HI John, Details please? And the results?
Thanks
Nick
|
If I may add to the conversation - my experience of using CB
meters is if they're the parallel-strip kind (very common), they
may loose some sensitivity at the low end.? Otherwise, they did a
fair to good job checking the SWR, which is a ratio anyway.? (At
the upper end of the 'usual' spectrum - sometimes TOO sensitive,
but I've used them with reasonable accuracy on 6m.)
Power measurements are a different story... but in those cases,
I'd rather use something more accurate.? The way many of them are
made, they are still accurate for measuring power between 15m and
10m only (my experience is that they're usually rather accurate at
the upper end of the HF spectrum if they're made for 11m).
On 09/09/2018 12:51 PM, Arv Evans
wrote:
toggle quoted message
Show quoted text
Output
of the uBITX is 50 ohms.? Your CB SWR meter should work for
the upper end of?
HF
range (20M through 10M) and maybe acceptably good for 80M
through 10M.? Many?
of
those old CB SWR meters were just copies of ham radio SWR
meters of the era.??
If
the CB SWR meter is not performing well, it does provide a
case, meter, and knob to?
use
in building a more modern bridge type SWR and power meter.
Arv
_._
|
45 Mhz filter installed with impedance matching transformers. PCB made with islands created with a x-acto hobby saw.
John
KC9OJV
|
George also modified the main 45MHz filter by adding transformer coupling ...........on? Sep 8???#5897173 Kees K5BCQ
|
Warren, my plot of the TOYOCOM 45E2BF filter using your 7 : 2t on BN43-2402 also. Clearly my filters have a different impedance than yours as loss is higher and ultimate rejection worse. But I guess it shows that buying 'other' filter types than yours might still be usable. I didn't do any further checks on actual impedance of my filters. glenn vk3pe 
|
Re: K5BCQ uBITX Relay Switched LPF/BPF board
It looks like great progress is being made on spur reduction, so back to LPF switching and a few other things. Received the first set of boards and have already made some modifications for better wireability.
1) I decided to eliminate R3 off the uBITX board and instead add it to the LPF Relay Board because it frees up space on the uBITX and allows more efficient RF wiring for receive. Since the "old R3" also switches M1 to M2, I'm changing that to how it's wired on the V4 uBITX by adding a 2N7000, changing R70 to 1K, add a 1K R78, add a 1uF C79, add a D14, and driving the 2N7000 with a line over to T/R (a 2N7000 driven directly by T/R is faster than any speeding relay contact).
2) Replace 3 sets of dual 2N3904 Transistors in the PA driver with 3 sets of dual 2N2222A Transistors. Allison had suggested changing the emitter resistors from 22 ohms to 10 ohms (for dual 2N2222A's ??
3) Add a three 1N4148 diode-OR from TxA,TxB, and TxC driver inputs to a TxD driver to pick that relay, which removes the 10m/12m/(15m) LPF when inserting the proper (A/B/C) LPF during Tx. Yes, that means 4 relays are active during TxA,TxB, or TxC transmit. All four of the LPFs use the existing inductor/capacitor components off the uBITX board. They are just moved over to a small 1.5" x 0.5" bare LPF board (that footprint is also the one QRP labs has for their LPF/BPF filters, but they don't sell blank boards.
4) uBITX Antenna will be wired to either one of two SMA connector pads.
5) T11 will be connected to the RF input on the LPF Relay Board with about 1" of coax.
6) Found some of the smaller 12V 10 pin DPDT bifurcated contact relays on ebay for about $1 each. They fit nicely.
7) Leave all the traces, just make a cut and remove 1/16" of the trace where needed.
8) Will provide pictures later.
73 Kees K5BCQ?
|
Did Change the output transformer (T11) to 2 FB43-801's like a binoc core ..3 T pri, 5 T sec ..just to start ..The other one was kinda making the waveshape look like a triangle wave generator (lotsa 3x harmonics I assume)
Jim
On Sunday, September 9, 2018, 8:55:06 AM PDT, ajparent1/KB1GMX <kb1gmx@...> wrote:
? It should be a 2:3? [maybe 4:6 turns] where 2:3 ratio nets about 22ohm drain load and it likely to have a chance at
10W IMD?being acceptable at 12V.??
Things you have to do to generate /clean/ power.
Allison
|
Just one step at a time ....Did replace R97 and R98 (47 ohm) on the mosfets gates with 10K resistors ...Improved drive and output Now Q90 is going into limiting at -17 dbm...Gotta check/redo the bias there (limits on + side so R81 is too small probably ..Get it to limit symmetrically and then see whats what
Pulled Q912 and Q's 92,92,96.97?? Can always put em back
Jim
On Sunday, September 9, 2018, 8:06:54 AM PDT, ajparent1/KB1GMX <kb1gmx@...> wrote:
Jim, The problem was I was peeling a very pungent onion. Allison
_._,_._,_
|
Re: Right-sided relay harmonic attempted fix for v3/4 ubitx
Hello Gordon,
Good to hear. I am looking forward to purchasing a few.
Ripley The words are mine but this iPad does what it will with them.
toggle quoted message
Show quoted text
On Sep 9, 2018, at 4:58 PM, Gordon Gibby < ggibby@...> wrote: Hi folks....
25 new blank boards for the simple-minded right-sided relay board fix are supposed to arrive from China on Tuesday.? ?If so, I'll re-enable? the Ebay advertisement and up the "count" (a learning experience) on Wednesday.? ?Was able to mail out five boards on Friday before leaving on a camping trip.? ?Hope they arrive OK!!!? ?I figured out how to mark them as "shipped" and send a note to each purchaser through Ebay.? ?With all the SPUR FIXES now being discovered, things are really shaping up around this little transceiver to make it have much fewer spurious responses.? ?Delighted to see the group progress.? ?Each person proceeds at? their own pace, but the group moves forward huge amounts.
Cheers,
gordon KX4Z
|
Warren,
Impressive plots and visually shows the effect of better filter matching, including what happens to the filter skirts. Now what to do about further gain reduction which also helped reduce the spurs.? ?
73 Kees K5BCQ
|
Just eyeballing the schematic, it looks to me like the source impedance for a filter replacing R27 would be about 400 ohms. I have no idea how to calculate the output impedance made up of the bifilar winding on T2 and it is likely to be different based on frequency. The best bet in this circumstance would be to assume a low impedance for the output of the filter transformer and probably no transformer would be needed for the input (the Q21 side). The two effects if it is a wrong assumption will be too low gain and a tilted passband. Too low gain is probably not a problem since we are trying to take some out. Tilted passband can be checked by sweeping a tone input from 300 - 2700 Hz and watching the output power. Variation more than 3 dB is probably unacceptable and both USB and LSB should be checked.
WA8TOD
|
Re: M1 and M2 tied together effect.
Kees,
I have done this with success, I will send a picture soon of how.
But basically, remove R70, bridge the front pad to the adjacent track, cut the adjacent track and short the relay sides of both tracks to ground...
I attach the pop fix the this point too.
73 Nick VK4PP
|
Great John! Just be aware, I do not know what the true interstage impedances really are. Maybe that has been calculated or stated in the past but I have not seen it that I remember. The actual impedances should be used and not just assume it is 50 ohms. I assumed that only for this proof of concept. It is pretty clear from the traces if you assume 600 ohms for the filter though, you will be close enough.
WA8TOD
|
Re: Right-sided relay harmonic attempted fix for v3/4 ubitx
Hi folks....
25 new blank boards for the simple-minded right-sided relay board fix are supposed to arrive from China on Tuesday.? ?If so, I'll re-enable? the Ebay advertisement and up the "count" (a learning experience) on Wednesday.? ?Was able to mail out five boards on Friday before leaving on a camping trip.? ?Hope they arrive OK!!!? ?I figured out how to mark them as "shipped" and send a note to each purchaser through Ebay.? ?With all the SPUR FIXES now being discovered, things are really shaping up around this little transceiver to make it have much fewer spurious responses.? ?Delighted to see the group progress.? ?Each person proceeds at? their own pace, but the group moves forward huge amounts.
Cheers,
gordon KX4Z
|
Hi All
Really sorry to ask this, but I'd appreciate your help setting up my uBitx. I've read countless ways of calibration, from KD8CEC and others on here, but cannot fathom how to get it right. What exactly is 'zero beat', do I select LSB or USB when setting it up? When I htink I've got it set I find out the sidebands are swapped (compared with a websdr site)
I've borrowed a 10.7MHz crystal marker that transmits a 1khz sine wave. I can pick this up with the box off. An app on my phone can generate a 1khz sound too. I've also got a picoscope 2105 with 25Mhz bandwidth if that helps. I'd appreciate some pointers what to do, what to look out for.
Many thanks
Graham
|
Per Warren's suggestion I build a pcb with impedance transformers and I checked before and after and the spurs are very low now relative to pre-filter. I'll post a photo of my installation.
John
KC9OJV
|
Pretty impressive differences!
On Sep 9, 2018, at 15:23, Warren Allgyer < allgyer@...> wrote:
toggle quoted message
Show quoted text
Here we have the eBay filter between a pair of 12:1 transformers (purple) wound 7:2 on a BN-43-2402 core, compared to a pair of 9:1 transformers (blue) wound 3:1, and a pair of 9:1 transformers (yellow) wound 6:2.
<9903.jpg>
WA8TOD
|
Here we have the eBay filter between a pair of 12:1 transformers (purple) wound 7:2 on a BN-43-2402 core, compared to a pair of 9:1 transformers (blue) wound 3:1, and a pair of 9:1 transformers (yellow) wound 6:2.  WA8TOD
|
Hiya guys, HELP!? UBITX Ver4.3 Built..Wiring triple checked. My problem on CW, I press the key and just get a repeat of dot dash and sometimes it takes several stokes of the hand key to repeat the same. Any idea's
of a sulution?
|
The only cb ones I have tried on 2 m are the long parallel rod pick up type, they were quite in accurate
For VHF/UHF I use ham products made for the purpose
Cheers
Gordon kx4z
toggle quoted message
Show quoted text
On Sep 9, 2018, at 13:59, Bill Cromwell <wrcromwell@...> wrote:
Hi,
It might start to be a little shaky on the two meter band. And maybe will work there too.
73,
Bill KU8H
On 09/09/2018 05:37 AM, gonewiththeego@... wrote:
I was thinking about an Albrecht SWR 20 which I can see that is used
only for CB. Do you think it should work for 20/40m band ? --
bark less - wag more
|
Nick VK4PP
Ripley
