Topics

Intermodulation Performance

ajparent1/kb1gmx
 

David,  the web page has a wiki...

Maybe the mods could harvest info and post there or borrow from mike at ubitx.net.

Allison

Warren Allgyer <allgyer@...>
 

Sarma

Thank you for the great suggestion. This design is not from me. It is the work of Kees K5BCQ. I agree...... a very nice job and I look forward to testing it.

Warren - WA8TOD

MVS Sarma
 

Warren,
 Thanks for nice job. We never get these vertical type relays. The filter caps may be  3  for each section,   so that the user  could reach closer value of capacvcitor by a combination.
regards
 sarma
 vu3zmv


On Wed, Aug 22, 2018 at 11:37 PM Warren Allgyer <allgyer@...> wrote:
Hi Kees

I would be honored to test and record data, publish if you wish, any filters you would be willing to send. I would of course return them after testing is complete. If you would like to proceed please contact me privately for shipping info. 

Thank you Kees. 

WA8TOD

 

Allison:

 

No, I have been around, just too busy to keep up with all the threads. I wish there was a “Status” page that could keep everybody posted on progress.

 

Thanks,

 

David A Posthuma, WD8PUO

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of ajparent1/KB1GMX
Sent: Wednesday, August 22, 2018 10:25 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Intermodulation Performance

 

David,

You must have missed the last three months.... and a pair of very long threads!  ;)

To clean that up yes, band pass filters are the option or some very fancy combination of
high pass and low pass which results in the same pass band as a band pass.

Generally the in band spurs happen to be extremely weak and as such not a worry
other than being annoying on receive.

Allison

ajparent1/kb1gmx
 

David,

You must have missed the last three months.... and a pair of very long threads!  ;)

To clean that up yes, band pass filters are the option or some very fancy combination of
high pass and low pass which results in the same pass band as a band pass.

Generally the in band spurs happen to be extremely weak and as such not a worry
other than being annoying on receive.

Allison

 

Allison:

 

So, then, are bandpass filters the only option? Are there in-band spurs?

 

David A Posthuma, WD8PUO

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of ajparent1/KB1GMX
Sent: Wednesday, August 22, 2018 5:46 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Intermodulation Performance

 

David,

 Will low-pass filters not correct the spurs generated as well as harmonics? Thanks for sharing your wisdom.


No.  Often the spurs are below the cutoff of a low pass frequency , they are low in frequency so they get to pass.
They are their to suppress harmonic and spurs that occur above the cutoff frequency.  Important but half the
job in some cases.

Good looking filter.

Allison

ajparent1/kb1gmx
 

Iz oos,

Its rare that distortion is heard on frequency.

Is the guy 3khz up or down from you that would like to not hear you and you sputter and splatter.
So with the good radio listen to your audio then flip its sideband and listen for stuff likely unintelligable
and then move up or down and listen.  

Did this onece on 6M (deserted part of the band) to prove a point tto someone that 
felt it was great ausio even though he had the knobs set to 11 on the scale of 10.
My commercial 6M rig if I run the audio up the image on the SA gets wide yet no one
on frequency hears much other than, its louder.  If I add over driving the power amp
its the same!  However at the extreme tested on the air one time The band width
at 15db down was 60khz and yet the guy maybe 10 miles away was sounds great
and he even knows my voice from club meetings.

Good audio reports are very misleading about all the stuff their receiver is filtering out
but the other poor guy trying to share the band is not enjoying it.

Allison

ajparent1/kb1gmx
 

David,

 Will low-pass filters not correct the spurs generated as well as harmonics? Thanks for sharing your wisdom.


No.  Often the spurs are below the cutoff of a low pass frequency , they are low in frequency so they get to pass.
They are their to suppress harmonic and spurs that occur above the cutoff frequency.  Important but half the
job in some cases.

Good looking filter.

Allison

 

Kees,

 

In no way am I questioning the strategies you and the team are working through. But can you educate me as to why uBitx doesn’t just use programming to simply select the appropriate band-specific low-pass filter such as presented by this 9-band $34 kit at https://www.ebay.com/itm/Lowpass-filters-for-HF-Amateur-Transceiver-LPF-9-bands-KIT-for-assembly-12V/172672764028?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2748.l2649? Will low-pass filters not correct the spurs generated as well as harmonics? Thanks for sharing your wisdom.

 

 

David A Posthuma, WD8PUO

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Kees T
Sent: Wednesday, August 22, 2018 3:01 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Intermodulation Performance

 

Allen and David,

Right now this is just a test to see what the results look like and "if there is a pony in the room". We may just provide the Gerber files, the LPF Relay boards, A complete LPF upgrade kit (not sure I can handle the potential demand after the AGC/Click activity), or just give it to someone else to run with ...?

73 Kees K5BCQ

Warren Allgyer <allgyer@...>
 

Iz

The primary problem caused by high IMD is splatter outside the bandpass of the sideband filter. This shows up on the opposite sideband and on the high (audio) frequency side of the desired sideband. We have all heard this when an overmodulated signal is parked 3 KHz away and we get "static crashes" in the 3 KHz that we are listening to. On a waterfall is shows up as a broadening of the base of the signal.

I don't think you will find the IMD products affecting the intelligibility of the audio even at the very high -12 dBc levels I measured. What did happen is the transmitted noise floor on the opposite sideband and outside the filter rose 20-30 dB over the the single tone level. If there is interest I can replicate that test and show what it looks like on the spectrum analyzer.

WA8TOD

 

I greatly appreciate your efforts and that of the rest of the team.

 

David A Posthuma, WD8PUO

1 (616) 283-7703

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Kees T
Sent: Wednesday, August 22, 2018 3:01 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Intermodulation Performance

 

Allen and David,

Right now this is just a test to see what the results look like and "if there is a pony in the room". We may just provide the Gerber files, the LPF Relay boards, A complete LPF upgrade kit (not sure I can handle the potential demand after the AGC/Click activity), or just give it to someone else to run with ...?

73 Kees K5BCQ

iz oos
 

Warren, you did quantitative tests that surprise me to a certain extent. Surely the uBitx is not an IC-7300. Even my SWL ears find the IC-7300 transmitted audio one of the best ever. But as I continously monitor my transmitted audio with an IQ SDR receiver I have not found the TX audio that terrible. Mine may sound tinny, the BFO is almost 1khz far from the passband but the opposite sideband seems to me quite well rejected. Does the audio sound distorted? Not really, reports were fine. I imagine that the IMD products may give more problems within the filter passband rather than outside. Maybe it would be worth to test the IMD with digital modes like PSK and see the reports by others.

Il 22/ago/2018 17:23, "Kees T" <windy10605@...> ha scritto:
>
> Hello Warren Allgyer,
>
> I want to thank you for all the effort you have put into the uBITX spur/harmonic problem definition and the excellent data presented. I realize your project is shelved ....but, would you be interested in trying out an 8 relay switched LPF board with 4 plug in LPFs using the parts off the uBITX board. You ran an experiment like that earlier with a perf. board. I have boards (75mm x 62mm) coming in soon and can supply the relays and misc parts (no charge).
>
> 73 Kees K5BCQ

Kees T
 

Allen and David,

Right now this is just a test to see what the results look like and "if there is a pony in the room". We may just provide the Gerber files, the LPF Relay boards, A complete LPF upgrade kit (not sure I can handle the potential demand after the AGC/Click activity), or just give it to someone else to run with ...?

73 Kees K5BCQ

Warren Allgyer <allgyer@...>
 

Hi Kees

I would be honored to test and record data, publish if you wish, any filters you would be willing to send. I would of course return them after testing is complete. If you would like to proceed please contact me privately for shipping info. 

Thank you Kees. 

WA8TOD

allen west
 

Mr. Kees, I am interested if you make this up as a consumer product like your AGC board.  Please let me know when you get the kit and pricing figures out.  Will you provide the ferrite cores?  I can do the winding.

Thanks, Al
KB4RA


On Aug 22, 2018, at 11:23 AM, Kees T <windy10605@...> wrote:

Hello Warren Allgyer,

I want to thank you for all the effort you have put into the uBITX spur/harmonic problem definition and the excellent data presented. I realize your project is shelved ....but, would you be interested in trying out an 8 relay switched LPF board with 4 plug in LPFs using the parts off the uBITX board. You ran an experiment like that earlier with a perf. board. I have boards (75mm x 62mm) coming in soon and can supply the relays and misc parts (no charge).

73 Kees K5BCQ
<PCB_LPFx4_.pdf>
<PCB_LPFx4_Individual_.pdf>

 

Kees K5BCQ:

 

You and your teammates appear to be making progress on a uBitx RF spur and harmonic solution. Two questions: 1) Do you hope to have a solution by any defined deadline; and 2, will this solution be sold to uBitx owners through HF Signals or through a third party?

 

David A Posthuma, WD8PUO

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Kees T
Sent: Wednesday, August 22, 2018 11:24 AM
To: BITX20@groups.io
Subject: Re: [BITX20] Intermodulation Performance

 

Hello Warren Allgyer,

I want to thank you for all the effort you have put into the uBITX spur/harmonic problem definition and the excellent data presented. I realize your project is shelved ....but, would you be interested in trying out an 8 relay switched LPF board with 4 plug in LPFs using the parts off the uBITX board. You ran an experiment like that earlier with a perf. board. I have boards (75mm x 62mm) coming in soon and can supply the relays and misc parts (no charge).

73 Kees K5BCQ

Kees T
 

Hello Warren Allgyer,

I want to thank you for all the effort you have put into the uBITX spur/harmonic problem definition and the excellent data presented. I realize your project is shelved ....but, would you be interested in trying out an 8 relay switched LPF board with 4 plug in LPFs using the parts off the uBITX board. You ran an experiment like that earlier with a perf. board. I have boards (75mm x 62mm) coming in soon and can supply the relays and misc parts (no charge).

73 Kees K5BCQ

jim
 



On Tuesday, August 21, 2018, 3:35:46 AM PDT, Warren Allgyer <allgyer@...> wrote:


I am finished. This is simply not worth the effort.


When it stops being fun, its time to quit
\
Jim

Gordon Gibby <ggibby@...>
 

Hi,Warren, I will always appreciate the data that you generated!

Nicer radios, are certainly nicer radios! Some people like Honda FIT , some prefer a high end BMW!

For the purposes of coaxing local club members into learning HF and some radio, some building techniques, & electronics, this is perfect!

For HF ALE monitoring, it even beats the heck out of my ICOM 718’s. For winning a contest? Nah!!

Thanks for all your input

Gordon

On Aug 21, 2018, at 06:35, Warren Allgyer <@allgyerw> wrote:

response

Warren Allgyer <allgyer@...>
 

I am finished. This is simply not worth the effort. The difference between this radio and my FT-817 is about $350. The difference between the uBitx and my HobbyPC RS-HFIQ is $100. Both are worth the increment in order to assure:

1) FCC/ITU compliant transmissions

2) Excellent IMD and in-band spurious response

3) Adequate audio output

4) AGC

5) ALC

Not to mention FM, 6m, 2m, 70 cm for the Yaesu.

I completely understand the attraction of making up your own box, modifying the code, and other customizations. But there is simply too much to be added to the basic uBitx as delivered in order to make it a compliant, user-friendly, neighbor-friendly rig. I maintain it is not possible to make compliant transmissions from this board without the knowledge and equipment to modify it for compliance and a properly equipped lab to set it up and monitor it.

My board is going on the shelf marked "Nice try....... not worth the effort", along with a complete set of filter relays, failed output filter attempts, octal to decimal decoders to drive the filters, 45 MHz SAW filters, and a stack of test data. It was fun. It is done.

WA8TOD