Date   
Re: RD16HHF1 power curve flattening...some

Nick VK4PP
 

HI John,
Could you please summarise your mods to get these results.
Thanks. Nick

Re: A simple VOX control circuit for the BitX-40 to allow it to be used for FT-8

John P
 

Well, I thank you all for the comments, but I think some of you kind of missed the point. Of course I could have used the EasyDigi gimmick (~$15) and a USB to RS-232 gimmick (~$10). Even had I not had all the parts already, this whole thingcost less than $10!

As for CAT control, I didn't really feel like hacking the software in the BitX, although I do have a CAT control interface set of functions using the Yaesu FT-891 command set I wrote for another project.
--
John - WA2FZW

uBITX Audio Breakout Plus board... #ubitx

Nick VK4PP
 

Ok, So it appears that the Audio Breakout has been very popular.

Now I am thinking of a new version.
Same interface between the uBITX and Audio connector, but this time, include and LM324 based AGC and the TLC274 CW Filter, Maybe even just use the same TLC274 chip in the AGC also? or vice versa....

Include a spot for the SSM2167 Mic AMP breakout board like I've done on the RaduinoI2C with the SI5153... ?

Thoughts and Ideas please.

73 Nick

Re: Erratic tuning with my new uBitx

Dexter N Muir
 

I forget where, but I recall a "shuttle tuning" scheme that does that. Other than that, there's a menu item. I seem to recall the digit that changes is underlined on-screen.

73 Dex, ZL2DEX

Re: FT8 on my uBITX #ubitx

Joe Puma
 

Yea that diode is pretty chunky. Please share

Joe

Band Drive Circuit

K9HZ <bill@...>
 

Guess I should share this with everyone.  Mike will post it on the uBITx.NET site soon.  RV1 in the yellow circle is the existing drive pot in the uBITx.  Remove it and connect the wires from the relay as shown.  Q17C, Q18C, and Q19C references connect to the transistor Q17, Q18, and Q19 collectors.  Then set RV1A, RV1B, RV1C, RV1D  basis the appropriate band selected to keep the power out flat.

 

 

 

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

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email:  bill@...

 

 


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Re: RD16HHF1 power curve flattening...some

K9HZ <bill@...>
 

Oh yeah, one more thing…  Those RD16HHF1s should draw about 500ma per part (1A total) to put them nicely into the class AB2 operating band for SSB.

 

I guess we better all get our heads together and write this up and a concerted effort so others can do it too…

 

I also ordered a pair of RD70HHF1s tonight to try as an add-in amplifier board at some point.  While these parts are not exactly spirit QRP,  I do like the idea of having 100W available when I want it… maybe with the flip of a switch.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Yahoo Group.

 

email:  bill@...

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of John
Sent: Tuesday, March 20, 2018 10:39 PM
To: BITX20@groups.io
Subject: Re: [BITX20] RD16HHF1 power curve flattening...some

 

Impressive, Bill.

I just tried 180pf across the primary of the output transformer, as opposed to the 33pf I had initially and as you mentioned from your simulations before it raises the power lower down to the point where I don't have the dip at 21Mhz anymore. With RV1 at 60%, 13,8V supply I get 22W at 80M, 20 at 40M, then tapering down to 12W at 15M then flat up to 10M. 

So I have wound down my RV1 to get 9 to 10W on the higher frequencies and I get 18-16W on the lower ones. As I wanted. I am now happy with the power curve, especially when compared to the initial one with the IRF510s (17W to less than 2W from memory).

73, John (VK2ETA)


Virus-free. www.avg.com

Re: PCB Price Comparison tool

ste007ste@...
 

I've used Seeedstudio Fusion PCB manufacture service a few times too. 
Start at only $4.9 but can fab very complicated boards. Excellent quality and service.

Re: BitX40 case from The Home Depot...

Jacob Farnes
 

Thanks for the details. I was thinking the same epoxy method was going to be required here. I was wondering if I was missing some tribal-knowledge method to get a panel screwed down without compromising the integrity of the case. I'll have to see if I can source some of that sign material- hopefully in a 2mm thickness.

How to test speaker resistance

David Wilcox
 

OK.  I am seeing various resistances listed for speakers.  How would I test one?  An ohm meter should indicate a short across the coil I would think.  Please help.

Dave K8WPE

Re: two-tone test on ubitx

Henning Weddig
 

Tim,

thanks for Your reply! For the overall carrier suppression two things are to be considered:

1)  the balance of the single balanced modulator

2) the additional suppression done by the slope of the xtal filter

For 2) normally the so called -20 dB point of the filter attenaution is chosen. This point is a function of the BFO frequency.

Regarding my unmodified BITX40 I noticed that I could hear the normal tone but it seemed that I also get a response from the "upper sideband". Further investigation showed that the BFO  (measured to be 11.998 051 MHz) was within the passband of the xtal-filter. The 3 dB points of the filter result in a bandwidth of 2 kHz, see the attached plots. 

The "resulting bandwidth" under these conditions is far too small, resulting in a "muffled sound" already reported by other users. A remedy of broadening the filter bandwidth is not the solution, althogh a bandwidth of a bit larger than only 2 kHz is advisable.

The BFO frequency should be at the location of the marker.  Replacing the 47 pF cap with a 20 pF trimmer (as originally forseen) shifted the  BFO frequency upwards.

For the uBITX the BFO is generated within the SI5351, so it should be easy the adjust this frequency to the correct point. To do this the filter center frequencxy, 3 dB points and 20 dB point must be known or individually determined, not easy to be done without test equipment.

For the balance of the modulator the following points have to be met:
    the exact symmetry of the windings including their center tap
    the exact balancing of capacitive (or inductive i.e. complex) impedances
    the exact equal performance of the two diodes (switches) in their on-resistance, off resistance and capacitances-- ok a double diode on a single wafer may guarantee this requirement.

Please have a look back on the "old" discrete double balanced mixers used as modualtors, they used:

    selected diode quads (even within a common housing e.g  offered as a quad  for instance OA154 Q to match the thermal behavoiour)
    a potentiometer to individually balance resitive component and exact symmetry fof the two center tapped windings of the modulator
     two caps (one fixed, one trimmer) to capacitively balance the modulator

Of course the carrier suppression is also a function of the wanted signal levels and IM performance of the modulator which is also a function on how large the wanted signals can be made and how "good" the IM performance has to be.

I have seen on other schematics using a single balanced mixer with a potentiometer (as formerly used by Ashar) AND the capacitive balancing has been implemented.
 
My guess is that a carrier suppression of at least 20 dB can be reached. With the additional carrier suppression done by the fitler  a carreir suppresion of 40 dB should be possible. 

I have built a double balanced mixer using two BN43-2402 cores with trifilar windings and four non selected 1N4148 diodes. Without further adjustments I got a carrier suppression of 26 dB, related to a singel tone, but I did not measure the IM performance with a two tone input. 

I am not sure if the equal spacing of the trifilar winding alone guarantees a perfect carrier suppresison.

So pelase determine the 12 MH x-tal filter bandwidth and -20 dB point(s) and then adjust the BFO frequency to this -20 dB point. But make sure that the lowest audio frequency to be passed through is still in the range of 300 Hz or so.

One problem exists: the xtal filter skirts are not equal (due to the ladder filter topology).  If the other sideband is to be used (for the BITX 40 in USB mode) by not shifting the VFO  the -20 dB point can result in a higher "lowest audio frequency".

Henning Weddig
DK5LV

Am 21.03.2018 um 02:54 schrieb Tim Gorman:

I forgot the attachments!



On Tue, 20 Mar 2018 20:40:15 -0500
"Tim Gorman" <tgorman2@...> wrote:

Henning,

I've looked at the balanced modulator in the ubitx. It is set up
differently than what I am used to but it should work.

The arrangement I am used to is shown in the first attachment. The
ubitx is in the 2nd attachment.

In looking at T7 the windings are not very well spaced on the core.
They are crammed together at the bottom near the circuit board. I
don't know if this could cause some stray capacitance that would
upset the balance of the circuit. 

I might see if I can take a probe and separate the windings and get a
little better spacing and see if that helps to balance the carrier
out.

I have to say that I am a little surprised that no one else has any
suggestions on how to better balance the carrier. 

tim ab0wr

 Tue, 20 Mar 2018 05:29:59 -0400 "Henning Weddig
via Groups.Io" <hweddig@...> wrote:

Tim, this is a nice measurement- 
At which output power did You take the measurement? What is the
attenauation of the power attenuator between the output of the uBITX
and the Input of the spectrum analysser? Your measaurement shows a
thrid intermodulation of 34 dB/ related to a tone, in relation to
PEP please add 6 dB results in 40 dB of d3! BUT: marker 1 shows the
supressed carrier is only 20 dB below the carrier, or 26 dB to PEP.
Commercial rigs suppress by at least 40 dB or better.  This result
is a"proof" of my worries concerning the unsuffiecient carrier
Suppression of the balanced modulator and xtal-filter..

Henning Weddig
DK5LV. 

-----Ursprüngliche Mitteilung----- 
Von: Tim Gorman <tgorman2@...>
An: BITX20 <BITX20@groups.io>
Verschickt: Mo, 19. Mrz 2018 22:46
Betreff: [BITX20] two-tone test on ubitx

Attached is a screen save from my spectrum analyzer for a two-one
test of my new ubitx. 

The tones were driving the finals to about 10watts output (not
quite, but close). I had a 30db external pad and a 10db internal
pad in the SA. 

The carrier was only down about 20db (marker 1). That's not as good
as I expected. I'll have to look at that and see what can be done to
improve it. 

The 3rd order IMD (marker 4) was down about 34.5db which is
adequate. 

The heat sinks get *hot* while running a key down measurement like
this. If you are going to use the rig for a digital mode it probably
needs to be set for about half-power out of the rig. That or a
significant increase in heat-sink capability should be installed. 

tim ab0wr












Re: How to test speaker resistance

Gordon Gibby <ggibby@...>
 

Put a 10 ohm  resistor in series with the speaker, run various Audio tones into the series system.  (you could even use one of the birdies in the receiver for this purpose). Measure voltage across speaker, and across resistor and total.

Speaker is a complex impedance . A bit of math and you can compute it’s impedance after measuring the values. 

(You may need an oscilloscope or else and amplifier or transformer  to step the voltages up so you can measure them accurately with the run-of-the-mill voltmeter. )

Back of the envelope estimation: if speaker voltage is about equal to the resistor voltage, Call it  eight ohms.
If half, call it four ohms if half, call it for ohms. If twice, call it  16 to 20 ohms

On Mar 21, 2018, at 06:25, David Wilcox via Groups.Io <Djwilcox01@...> wrote:

OK.  I am seeing various resistances listed for speakers.  How would I test one?  An ohm meter should indicate a short across the coil I would think.  Please help.

Dave K8WPE

Re: A better Raduino PCB

Michael Rothe
 

Mike, I'm also looking for a replacement board and wondering if you have them in stock.
I sent you an email that appeared in this post but no reply.
Thanks
Mike, AB8VS

Re: RD16HHF1 power curve flattening...some

John <passionfruit88@...>
 

Hello Nik,

How did you go with the feedback issue?

My power amp mods in summary:  finals as RD16HHF1s, feedback resistors R261/R262 as 820 Ohms, Transformer 2T primary / 3T secondary on BN43-202, 180pF across the output transformer primary and 330pf across R87/R88. That's all...in a way.

Heavily inspired by Erhard's (DF3FY) information as displayed on uBitx.net.

Results per band at 14V supply, RV1 at %60, RD16's biased at 250mA each:
Band      output power   Total current
80M        22W                         2.9A
40M        20W                         3.2A
30M        16W                         2.3A
20M         16W                        2.7A
17M         15W                        2.4A
15M         12W                        1.6A
12M         12W                    not measured
10M         12W                        1.7A

At 22W the output transformer does get warm but not the LPFs.

Wound back RV1 to get 9-10W on the high frequency bands and 16-18W on the lower ones.

All the best,

73, John (VK2ETA)

Re: RD16HHF1 in the uBITX #ubitx

Bruce Anderson
 

Hi Bill,

How did you tap the TXA, TXB, TXC signals?  Before or after the switching transistors?  If after, underneath the relays?  I’m interested not only in this mod (to drive every band at 5W key down), but to band-switch a linear amp, too.  It would be great to keep those signal wire above the board, though. 

Thanks de W1BWA

Re: RD16HHF1 power curve flattening...some

Henning Weddig
 

even with the mods. the TX string shows a 3 dB drop in output power...

Please exchange the two single chokes L8 / L9 with a bifilar wound coil on a e.g. FT43-50 core, see the reasons for that mod in the description already cited in this forum  "ludens.cl".

BTW: how was the output power determined?

How does the power curve PIn - POut look like,

Is the output power measured at the 1 dB compresion point?

Tests on my tries to build a PA with the RD16HFF1´s using different output transformer configurations (even with a 1:4 guanella transformer with 25 ohm coaxial cable on two BN43-202 cores + Balun with 50 ohm coaxial cable on a FT43-80 torroid core + bifilar choke (FT43-50 torroid) + extra choke on the center tap  with a R-C combinaiton to terminate even harmonics) I was not able to get more than 10 W output power at P1dB.  Therefore I am really sceptical about the high power results of > 16 W.

The "hot" cores show that something must be wrong!

Did You measure the suppression of the even harmonics which should be well suppressed  (at least 40 dB) ? How good are the odd harmoncis suppressed?  If the third harmonic is only 10 dB down (1/3 of the amplitude of the fundamental wave) the PA produces square waves, which is not a performance of a linear amp.

IM performance??

Henning Weddig
DK5LV

Am 21.03.2018 um 12:41 schrieb John:

Hello Nik,

How did you go with the feedback issue?

My power amp mods in summary:  finals as RD16HHF1s, feedback resistors R261/R262 as 820 Ohms, Transformer 2T primary / 3T secondary on BN43-202, 180pF across the output transformer primary and 330pf across R87/R88. That's all...in a way.

Heavily inspired by Erhard's (DF3FY) information as displayed on uBitx.net.

Results per band at 14V supply, RV1 at %60, RD16's biased at 250mA each:
Band      output power   Total current
80M        22W                         2.9A
40M        20W                         3.2A
30M        16W                         2.3A
20M         16W                        2.7A
17M         15W                        2.4A
15M         12W                        1.6A
12M         12W                    not measured
10M         12W                        1.7A

At 22W the output transformer does get warm but not the LPFs.

Wound back RV1 to get 9-10W on the high frequency bands and 16-18W on the lower ones.

All the best,

73, John (VK2ETA)

FDIM/Dayton hamvention, room to share

David Wilcox
 

I have a room one block up from the Holiday Inn Fairborn and my usual buddies cannot attend this year. So, I am willing to share and split the cost with one or two other hams who (like me) were too late registering for a room at the Holiday Inn. I do not smoke or snore. I can provide references. In the past I have picked up folks from the Dayton Airport on my way down Wednesday.

Please reply direct to Djwilcox01 AT gmail DOT com

Dave K8WPE
Check out my QRZ bio.

Re: RD16HHF1 in the uBITX #ubitx

K9HZ <bill@...>
 

Well i just took the signal off the existing relay pins for the band filters because they are big and easy to solder too underneath, but you could easily just connect to the collectors of the relay drive transistors if your eyes are better than mine!


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com


email:  bill@...

 


On Mar 21, 2018, at 6:57 AM, Bruce Anderson <bwanderson@...> wrote:

Hi Bill,

How did you tap the TXA, TXB, TXC signals?  Before or after the switching transistors?  If after, underneath the relays?  I’m interested not only in this mod (to drive every band at 5W key down), but to band-switch a linear amp, too.  It would be great to keep those signal wire above the board, though. 

Thanks de W1BWA

Re: uBITX Audio Breakout Plus board... #ubitx

Paul Galburt - K2AYZ
 

The LM324 is a rock solid device and has been around for decades. It is a bit noisy (35 nV/Hz^-2) and has a low slew rate (0.7V/uS). This means that at 8 volts peak audio, it will become slew rate limited at 10KHz. This is all acceptable for speech in a radio. The LM324 can handle much higher supply voltages (32V) than are seen in the uBitx design. About $0.50 each.

The TLC274 is has a higher slew rate (3.6V/uS) and will never slew rate limit. Oddly, it has a lower gain-bandwidth product (0.32 MHz vs 0.7 MHz) and a slightly lower noise (25nV/Hz^-2). But, the maximum power voltage is 16V. It costs about $1.60

My choice would be to use the LM324 all around for modest gain speech frequency audio and DC applications.

73,

K2AYZ

Re: Erratic tuning with my new uBitx

Chris Clarke G3SQU
 

Thanks for that info, Howard.

I had been finding it difficult to use the  "Set Tune Step?" function because it seemed to double up with toggling the 'tuning lock',  with tuning lock seeming to be the primary function when holding down the encoder, rather than "Set Tune Step?".

After much repetition of trying to set the tune step, however, it has now stopped toggling the tune lock when I hold the encoder down.

I do feel there was actually something going wrong with the Tune Step routine in my uBITx. Could the tune lock behaviour be a problem with the 'debounce' code or digital noise? At one point the tune step showed 200Hz on the display but it actually used a step of 10Hz. I managed after some repetitions of trying to alter the Tune Step to get it back to stepping at 200Hz. Could this be an inadvertent application of the hardware encoder lock caused by an earthing issue?

I also have a little bit of a problem getting the Extended Menu after selecting "Setup On?". Sometimes I get the Extended Menu, mostly I don't. I haven't discovered a surefire way of getting the Extended Menu, just seems a matter of luck. Fortunately it's not something I need to return to often.

Also it seems the maximum tuning step is 200Hz. This is not a very useful value - 1MHz would be much more useful to me.  I'm looking at the code to see if and how I could change the values for "tuneStepIndex". Are you able to you advise on this?

Chris G3SQU