the values and try them is easier.
How wide should it be?
Other than my personal preference, a SSB filter is considered very tight at 2khz and wide
at 3khz so there is plenty of room to allow for anything in that range.? Also I have two radios
that have adjustable digital bandwidth (IF DSP) that goes down to 200hz and up to 2800
so 2300 to 2500 is fairly normal sounding 2000 or less is really narrow sounding.
For radios where I've built the filter from the ground up I shoot for about 2400hz
a variation 100hz either way is hard to hear and still very good.?
For CW nothing beats 500hz or so unless tuning then wider is easier.
Hope that helps.
Allison
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Re: #ubitx SSM2167 mic compressor speaker feedback issue - resolved
#ubitx
Hi John,
could you perhaps put up a schematic drawing of everything you did to install this module ?
thanks,
kevin rea
k6rea
lancaster, calif.
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Re: Harmonics measured by Warren. How bad?
I set out to design a bandpass filter that could replace Filter 4 for use on 12 and 10 meters. I wanted to see if it was possible to design a simple filter that had steep enough skirts to attenuate both the harmonics and the "45 MHz - Carrier" spurs. I wanted to see how simple a filter could be and still meet this requirement.
Here is a very simple third order filter that appears to fill the bill. Shown are the original design, the actual implementation, and the measured results. It does the job (just barely, in the case of 12 meters but good enough) and is only a third order filter as opposed to the fifth order designs for the original low pass Filter 4.
I used the online 66Pacific toroid calculator which called for 5, 20, and 5 turns respectfully on T-6-25 cores. I ended up measuring and trimming these to 4,17, and 4 in the final design. Similarly, the design called for 480, 32, 480 pf for the caps..... I ended up using 440 (2 x 220), 27, 440 pf to get the profile shown in the measured spectrum.?
In the end, one filter that meets both harmonic and spur requirements at 2 watts. It can be done!
?
WA8TOD
?
  
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Re: Test for solving Spurs
#ubitx
My understanding is that these spurs arise primarily in the mixer, not in the 45mhz IF amp itself. First off, the Si5351 with the 6dB pad is not giving anywhere near 7dBm into the mixer LO port, more like 0dBm. The 45mhz signal entering the mixer should be 10dB below the local oscillator, so roughly -10dBm, anything more than that and the mixer starts misbehaving.? ? These are some very round numbers, but should give an idea. Gain distribution in the transmitter is such that we can have too much 45mhz signal entering the first mixer, even if we did have 7dBm at the LO port. Especially true if you crank up the audio to get maximum?power out to the antenna. Farhan mentioned ALC as a possible solution to this. Seems simpler to design the 45mhz amp to give constant gain regardless the actual performance of the transistor in that particular rig, this means we need e a transistor with a higher Ft than the 2n3904. Also, a procedure for measuring the maximum audio signal out of the mike amp, a DVM set to AC volts? might be sufficient. If ALC is desired, John VK2ETA's scheme of moving the 45mhz IF signal around within the 45mhz filter passband is a zero additional hardware solution that gives good results. ? ?? /g/BITX20/topic/16737180Allison also had a solution involving 1n4007 pin diodes in the emitters of the IF amps, a $0.25 hack. But ALC for transmit seems an unnecessary complication for a simple rig like the uBitx. Jerry, KE7ER ?
On Sat, Aug 11, 2018 at 08:49 AM, Henning Weddig wrote:
Allison,
I was wondering why the first IF could cause problems! But due to Your explanation I now understand the problem! It is not caused by the If filter itself but in TX mode by the amp beween the 45 MHz filter and the mixer, producing a second harmonic and even higher harmonics if driven too hard. So the effect must be output power related. As the transistors within this amp are limited in gain? due to their limited gain bandwidth product (my LTSPICE simulation showed a 3 dB gain reduction) higher harmonics must be much lower.? Using e.g. BFR106 insteead could worsen the spur problem.
A simple remedy could either be a lowpass filter between the output of the 45 MHz TX am and the mixer input or simply a 90 MHz trap (bandstop filter)? Maybe a 45 MHz LC bandpass filter also could help.
? Henning Weddig
DK5LV
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Re: Finding the right version of schematic, voltage and signal at test points
#ubitx-help
Thanks, Allison. Because it was easy I checked the bias voltages versus frequency for the transistors that sink the 12v to trip the filter relays. I put a separate topic-question out to see if anyone has measured those, and if so, are their measures like mine. So far I'm getting suggestions of flies to swat but no voltages. I think I'll need to borrow a friend's uBitX and check them. If that yields no obvious fault it's off to cobbling up a RF sampler box for my scope, building an AF signal generator and tracking the signal through the circuit.
I am greatly enjoying reading the schematic, getting into the circuit and seeing how it works. It takes me back decades to when I did that work and was technically competent.
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I'm using the KD8CEC software that gives me 160m band coverage. ?It occurred to me that the 160m 3rd harmonic is less than the cutoff frequency for the 80m LPF in the uBITX! ?Duh!! ?I listened on the Eagle and sure enough it was as strong as the fundamental.?
So, I put 950pF ?(parallel 470 pf silvered mica caps) across one of the 900nF coils in that LPF and also 250 pF across another of the 900nF coils to reduce the 80m 3rd harmonic. ?Both bands now are noticeably weaker at 3X. ?power is down a watt or so on both bands.
I would say that it probably isn't all the way fixed but I don't expect to be on either band much before an authoritative and do-able fix is found here.
73,
Tom ?W1EAT
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Re: Test for solving Spurs
#ubitx
Ian.
In the analog realm code code for the Raduino can only assure the oscillators (SI5351)
are on the right frequency.? Not many levers we can apply there.
Since we are analog for the RF the solutions are improve or add filters.
I'm old and computers then were big and insanely expensive.? I'm glad I studied both!
Computers got smaller, cheaper, and analog keeps going.
Allison
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Re: Compliance Summary - other radios
Iz ooz,
The only RM Italy amps I've seen were the ones with selectable filters.
They worked well and were clean.? The owners liked them.? I thought
them a bit pricey.
Allison
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Re: Compliance Summary - other radios
When I tested the ubitx it triggered exactly the same question.??
How are the other radios?
The list includes:
FT817, Argonaut 505, Triton m540, Eagle, KNQ7A, 20 Slopbucket, Kitsandparts 1W (cw only),
and homebrew SSB monoband radios for 40,20,15,10.? For ancient to compare to I
warmed up the HW101, Siltronix 1110C, and Tempo-one as an excuse to make sure
they were ok and put a little time on them.??
The verdict was all passed with margin.? Some the margin was more than 20db.?
For example my 1977 (manufacture date) Tentec Triton M430 the specs said not?
less than -60dbc and it was better than spec 43 years later for everything.? The?
modern OK mines about 12 years old) FT817 was spec or better.??
The poorest exceed spec was the 20M Small wonder labs White Mountain
SSB as harmonics were-43dbc (at max power 3W) and the peak was?
second harmonic with the rest better and carrier was -46dbc.? Not?
bad for a 20 year old design and in use for the last 14 years.
A recent build is the 20M slopbucket a KD1JV design.? Harmonics better?
than -45 for second and better for higher. Carrier was -49db.
For many simple radios the second harmonic is to be watched because?
of the single ended output as its also harder to filter.? the WM20, Slopbucket,
and KNQ7A and nearly all of mine fall into that category.? They pass.
Also I can take any radio and push it to get truly horrific results.? Can't
blame the radio for that.
The tube rigs were interesting as once dialed up for the band it was good
but over driven or tuned up wrong the second harmonic could climb out of
accept range.? Considering the output of both of those were only single
section pi networks for the outputs one would expect worse.? OF note
was that spurs other than harmonics were not at all strong most being
better than -55dbc.? This is attributed to much filtering (tuned preselection)
in the lower level stages and the driver as well.? Considering the
Siltronix 1011C? goes back to the days was 11M was a?ham band
it was fine on 10M and fun.
Filtering in the early stages does help and all do it that way with low
pass filters for harmonic clean up due to the amplifiers used.? AS a result
spurs were non existent or very low.
One odd item as a response...? I have a siltronics 100W "cb" amp.
With mods (bias circuit added) for class AB1 (1a standing current)?rather
than class B (zero bias) the push pull amps is close to that of Motorola AN63
with MRF454s.? So I tested it without the nominal low pass filters used with
it.? The drive was FT817 at 5W so the output was about 63W for 80 and 40
(works well higher but not tested for this) and harmonics were -38DBC for
second harmonic and -33dbc for the third harmonic the rest were lower.? Of
course it didn't pass but as to calling it filthy, not so?much.? ? With external
filters normally used in place in the results were easily 15db (for second)
and 23db (for the third)?which is better than required.? With harmonic
suppression in the? mid -50s, 53dbc and 56dbc for both bands case closed.
The filters, a set of filters built almost like those for the ubitx using the
same values?with differences, bigger toroids, higher voltage caps and used a?
dual section 4 position switch. Covers 80-60, 40, 20-17, 21-29mhz.
I built it?last year so I never thought?to try it with ubitx but based on?
this it would clean it up.
Allison
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VBW is the postprocessing of the spectrum analyzer data before throwing it up on the screen,
and determines how many hz wide a swath of acquired data will be included in that pixel of the display.
Since the display is not blocky, I assume the center of the window is weighted heaviest,
and as you approach VBW/2 away from the center the contribution of that acquired data approaches zero.
But I'm left wondering if the display accurately shows the true peak power in dBm for each fundamental, harmonic, and spur.
?
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On Sat, Aug 11, 2018 at 09:11 AM, Jerry Gaffke wrote:
I'm not familiar with spectrum analyzers, still a little bit hazy about VBW.
But from what little I know the RBW and VBW selections seem good enough.
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UBitx Crystal filter capacitor Q
Larry N2AJX Wrote ¡°I swept the crystal filter and found its 3dB bandwith at only 1.2 kHz, less than half of what it should be. So I experimented a little and found that by changing the 5 capacitors from the crystals to ground from 100 pF each to 82 pF each, the bandwidth increased to 2.4 kHz¡±
(sorry for the size change with Pasting) On uBitx.net under Crystal Experimentation it says ¡± 3) As suggested by Allison KB1GMX, 82pF is working just fine in the filter and achieves a bandwidth of around 2.2Khz. Capacitor value is bit touchy between 82 to 100pf.
4) The Q of capacitors used has a major impact on the filter response. Parallelling up two values to arrive at a desired overall capacitance value results in a better response.¡±
so
do we want hi or low Q?
how is the ¡°response¡± better?
does paralleling capacitors increase or lower the Q?
what does ¡°touchy¡±mean when talking about values between 82 and 100pF?
Thanks!
For ever clueless,
jer aa1of
(really, I do much better if you spell it out...)
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Such wonderful data!? ?Warren, hoorah!
I'm stuck at a medical education seminar getting terabytes of knowledge being poured into my head on pacemakers and their application and interrogation.....but at slow moments?working on my simple "right-hand-side-of-filters relay system" printed
circuit board layout.? ?Using the DIPTRACE that you folks got me to learn how to use....? and at the same time one of our more-brilliant ARES volunteers has just figured out how to use PAT to do automated WINLINK from raspberries....which means he's
going to be providing yet another need for uBitx's....? ?It is good to see that on SSB they aren't THAT far out of compliance....but can be better!? ??
Below is a redrawn schematic showing the cuts to the traces that I think have to be made. (double red lines, and then the trace is erased).? ?
?Not quite sure what to do with the remaining, unnecessary? "between-relay" traces ---perhaps just GROUND them?
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Here's where Warren parked his screenshots.
? ??
I'm looking at the screenshots for harmonics of the major bands of 80,40,20,15,10m
Ignoring purple CW traces as there's an easy fix for that, just looking at the blue SSB traces.
Ignoring the WARC bands, as I seldom use them and we have plenty on our plate already.
In all cases, the transmitter is adjusted for peak at the transmitted frequency is at +33dBm, or 2 Watts,
this adjustment might be made by varying the amplitude of a 1khz audio sine wave into the mike jack.
The horizontal green cursor line is set 43 dB below that, or at -10dBm.
Any harmonics or spurs that get above the green line are non-compliant.
These displays are being generous, crank up the audio amplitude for more power than 2 Watts
and the non-compliant emissions will likely be worse.
80m looks clean, I assume the peak at the far left edge is an artifact of the spectrum analyzer
At 40m the 3'rd and 5'th harmonics are slightly non-compliant by 1 to 3dB, some might say that's not just too troubling.
By 20m, the third harmonic non-compliant by about 5dB , out of complince,? more like 5dB
At 15m, there' some cruft I don't understand well below 21mhz, otherwise compliant
At 10m, same as 15m, looks compliant enough to me except the cruft at around 11.3mhz.
So what's the low freq cruft I see on 15m?? Just artifacts of the test setup, or real emissions?
Perhaps Allision has a point, and this will only be cleaned up by appropriate per-band BPF's at L1,2,3,4 of the uBitx.
There is a short blip at??(45mhz - FOp) = 24mhz, but it is fully compliant.
I'd guess it becomes non-compliant only when power is increased (by increasing the audio level into the mike) above 2W.
??
On 10m, the only non-compliant spur is a peak at about 11.3mhz, what's that?
There is also a just barely compliant spur at 16mhz, which is our expected? (45mhz - FOp) spur.?
I'm not familiar with spectrum analyzers, still a little bit hazy about VBW.
But from what little I know the RBW and VBW selections seem good enough.
The x axis is unfortunately not labeled in mhz.??
For those confused, consider the 10m screen shot here:??
At the bottom it says span=80mhz, center=50mhz, and there are 10 horizontal divisions shown in the display.
So each division is 80mhz/10 = 8mhz, and the far left edge is 50mhz - 8mhz*5divisions = 10mhz
The non-compliant peak is about 1/6'th of a division to the right of the far left edge, so at 10mhz + 8mhz/6 = 11.3mhz
?
Jerry, KE7ER
On Sat, Aug 11, 2018 at 07:00 AM, Warren Allgyer wrote:
Farhan
My scans are in the Photos section on this board. They show non-compliant harmonics at two watts out on all bands, all modes through 20 meters with the one exception of 80 meter SSB.?
Not shown in the files , although I can retest and post them, are non-compliant ¡°45 MHz minus Cartier¡± spurs on all bands 20 meters and higher.?
On Sat, Aug 11, 2018 at 06:31 AM, Ashhar Farhan wrote:
Warren,
I had compiled data from your own scans. It didnt show any troubling harmonics until 14 mhz. Can you confirm that??
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Can you send me a copy of the BOM for the uBITX?
Thanks,
Jim W0CHL
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Re: BITX40: Qui peut m¡¯aider ? Who can help me ?
?
Merci ¨¤ tous les amis qui m'ont aid¨¦, mais difficile ¨¤ trouver.
Heureusement un ami informaticien a trouv¨¦.
Logiviel Arduino mal install¨¦ et bug dans le fichier. Murphy ¨¦tait au QRA.
Mais tout fonctionne super, on va pouvoir avancer.
Mais n'¨¦tant pas dou¨¦ en Anglais et en informatique c'est dur.
73¨¤ tous
³Ò¨¦²µ¨¦
?
?
?
> Message du 10/08/18 22:43
> De : "f1apy - Jacques" <f1apy@...>
> A : [email protected]
> Copie ¨¤ :
> Objet : Re: [BITX20] BITX40: Qui peut m¡¯aider ? Who can help me ?
>
>
Bonjour F6CXO,
?
Je peux vous aider pour la prog arduino, le mieux c¡¯est de passer en mail priv¨¦
f1apy at orange.le bon pays.
Hi gege, I can help you to program Arduino, please contact me at my address before.
73¡¯s de Jacques ¨C F1APY
?
?
From: [email protected] [mailto:[email protected]] On Behalf Of f6cxo
> Sent: Friday, August 10, 2018 4:53 PM
> To: [email protected]
> Subject: Re: [BITX20] BITX40: Qui peut m¡¯aider ? Who can help me ?
?
> Bonjour Gilles et all
> Mon BITX40 est un mod¨¨le tout mont¨¦ ( comme tous, 2 platines a assembler)
> Je suis ¨¤ la V1.01 et je veux changer la version car j'ai des tac tac pendant la rotation du potar fr¨¦quence.
> Je veux la compilation pr¨ºte(V1.28 je crois) pour le logiciel Arduino et mettre dans l'appareil. Mais n'¨¦tant pas dou¨¦ en informatique quand je fais v¨¦rifier il y a des erreurs qui empechent toute prog.
> J'esp¨¨re avoir ¨¦t¨¦ assez cvlair
> 73 ³Ò¨¦²µ¨¦
> ?
> ?
> ?
> ?
> Message du 10/08/18 11:16
> > De : "Gilles Delpech" <gilles.f1bfu@...>
> > A : [email protected]
> > Copie ¨¤ :
> > Objet : Re: [BITX20] BITX40: Qui peut m¡¯aider ? Who can help me ?
> >
> >
Bonjour
Je n'ai?qu'un?uBitx avec?la version usine du firmware donc je n'ai pas encore commenc¨¦ ¨¤ remplacer le logiciel par une nouvelle version.
Je fais d¨¦j¨¤ quelques modifications hardware avant de changer de version du firmware.
Votre bitx40 est un mod¨¨le tout mont¨¦ par Farhan ou l'avez vous mont¨¦ vous-m¨ºme ?
Voulez-vous changer les param¨¨tres de l'appareil ou charger une nouvelle version du logiciel ?
Si vous voulez charger une nouvelle version du logiciel, fa?tes-vous la compilation ¨¤ partir des sources ou chargez-vous des fichiers .hex ?
Donnez-nous plus d'informations.
> >
Le?ven. 10 ao?t 2018 ¨¤?09:56, f6cxo <f6cxo@...> a ¨¦crit?:
> >
> > Bonjour Laurent
> > Mon Anglais ¨¦tant inexistant, j'utilise GOOGLE traduction etl'¨¦change est long.
> > J'essaie de programmer la version 1.28 sur mon BITX40 et il y a des messages d'erreur qui emp¨ºchent la programmation.
> > 73 ³Ò¨¦²µ¨¦
> > ?
> > ?
> > ?
> > ?
> Message du 09/08/18 21:15
> > > De : "DREYFUSS Laurent via Groups.Io" <f4czi=[email protected]>
> > > A : "[email protected]" <[email protected]>
> > > Copie ¨¤ :
> > > Objet : Re: [BITX20] BITX40: Qui peut m¡¯aider ? Who can help me ?
> > >
> > >
C'est vrai qu'un peu plus de participation en fran?ais serait la bienvenue. Par contre, une r¨¦ponse directe prive automatiquement les autres personnes int¨¦ress¨¦es par le sujet d'informations pouvant ¨ºtres utiles.
De?: f6cxo <f6cxo@...>
> ??: [email protected]
> Envoy¨¦ le : Jeudi 9 ao?t 2018 8h11
> Objet?: [BITX20] BITX40: Qui peut m¡¯aider ? Who can help me ?
?
Y at'il des OMs francophones sur la liste
J'ai achet¨¦ un BITX40 et je n'en suis pas satisfait, j'ai un tac tac pendant la rotation du bouton Fr¨¦quence qui est assez p¨¦nible.
Merci de me r¨¦pondre en direct sur mon adresse : f6cxo@...
?
?
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Re: BITX40: Qui peut m¡¯aider ? Who can help me ?
Il faut aussi faire attention a un compte non administrateur sous Windows, cela g¨¦n¨¨re des messages d¡¯erreur sur l?ide arduino ressemblant ¨¤ des erreurs de compilation-> Faire la manip avec un compte administrateur.
you have to take care to a non-admin windows user that display some messages looking like compilation errors -> try with an windows administrator user
remi f1mqj
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Re: Compliance Summary - other radios
Tim, I am not absolutely sure but regarding the RM-Italy without lowpass filters I think they are not imported in the USA. If you download the manuals from their site they state the user must provide a low pass filter and they sell a 30mhz low pass filter for 10 meters. If you use it without a proper filter that is not allowed. They warn the buyer at least. There are other RM Italy models that have low pass filters for all the HF bands. They cost more of course and I think these models are exported to the US.
Il 11/ago/2018 17:52, "Timothy Fidler" < engstr@...> ha scritto: arghgh rew WBand SSB that might be one of those MPa'70 home built? amps as in 20 dollars on ebay and no filter set? or perhaps an RM Italia amp with no filter (some yes,? some no plenty of hoods off photos on the internet to show the awful truth)? ?and run right at the stops in terms of drive. .. and the FCC does nix even though they are factory built amps and should have compliance tests before entry. ? Timothy E. Fidler : Engineer BE Mech(1) Auckland , NDT specialist AINDT UT /RT3 , MT2?
Telephone Whangarei?? 022? 691 8405
e: Engstr@...
----- Original Message -----
To: <[email protected]>
Cc:
Sent: Sat, 11 Aug 2018 06:03:33 -0400
Subject: Re: [BITX20] Compliance Summary - other radios
Hi,
I have some other solid state gear and the filtering is more serious. My
latest purchase (used) is a Hendricks PFR-3 and with only three bands it
contains as many of those funny little donuts than the uBitx. They are
also well placed. My old Atlas has a complete set of low pass filters on
the output AND the interstage filters. It resembles a box of donuts from
a real donut shop. I have a Ten Tec receiver that covers from 300 kHz to
30 MHz and has seven switched filters in just the front end and some
more in the synthesizer section.
I also have a Dentron 80 meter rig rated for 12 watts with absolutely no
filter after the final!! I have it sitting on the shelf just because I
cared to remove the cover and look. No filter shows up on the schematic.
Can't be. But it is. Now that uBitx has my attention I will probably
roll a set of filters for that Dentron too.
UBitx is fixable.
73,
Bill KU8H
On 08/11/2018 12:32 AM, Dennis Yancey wrote:
> I wonder what other kits and factory radios actually look like in
> comparison on exactly the same teapots. For instance, I was listening to
> a gentleman who is an extra class talking on 40 meters last night. He
> USA using a high dollar radio, so he said, a high dollar amplifier and
> he was 3 states away from me. His emissions were covering 8 kHz on
> either side of the frequency he was using. That is just one of many. .
> --
> 72 and God bless
> KD4EPG
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Re: Test for solving Spurs
#ubitx
Allison
Thank you for your feedback and test results.?I am not an RF expert like you. My major is not RF.
I just wondered how Harmonics and Spurs can be easily tailored to the level that users want.
Looking at the circuit and the source code, I figured out a couple of things to solve, but it seems like it was my mistake.
I have one or two experiments left for this issue, but?I knew my experiment was wrong, so I do not think I need to go any further.
Once this problem is solved by experts, I can expect to learn about it.
Thank you again for testing.
Ian KD8CEC 2018? 8? 12? (?) ?? 12:29, ajparent1/KB1GMX < kb1gmx@...>?? ??:
On Sat, Aug 11, 2018 at 06:54 AM, Ian Lee wrote:
learned Spurs while reading the group 's mail today.
It seems to be difficult to control with LPF or BPF because it occurs near the main transmission frequency.
And I understood that it was caused by the frequency generated to pass the 45Mhz Filter.
The spurs development is a side effect of DBM (MIXERs) operation.? The 45mhz I refer to is the IF output?
that feeds the last DBM the other signal is the local oscillator (raduino osc-2).? ?
The simple explanation is any time you mix two signals you get two more and those mixed with the first two give you 8 more....
IF you add the fact that those first two signals have harmonics each possible pair do as above creating more pairs of many pairs...
Some of those will be desired, others are a side effect of the process and those will have varying strength according to the?
their harmonic order.?
The specific one that is most troublesome is the 2IF-LO (the 45mhz if *2) and the LO is clk-2..? So at 28mhz
that is a LO nominally a LO of 73mhz to convert 45mhz to 28mhz.? It happens that 90mhz (2IF)- LO is 17mhz.
( you get the same this of you say 45(if)-dial frequency of 28mhz =17mhz).? ?It is a problem because the radio
uses very few filters to eliminate undesired results so the 17mhz signal is amplified in the power amp and
escapes along with the desired 28mhz.
The presence is not the problem, it is the intensity of it (strong).? Because the dial frequency changes?
so does the spur frequency.
There is no way to control that in software as ubitx is an analog radio (in SDR its possible) so the
analog solution is add the missing filters.
**** for those looking to pick and ding I used round numbers to keep the concept clear.? It makes zero
? ? ? difference if I go to the nearest 1 Hz as a 16.983... hz, the spur is as unacceptable.? We do not
? ? ?need to be be precise to say its not allowed as its outside any Amateur Radio band.
I read that the Spurs were slightly beyond specification.
I have experience certifying commercial electronic devices, but I am not familiar with FCC amateur radio test specifications.
The US spec is -43dbc for all harmonics and spurs.? ?FCC years back did this to make USA in line with the ITU standards.
In some cases its an improvement and other cases it was a relaxed number.? The one I'm not certain on is if the FCC
PART-15 standards below 30mhz? also apply for out of amateur band signals as they do for most every other device.?
If so that is stricter as its a radiated signal standard.
I also have worked in EMI/RFI engineering prior to entering the antenna engineering and development field about 9 years ago.
Allison
-- Best 73 KD8CEC / Ph.D ian lee kd8cec@...
(my blog)
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Re: A note about real vs. clone Arduino Nanos
Larry i ve seen a page comparing arduino consumptions genuine and clone, it wasn¡¯t so different, more reliable with genuine (quality test) but not bad at all for the great majority of clones
remi f1mqj
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Bruce W4BRU