Topics

One question only...


Bill Cromwell
 

Hi Walt,

From what I have seen in these threads about spurs, harmonics, and (lack of) filtering the troublesome unintended 'signals' are just about at the legal limit and slightly over. Over is over. Unacceptable. The way I use my radio I think the trash can be sufficiently cleaned up for 'safe', responsible use. It would be much better if that cleanup took place inside the radio and by design. It is too late for that. Later I might do some of my own investigation and attempt to correct the deficiencies. Maybe just follow what somebody else comes up with. But please don't hold your breath. I have other irons in the fire:)

I haven't modded mine at all yet and none of the mods for 'more power' is on my agenda. I like some of the features available in the CEC software. And something *must* be done about that million decibel side tone. OMG. I cracked a shop window with that thing!

I have other gear and will be buying more. Hans Summers's QCX and some other toys from his shop are on my hit list. If uBitx hadn't shown up in my world I would already be using some of those. When I decided to buy the uBitx first it was not a rejection of the QCX:) Those are next.

73,

Bill KU8H

Michigan QRP Club

On 08/06/2018 09:45 AM, WaltR wrote:
Thanks Bill,

I, as many others enjoyed assembling the bitx40 and the ubitx, for my
purposes, dragging around a bag full of outboard filters and other
accessories will not work. Perhaps to some degree I am spoiled by having
access to high end gear, but I am aware that it’s not prudent to compare
a Harris to a ubitx. I wish not to besmirch Harris by putting the ubitx
in the same sentence.

my understanding is the bitx was designed and built as a kit for those
that wish to assemble, experiment, dabble in Arduino sketches etc, and
by the number that have been sold obviously has a large following.
There is a need for a simple solid rig that doesn’t require a lot of
fiddling about, and is reasonably priced and meets regulatory criteria.

There should be some warning or reminder that if you plan on doing any
modifying or hacking that you should ensure that you don’t produce any
transmitted products that may interfere with other services, especially
any that might fall in the spectrum allocated to government agencies and
services, as well as commercial, and international interests. You might
get away with it in the ham bands but you certainly won’t if you cause
superfluous transmissions in other spectrum allocations.

Buy filters, there are some great little devices available at QRP LABS.

Cheers and 73

WRS

IF THE PROCESS IS FLAWED, THE OUTCOME MOST SURELY WILL BE FLAWED
--
bark less - wag more


Scott McDonald
 

Hi Allison,
 
Do you have an opinion on whether the 5351 with bandpass filters like the QRP Labs set up is good enough for SWR and filter BW?
 
Thanks, Scott
 
 

-----Original Message-----
From: ajparent1/KB1GMX <kb1gmx@...>
To: BITX20 <BITX20@groups.io>
Sent: Mon, Aug 6, 2018 8:51 am
Subject: Re: [BITX20] One question only...

I used to use a signal generator (analog), frequency counter, and a diode load
so adding even a digital oscillator DDS or NCO was a giant step forward in
making basic measurements.

If a SA at ~1500$US is out of reach the lowly 9850 DDS and arduino plus a
RF power sensor (8307 or one of the many others) will allow many of the
same measurements at a fraction of the cost in exchange for time to plot
the points.

It is also possible to use the above to plot to a graphic display 
by taking the power sensor output to the analog input of the arduino
allowing graphic display of the results. 

The 5351 is good but the square wave output will mess you up for many
measurements due to the rich harmonic output.  Two common measurements
are SWR and filter bandwidth/cutoff are hard to do with harmonics present.

Allison


iz oos
 

To answer the original question, if it might be illegal, make it legal. My solution is using plug and play external low pass filters. And to avoid the issue of spurs pointed out by Allison I don't use SSB on 15 and 12m. For 10 meters I also added a high pass filter.


Il 06/ago/2018 16:42, "Scott McDonald via Groups.Io" <ka9p=aol.com@groups.io> ha scritto:
Hi Allison,
 
Do you have an opinion on whether the 5351 with bandpass filters like the QRP Labs set up is good enough for SWR and filter BW?
 
Thanks, Scott
 
 
-----Original Message-----
From: ajparent1/KB1GMX <kb1gmx@...>
To: BITX20 <BITX20@groups.io>
Sent: Mon, Aug 6, 2018 8:51 am
Subject: Re: [BITX20] One question only...

I used to use a signal generator (analog), frequency counter, and a diode load
so adding even a digital oscillator DDS or NCO was a giant step forward in
making basic measurements.

If a SA at ~1500$US is out of reach the lowly 9850 DDS and arduino plus a
RF power sensor (8307 or one of the many others) will allow many of the
same measurements at a fraction of the cost in exchange for time to plot
the points.

It is also possible to use the above to plot to a graphic display 
by taking the power sensor output to the analog input of the arduino
allowing graphic display of the results. 

The 5351 is good but the square wave output will mess you up for many
measurements due to the rich harmonic output.  Two common measurements
are SWR and filter bandwidth/cutoff are hard to do with harmonics present.

Allison



Skip Davis
 

Bill,
For the sidetone level I replaced R250 with a 10k trimmer to adjust it to a manageable level with headphones. Also check to see what your R253 value on mine it is marked 224 on a V3 board, if yours is the 1k (like the schematic) I would use a larger value trimmer for R250. I also have a V2 board and checked R253 and it is the 224 (220k) resistor too.

Skip Davis, NC9O

On Aug 6, 2018, at 10:29, Bill Cromwell <wrcromwell@...> wrote:

Hi Walt,

From what I have seen in these threads about spurs, harmonics, and (lack of) filtering the troublesome unintended 'signals' are just about at the legal limit and slightly over. Over is over. Unacceptable. The way I use my radio I think the trash can be sufficiently cleaned up for 'safe', responsible use. It would be much better if that cleanup took place inside the radio and by design. It is too late for that. Later I might do some of my own investigation and attempt to correct the deficiencies. Maybe just follow what somebody else comes up with. But please don't hold your breath. I have other irons in the fire:)

I haven't modded mine at all yet and none of the mods for 'more power' is on my agenda. I like some of the features available in the CEC software. And something *must* be done about that million decibel side tone. OMG. I cracked a shop window with that thing!

I have other gear and will be buying more. Hans Summers's QCX and some other toys from his shop are on my hit list. If uBitx hadn't shown up in my world I would already be using some of those. When I decided to buy the uBitx first it was not a rejection of the QCX:) Those are next.

73,

Bill KU8H

Michigan QRP Club


On 08/06/2018 09:45 AM, WaltR wrote:
Thanks Bill,

I, as many others enjoyed assembling the bitx40 and the ubitx, for my
purposes, dragging around a bag full of outboard filters and other
accessories will not work. Perhaps to some degree I am spoiled by having
access to high end gear, but I am aware that it’s not prudent to compare
a Harris to a ubitx. I wish not to besmirch Harris by putting the ubitx
in the same sentence.

my understanding is the bitx was designed and built as a kit for those
that wish to assemble, experiment, dabble in Arduino sketches etc, and
by the number that have been sold obviously has a large following.
There is a need for a simple solid rig that doesn’t require a lot of
fiddling about, and is reasonably priced and meets regulatory criteria.

There should be some warning or reminder that if you plan on doing any
modifying or hacking that you should ensure that you don’t produce any
transmitted products that may interfere with other services, especially
any that might fall in the spectrum allocated to government agencies and
services, as well as commercial, and international interests. You might
get away with it in the ham bands but you certainly won’t if you cause
superfluous transmissions in other spectrum allocations.

Buy filters, there are some great little devices available at QRP LABS.

Cheers and 73

WRS

IF THE PROCESS IS FLAWED, THE OUTCOME MOST SURELY WILL BE FLAWED
--
bark less - wag more



ajparent1/KB1GMX <kb1gmx@...>
 

Scott,

That may work.  But there will be a lot of switching and what if the filter
does not cover the desired frequency?  You can also use low pass filters 
but the filters have to be switches at the 1/2 to 2/3rds octave and 
again lots of switching and about 5 filters.

I never tried it as the DDS board are cheap and the output is sine wave.
It also makes for less hardware.

Checkout KD1JV site for a design based on that I know works. 

http://kd1jv.qrpradio.com/arduino/Arduino_tuner_aid.htm

That SWR system uses the Tayloe bridge for SWR and a led.  However the basic DDS output
is very useful as applied to other RF measuring gear.

Allison


Kees T
 

Allison,

Why not replace that "troublesome uBITX trace" with RG-174 or RG-188 coax ? Maybe even jumper the ground across the trace to reduce the effect of the "break" in the ground plane.  

i sometimes think I need a second uBITX for "bench experimentation" .....great fun for some of us. This CAN be fixed.

73 Kees K5BCQ


Alan de G1FXB
 

Hi Bill,
I feel like you. There have being whispers, now it's out.
I don't mind improving on a design by standing on the shoulders of others,  however I don't have an RF bench, or the expertise to use the instruments if I did.
(The EFHW thread proves that experts can disagree.....)


However don't throw the baby out with the bath water.


Put it in a shoe box and forget about it, it may take 3 months or more but ride it out for the time being.
Folks are now taking radical steps finding the route causes, and how fixes can be implemented to the existing units purchased.
Not every one is in a position to cut up their uBIX however it illustrates perhaps moving forward the benefits of the modular approach.
Especially if it's always going to be advertised as a starting point to something to modify / experiment.
Should we be lacking stage gain or filtering in a signal path we can hack / replace just that stage.
And not building mezzanine boards top & bottom to overcome the deficiencies.
It's going to push the kit costs up, we will accept that.
Economies of scale should still make it more affordable than if we were each doing the same thing on our own.
And we can all continue to do our own builds on a sound design. (Without a doubt this is probably the reason Farhan did not
find the problems at the modular? breadboard stages.)

For existing kits
The bath water is getting dirty, It was a $109 radio at the time,
for me the fix(s) need to be priced accordingly and integrated.
A box of band selected external filters wouldn't cut it for me.

Before the uBiX came along I looked for alternatives. It's a genuine question:-
Anyone used / any advice on the N2APB SDR Cube Transceiver? Assembly only kit @ $209
http://www.sdr-cube.com/products.html

Alan

On 06/08/2018 15:29, Bill Cromwell wrote:
Hi Walt,

From what I have seen in these threads about spurs, harmonics, and (lack of) filtering the troublesome unintended 'signals' are just about at the legal limit and slightly over. Over is over. Unacceptable. The way I use my radio I think the trash can be sufficiently cleaned up for 'safe', responsible use. It would be much better if that cleanup took place inside the radio and by design. It is too late for that. Later I might do some of my own investigation and attempt to correct the deficiencies. Maybe just follow what somebody else comes up with. But please don't hold your breath. I have other irons in the fire:)

I haven't modded mine at all yet and none of the mods for 'more power' is on my agenda. I like some of the features available in the CEC software. And something *must* be done about that million decibel side tone. OMG. I cracked a shop window with that thing!

I have other gear and will be buying more. Hans Summers's QCX and some other toys from his shop are on my hit list. If uBitx hadn't shown up in my world I would already be using some of those. When I decided to buy the uBitx first it was not a rejection of the QCX:) Those are next.

73,

Bill  KU8H

Michigan QRP Club


On 08/06/2018 09:45 AM, WaltR wrote:
Thanks Bill,

I, as many others enjoyed assembling the bitx40 and the ubitx, for my
purposes, dragging around a bag full of outboard filters and other
accessories will not work. Perhaps to some degree I am spoiled by having
access to high end gear, but I am aware that it’s not prudent to compare
a Harris to a ubitx. I wish not to besmirch Harris by putting the ubitx
in the same sentence.

my understanding is the bitx was designed and built as a kit for those
that wish to assemble, experiment, dabble in Arduino sketches etc, and
by the number that have been sold obviously has a large following.
There is a need for a simple solid rig that doesn’t require a lot of
fiddling about, and is reasonably priced and meets regulatory criteria.

There should be some warning or reminder that if you plan on doing any
modifying or hacking that you should ensure that you don’t produce any
transmitted products that may interfere with other services, especially
any that might fall in the spectrum allocated to government agencies and
services, as well as commercial, and international interests. You might
get away with it in the ham bands but you certainly won’t if you cause
superfluous transmissions in other spectrum allocations.

Buy filters, there are some great little devices available at QRP LABS.

Cheers and 73

WRS

IF THE PROCESS IS FLAWED, THE OUTCOME MOST SURELY WILL BE FLAWED




Scott McDonald
 

Thanks Allison.  I'm still working my way through Jack's book and C for Dummies, but I see the sketch is right there so it may be possible for even me to go that route soon. Appreciate it.
 
Scott ka9p
 
 

-----Original Message-----
From: ajparent1/KB1GMX <kb1gmx@...>
To: BITX20 <BITX20@groups.io>
Sent: Mon, Aug 6, 2018 10:28 am
Subject: Re: [BITX20] One question only...

Scott,

That may work.  But there will be a lot of switching and what if the filter
does not cover the desired frequency?  You can also use low pass filters 
but the filters have to be switches at the 1/2 to 2/3rds octave and 
again lots of switching and about 5 filters.

I never tried it as the DDS board are cheap and the output is sine wave.
It also makes for less hardware.

Checkout KD1JV site for a design based on that I know works. 

http://kd1jv.qrpradio.com/arduino/Arduino_tuner_aid.htm

That SWR system uses the Tayloe bridge for SWR and a led.  However the basic DDS output
is very useful as applied to other RF measuring gear.

Allison


ajparent1/KB1GMX <kb1gmx@...>
 

Kees,

Did you see the last posting about the filters and the lack of effectiveness?
A few jumpers will not fix that.  Even the filters raw (no relay) are pretty poor.

Imagine a a good filter with a 2pf cap from input to output.  Or better take
one of yours and add that and sweep it.  It degrades the filter significantly.

The telling sweep was in RX mode from the TX (tracking generator) in to t
he relays and the output to the antenna port to the SA.  Its the "blow though"
no relay energized and in RX mode.  That is a serious lack of isolation.

Allison



ajparent1/KB1GMX <kb1gmx@...>
 

Alan,

I believe your approach is sane.

The back half TX and filters can be improved.  The easy way is a whole mezzanine
board with cleaned up power switching, band pass filters amp and output filters
can be done. 

Its worth doing as it also module for the builders/makers the difficult part
of a radio the power amplification and filtering and makes it if done well
a component not unlike Arduino and its shields.

Then do a tweak on the font half to fix a few things and we have three boards 
that plug and play or can be modded to suit or used as components to other
radios.  Its filtering the bathwater, saving the baby.

Allison


Kees T
 

Allison,

Yes, I see that another thread (Harmonic performance - SSB vs CW) is also discussing the same subject and the plots are "troublesome". No offense, but I hope those plots were taken "correctly" ......50 ohm impedance matching and terminations, proper grounding, etc. Looks like some work to be done. Might be interesting to understand how the original testing was done.

Yes, any filter with x pF connected from input to output screws up the filter performance. I have seen that many times in the testing I have done with my old Marconi SA/TG.  

This will be interesting and fun to resolve.

73 Kees K5BCQ


m5fra2@...
 

That’s what I was thinking.

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of ajparent1/KB1GMX
Sent: 06 August 2018 17:01
To: BITX20@groups.io
Subject: Re: [BITX20] One question only...

 

Alan,

I believe your approach is sane.

The back half TX and filters can be improved.  The easy way is a whole mezzanine
board with cleaned up power switching, band pass filters amp and output filters
can be done. 

Its worth doing as it also make for the builders/makes the difficult part of a radio
the power amplification and filtering and makes it if done well a component not
unlike arduino and its shields.

Then do a tweak on the font half to fix a few things and we have three boards
that plug and play or can be modded to suit.  Its filtering the bathwater, saving
the baby.

Allison


Arvo W0VRA
 

So could I, for example, use Ian's software to do a WSPR transmission on a given band, and then use the RSP1A and SDRplay's spectrum analyzer software to get a good look at the frequency content of the transmission, and then I'd know for my installation, what the actual spurious emissions would be?

https://www.sdrplay.com/community/viewforum.php?f=12


ajparent1/KB1GMX <kb1gmx@...>
 

Kees,

I've done this for commercial work so accepted techniques and methods applied.
I have a bin full of SMA attenuators and all.  

Signal introduced at pin12 of KT1 and ground next to it via a sma terminated piece
of RG316 duobraid and the output at the normal antenna port with a SMA connector.
Two pads at each end and normalization check for cal.  Problably should have put
in the directional coupler in to see what the S11 looked like for all cases but by then
I was sufficiently shocked to say forget it.

The one picture was with all the relays not energized.  So we have the TR relay
open and the default 30mhz filter in place as its on the NC contact set.
If the relays and layout were decent that should have the max attenuation possible
which in this case is noteably poor.  The rest of the images is what the TX filters
actually do with K3 Energized and the various filters selected.   Warren got a
poorer numbers but, adding the relay shield does help but not anywhere near
enough. 

Also the board segment was literally isolated from the rest.  I even applied a layer
of tape on each relay to give it a grounded shell (about 3db improvement midband).
Let say this I gave it every chance to look good.  It didn't.

I have a low pass filter board from a Tentec Century 21.  Its only a 5 element filter
(ca1975ish) but it performs as expected.  I included C21b plot for 3.5Mhz.

It was an issue when trying to flatten the amps gain and at about 60db (q90 to output)
it would sing like a bird at about 19-23mhz at full power.   Cut the boards up and
the amp was much more well behaved.  Seems the relay despite switching the RX
line to ground were a potent feedback path.  The only reason all of them do not
oscillate is at the mid to high end the gain is well down (8 to 11db). 

Its a fundamental board layout issue that goes beyond a few bits of coax or better relay.
There are not enough vias and stitched pours to establish a good current return path.

I have a VHF differential probe for EMI/RFI work and the board between any two
points ground to ground is quite live.  The current paths are poorly controlled
and not localized.

Image of the sliced board included.


Henning Weddig
 

All,

when I first looked on the schemtaic of the µBITX I felt a bit sceptical about the way how the low pass filters are switched. Only one relay for input and output of the lpf? What about the crosstalk within the relay?

So my scepticism comes true.

Personally I always would use two relays one of the input and one for the output, even short circuiting the non switched filter. And remember: every relay contact has a few pF of capacitance. This will add to the existing filter cap.

The remedy would be an extra lpf board.

And in addition please also use bpf´s in the transmit and receive path in order not to overdrive the first stages / mixer.

Recently i read an interesting blog from an austrian ham: he destroyed xtal-filters when his high performance (high IP3) receiver was connected to a high performing antenna! Out of ham band stations were overdriving the stages--- please remind that xtal filters do not want "high power signals" in the range >0 dBm even at stop band!!!

Henning Weddig
DK5LV

Am 06.08.2018 um 18:26 schrieb Kees T:

Allison,

Yes, I see that another thread (Harmonic performance - SSB vs CW) is also discussing the same subject and the plots are "troublesome". No offense, but I hope those plots were taken "correctly" ......50 ohm impedance matching and terminations, proper grounding, etc. Looks like some work to be done. Might be interesting to understand how the original testing was done.

Yes, any filter with x pF connected from input to output screws up the filter performance. I have seen that many times in the testing I have done with my old Marconi SA/TG.  

This will be interesting and fun to resolve.

73 Kees K5BCQ


Kees T
 

I just looked at the uBITX schematic for 2017 (I believe it to be level V3) and looked how the band switching of 4 LPFs is done with 3 Relays KT1 - KT3. I assume V4 is wired the same way ?

The 3 relay control signals are TXA (KT1), TXB (KT2), and TXC (KT3) which come from the Raduino board. 

The 4 stages of TXA/TXB/TXC are (0 indicates relay not "picked", 1 indicates relay "picked") :
0,0,0 which selects the High Band LPF and uses 3 series relay contacts,
1,0,0  which selects the Hi Midband LPF and uses 5 series relay contacts.
1,1,0  which selects the Lo Midband LPF and uses 7 series relay contacts
1,1,1 which selects the Low Band LPF and uses 7 series relay contacts.

That's a lot of series (resistive) relay contacts and associated (capacitive) wiring. Adding one more relay,  and associated driver, could cut that down to a max of 2 series relay contacts for each band and "bus" type LPF wiring (less overall wiring). 

73 Kees K5BCQ


ajparent1/KB1GMX <kb1gmx@...>
 

Kees,
V4 is identical.  I looked.

Initially I looked at it and thought it clever.  Then it started nagging at me.
The contact capacitance or isolation is worrisome. Did a maybe the relay
has majik and it works.  Testing was, Oh, my!

As to your conclusion. Resistance is very small save for dry and hopefully
bifurcated contacts and the right material or it will age badly and maybe
become open(intermittent).   Long term issue.

More relays and better layout, Exactly.   

I'd also opt for better placement of the TR relay and paths.

No need for three control lines for 4 states as well.   I'm sure many would
want to have a spare IO  pin.  I did!


Allison


Timothy Fidler
 

one 74LS42 with bcd firing from the three output ports assuming they are TTL compatible  and  say 5 BS250s P channel (or four given the number of  relays now available)  say 80 40 20 and 10 mtr  BPF drivers) small signal Mosfets for switch on zero, (or a ULN 2003 (30c US at Futurlec.com in one off qty)..

Say total cost $1.50 could have put a stake thorough this demon...KISS ?? of course it is board space and cost that drives these decisions.

Alternative for physical relays for switching RF up to say 6W level in 50 z impedance circuits...

 a possibly foolish thought for likes of Kees and Ashar F  for any weakware rework concept.. if you fire the gate of a 2N7000 N mosfet  and drive it hard on from an isolated 10V dc supply* with a limiting resistor and a decent say 1mH mini inductor in both the  supply and return legs of the 5V psu - will the thing pass RF as if it were a small signal relay contact ?  RDS fully on for above part approx 1.2 ohms.

* homemade with a Hartley osc design to reduce the snap and crackle.


WaltR <waltrseiler@...>
 

Hello Bill,

Its very unfortunate that a well intended kit that was assembled with questionable quality parts, circuit and several other anomalies beyond my comprehension, is in its present quandary. The principals it appears, had good intentions and are to be commended for that. However, they have no authority in North America. In fact the Border agencies of both our countries are probably raising their eyebrows over the entire fiasco,  If not they soon will be. As I said earlier in my position As XO on board ship I can’t afford to run afoul of the authorities so my bitx 40 and ubitx have been destroyed. Sad really, I will be looking at the kits from QRP LABS. Or maybe I should purchase a good used FT817.
As an aside I had SIGINT techs look at the harmonic signature on the Harris, Wolfsburg and Bendix King gear and found them to exceed requirements by 30%, but of course again I’m comparing caviar to peanuts. My wife chastises me for my attitude ergo I’m at sea for 6 months of the year. I’m trying to do better hi hi. It’s no wonder I’m not allowed in the house before dark.

The sheer number of builders, the responses in this group, would suggest that there is a strong need for a simple affordable all band QRP rig, that is a fact, It will be interesting to see what happens in the next while.

In the research I have done there are some kits available from China, Russia and also Malaysia , they may be more in cost but perhaps ???


On a final observation you can buy all kinds of brands of test gear but there are only certain brands that are deemed to be certification instruments when operated by a certified knowledgeable technician, just because you go out and buy a Rigol
doesnt mean that now you are instantly an industry expert.

Early day tomorrow, anchors aweigh at 0400

cheers and 73
WRS


Timothy Fidler
 

Belay all that .. Japanese LPF cct sent to the VK who is designing a replacement board.  It gets 5 bands out of three signals ie 00 is also interpreted as a command. as usual old Timmo Fidler went off half cocked but at least the archives kicked in.