Date   
Re: Tracing receive signal for low signal

Dave Space
 

Yep that was a great suggestion by you.  Those measurements were at VOL- high.

TP 1 @ 7.150MHZ 700uV gave 0.1 p-p
TP2 "                      200uV gave 0.1 p-p

TP16 took like 300uV to get to 0.1 p-p, so a lot more
TP17 took much more like maybe over 2000uV.. have to go back and measure.  


On Fri, Jan 11, 2019 at 10:42 AM, jim wrote:
 
 
 
On Sunday, January 6, 2019, 7:43:06 PM PST, jim <ab7vf@...> wrote:
 
 
Just as a suggestion ..Use the "VOL-H" point as a reference on testing rf levels ...that way both the V3 and V4 boards will be applicable
 
Jim

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Re: Tracing receive signal for low signal

Dave Space
 

I'm wondering about the crystal filter.  I input a signal at tp17 11.996 or around there to get a tone at 290mv it only comes out at <10mv peak-peak that's like -29db does that sound right? I'm measuring with the oscilloscope at tp20.  Seems like an awful lot of loss or I'm detuning the filter or something with the test. 

Re: Tracing receive signal for low signal

Bob Lunsford <nocrud222@...>
 

The type tip/cable you use on the tp may also be a factor.
Maybe you use an isolated tip but if not, the tip/cable's
input impedance and resistance may be affecting the
signal. Just a reminder. I'm also assuming it's an RF tip.

Bob — KK4R

--------------------------------------------

On Fri, 1/11/19, Dave Space <davesspacebar@...> wrote:

Subject: Re: [BITX20] Tracing receive signal for low signal
To: BITX20@groups.io
Date: Friday, January 11, 2019, 8:21 PM

I'm wondering about
the crystal filter.  I input a signal at tp17 11.996 or
around there to get a tone at 290mv it only comes out at
<10mv peak-peak that's like -29db does that sound
right? I'm measuring with the oscilloscope at tp20. 
Seems like an awful lot of loss or I'm detuning the
filter or something with the test.

Re: Tracing receive signal for low signal

Dave Space
 

Hmm..I am rather new to this... I'm using the oscilloscope probes for both the signal generator input (set to 1x) at tp17 and oscilloscope probe at tp20 also set to 1x (as I believe I should be able to see the ~1khz or so signal at that point right? In the MHZ range I'd have to have it switched to 10x but figured I'm looking for low frequency 1x gives more granular voltage down to 2mv)  I tried using a small cap but I think it offset the voltage... might have to try it again with that ac coupled maybe.




On Fri, Jan 11, 2019 at 05:37 PM, Bob Lunsford wrote:
The type tip/cable you use on the tp may also be a factor.
Maybe you use an isolated tip but if not, the tip/cable's
input impedance and resistance may be affecting the
signal. Just a reminder. I'm also assuming it's an RF tip.

Bob — KK4R

--------------------------------------------
On Fri, 1/11/19, Dave Space <davesspacebar@...> wrote:

Subject: Re: [BITX20] Tracing receive signal for low signal
To: BITX20@groups.io
Date: Friday, January 11, 2019, 8:21 PM

I'm wondering about
the crystal filter.  I input a signal at tp17 11.996 or
around there to get a tone at 290mv it only comes out at
<10mv peak-peak that's like -29db does that sound
right? I'm measuring with the oscilloscope at tp20. 
Seems like an awful lot of loss or I'm detuning the
filter or something with the test.

Re: Tracing receive signal for low signal

jim
 

Oscilloscope probes may have high impedance ..try measureing the dc resistance of the probes ..in both x1 and x10 positions ..really best to 'somehow' try to match the output impedance of the rf generator to the input impedance of the circuit under test

use a dc blocking capicitor (.01 uF is fine) between the rf generator and the circuit under test ..You will need to tune the rf gen for max output thru the filter ..may not be exactly 11.997 or whatever mhz ...depends on the crystals and the caps in the filter

Jim

On Friday, January 11, 2019, 5:56:14 PM PST, Dave Space <davesspacebar@...> wrote:


Hmm..I am rather new to this... I'm using the oscilloscope probes for both the signal generator input (set to 1x) at tp17 and oscilloscope probe at tp20 also set to 1x (as I believe I should be able to see the ~1khz or so signal at that point right? In the MHZ range I'd have to have it switched to 10x but figured I'm looking for low frequency 1x gives more granular voltage down to 2mv)  I tried using a small cap but I think it offset the voltage... might have to try it again with that ac coupled maybe.




On Fri, Jan 11, 2019 at 05:37 PM, Bob Lunsford wrote:
The type tip/cable you use on the tp may also be a factor.
Maybe you use an isolated tip but if not, the tip/cable's
input impedance and resistance may be affecting the
signal. Just a reminder. I'm also assuming it's an RF tip.

Bob — KK4R

--------------------------------------------
On Fri, 1/11/19, Dave Space <davesspacebar@...> wrote:

Subject: Re: [BITX20] Tracing receive signal for low signal
To: BITX20@groups.io
Date: Friday, January 11, 2019, 8:21 PM

I'm wondering about
the crystal filter.  I input a signal at tp17 11.996 or
around there to get a tone at 290mv it only comes out at
<10mv peak-peak that's like -29db does that sound
right? I'm measuring with the oscilloscope at tp20. 
Seems like an awful lot of loss or I'm detuning the
filter or something with the test.

Re: Tracing receive signal for low signal

jim
 

To amplify a little bit ..Just measured my Tektronix P6100 probe ..100 ohms dc resistance at X1 and 9 Meg at X10 ...In the theoretical world, an ideal voltage source has Zero ohms impedance ..reality ..maybe 1 or 2  ohms ..they (the manufacturer of the test set) stuff some kind of network on the output to make it 50 ohms for rf ...used to be 600 ohms for audio ..dono if thats still true ..so...if your probes are 100 ohm at X1 then :   Rf Gen 50 ohm>>scope probe 100 ohm>>> terrminated at 50 ohm load ..equals 150 ohm in series with 50 ohm ..voltage drop across 150 ohm will decrease generator "ideal" output... 75% dropped across the generator/test lead resistance ..25% across the load

To test ..first measure rf gen output without it connected to circuit ...connect to circuit ,,measure at point where connected

Different?

Jim



On Friday, January 11, 2019, 11:04:54 PM PST, jim via Groups.Io <ab7vf@...> wrote:


Oscilloscope probes may have high impedancer  ..try measureing the dc resistance of the probes ..in both x1 and x10 positions ..really best to 'somehow' try to match the output impedance of the rf generator to the input impedance of the circuit under test

use a dc blocking capicitor (.01 uF is fine) between the rf generator and the circuit under test ..You will need to tune the rf gen for max output thru the filter ..may not be exactly 11.997 or whatever m Xhz ...depends on the crystals and the caps in the filter

Jim
On Friday, January 11, 2019, 5:56:14 PM PST, Dave Space <davesspacebar@...> wrote:


Hmm..I am rather new to this... I'm using the oscilloscope probes for both the signal generator input (set to 1x) at tp17 and oscilloscope probe at tp20 also set to 1x (as I believe I should be able to see the ~1khz or so signal at that point right? In the MHZ range I'd have to have it switched to 10x but figured I'm looking for low frequency 1x gives more granular voltage down to 2mv)  I tried using a small cap but I think it offset the voltage... might have to try it again with that ac coupled maybe.




On Fri, Jan 11, 2019 at 05:37 PM, Bob Lunsford wrote:
The type tip/cable you use on the tp may also be a factor.
Maybe you use an isolated tip but if not, the tip/cable's
input impedance and resistance may be affecting the
signal. Just a reminder. I'm also assuming it's an RF tip.

Bob — KK4R

--------------------------------------------
On Fri, 1/11/19, Dave Space <davesspacebar@...> wrote:

Subject: Re: [BITX20] Tracing receive signal for low signal
To: BITX20@groups.io
Date: Friday, January 11, 2019, 8:21 PM

I'm wondering about
the crystal filter.  I input a signal at tp17 11.996 or
around there to get a tone at 290mv it only comes out at
<10mv peak-peak that's like -29db does that sound
right? I'm measuring with the oscilloscope at tp20. 
Seems like an awful lot of loss or I'm detuning the
filter or something with the test.

Mini PA für my uBITX #ubitx

DC3MS
 

Hi. I cant thank Ashhar Farhan and Ian (KD8CEC) enough for bringing me back into ham radio.

The ubitx and Ians software are so much fun.

I just completed my little PA using eBay modules ( MRF186 + LPF Board ) and a NANO connected via i2c to control it.

Just wanted to share it.

Regards Mark, DC3MS

 

Re: Mini PA für my uBITX #ubitx

Art Boelke
 

Nice!

On Sat, Jan 12, 2019 at 2:46 AM Mark Schraven <mark.schraven@...> wrote:

Hi. I cant thank Ashhar Farhan and Ian (KD8CEC) enough for bringing me back into ham radio.

The ubitx and Ians software are so much fun.

I just completed my little PA using eBay modules ( MRF186 + LPF Board ) and a NANO connected via i2c to control it.

Just wanted to share it.

Regards Mark, DC3MS

 

Re: Mini PA für my uBITX #ubitx

Brian Arnott
 

Nice looking setup Mark. Any chance of more detail?

Regards

Brian

Re: Tracing receive signal for low signal

Bob Lunsford <nocrud222@...>
 

Simple way to see if the probe's inductance, if there is any, has
any effect is to touch an oscillator's connections in the frequency
selection area to see if the frequency shifts.

Another factor is the loading and this means resistance. If you have
two forms of signal level reading, put one on at a later stage while
touching an earlieer stage. If the earlier stage is not at a gain that
is saturated, the later stage should not be affected by touching an
earlier stage.

It is common in metrology to use different pieces of test equipment
to check each other. In fact, this is precisely what is done. I worked
in test equipment calibration and certification at Fort Hood for six
years and we had A-level calibration there which is good as the
Pueblo, CO standards bureau. We were C-level calibration. We
repaired, tested and certified the equipment and it was then passed
to the A-level for their testing and certification.

Probes have considerations of both [residual] inductance and
resistance. The ideal is zero inductance and a high resistance. This
is why one wants a high resistance multimeter and why a 20K/volt
over a 1K/volt meter was wanted in the old days. Today, meters
are generally at least 20K/volt and no worries unless a needle
movement type is contemplated.

The idea is to use a probe that has the least effect on the circuit under
test. If this means using a X10 probe and doing some math or using
a different scale, this should be done to avoid affecting the readings
and coming up with something that has less real-world meaning.

Bob — KK5R

--------------------------------------------

On Sat, 1/12/19, jim via Groups.Io <ab7vf=yahoo.com@groups.io> wrote:

Subject: Re: [BITX20] Tracing receive signal for low signal
To: BITX20@groups.io
Date: Saturday, January 12, 2019, 2:43 AM


To amplify a little bit ..Just measured my
Tektronix P6100 probe ..100 ohms dc resistance at X1 and 9
Meg at X10 ...In the theoretical world, an ideal voltage
source has Zero ohms impedance ..reality ..maybe 1 or
2  ohms ..they (the manufacturer of the test set) stuff
some kind of network on the output to make it 50 ohms for rf
...used to be 600 ohms for audio ..dono if thats still true
..so...if your probes are 100 ohm at X1 then :  
Rf Gen 50 ohm>>scope probe 100 ohm>>>
terrminated at 50 ohm load ..equals 150 ohm in series with
50 ohm ..voltage drop across 150 ohm will decrease generator
"ideal" output... 75% dropped across the
generator/test lead resistance ..25% across the
load
To test ..first measure rf gen output without it
connected to circuit ...connect to circuit ,,measure at
point where connected

Different?

Jim









On Friday, January 11, 2019, 11:04:54 PM
PST, jim via Groups.Io <ab7vf=yahoo.com@groups.io>
wrote:






Oscilloscope probes may have high
impedancer  ..try measureing the dc resistance of the
probes ..in both x1 and x10 positions ..really best to
'somehow' try to match the output impedance of the
rf generator to the input impedance of the circuit under
test
use a dc blocking
capicitor (.01 uF is fine) between the rf generator and the
circuit under test ..You will need to tune the rf gen for
max output thru the filter ..may not be exactly 11.997 or
whatever m Xhz ...depends on the crystals and the caps in
the filter
Jim






On Friday, January 11, 2019, 5:56:14 PM
PST, Dave Space <davesspacebar@...> wrote:





Hmm..I
am rather new to this... I'm using the oscilloscope
probes for both the signal generator input (set to 1x) at
tp17 and oscilloscope probe at tp20 also set to 1x (as I
believe I should be able to see the ~1khz or so signal at
that point right? In the MHZ range I'd have to have it
switched to 10x but figured I'm looking for low
frequency 1x gives more granular voltage down to 2mv) 
I tried using a small cap but I think it offset the
voltage... might have to try it again with that ac coupled
maybe.




On Fri, Jan 11, 2019 at 05:37
PM, Bob Lunsford wrote:

The type tip/cable you use on the tp may also be
a factor.
Maybe you use an isolated tip but
if not, the tip/cable's
input impedance
and resistance may be affecting the
signal.
Just a reminder. I'm also assuming it's an RF
tip.

Bob — KK4R

--------------------------------------------
On Fri, 1/11/19, Dave Space
<davesspacebar@...> wrote:

Subject: Re: [BITX20] Tracing receive signal
for low signal
To: BITX20@groups.io
Date: Friday, January 11, 2019, 8:21 PM

I'm wondering about
the crystal filter.  I input a signal at
tp17 11.996 or
around there to get a tone at
290mv it only comes out at
<10mv
peak-peak that's like -29db does that sound
right? I'm measuring with the oscilloscope
at tp20. 
Seems like an awful lot of
loss or I'm detuning the
filter or
something with the test.

Re: Mini PA für my uBITX #ubitx

DC3MS
 

Thank you Brian.

The PA board is available on eBay from different sellers. The boards are also used in the MX-P50M. https://vk2qr.wordpress.com/2014/11/25/mx-p50m-hf-amplifier-review/
I added a tandem match from eb104.ru, 4 arduino relays for PTT and ATT (-6dB) and an optocoupler board for switching the LPFs.

The Nano is connected to the ubitx via i2c. I had to insert some lines to send the frequency and PTT info. A tight fit in Ians software, not much memory left.

I tend to forget to switch antennas when changing fom 40/80m to higher bands and blew up a few finals in the past, so the code in the amplifier demands a low power tune after band changes.

When transmitting and high SWR occurs, PTT is disabled.

ATT is enabled on 20-80m as my ubitx puts out more then 5W on These bands.

Will gladly share all details when interested,  

Re: Mini PA für my uBITX #ubitx

Art Olson
 

Mark

Great job. I would be interested in details also

Art
N2AJO

On Jan 12, 2019, at 7:10 AM, DC3MS <mark.schraven@...> wrote:

MX-P50M

Re: ND6T AGC Troubleshooting

DJ2AG
 

Hi Rich,

I‘m interested in your AGC controller. Is it possible to get the circuit diagram or some more infos?

kind regards 
Armin, DJ2AG

Re: Mini PA für my uBITX #ubitx

Brian Arnott
 

Many thanks, will look forward to any updates on the info


On Sat, 12 Jan 2019 at 12:29, Art Olson via Groups.Io <olsonaj6927=yahoo.com@groups.io> wrote:
Mark

Great job. I would be interested in details also

Art
N2AJO
> On Jan 12, 2019, at 7:10 AM, DC3MS <mark.schraven@...> wrote:
>
> MX-P50M



Re: Tracing receive signal for low signal

Dave Space
 

Thanks for all the info.  Ok trying to see if I got this. It does look like loading.

1x probe is 1.2k
10x probe is 8.9 Mohms

I checked the probe directly outputting 50mv verified 50mv through a .01uF blocking cap @ 11.996MHZ
I put the generator into tp17 and measured at tp17 and I would say less than 5mv p-p was being read from what I could tell.

I wasn't understanding if there is a way to now match this better or not?

Thanks

Re: Tracing receive signal for low signal

Dave Space
 

Forgot to mention I measured tp17 with the probe set at 10x as my oscilloscope can't measure into the megaherts range with a 1x probe setting I think.

Re: ND6T AGC Troubleshooting

WA6PXC Rich <sigma@...>
 

Hi Armin,
I developed this AGC because all of the others act on the audio signal.
When the signal is really large, the audio is already distorted so we
just control a distorted signal. Please see the Attachment.

To get an idea of how well this type of AGC will work on your radio,
remove R-12 and replace it with the FET as shown in the schematic,
with just the 10K resistor going to the gate.
Using a 10K pot, connect it across 5v and connect the wiper to the Gate resistor.
As you turn the pot, it will vary the RF gain.

Have fun...
Rich

-----Original Message-----
From: DJ2AG
Sent: Jan 12, 2019 5:42 AM
To: BITX20@groups.io
Subject: Re: [BITX20] ND6T AGC Troubleshooting

Hi Rich,

I‘m interested in your AGC controller. Is it possible to get the circuit diagram or some more infos?

kind regards 
Armin, DJ2AG

Re: Tracing receive signal for low signal

Bob Lunsford <nocrud222@...>
 

Use the 10K probe and take the onscreen o'scope readings and
compensate with the readings using a factor of 10... You can then
use the scope's vertical amplifier to bring the reading up to a viable
trace/reading and using the scale see what you have.

The "10X" probe means it is ten times less likely to load the circuit
being read which is what you really want. Some 'scopes also have
an instantaneous digital reading but those tend to be relatively
expensive.

The secret is to take readings with the same techniques at all
points and do the math to interpret the readings. Then you can
come up with useful data.

Bob — KK5R

--------------------------------------------

On Sat, 1/12/19, Dave Space <davesspacebar@...> wrote:

Subject: Re: [BITX20] Tracing receive signal for low signal
To: BITX20@groups.io
Date: Saturday, January 12, 2019, 11:17 AM

Thanks for all the
info.  Ok trying to see if I got this. It does look like
loading.

1x probe is
1.2k
10x probe is 8.9 Mohms

I checked the probe directly
outputting 50mv verified 50mv through a .01uF blocking cap @
11.996MHZ
I put the generator into tp17 and
measured at tp17 and I would say less than 5mv p-p was being
read from what I could tell.

I wasn't understanding if there is a way to
now match this better or not?

Thanks

Re: ND6T AGC Troubleshooting

Jerry Gaffke
 

Rich,

You are correct, it is better to have AGC reduce gain at RF or in one of the IF amps.
The audio pre-amp at Q70 of the uBitx (or Q16 of the Bitx40) is the weak link, 
restricting available dynamic range if AGC attenuation occurs after that audio pre-amp.

However, take another look at the ND6T AGC, it attenuates the RF as it comes in from the antenna.
Not unlike your design, but using FET's instead of op-amps.
Simple and effective.

Would be interesting to do an A/B comparison of your implementation vs the ND6T AGC.
Lots of variables here regarding dynamic range of the attenuation, attack and release times, distortion, ...

Jerry, KE7ER


On Sat, Jan 12, 2019 at 08:46 AM, WA6PXC Rich wrote:
Hi Armin,
I developed this AGC because all of the others act on the audio signal.
When the signal is really large, the audio is already distorted so we
just control a distorted signal. Please see the Attachment.
 
To get an idea of how well this type of AGC will work on your radio,
remove R-12 and replace it with the FET as shown in the schematic,
with just the 10K resistor going to the gate.
Using a 10K pot, connect it across 5v and connect the wiper to the Gate resistor.
As you turn the pot, it will vary the RF gain.
 
Have fun...
Rich

Re: Tracing receive signal for low signal

Bob Lunsford <nocrud222@...>
 

My previous comment requires an edit. Eliminate the first
paragraph and make the comment like this:

The "10X" probe means it is ten times less likely to load the circuit
being read which is what you really want. Some 'scopes also have
an instantaneous digital reading but those tend to be relatively
expensive.

The secret is to take readings with the same techniques at all
points and do the math to interpret the readings. Then you can
come up with useful data.

Bob — KK5R

--------------------------------------------

On Sat, 1/12/19, Bob Lunsford via Groups.Io <nocrud222=yahoo.com@groups.io> wrote:

Subject: Re: [BITX20] Tracing receive signal for low signal
To: BITX20@groups.io
Date: Saturday, January 12, 2019, 12:15 PM

Use the 10K probe and take the onscreen
o'scope readings and
compensate with the readings using a
factor of 10... You can then
use the scope's vertical amplifier to
bring the reading up to a viable
trace/reading and using the scale see
what you have.

The "10X" probe means it is ten times
less likely to load the circuit
being read which is what you really
want. Some 'scopes also have
an instantaneous digital reading but
those tend to be relatively
expensive.

The secret is to take readings with the
same techniques at all
points and do the math to interpret the
readings. Then you can
come up with useful data.

Bob — KK5R

--------------------------------------------
On Sat, 1/12/19, Dave Space <davesspacebar@...>
wrote:

Subject: Re: [BITX20] Tracing receive
signal for low signal
To: BITX20@groups.io
Date: Saturday, January 12, 2019,
11:17 AM

Thanks for all the
info.  Ok trying to see if I got
this. It does look like
loading.

1x probe is
1.2k
10x probe is 8.9 Mohms

I checked the probe directly
outputting 50mv verified 50mv through
a .01uF blocking cap @
11.996MHZ
I put the generator into tp17 and
measured at tp17 and I would say less
than 5mv p-p was being
read from what I could tell.

I wasn't understanding if there is a
way to
now match this better or not?

Thanks