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Hi guys, I've been using my Bit40 for a decent number of months off and on. ?When I calibrated LSB I pretty much just listened to a QSO and adjusted to offset until I thought the people in the QSO sounded correct. ?I'm sure I'm calibrated close but not right on. ?The only thing that I have that can be used as a signal generator is my RigExpert AA-170 analyzer. ?According to the instructions I guess all I have to do is select the frequency on the AA-170 and put it in the SWR mode and it will emit the frequency. Is it possibly for me to connect the antenna jack on the AA-170 directly into the Bitx40 without wiping out the front end on the Bitx40 or is this not a proper method for calibrating LSB? ?I did install the protection diodes. Here is what the manual for the RigExpert antenna analyzer says about using it as a signal generator:
5.4. RF signal generator
The output signal of the AA-170 has rectangular waveform and level of about -10 dBm (at the 50 Ohm load). Therefore this analyzer can be used as a source of RF signal for various purposes.
For frequencies up to 30 MHz, first harmonic of output signal can be used; in the range of 30 to 100 MHz ¨C third harmonic; in the range of 100 to 170 MHz ¨C fifth harmonic.
Enter the SWR mode or the Show all mode, press ok to start, then press the 2 key to generate an uninterrupted RF signal.?
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On Thu, Sep 28, 2017 at 01:07 pm, Curt M. wrote:
Hi guys, I've been using my Bit40 for a decent number of months off and on. ?When I calibrated LSB I pretty much just listened to a QSO and adjusted to offset until I thought the people in the QSO sounded correct. ?I'm sure I'm calibrated close but not right on. ?The only thing that I have that can be used as a signal generator is my RigExpert AA-170 analyzer. ?According to the instructions I guess all I have to do is select the frequency on the AA-170 and put it in the SWR mode and it will emit the frequency.
Is it possibly for me to connect the antenna jack on the AA-170 directly into the Bitx40 without wiping out the front end on the Bitx40 or is this not a proper method for calibrating LSB? ?I did install the protection diodes.
Here is what the manual for the RigExpert antenna analyzer says about using it as a signal generator:
5.4. RF signal generator
The output signal of the AA-170 has rectangular waveform and level of about -10 dBm (at the 50 Ohm load). Therefore this analyzer can be used as a source of RF signal for various purposes.
For frequencies up to 30 MHz, first harmonic of output signal can be used; in the range of 30 to 100 MHz ¨C third harmonic; in the range of 100 to 170 MHz ¨C fifth harmonic.
Enter the SWR mode or the Show all mode, press ok to start, then press the 2 key to generate an uninterrupted RF signal.?
?-10dBm is 71mV and 0.1mW (100uW) S9 is 50uV or -13dBm (using the MiniCircuits PDF) so I don't think it will be an issue. I typically (because of the late hours I get to work on the radio) hookup the radio into the line-in of a computer and use the fldigi waterfall at audio level to ensure that the signal is zerobeat rather than <100Hz.
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S9 is 50uV or -73dBm ?(not -13dBm) Your signal generator at -10dBm or 71mV ?rms would be an extremely strong radio signal for the receiver, but would have to be more like 500mV rms to endanger the Vbe junction of the 2n3904 at Q13. So your radio would be badly overloaded by -10 dBm but should survive. If you want the signal generator to feed an S9 signal into your radio,? you need to cut that 71mV signal down to 0.050mV, so a ration of 71/0.050 = 1420 I'd suggest coax from signal generator to an attenuator consisting of 50 ohms to ground followed? by a series combination of a 1420*50/2 = 35.5k resistor plus a 50 ohm resistor to ground, feed the receiver from across that second 50 ohm resistor. The divide-by-two is there because the 50 ohm receiver and the 50 ohm second resistor of the attenuator in parallel present a 25 ohm load. Here's a thread on adding front end protection for Q13 to your Bitx40 if you plan to have it hooked up to an antenna? that is near some other antenna that happens to have a high power transmitter on it: ? ?? /g/BITX20/message/30600Here's a good start on the math around the S-meter: ? and on what a dBm is: ?
On Thu, Sep 28, 2017 at 11:27 pm, Jacob Farnes wrote:
?-10dBm is 71mV and 0.1mW (100uW)
S9 is 50uV or -13dBm (using the MiniCircuits PDF) so I don't think it will be an issue. I typically (because of the late hours I get to work on the radio) hookup the radio into the line-in of a computer and use the fldigi waterfall at audio level to ensure that the signal is zerobeat rather than <100Hz.
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I was glad to see that the source Jerry quoted for the S-meter correctly pointed out that it derives from the IF, not audio, chain. Using the audio chain (e.g., running from the LM386) is still very useful, but is more along the lines of a VU meter rather than an S-meter.
Jack, W8TEE
From: Jerry Gaffke via Groups.Io <jgaffke@...>
To: [email protected]
Sent: Friday, September 29, 2017 5:51 AM
Subject: Re: [BITX20] Zero Beating Bitx40
S9 is 50uV or -73dBm ?(not -13dBm) Your signal generator at -10dBm or 71mV ?rms would be an extremely strong radio signal for the receiver, but would have to be more like 500mV rms to endanger the Vbe junction of the 2n3904 at Q13. So your radio would be badly overloaded by -10 dBm but should survive. If you want the signal generator to feed an S9 signal into your radio,? you need to cut that 71mV signal down to 0.050mV, so a ration of 71/0.050 = 1420 I'd suggest coax from signal generator to an attenuator consisting of 50 ohms to ground followed? by a series combination of a 1420*50/2 = 35.5k resistor plus a 50 ohm resistor to ground, feed the receiver from across that second 50 ohm resistor. The divide-by-two is there because the 50 ohm receiver and the 50 ohm second resistor of the attenuator in parallel present a 25 ohm load. Here's a thread on adding front end protection for Q13 to your Bitx40 if you plan to have it hooked up to an antenna? that is near some other antenna that happens to have a high power transmitter on it: ? ?? /g/BITX20/message/30600Here's a good start on the math around the S-meter: ? and on what a dBm is: ? On Thu, Sep 28, 2017 at 11:27 pm, Jacob Farnes wrote:
?-10dBm is 71mV and 0.1mW (100uW)
S9 is 50uV or -13dBm (using the MiniCircuits PDF) so I don't think it will be an issue. I typically (because of the late hours I get to work on the radio) hookup the radio into the line-in of a computer and use the fldigi waterfall at audio level to ensure that the signal is zerobeat rather than <100Hz.
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Curt,
Out of interest:-
what do RigExpert claim to their frequency calibration accuracy?
(I don't think it's going to be any
better than perhaps you have already achieved, and is one more
variable to maybe cause more confusion.)
If you have a digital rather
than the analogue VFO variant, could you not temporary jumper
across the BiTX input BPF and see if you can receive one of the
off air frequency standard transmissions.? Costs nothing more than a piece of wire and
a few minutes?
Or zero beat a commercial broadcast station having made sure it
not an image product.
Find one in 41 Metre band and chances are you will not need to
jumper the BPF.
Alan
On 28/09/2017 21:07, Curt M. wrote:
toggle quoted message
Show quoted text
Hi guys, I've been
using my Bit40 for a decent number of months off and on. ?When I
calibrated LSB I pretty much just listened to a QSO and adjusted
to offset until I thought the people in the QSO sounded correct.
?I'm sure I'm calibrated close but not right on. ?The only thing
that I have that can be used as a signal generator is my RigExpert
AA-170 analyzer. ?According to the instructions I guess all I have
to do is select the frequency on the AA-170 and put it in the SWR
mode and it will emit the frequency.
Is it possibly for me to connect the antenna jack on the AA-170
directly into the Bitx40 without wiping out the front end on the
Bitx40 or is this not a proper method for calibrating LSB? ?I did
install the protection diodes.
Here is what the manual for the RigExpert antenna analyzer says
about using it as a signal generator:
5.4. RF
signal generator
The output signal of the AA-170 has
rectangular waveform and level of about -10 dBm (at the
50 Ohm load). Therefore this analyzer can be used as a
source of RF signal for various purposes.
For frequencies up to 30 MHz, first harmonic
of output signal can be used; in the range of 30 to 100
MHz ¨C third harmonic; in the range of 100 to 170 MHz ¨C
fifth harmonic.
Enter the SWR
mode or the Show all mode,
press ok to
start, then press the 2
key to generate an uninterrupted RF signal.?
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If you calibrate from a broadcast station on the air, it must be a station near the desired operatng frequency.
The calibrate scheme must deal with a fixed additive error in the BFO
plus any error in the VFO from the si5351 that is proporional to the error in the 25mhz reference oscillator.
The compromise made in V1 firmware is o assume it is all additive.
Only once Allard comes out with V2 firmware with the BFO driven from the si5351's CLK0
will it be advisable to calibrate from something out of band, such as WWV.
The 41m broadcast stations are usually accurate enough, and usually on even 5khz increments.
toggle quoted message
Show quoted text
On Fri, Sep 29, 2017 at 06:11 am, Alan de G1FXB wrote:
If you have a digital rather than the analogue VFO variant, could you not temporary jumper across the BiTX input BPF and see if you can receive one of the off air frequency standard transmissions.? Costs nothing more than a piece of wire and a few minutes?
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If audio derived S-Meter readings are inherently incorrect, then Jerry was just lucky. I'm assuming they are made before any gain control or AGC action. The problem with the S-Meter schemes proposed here thus far is they all give a linear response, whereas it should be logarithmic, and that they use a diode detector incapable of seeing low level signals. ?Another problem that goes beyond just S-Meter readings is that the audio pre-amp at Q16 does not give us much dynamic range, as pointed out by Henning:? ? ?? /g/BITX20/topic/5945215? Of course, "accurate" S-Meter readings don't mean much to the guy at the far end unless you can fully describe the efficiency and pattern of your antenna system. The S-meter will only tell how much signal is reaching your receiver. Jerry
On Fri, Sep 29, 2017 at 05:26 am, Jack Purdum wrote:
I was glad to see that the source Jerry quoted for the S-meter correctly pointed out that it derives from the IF, not audio, chain. Using the audio chain (e.g., running from the LM386) is still very useful, but is more along the lines of a VU meter rather than an S-meter.
?
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I had trouble detecting an exact zero beat by ear.
My solution to generate a signal with a known accurate
source (my "big" rig) and set the BITX40 to 1 kHz away
from that frequency. I then used a frequency counter
app on my phone to calibrate it for exactly a 1 kHz tone.
--
73 Keith VE7GDH
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Jerry,
True.
Just pointing out that the RigExpert was perhaps a poor choice as
a frequency reference, and with no to a little effort there are
choices.
With a bit more effort, still
with a stock BiTX before V2 arrives.
Plenty sketches out there that lock a Si5351 to GPS 1PPS, that's
accurate enough for WSPR which has the tightest requirements to
frequency accuracy of the current digital modes?
Gene Marcus to name but one, if anyone
wants pointers for code.
Alan
On 29/09/2017 16:10, Jerry Gaffke via
Groups.Io wrote:
toggle quoted message
Show quoted text
If you calibrate
from a broadcast station on the air, it must be a station near the
desired operatng frequency.
The calibrate scheme must deal with a fixed additive error in the
BFO
plus any error in the VFO from the si5351 that is proporional to
the error in the 25mhz reference oscillator.
The compromise made in V1 firmware is o assume it is all additive.
Only once Allard comes out with V2 firmware with the BFO driven
from the si5351's CLK0
will it be advisable to calibrate from something out of band, such
as WWV.
The 41m broadcast stations are usually accurate enough, and
usually on even 5khz increments.
On Fri, Sep 29, 2017 at 06:11 am, Alan de G1FXB wrote:
If you have a digital rather than the
analogue VFO variant, could you not temporary jumper across
the BiTX input BPF and see if you can receive one of the off
air frequency standard transmissions.? Costs
nothing more than a piece of wire and a few minutes?
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El 29/09/17 a las 11:10, Jerry Gaffke via Groups.Io escribi¨®: The 41m broadcast stations are usually accurate enough, and usually on even 5khz increments. Hi, I have used Broadcasting signals in the 41m band for fast calibration since a few years ago, they prove to be almost within a few Hz (<5 Hz) of the stated frequency when you test it against WWV on 2.5, 5 or 10Mhz. (Just use Big ones) My favorite is Radio Catholic Mondiale on 7.315 in the afternoon - night period (at least in the Carribean/Americas) they are zero beat with almost 0Hz error as per my measures against WWV in 2.5/5/10 Mhz. My method: Fldigi feed with the audio of the SSB RX (an auxiliary receiver, I use my veteran FT-757-GX ), I place the dial as I get the carrier at 1khz on the audio spectrum for example: WWV in 10.000000 Mhz If LSB tune to 10.001000 Mhz if USB tune to? 9.999000 Mhz Then use your VFO to generate 10.000000 Mhz (use it as a signal generator not as a receiver) and feed a sample of RF to the receiver "et viola" you will find a carrier near (or not) the carrier of the WWV... Tune your hardware/software settings in a way that your 10.0000 Mhz test signal get superimposed in the WWV carrier (use waterfall zoom to get more accuracy) Needless to say that you must make this calibration test with both receivers warmed up for at least 30 min before the test to allow settling of the thermal drift on both. This is the way a calibrate the aging XTL oscillators and freq accuracy for some old/ancient ham gears when repairing. [By checking the soundcard accuracy and then testing other freqs against that over the auxiliary/test receiver] Please note that the audio card has it's own XTAL and may have a error, so 1.0khz in your waterfall may be off by a few hz (I had a old PCI audio card that was almost a 300 Hz off, my Desktop PC has +50 Hz or so and my Lenovo Laptop has -20 Hz or so) So the best results are using a auxiliary receiver to receive a very accurate signal (WWV) and no matter where in the waterfall this signal is, if you match that signal for the same generated freq you will be right on spot, and no matter what is the soundcard xtal/PC error) But for ham radio purposes just beating a broadcasting by ear will put you withing 100Hz or so of the target freq, even 50 Hz or so for the trained ear... ;-) 73 CO7WT Pavel.
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Go figure I would misread that. Thanks.
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Hi guys, I¡¯ve been tied up for a few days and just been able to revisit my original post.
I have a 50 ohm 20db attenuator. If I run my RigExpert analyzer into the attenuator and then the attenuator into the Bitx40, does this get me in an acceptable range to try and calibrate LSB or will the signal still be too high?
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Your signal generator is -10dBm, and an S9 signal is -73dBm.
So to make it so the signal generator sounds like an S9 signal you need 63dB of attenuation.
Stacking 3 of those 20dB attenuators would work.
Alternately, I suggest you set the signal generator down on the far side of the room, have it drive a
couple feet of copper wire connected to the center pin of that BNC.
Put a couple feet of wire on your Bitx40's antenna jack too.
Tune the Bitx40 to receive the signal generator, then reduce the length of those
wires till it sounds like a good amateur band signal.
?
toggle quoted message
Show quoted text
On Sun, Oct 1, 2017 at 07:42 pm, Curt M. wrote:
I have a 50 ohm 20db attenuator. If I run my RigExpert analyzer into the attenuator and then the attenuator into the Bitx40, does this get me in an acceptable range to try and calibrate LSB or will the signal still be too high?
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Hi with a little patience you can easily make your own step attenuators. The one in the first link can attenuate signals up to 80dBs
The one in the second link one can attenuate signals up to 71dBs With these attenuators you can attenuate the signal in steps of 1dB. You can also use such an attenuator at the Input of the RECEIVER to reduce a signal that is overloading your receiver but NOT at the output of the TRANSMITTER because you will burn it as the resistors can only only 250 milliwatts maximum. Have a look at these links.
Regards Lawrence
On Mon, Oct 2, 2017 at 6:10 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote: Your signal generator is -10dBm, and an S9 signal is -73dBm.
So to make it so the signal generator sounds like an S9 signal you need 63dB of attenuation.
Stacking 3 of those 20dB attenuators would work.
Alternately, I suggest you set the signal generator down on the far side of the room, have it drive a
couple feet of copper wire connected to the center pin of that BNC.
Put a couple feet of wire on your Bitx40's antenna jack too.
Tune the Bitx40 to receive the signal generator, then reduce the length of those
wires till it sounds like a good amateur band signal.
?
On Sun, Oct 1, 2017 at 07:42 pm, Curt M. wrote:
I have a 50 ohm 20db attenuator. If I run my RigExpert analyzer into the attenuator and then the attenuator into the Bitx40, does this get me in an acceptable range to try and calibrate LSB or will the signal still be too high?
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Similar to what Jerry suggested I connected my KX3 to 50 ohm dummy load that I had built into an Altoids box. I opened the box to let a bit of RF leak and connected a jumper wire to the BIX40 antenna center. Between the wire position and the KX3 output I could get any level signal I wanted.
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Ok, I¡¯ll give these suggestions a try and see what happens. Thanks!
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Alan de G1FXB
Bob Benedict, KD8CGH