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Re: Help me understand the USB (upper side band) mod
Gordon Gibby
¿ªÔÆÌåÓýMaybe just a little more clarification on that.
When you mix and take the sum, you don't change the side band.
When you mix and take the difference, you actually invert the side band.
The relationship between the BFO oscillator & the crystal filter passband forces which side band will be created (transmitter) ?or detected (receiver). ? Unless you can move the BFO freq you can't pick up both sidebands, no matter
how you turn the VFO dial. ?
Sent from my iPhone
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Re: Help me understand the USB (upper side band) mod
The crystal filter is just a gateway it doesn't carevwhat type of rf gets through...? We're simply choosing which half of an am signal to pass...? By moving the signal up or down the spectrum by changing the signal frequency. We can theoretically pass the carrier and a small portion of both sidebands by selecting the proper frequency on the dial
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Re: BITX40
Yeah you could try an external pull up resistor of 10-47K.
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Perhaps the internal pull up resistor is faulty. 73 Allard PE1NWL On Tue, November 28, 2017 17:07, Gert Krause wrote:
Hi Allard |
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Re: Help me understand the USB (upper side band) mod
Gordon Gibby
¿ªÔÆÌåÓýHmmm....? some confusion here.? ?
If double sideband looks like
..;;\\? //;;..
then upper sideband looks like //;;..? no matter whetehr it is made by a bitx, an iCOM or a Heahtkit......
In all cases, the lowest audio frequencies go with the lowest RF freequencies for Upper side band
In the bitx the BFO is above the crystal filter in frequency, so the filter passes the lower sideband;? ?subtracting it from a 19 MHz VFO inverts the spectrum and converts it back to upper sideband.? ?Two subtractions make an addition, so to speak.? ?
I had to walk through it with a couple of audio frequencies to convince myself.
And....from practical experiments, upper sideband coming out of my bitx is perfectly decoded by a 45 year old heathkit (in USB mode); and? lower sideband coming out of my bitx is also perfectly decoded by my 45 year old heathkit (in LSB mode)? The bitx40 allows for a lot of meditation on how all of this exactly works...... Useful to get us all thinking!
From: [email protected] <[email protected]> on behalf of David Arthur <mumrah@...>
Sent: Tuesday, November 28, 2017 12:44 PM To: [email protected] Subject: Re: [BITX20] Help me understand the USB (upper side band) mod ?
Richie, ok so I guess the passband crystal filter is symmetric in which case it doesn't care.
Gordon, so if the receiver is decoding in USB and receives a USB signal like "..::?" (as would come from the bitx) where the lower frequency audio in the vocal range ends up on the higher end of the signal, wouldn't this lead to some strange sounding audio? |
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Re: AD9850 Issue?
#w8tee
Perhaps, I'll have to check that.
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However, both my test sketch and the B40 sketch are using the same hardware and setting or attempting to set the same 5Mhz frequency on the AD9850.? With that set of data and circumstances, it would seem to point to something in the B40 sketch that is overwriting or somehow messing with the output frequency on the AD9850. I'm unfamiliar with the AD9850 and the?AD9850SPI library. I'll have to do some deeper investigation. Thanks, -Rob (N4MN)?? On Mon, Nov 27, 2017 at 08:03 pm, Mvs Sarma wrote:
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Re: Help me understand the USB (upper side band) mod
Richie, ok so I guess the passband crystal filter is symmetric in which case it doesn't care.
Gordon, so if the receiver is decoding in USB and receives a USB signal like "..::?" (as would come from the bitx) where the lower frequency audio in the vocal range ends up on the higher end of the signal, wouldn't this lead to some strange sounding audio? |
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Re: Help me understand the USB (upper side band) mod
Gordon Gibby
¿ªÔÆÌåÓý?typo:? meanto to say,
""the filter can't tell and doesn't care whether the spectrum going through it is upper or lower sideband"
From: [email protected] <[email protected]> on behalf of Gordon Gibby <ggibby@...>
Sent: Tuesday, November 28, 2017 12:35 PM To: [email protected] Subject: Re: [BITX20] Help me understand the USB (upper side band) mod ?
?the filter can tell and doesn't care whether the spectrum going through it is upper or lower sideband.....
What makes it upper or lower sideband is the relative relationships between the radio frequencies that resulted from low- or high-frequency audio waveforms.
In upper sideband, the higher audio frequencies cause higher RF frequencies.
In lower sideband, the reverse occurs.
The Receiver must provide the carrier back on the proper SIDE of the received spectrum in order to mix (demodoulae) to a recognizable voice signal.
Gordon
From: [email protected] <[email protected]> on behalf of Richie Chambless <rchambless7@...>
Sent: Tuesday, November 28, 2017 12:23 PM To: [email protected] Subject: Re: [BITX20] Help me understand the USB (upper side band) mod ?
Hey David,
I figured this out last year when I could never resolve SSB in any superhet that I built. I got a copy of EMRFD and it all came together. Here is my attempt at explaining it. First, the crystal filter should have a pass band that¡¯s only wide enough for one sideband (about 3,000 hertz). The BFO frequency positions you on the side band you want to hear. To be in the middle of the pass band, the two BFO frequencies must be 1,500 + - from the center of the filter, which is 3,000 from each other. I hope that helps. |
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Re: Help me understand the USB (upper side band) mod
Gordon Gibby
¿ªÔÆÌåÓý?the filter can tell and doesn't care whether the spectrum going through it is upper or lower sideband.....
What makes it upper or lower sideband is the relative relationships between the radio frequencies that resulted from low- or high-frequency audio waveforms.
In upper sideband, the higher audio frequencies cause higher RF frequencies.
In lower sideband, the reverse occurs.
The Receiver must provide the carrier back on the proper SIDE of the received spectrum in order to mix (demodoulae) to a recognizable voice signal.
Gordon
From: [email protected] <[email protected]> on behalf of Richie Chambless <rchambless7@...>
Sent: Tuesday, November 28, 2017 12:23 PM To: [email protected] Subject: Re: [BITX20] Help me understand the USB (upper side band) mod ?
Hey David,
I figured this out last year when I could never resolve SSB in any superhet that I built. I got a copy of EMRFD and it all came together. Here is my attempt at explaining it. First, the crystal filter should have a pass band that¡¯s only wide enough for one sideband (about 3,000 hertz). The BFO frequency positions you on the side band you want to hear. To be in the middle of the pass band, the two BFO frequencies must be 1,500 + - from the center of the filter, which is 3,000 from each other. I hope that helps. |
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Re: Help me understand the USB (upper side band) mod
Hey David,
I figured this out last year when I could never resolve SSB in any superhet that I built. I got a copy of EMRFD and it all came together. Here is my attempt at explaining it. First, the crystal filter should have a pass band that¡¯s only wide enough for one sideband (about 3,000 hertz). The BFO frequency positions you on the side band you want to hear. To be in the middle of the pass band, the two BFO frequencies must be 1,500 + - from the center of the filter, which is 3,000 from each other. I hope that helps. |
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Help me understand the USB (upper side band) mod
So, as I understand it, a SSB signal is where half of an AM signal and the carrier are suppressed. For illustrative purposes, I'll draw a full AM signal like ..::||::.., where || is the carrier and the dots are the upper and lower parts of the signal envelope.?
Ok, so a normal LSB signal should look like "..:: " and USB should look like " ::..". The USB mod for the Raduino appears to simply change the output frequency be 1500 hz lower. So really, we're transmitting a LSB signal at an offset, which means instead of " ::.." we get "..:: " in the air. Wouldn't this cause problems on the receivers end? I'm assuming their RX filtering would be expecting most of the signal near the carrier, not on the other end.? For a "true" USB mode, would we need a different filter circuit to suppress the lower side band? I'm still pretty new to this and learning more everyday, please spare no detail in any explanation :) -David |
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Re: Just want a USB switch
Gordon Gibby
¿ªÔÆÌåÓý?Getting it to do upper side band isn't that terribly difficult, a small mod or two in the raduino sketch will do it ---- but it is just as easy to upload one of Allards' sketches and then it handles the calibration much better and everything else.? ?
I am kinda using his 1.24 sketch and happily modifying that for my purposes.? ?
From: [email protected] <[email protected]> on behalf of tausciam@... <tausciam@...>
Sent: Tuesday, November 28, 2017 10:30 AM To: [email protected] Subject: Re: [BITX20] Just want a USB switch ?
Yes. She's 9. We just want a pushbutton to switch from LSB to USB and back again.
So, that's what I'd like to figure out how to do. I've got a heatsink for the final and removed C91 and c92 |
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Re: First real try at 80 meters using QRPKITS 80M low pass filter
chris gress
That heatsink only 1cm thick but works OK I like to look after the pa I waiting on a kit from EA3GCY called ILER-17+ dds? Going to put it on 15,12,10m its my new winter project chris On 28 Nov 2017 14:40, "chris gress" <Chrisg0wfh@...> wrote:
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Re: Just want a USB switch
No but,
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If you want any of the features that Allards sketch provides then go for it. You could add some components to the BFO and have USB. Raj At 28-11-2017, you wrote:
Do I really have to use Allard's sketch for this one single mod? I just want a switch to go from LSB to USB. |
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Re: First real try at 80 meters using QRPKITS 80M low pass filter
chris gress
Yep feel free I have built 3 sets all the same looking I had the dds programmed for me so no credit for them. Chris On 28 Nov 2017 14:36, "chris gress" <chrisg0wfh@...> wrote:
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Re: First real try at 80 meters using QRPKITS 80M low pass filter
Gordon Gibby
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From: [email protected] <[email protected]> on behalf of chris gress <Chrisg0wfh@...>
Sent: Tuesday, November 28, 2017 9:36 AM To: [email protected] Subject: Re: [BITX20] First real try at 80 meters using QRPKITS 80M low pass filter ?
Cool it worked I upgraded my heatsinks on my pa,s I have added photo the pa never gets hot?
On 28 Nov 2017 14:23, "chris gress" <Chrisg0wfh@...> wrote:
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Allard PE1NWL
Rob Cox (N4MN)
Arvo W0VRA
Raj vu2zap