Kees,
I tried with and without R27. With R27 the 45MHz signal @ mixer drops a lot and only 6db without.
But the power out drops very little with or without. R27 reduces the spurs a little.
I had suggested removing the C22 and placing it there. I learnt a lesson the hard way.. the xtal filter
pin shorted to ground and the transistor failed !!! So the cap came back. I chose to place a 120pF
cap at C22 as that is enough to pass 45MHz without much attenuation. This RC roll off at 3 MHz
will be at least 20db.. I propose to replace the other coupling caps and emitter bypass with a
calculated lower value to attenuate as much below 30MHz as possible.
I think it will be helpful to have the 45M IF stage respond less to HF so that its pickup of the output
signal and amping it is further reduced. This the thought that brought out filter as quick solution!
The harmonics below 20Mhz is worrying me.
Raj
Ps Please leave in the parts that you are replying to! I read mails in Eudora and not on the web.
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At 08-09-18, you wrote: Raj,
Doesn't leaving R27 in place give you better impedance matching ? Did you try cutting the trace in between and just putting the filter between C22 and R27 ?
73 Kees K5BCQ
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Richard Chan? If you are willing to work on 6m then this may be of a lot of interest in terms of a practical stealth antenna?
you can use a combination of a? 50mm coil former (see art.)? and a THIN modified surfcasting rod to produce a? 2.8mL ish dipole Stealth antenna for? 50 Mhz as per instructions.? you simply need a window or a port out of the building . Not necessarily a balcony.? ?
There are at least two off 6 m repeaters in the Toronto area,? based on my very quick web search.
uBitx can allegedly be conv to one band on? 6m,? but it is a big job.? Send a message to Mad radio modder and if he will talk to you you may be able to get the low down on it.?
A dipole perp to building facade is going to be? a HELL of a LOT? more efficient than some magnetic loop inside.
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Farhan
I am not sure I understand the statement: "The IMD is not a major challenge on the TX side as the signals are at a consistent amplitude. Hence, the filter is on the tx side alone."
In both cases of use of the bi-directional amplifiers one of the two signals being mixed during TX originates in the SSB generator and, by definition, is both of highly inconsistent amplitude and is very susceptible to IMD whenever it encounters non-linearities. Is this really what you meant to write?
WA8TOD
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That seems to be a British version of One of the ones I¡¯ve used. ?It should work fine. ?I would expect that it has a toroid-based pick up system inside. ?
In the forward (sometimes labeled CAL )position, while sending CW, Adjust the sensitivity knob until the needle is at the top. Then move the switch to the reverse position sometimes labeled SWR, and read the standing wave ratio from the scale?
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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 ?
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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 ?
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Show us a photo of the swr meter you¡¯re considering.?
See:
I think I use all of the above at one time or another?
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Thank you very much for your nice "Welcome aboard", indeed I appreciate all of the answers above and I'm pretty sure that this topic will have some "echo" throughout community. These are maybe the most common questions asked by those with just the license
of operation in hand and a few basic knowledge of electronics. I can't wait to see the uBitx on my desk. Meanwhile, I can't find some genuine information about the output impedance of the uBitx itself. Is it 50 ohms ? Gordon Gibby previously sugested that
a CB SWR-Meter will do the job on HF also. I found one but it's rated to 11m band only, or at least that's what on the label. Can someone tell me what can go wrong it I start using it ? And by experiment, does anyone know how much SWR can uBitx handle without
permanent damage?
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Thank you very much for your nice "Welcome aboard", indeed I appreciate all of the answers above and I'm pretty sure that this topic will have some "echo" throughout community. These are maybe the most common questions asked by those with just the license of operation in hand and a few basic knowledge of electronics. I can't wait to see the uBitx on my desk. Meanwhile, I can't find some genuine information about the output impedance of the uBitx itself. Is it 50 ohms ? Gordon Gibby previously sugested that a CB SWR-Meter will do the job on HF also. I found one but it's rated to 11m band only, or at least that's what on the label. Can someone tell me what can go wrong it I start using it ? And by experiment, does anyone know how much SWR can uBitx handle without permanent damage?
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Imaging me with egg all over my face ...not a pleasant sight ...You are indeed correct ...I apologize (if I can )? t9 to t10 bypassing the 4 transistor array ..Feeding directly to the gates of the mosfets? I found that the collectors on the 4 transistor array were swinging +- 10 v ...Cutting off and or? driving the mosfets into saturation ...No wonder such cruft was being generated
Re Jerry ..Donno... need to start making some transconductance measurements too anyway ?? I was looking at the gate voltage on the mosfets ..4 V at 100 ma bias ...More swing that +/- 4 volts and distortion rears its ugly head (more like 3 volts, but who's counting
Jim
On Saturday, September 8, 2018, 9:24:02 PM PDT, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
Going T9 to T11 means you are bypassing the 4 transistor driver plus the IRF510's. T10 is before the IRF510's, T11 is after the IRF510's. So I think you mean T9 to T10. In the very informative post? ? ? ? /g/BITX20/message/51743Allison reports that the IRF510's might have a gain of 13dB at 30mhz. So if we want 5W out, we need to have at least 250mW of power to drive those gates. And the pre-driver only gives about 8mW? at (I assume) 30mhz. Hence, I'd be surprised if getting rid of that driver stage is going to work for you. At DC, the IRF510's don't take any power at all at the gates. However, at 30mhz the story is quite different. Jerry
On Sat, Sep 8, 2018 at 09:06 PM, jim wrote:
Well ..It shows T9 to T11 because I did on purpose bypass the 4 transistor dirver stage ... Maybe Ciss being what? couple hundred puf's ??? what is shown is exactly as it is Be aware I have NOT verified the (absolute) output level nor the spur level ..Just wanted to share the concept..Nothing more? I am not driving it with any power ....Just to see...? A triode with positive grid bias maybe?
?
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Going T9 to T11 means you are bypassing the 4 transistor driver plus the IRF510's. T10 is before the IRF510's, T11 is after the IRF510's. So I think you mean T9 to T10. In the very informative post? ? ? ? /g/BITX20/message/51743Allison reports that the IRF510's might have a gain of 13dB at 30mhz. So if we want 5W out, we need to have at least 250mW of power to drive those gates. And the pre-driver only gives about 8mW? at (I assume) 30mhz. Hence, I'd be surprised if getting rid of that driver stage is going to work for you. At DC, the IRF510's don't take any power at all at the gates. However, at 30mhz the story is quite different. Jerry
On Sat, Sep 8, 2018 at 09:06 PM, jim wrote:
Well ..It shows T9 to T11 because I did on purpose bypass the 4 transistor dirver stage ... Maybe Ciss being what? couple hundred puf's ??? what is shown is exactly as it is Be aware I have NOT verified the (absolute) output level nor the spur level ..Just wanted to share the concept..Nothing more? I am not driving it with any power ....Just to see...? A triode with positive grid bias maybe?
?
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Well ..It shows T9 to T11 because I did on purpose bypass the 4 transistor dirver stage ... Maybe Ciss being what? couple hundred puf's ??? what is shown is exactly as it is Be aware I have NOT verified the (absolute) output level nor the spur level ..Just wanted to share the concept..Nothing more? I am not driving it with any power ....Just to see...? A triode with positive grid bias maybe?
Jim
On Saturday, September 8, 2018, 7:57:38 PM PDT, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
I assume that's T9 to T10, not T9 to T11.
Would be surprising if you could still make it work well 80-10m after removing the driver stage.
It takes significant power to drive the capacitive load presented by the IRF510 gates,
especially given the drain-to-gate Miller capacitance.
Your SA screen shot is showing 20mhz, if it's giving 5W at 20mhz I'm plenty surprised right there.
?
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Move it off the processor board?? Mount it on the (ground plane) backside?? use some formable small diameter coax to feedpoints ?
JIm
On Saturday, September 8, 2018, 3:38:29 PM PDT, Glenn <glennp@...> wrote:
On the assumption that leads to a buffer board out of the Si5351 outputs being a good idea, I drafted one up that fits onto the uBITX board as shown.? Requires 3 track cuts on the uBITX, pcb is fitted using existing thru holes for the ground points and short links to the input and output sides. Buffer chips 74LVC1G04GW. Board is tiny and parts are also, so not for everybody. 
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On Sat, Sep 8, 2018 at 06:11 PM, RCBoatGuy wrote:
Great find!? That information is not in the most recent datasheet.
Welcome,? It can be annoying when data sheets get revised and important information left out.? Just found a 1978 Fairchild diode data book online. While using such an old data book may have hazards of its own, it was amazing how much more characterization information was there. I guess solid state diodes were still new and exciting back then. Tom, wb6b
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Hi Allison,
I agree the drivers are a good idea, would be a way to increase the drive to the mixers, especially if the driver is placed closer to the mixer, and reduce crosstalk.
My comments on the current limiting was referencing the concerns about drawing excessive current form the Si5351 outputs.
Tom, wb6b
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I assume that's T9 to T10, not T9 to T11.
Would be surprising if you could still make it work well 80-10m after removing the driver stage.
It takes significant power to drive the capacitive load presented by the IRF510 gates,
especially given the drain-to-gate Miller capacitance.
Your SA screen shot is showing 20mhz, if it's giving 5W at 20mhz I'm plenty surprised right there.
?
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On Sat, Sep 8, 2018 at 06:34 PM, Jim Tibbits wrote:
So ..Thinking of this and that ...Came to the blinding revelation that the IRF150 is NOT a current controlled device, but a voltage controlled device ...With that in mind, I bypassed the main current drivers in the pa Q92,93,96,97 and connected directly from T9 to T11...Circuit alterations in pix as well as sweep of PA pass-band ...Output seem on the order of 5 watts ...Spur checking tomorrow
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"I got better results by replacing C22 with filter and leavening R27 intact!"
Raj
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???? ? I wrote that response after reading the above comment from Raj. I'm talking about the second 45MHz filter Raj added.
73 Kees K5BCQ
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Re: M1 and M2 tied together effect.
Allison,
Sorta..... Removing that R3 from the board frees up several cubic inches in that area and moving the Tx/Rx function to another "R3" on the LPF relay board greatly reduces the RF wiring lengths. That leaves the M1 to M2 connection to handle
and your suggestion to use a 2N7000 (faster than a speeding relay) to shunt the point to ground during Tx, especially if driven by the actual T/R line, helps reduce anti-thump-pop too. I see that was done on the V4.
73 Kees K5BCQ
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Kees, The diode mixer needs a non reactive, 50 ohm match on the IF side. If this is not so, it will generate distortion and birdies. That's one of the two purposes of the bidi amp. Directly connecting the filter to the diode mixer will drop the sensitvity by about 4 to 5 db and increase the birdies by a large amount.? The IMD is not a major challenge on the TX side as the signals are at a consistent amplitude. Hence, the filter is on the tx side alone. - f
Raj,
Doesn't leaving R27 in place give you better impedance matching ? Did you try cutting the trace in between and just putting the filter between C22 and R27 ?
73 Kees K5BCQ?
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So ..Thinking of this and that ...Came to the blinding revelation that the IRF150 is NOT a current controlled device, but a voltage controlled device ...With that in mind, I bypassed the main current drivers in the pa Q92,93,96,97 and connected directly from T9 to T11...Circuit alterations in pix as well as sweep of PA pass-band ...Output seem on the order of 5 watts ...Spur checking tomorrow Jim  
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Ah, Siri!
That was supposed to be the most wire, not the most water!
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Ricbard, you might consider a Magnetic Loop. It will be hard to get high efficiency on 40 metres, but at 20 metres I have had success with a 1 Metre diameter MFJ loop and 10 watts. If you have a large window though, I would try for a dipole, either straight
or bent as Curt suggested.?
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Ricbard, you might consider a Magnetic Loop. It will be hard to get high efficiency on 40 metres, but at 20 metres I have had success with a 1 Metre diameter MFJ loop and 10 watts. If you have a large window though, I would try for a dipole, either straight or bent as Curt suggested.?
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Raj vu2zap
YO8UFO
Brent Seres/ VE3CUS