Date   
TIA amplifiers

George
 

Dear members you can check:
1. Add parallel to R12 C=470 pF: in my analiser I could see 3 dB gain rising on 30 MHz, 0805 smd resistor over R12;
2. Added two 100 Ohm  to collectotrs Q11 and Q12 (had to cut PCB roads to them). Emitter-follower do not like HF signals and small collector resistor gives light feed back.
3. After this reception has become more sensitive - I had to change my switching Power Supply to transformer analog one.
Best 73s to all George 

Re: uBitx Unfiltered

MadRadioModder
 

Sort of… I added a second receiver to my uBITx on VFO B.  It’s great for DXing. I, like you, do like the uBITx receiver.  You can even do some clever things with the audio (stereo channels one for each receiver) and even diversity with a second antenna input.

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Michael Babineau
Sent: Monday, September 3, 2018 9:26 AM
To: BITX20@groups.io
Subject: Re: [BITX20] uBitx Unfiltered

 

W.r.t the current discussions on ubitx transmitter woes ... the route forward that I chose was to order LPFs plus the relay board from QRP Labs. My thoughts were to use a 2nd Arduino Nano clone configured as an I2C slave to allow the Raduino to communicate with the LPF board over I2C. This would require some very minor code changes to send band change info to the new filter board.

 

This solution would give me clean CW TX from 160m through 10m but does nothing to address the spur problem on the higher bands when using SSB nor the more recent concerns about other IMD. 

 

This got me thinking that for another $20 I could just order the QRP Labs 5W PA kit and build a separate 160m to 10m CW TX with raised cosine wave shaping.

I do mostly CW anyway so giving up SSB wouldn't be a big loss for me.

 

So now I am considering the option of just using my ubitx as an HF receiver. The RX works quite well so if I just forget the TX, at a little over $100 for my v3 ubitx is was still a great deal IMHO. 

 

Has anyone else thought  of just designing  a separate  TX board  for use with the V3/V4 ubitx? I know that this sounds like giving up ... but in many ways this could be a simpler solution than attempting major surgery on the existing ubitx.

 

I have yet to package my ubitx in a permanent enclosure so for now I am going to put it aside and wait a month or two to see if there is a better option.

 

Cheers 

Michael VE3WMB 

 

 

 

 


Virus-free. www.avg.com

--

…_. _._

Re: CW OPERATION

Gordon Gibby
 

Ron

Where do I go to look for your group software? 

Now that I got my harmonic somewhat more under control, I’m going to want to pick out good software modify it if needed and have it ready for our local group.  

Thanks!

Gordon




On Sep 3, 2018, at 09:54, W2CTX <w2ctx@...> wrote:

Well maybe no one is paying attention but our software has CAT control, S-meter display, Pass Band Tuning, and

we build "memory manager" into the software so, you do not need a pc to change things. We also have a

companion Remote Control Program that allows control of the uBITX from a PC.  We also include keyboard control and

keyboard CW sending.


We are not in competition with Ian, we are just a few guys trying to make the best uBITX possible.  We make our

efforts available if people want to try them.


rOn


On September 3, 2018 at 9:00 AM MadRadioModder <madradiomodder@...> wrote:

Jim… I think you may have missed many of the positive features of the Nextion display… and in particular BECAUSE of that editor, anyone can move those, how did you call it… clutter?, things around… add and subtract easily to fit their needs without understanding and writing hundreds of lines of code like others implementations?.  That is a real BIG plus.  And… if the popularity of the Nextion keeps up, it will be no time before, feeling left out of the game, the “competition” follows suit with their own clone-ish display.  Now Ian’s code isn’t perfect, but it has brought us a lot of positive things… decent CAT control, usable “S” meter circuitry, IF shift for attenuation… etc.  And the memory manager.  Yeah at some point it makes sense for some real programmers to do a rewrite…

 

Dumping on Ian isn’t a good sales tactic given his base…



Virus-free. www.avg.com

 

--

…_. _._

 

Re: CW OPERATION

Jim Sheldon
 

Gordon and all,  His software is on our group website in the "Files" section.

Jim, W0EB

http://www.w0eb.com     we do not use github

------ Original Message ------
From: "Gordon Gibby" <ggibby@...>
To: "BITX20@groups.io" <BITX20@groups.io>
Sent: 9/3/2018 10:23:01 AM
Subject: Re: [BITX20] CW OPERATION

Ron

Where do I go to look for your group software? 

Now that I got my harmonic somewhat more under control, I’m going to want to pick out good software modify it if needed and have it ready for our local group.  

Thanks!

Gordon




On Sep 3, 2018, at 09:54, W2CTX <w2ctx@...> wrote:

Well maybe no one is paying attention but our software has CAT control, S-meter display, Pass Band Tuning, and

we build "memory manager" into the software so, you do not need a pc to change things. We also have a

companion Remote Control Program that allows control of the uBITX from a PC.  We also include keyboard control and

keyboard CW sending.


We are not in competition with Ian, we are just a few guys trying to make the best uBITX possible.  We make our

efforts available if people want to try them.


rOn


On September 3, 2018 at 9:00 AM MadRadioModder <madradiomodder@...> wrote:

Jim… I think you may have missed many of the positive features of the Nextion display… and in particular BECAUSE of that editor, anyone can move those, how did you call it… clutter?, things around… add and subtract easily to fit their needs without understanding and writing hundreds of lines of code like others implementations?.  That is a real BIG plus.  And… if the popularity of the Nextion keeps up, it will be no time before, feeling left out of the game, the “competition” follows suit with their own clone-ish display.  Now Ian’s code isn’t perfect, but it has brought us a lot of positive things… decent CAT control, usable “S” meter circuitry, IF shift for attenuation… etc.  And the memory manager.  Yeah at some point it makes sense for some real programmers to do a rewrite…

 

Dumping on Ian isn’t a good sales tactic given his base…



Virus-free. www.avg.com

 

--

…_. _._

 

Re: raduino 1.27 upgrade

giuseppe.cavarretta@...
 

Hello Allard,
I am a CW-only ham, so your 1.27.7 sketch made me love the BITX40.
Today I tried to upload the 1.28 upgrade but, surprisingly, it does not sense the key and transmit CW any more.
Moreover, the command-driven menus are not working as before.
I came back to the 1.27.7 version and now all is working as it should.
Did I miss something?
Thank you so much, best 72
Joe, IZ0WIT

Re: CW OPERATION

Vince Vielhaber
 

Gordon. we have people with their extra that can't figure out how to connect the key to their radio (not just bitx radios, commercial too). How do you figure they're able to detect their band edges on USB and LSB? Yeah, it was on the test, but so many people cram for a test and forget everything the second they finish taking it.

Vince - K8ZW.

On 09/03/2018 09:07 AM, Gordon Gibby wrote:
9h1avlaw​


of course you risk outof band transmissions if you aren't at least able
to recognize which WAY your sideband is going, and how close to the band
edge you are.....exactly the same is true of upper side band and lower
sideband voice opeeration.


We expect people with the General class or higher license class to
understand those sideband type pesky issues...in fact, it is a question
or two in the exam packet! and if you were to use FM...or AM....then
you have sidebands on BOTH sides.....so if you're going to be a RADIO
amateur you need to understand just a bit about MODULATION.....


Cheers, my friend!


gordon


------------------------------------------------------------------------
*From:* BITX20@groups.io <BITX20@groups.io> on behalf of Lawrence Galea
<9h1avlaw@...>
*Sent:* Monday, September 3, 2018 8:57 AM
*To:* BITX20@groups.io
*Subject:* Re: [BITX20] CW OPERATION

If you are near the band edge you risk out of band transmissions

On Mon, Sep 3, 2018 at 4:35 AM Gordon Gibby <ggibby@...
<mailto:ggibby@...>> wrote:

You can do it the other way around, with the transmitter upset, but
then you have to be absolutely certain that the user knows that
their transmissions are offset from the dial number.

That’s not terrible, that’s exactly what happens when you’re doing
upper or lower sideband, and certainly when you’re doing pseudo CW
by injecting an pure audio sinewave signal into a single side band
system. FLDIGI will do that, and you can even rig it so your
computer shows your correct transmitting frequency


On Sep 2, 2018, at 22:31, Jim Tibbits <ab7vf1@...
<mailto:ab7vf1@...>> wrote:

Gotta offset, can't hear em on the carrier

On Sun, Sep 2, 2018 at 7:01 PM W2CTX <w2ctx@...
<mailto:w2ctx@...>> wrote:

__

Found this video explaining CW Zero-beating. So based on this
explanation the following is illustrated

for 7.040.000: Dial displays 07.040.000, you transmit on
07.040.000, and the receive is offset by the

sidetone value.


Of course this is based on the video being correct.


https://www.youtube.com/watch?v=CrC7JmNw1eY
<https://urldefense.proofpoint.com/v2/url?u=https-3A__www.youtube.com_watch-3Fv-3DCrC7JmNw1eY&d=DwMFaQ&c=pZJPUDQ3SB9JplYbifm4nt2lEVG5pWx2KikqINpWlZM&r=3ELgZgmTnPzGsfvQxkd1S_2NGLYM8sHTxVCQKFxhVXQ&m=wutQLbqUypKEwTZtPoqsR2c1uYOB2W1T82eBdqp_rW4&s=xkoCsoSDg_NeY_8HEYP-eD9p6qVd-te_uodlU96Tfm0&e=>


rOb

Re: CW OPERATION

 

There is also the outstanding, yet related, issue with switching sidebands on CW (i.e. CWU to CWL or vice versa) with KD8CEC's code which I had 
previously documented. 

Try this on any commercial rig ....

Properly tune in a CW station and then switch to CWR or whatever the "other" CW sideband is called on your
rig ... you can still hear the station. That is the whole point. Switching back and forth doesn't alter your TX frequency it only changes the BFO/offset
so that you are listening on the other side of true Zero-beat (i.e. the other side of his carrier frequency).  This is a "trick" used by CW operators to avoid QRM as often
you can manage to avoid a loud station QRMing your QSO by just listening to your intended station on the opposite sideband. You should always be able to switch
back and forth without touching the tuning knob, assuming that you have the station tuned in properly. 

Currently when you switch sidebands on CW on the KD8CEC software both your TX and RX frequencies change so not only can you not hear the other
station you were working, he can't hear you anymore either !  

I would be nice if it was possible to submit bug requests again the KD8CEC software within GITHUB itself. GITHUB supports this but it seems that this
option is somehow not enabled for https://github.com/phdlee/ubitx

There seems to be no "official" channels for reporting real bugs against this software so getting things fixed is a bit "hit or miss". 

Not to be totally negative, Ian has done some great stuff and he has responded to many of my suggestions and implemented features and fixes
that I suggested. The problem is that it seems that this list has way too much traffic for any one person to stay on top of everything discussed. 

Cheers

Michael VE3WMB 

Re: Arduino/Clock question/resolution

Howard Fidel
 

I solved the root cause, an open wire. But, now the Arduino does strange things, it locks up, sometimes I get very distorted CW xmit waveforms. The mystery continues.

On 9/2/2018 3:10 PM, Howard Fidel wrote:

I replaced the Arduino Nano and the SI clock chip and got the uBitx running. I then noticed a short on 2 data lines to the relays. I cleared the short, but after that the i2c bus always is sending data to the SI chip, and I usually get no clocks out, although sometimes I get one or two but not three. I don't think the i2c bus should have data on it unless something changes, ie the band or tuning after initialization. My question is what could keep it in this mode continually outputting data? I don't understand the code well enough to figure this out. I see two locations on ubitx_si5351 that cause data to be sent, but I don't follow what initiates them. The tuning works, updating the display, which means the Arduino is running the main loop. I fear the Ardunio has again gone south, but I don't want to pull it out again unless i am sure.

Thanks,

Howard


Re: UBITX TX level diagramme

ajparent1/KB1GMX
 

MRM,

The not so funny part Is I've been saying that for over two years and especially the last two months.

The whole idea of minimally filter 3-30 mhz radio is wishful thinking.  When I first said that
it was "you need to think outside the old box", when I mentioned it will not behave well I was told 
"you don't know what your talking about".  So I shut up for a while and waited for the stuff to
hit the fan.  

I for one would like the concept to work save for over 50 years of radio engineering... it never does.


Allison

Re: CW OPERATION

Gordon Gibby
 

That’s funny! Best little joke today!! Even a novice in my day knew that kind of stuff.

Oh how times change !!

On Sep 3, 2018, at 12:20, Vince Vielhaber <vev@...> wrote:

Gordon. we have people with their extra that can't figure out how to connect the key to their radio (not just bitx radios, commercial too). How do you figure they're able to detect their band edges on USB and LSB? Yeah, it was on the test, but so many people cram for a test and forget everything the second they finish taking it.

Vince - K8ZW.



On 09/03/2018 09:07 AM, Gordon Gibby wrote:
9h1avlaw​


of course you risk outof band transmissions if you aren't at least able
to recognize which WAY your sideband is going, and how close to the band
edge you are.....exactly the same is true of upper side band and lower
sideband voice opeeration.


We expect people with the General class or higher license class to
understand those sideband type pesky issues...in fact, it is a question
or two in the exam packet! and if you were to use FM...or AM....then
you have sidebands on BOTH sides.....so if you're going to be a RADIO
amateur you need to understand just a bit about MODULATION.....


Cheers, my friend!


gordon


------------------------------------------------------------------------
*From:* BITX20@groups.io <BITX20@groups.io> on behalf of Lawrence Galea
<9h1avlaw@...>
*Sent:* Monday, September 3, 2018 8:57 AM
*To:* BITX20@groups.io
*Subject:* Re: [BITX20] CW OPERATION

If you are near the band edge you risk out of band transmissions

On Mon, Sep 3, 2018 at 4:35 AM Gordon Gibby <ggibby@...
<mailto:ggibby@...>> wrote:

You can do it the other way around, with the transmitter upset, but
then you have to be absolutely certain that the user knows that
their transmissions are offset from the dial number.

That’s not terrible, that’s exactly what happens when you’re doing
upper or lower sideband, and certainly when you’re doing pseudo CW
by injecting an pure audio sinewave signal into a single side band
system. FLDIGI will do that, and you can even rig it so your
computer shows your correct transmitting frequency


On Sep 2, 2018, at 22:31, Jim Tibbits <ab7vf1@...
<mailto:ab7vf1@...>> wrote:

Gotta offset, can't hear em on the carrier

On Sun, Sep 2, 2018 at 7:01 PM W2CTX <w2ctx@...
<mailto:w2ctx@...>> wrote:

__

Found this video explaining CW Zero-beating. So based on this
explanation the following is illustrated

for 7.040.000: Dial displays 07.040.000, you transmit on
07.040.000, and the receive is offset by the

sidetone value.


Of course this is based on the video being correct.


https://urldefense.proofpoint.com/v2/url?u=https-3A__www.youtube.com_watch-3Fv-3DCrC7JmNw1eY&d=DwIDaQ&c=pZJPUDQ3SB9JplYbifm4nt2lEVG5pWx2KikqINpWlZM&r=3ELgZgmTnPzGsfvQxkd1S_2NGLYM8sHTxVCQKFxhVXQ&m=npaSmT3y0oYYiz2iEQpA2UUgFinOaMT9ySVWLD1Bzcg&s=gUvkgOCxbe9ab1cOT5cHbrv3gHMhpaU4wXb9nb88PfQ&e=
<https://urldefense.proofpoint.com/v2/url?u=https-3A__www.youtube.com_watch-3Fv-3DCrC7JmNw1eY&d=DwMFaQ&c=pZJPUDQ3SB9JplYbifm4nt2lEVG5pWx2KikqINpWlZM&r=3ELgZgmTnPzGsfvQxkd1S_2NGLYM8sHTxVCQKFxhVXQ&m=wutQLbqUypKEwTZtPoqsR2c1uYOB2W1T82eBdqp_rW4&s=xkoCsoSDg_NeY_8HEYP-eD9p6qVd-te_uodlU96Tfm0&e=>


rOb
--
Michigan VHF Corp. https://urldefense.proofpoint.com/v2/url?u=http-3A__www.nobucks.net_&d=DwIDaQ&c=pZJPUDQ3SB9JplYbifm4nt2lEVG5pWx2KikqINpWlZM&r=3ELgZgmTnPzGsfvQxkd1S_2NGLYM8sHTxVCQKFxhVXQ&m=npaSmT3y0oYYiz2iEQpA2UUgFinOaMT9ySVWLD1Bzcg&s=e7uLz9T_S9uLQyK5sB-vg85vdbq6q_zg6xvyBonFa-g&e= https://urldefense.proofpoint.com/v2/url?u=http-3A__www.CDupe.com_&d=DwIDaQ&c=pZJPUDQ3SB9JplYbifm4nt2lEVG5pWx2KikqINpWlZM&r=3ELgZgmTnPzGsfvQxkd1S_2NGLYM8sHTxVCQKFxhVXQ&m=npaSmT3y0oYYiz2iEQpA2UUgFinOaMT9ySVWLD1Bzcg&s=R4EzkukzEh7g2tPUZqEgs1MeDkg3U-1QuUCHSKgejWo&e=
https://urldefense.proofpoint.com/v2/url?u=http-3A__www.metalworkingfun.com&d=DwIDaQ&c=pZJPUDQ3SB9JplYbifm4nt2lEVG5pWx2KikqINpWlZM&r=3ELgZgmTnPzGsfvQxkd1S_2NGLYM8sHTxVCQKFxhVXQ&m=npaSmT3y0oYYiz2iEQpA2UUgFinOaMT9ySVWLD1Bzcg&s=1rV5mzIl9OLg4h9GTkqW7Mu9CQ68iecy4N1B182WAsM&e=


Re: UBITX TX level diagramme

ajparent1/KB1GMX
 

Lawrence G.,

I tried a few things along that path.  made matters worse and that was also tried with
external level 7 mixer and level 17 external mixers.   It was then a rock fell on me
and I realized the output of the 45mhz amp with the TX producing power was filthy.
Add a filter module it got better but by then I had so many outboard modules
its was almost a breadboard radio.  Everything is talking to everything by sneak
paths.  

Allison
We need only one magik part.

Re: UBITX TX level diagramme

ajparent1/KB1GMX
 

Henning,

There are errors in the diagram and the levels are really different than shown.

Looked at your diagram and its assumptions are wrong.  If the final mixer can accept -1dbm without
producing spurs then why start with -16dbm at the very first (balanced modulator)?

The input to the balanced modulator would be around -10dbm(audio) an that bumps up the levels 6db.
The problem with the pad at the output is that and the filter (about 8db total) reduce the carrier to signal
ratio by that amount (not allowing for bad layout causing blow by).  Excess gain makes it worse.

Having input to the final mixer  of more than -10dbm causes great amounts of distortion and spurs.
So at that point you are showing about 9db of excess gain.  Also the assumption is the mixers have
enough drive.  When I tested the 5351 was set to 1,1,1 or 4ma (factory code) and at 3,3,3 or 8ma I
did get the stated 13dbm but exceeded to the total current for three outputs if I understand the spec. 
That is only part of that story, for the moment.

So we are both under driving one and over driving mixers and hoping for a good result.  
The output of the last mixer should be around -17dbm (+-2db) for a 7dbm input, about
7db loss and a -10 dbm input.

the two TIA amps the 12mhz nearly hits the 20db mark (actual on 2 were 19) and at
45mhz not even close maybe 14db mine measured 13db.  Good thing too or the
over drive would be worse.

I The filter is before Q90! that means Q90 is part of the power amp chain.  Than means
there is a gain block before the pre-driver and driver missing in the drawing.

Also the design gain of the amp is 3 stages (Q90 through q97) of 16++ db per stage and
1 stage of  about 13db my match says that is 61db and most seem  to do that at 3.5 and
maybe 7mhz.  After that the gain falls by easily 11db to 10M.  So the diagram does not
match the actual.

FYI the second bidirectional amp is not shown (post 45mhz fitler and before last mixer)

The line up should be 45mhz fitler, 45mhz bidirectional amp, mixer, 33mhz low pass fitler, then Q90 tx preamp.

Allison
Being PDF I cannot edit the drawing it does have errors.

Re: TIA amplifiers

ajparent1/KB1GMX
 

An alternate improvement is replace Q10/11/12 with mmbt2369 or BFr106
as the 3904 is not impressive at 45mhz.

Allison

80 Meters Harmonics Fix Proposal

Howard Fidel
 

I previously mentioned that I would try to reduce the harmonics by changing the output to 25 ohms and adding a step up transformer to go back to 50 ohms for the output. This would allow tripling the values of the capacitors at the input and output of the filters, reducing the effect of the stray relay and layout capacitance. I experimented some more with a simulator, and decided just to change the filter characteristics so I could stay with 50 ohms. I was able to come up with a filter that doubles the capacitance. The improvement is not as great, but at least on 80 meters, the harmonics don't exceed -45 dB in my tests. Not as much margin as I would like, but legal. I changed the 3 inductors to 1.6 uH by adding 2 turns on each. I added an extra 1000 PF cap in parallel with the input and output caps, bringing the total to 2000 pF, and I added a 620 pF cap in parallel with the one of the two paralleled 1000 pF caps in the middle two sections for a total of 2620 pF there. (750 pF would have been better, but I didn't have them). I attached the simulation for the design. 
If someone with good test equipment could validate what I have done, it would be great to get more data points. 
After validation of 80 I will try the 40 meter band. My test equipment is not good enough for the higher bands.(My analyzer only works to 30 MHz). 

Howard

PS my Arduino problems were probably a ground loop. They seem to have gone away by moving some cables.

Re: K5BCQ uBITX Relay Switched LPF/BPF board

 

Kees & Group:

 

Please Clarify: I thought I was told some time ago on this post that only passband filters would address the uBitix issues. If that earlier statement was correct, why are people working on solutions using lowpass filters???

 

David A Posthuma, WD8PUO

1 (616) 283-7703

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Kees T
Sent: Monday, September 03, 2018 10:23 AM
To: BITX20@groups.io
Subject: Re: [BITX20] K5BCQ uBITX Relay Switched LPF/BPF board

 

 W0PWE

Sep 2   

 

Kees - With 6 filters is the plan as follows?
LPF1 = 80M
LPF2 = 40M and 30M
LPF3 = 20M and 17M
LPF4 = 15M
LPF5 = 12M
LPF6 = 10M

Re: 80 Meters Harmonics Fix Proposal

Warren Allgyer
 

Howard

When I measured 80 meter harmonics the particularly troublesome ones were 5th at 18 MHz and 7th at 25 MHz. In both cases the attenuation of the stock uBitx at those frequencies was limited by the layout of the board and by the coupling of relays sharing both filter input and output in the same frame. In such cases the characteristics of the filters, both existing and any modifications are immaterial. The attenuation of the stock filter supplied is more than adequate. But the harmonics bypass the filter and go via I/O coupling straight to the output. Please measure the 5th and 7th harmonics on CW. I think you will find you have not done much to improve the stock situation.

WA8TOD

Re: K5BCQ uBITX Relay Switched LPF/BPF board

 

Kees:

 

Why manual band switching? Could not the code select the proper filter according to frequency the user selects on the uBitx? Could not the RF Switching be done using pin diodes or FET switching? I’m just trying to learn, thanks.

 

David A Posthuma, WD8PUO

1 (616) 283-7703

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Kees T
Sent: Monday, September 03, 2018 10:13 AM
To: BITX20@groups.io
Subject: Re: [BITX20] K5BCQ uBITX Relay Switched LPF/BPF board

 

Since most keep talking about the need for BPFs for certain bands, I "guess" the 80m-10m uBITX direction should be a board with 6 filter capability. How about a basic dual relay switched filter board (3-1/4" x 3-7/8") with up to 6 pluggable filters, all manually selected with a 6 position rotary switch --AND-- you can add a small mux board with 2N3904 relay drivers for the filters and a CD4028B mux to go from the 3 Raduino pins to the filters. Start with the existing 111,110,100,000 and add two others when you have the code modified.

73 Kees K5BCQ 

Re: K5BCQ uBITX Relay Switched LPF/BPF board

ajparent1/KB1GMX
 

On Mon, Sep 3, 2018 at 12:10 PM, David Posthuma wrote:

Why manual band switching? Could not the code select the proper filter according to frequency the user selects on the uBitx? Could not the RF Switching be done using pin diodes or FET switching? I’m just trying to learn, thanks.

 

David A Posthuma, WD8PUO

First there are two issues one being poor harmonic filtering and Kees is addressing that here.

The other is spurs from inadequate filtering above 17M,  That requires band pass filters before
the power amp.  The tail end low pass filter cannot fully try to address that.

I doubt the band pass filters he sells can stand 10W in that location.   Kees comment please?

Allison

Re: 80 Meters Harmonics Fix Proposal

Howard Fidel
 

Warren:
The fifth and the 7th are at -45dB now. You are missing my point. The design of the filter directly effects the level of the harmonics. Yes, the stray  capacitance creates a "sneak" path around the filter. However, the input and output capacitors of the filter act as a divider to that "sneak" signal. If you double the output capacitance, you 1/2 the sneak signals amplitude, reducing it 6 dB. If you create a model of each  of the filters in a simulator, and put 8 pF from input to output, you can clearly see the improvement in the attenuation of the filter for the higher output capacitance.
All the data I have seen shows that a 6 dB improvement would just make the uBitx legal.

Howard

On 9/3/2018 2:51 PM, Warren Allgyer wrote:
Howard

When I measured 80 meter harmonics the particularly troublesome ones were 5th at 18 MHz and 7th at 25 MHz. In both cases the attenuation of the stock uBitx at those frequencies was limited by the layout of the board and by the coupling of relays sharing both filter input and output in the same frame. In such cases the characteristics of the filters, both existing and any modifications are immaterial. The attenuation of the stock filter supplied is more than adequate. But the harmonics bypass the filter and go via I/O coupling straight to the output. Please measure the 5th and 7th harmonics on CW. I think you will find you have not done much to improve the stock situation.

WA8TOD


Re: 80 Meters Harmonics Fix Proposal

Gordon Gibby
 

Howard, I get your point. And a six DB improvement makes the device a much better transceiver per the regulations

With simple unshielded wiring to three external relays, in my tests I found the fifth harmonic of 80 meter CW was basically obliterated, but the seventh only went down by about six dB.  (I don’t have an explanation for the disparity ) I haven’t tried any shielded wiring to see if that would make any better — but it certainly might. 


In my case It might be simpler to add in a permanent low pass filter above 15 MHZ in my case.     Your idea of lowering the capacitance is interesting.  And it’s pretty simple also!   For many people that might be the easiest solution to the harmonic problem. 




On Sep 3, 2018, at 15:47, Howard Fidel <sonic1@...> wrote:

Warren:
The fifth and the 7th are at -45dB now. You are missing my point. The design of the filter directly effects the level of the harmonics. Yes, the stray  capacitance creates a "sneak" path around the filter. However, the input and output capacitors of the filter act as a divider to that "sneak" signal. If you double the output capacitance, you 1/2 the sneak signals amplitude, reducing it 6 dB. If you create a model of each  of the filters in a simulator, and put 8 pF from input to output, you can clearly see the improvement in the attenuation of the filter for the higher output capacitance.
All the data I have seen shows that a 6 dB improvement would just make the uBitx legal.

Howard

On 9/3/2018 2:51 PM, Warren Allgyer wrote:
Howard

When I measured 80 meter harmonics the particularly troublesome ones were 5th at 18 MHz and 7th at 25 MHz. In both cases the attenuation of the stock uBitx at those frequencies was limited by the layout of the board and by the coupling of relays sharing both filter input and output in the same frame. In such cases the characteristics of the filters, both existing and any modifications are immaterial. The attenuation of the stock filter supplied is more than adequate. But the harmonics bypass the filter and go via I/O coupling straight to the output. Please measure the 5th and 7th harmonics on CW. I think you will find you have not done much to improve the stock situation.

WA8TOD