Keyboard Shortcuts
Likes
- BITX20
- Messages
Search
Re: Harmonic performance - SSB vs CW
Warren Allgyer
Understood Allison. I do not expect any design that routes input and output through the same relay will be satisfactory due to capacitive coupling in the relay and necessary proximity of IO to get to the relay. I think the only viable switching would be separate relays (or PIN diodes) for input and output and separated physically by the filter itself.?
I actually plan to migrate the other three filters over to this over to this board and use it without switching; manually patching the required filter. WA8TOD? |
Re: Need Help
Assuming your evaluation of the wireing is sound the problem is either bad encoder, testable with ohmmeter
disconnected from raduino.? Or raduino issue.? Two possible are reload the software, if it starts working great.? Or it doesn't, bad input pin. I'd go with 4.3 as it has a few improvements.? Your call. Allison |
Re: Harmonic performance - SSB vs CW
Warren,
Good, I didn't have time to try that.? Though a lesser filter from a different radio convincedme it was relays and layout. However while it confirms bad layout it didn't test the relay contact part of the layout issue.? We need that to confirm if the open contact capacitance (isolation) will corrupt the filter performance. The give away is the fact that the filter parts and characteristics are good but blow by is a significant part of the problem. Allison |
Re: Need Help
Good afternoon Allison, ? I still need help! ? I¡¯m still having experiencing difficulties getting up and running. I rechecked all the wiring, replaced the 8 pin connectors and checked for cold solder joints. I see that the POW and the L led on the nano board are illuminated red.? ? Any thoughts on what might be happening, does the sketch need to be reloaded what is the sketch that is being used with the uBITEX V4.3? ? Best regards, Bert VE3TYS |
Re: microphone
¿ªÔÆÌåÓýFolks, the mic amp can not work! WHY?? Please have a look on the shcematic: the "high impedance output"
of the mic amp (let?s assume R65 is the output impecance) drives
the? double diode D5. If this diode has a negilibliable dynamic on
resistance? each of the two diodes in D5 will alternatively? route
(each half cycle of the BFO signal) the AF signal to the 4 dB 50
ohm attenuator (R114 to R116). This means that the mic amp "sees"
a load of 50 ohms!?? Corect? Henning Weddig DK5LV Am 06.08.2018 um 16:16 schrieb Dennis
Yancey:
Try this link.? |
Re: Harmonic performance - SSB vs CW
Gordon Gibby
¿ªÔÆÌåÓý?great news warren --- now we need a? way to capitalize on what has been learned and re - do the signal paths.....
Gordon
From: [email protected] <[email protected]> on behalf of Warren Allgyer <allgyer@...>
Sent: Monday, August 6, 2018 2:39 PM To: [email protected] Subject: Re: [BITX20] Harmonic performance - SSB vs CW ?
I removed the 80 meter toroids and assembled them, along with the requisite SMD 1000 pF caps on the underside, in line of perf board.? I cut the RF trace from T11 to the relays and routed it out to the new filter via teflon coax. The 3rd harmonic of the 80 meter CW signal is marginal but would pass FCC scrutiny at -46 dBc. Higher order harmonics are obliterated. WA8TOD |
Re: Harmonic performance - SSB vs CW
¿ªÔÆÌåÓýI¡¯m not suggesting it, I¡¯ve done it.? With a good outboard LPF set, it works and can be compliant with the right set of filters. ? From: [email protected] [mailto:[email protected]] On Behalf Of ajparent1/KB1GMX ? Madradiomodeler, -- ¡_. _._ |
Re: Harmonic performance - SSB vs CW
Warren Allgyer
I removed the 80 meter toroids and assembled them, along with the requisite SMD 1000 pF caps on the underside, in line of perf board.? I cut the RF trace from T11 to the relays and routed it out to the new filter via teflon coax. The 3rd harmonic of the 80 meter CW signal is marginal but would pass FCC scrutiny at -46 dBc. Higher order harmonics are obliterated. WA8TOD |
Re: One question only...
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 |
Re: Harmonic performance - SSB vs CW
Gordon Gibby
¿ªÔÆÌåÓý?yup....pretty sad.? ?This is progress, however!!!!? ? From: [email protected] <[email protected]> on behalf of ajparent1/KB1GMX <kb1gmx@...>
Sent: Monday, August 6, 2018 2:22 PM To: [email protected] Subject: Re: [BITX20] Harmonic performance - SSB vs CW ?
For everyone to see...
Here is a sweep of the 1970s Tentec Century 21 filter board the 3.5mhz filter. Its a simpler 5 element and would be marginal with the current -43dbc spec. It's day and night better.? its image C21b I include as well the 3.5mhz filter in the ubitx. A presumably better 7 element filter. Image F35 Allison |
Re: Harmonic performance - SSB vs CW
For everyone to see...
Here is a sweep of the 1970s Tentec Century 21 filter board the 3.5mhz filter. Its a simpler 5 element and would be marginal with the current -43dbc spec. It's day and night better.? its image C21b I include as well the 3.5mhz filter in the ubitx. A presumably better 7 element filter. Image F35 Allison |
Re: One question only...
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 |
Re: Humble suggestion future Ubitx versions
#ubitx
RICHARD
¿ªÔÆÌåÓýLast month QST did a write up on the BITX40, with all the published lab tests.? It would be interesting if they were do the same with the uBitx.? ??It might get FCC attention and stop all future imports to the USA,? is that what we want? ?Maybe it is time to tone down all the attention to these problems. Just a thought. K6KWQ ? Sent from for Windows 10 ? From: [email protected] <[email protected]> on behalf of ajparent1/KB1GMX <kb1gmx@...>
Sent: Monday, August 6, 2018 9:30:20 AM To: [email protected] Subject: Re: [BITX20] Humble suggestion future Ubitx versions #ubitx ?
Iz oos,
For some its was the FT817 for 109$.? There is a lot of distance and people complain about the FT817! I also agree if you transmit, do so cleanly.? Its a kindness to friends around the world? The bitx40 is far cleaner. As to many rigs... guilty. For hf I have two old Tentec the 505 QRP 5 band and its bigger brother the 340 100W 5 band. I have no worries depite the fact they were design in the 19070s that they meet current standards or maybe even exceed them. More modern a Ft817 and the Tentec Eagle. That and KNQ7A, KD1JV Slopbucket20, WM20, and Diz's 1W, for the kit radio world.? Then I have my first 20M SSB , 10M SSB, 15M SSB, radios from the ground up.? All meet the numbers required and then some. All have decent carrier suppression.? The only one with issues that needed help was the KNQ7A that being a really loud pop on TX, easy fix too. Others manage to do it well and inexpensively and with attention it works. As is the ubitx has more of my time in it than a few scratch builds including building their? filters and PLL systems(pre Si 5xx parts). Mine however is in the "junkbox" as a result of slicing it up to get to root causes. Its salvageable but a clean sheet would be less time consuming. Allison |
Re: One question only...
¿ªÔÆÌåÓýAll, when I first looked on the schemtaic of the ?BITX 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!!! DK5LV Am 06.08.2018 um 18:26 schrieb Kees T:
Allison, |
Re: One question only...
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. |