Re: uBITX - A reboot of the old BITX
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Jerry, I am pretty sure the component values used by Ashhar for the transmit filters agree with this article as I used to ELSIE program to display the frequency response using the values listed on the Microbitx schematic.? The resulting plot agreed exactly with the desired low pass response of 7 Mhz with a notch at 10.5Mhz and the other filter of a low pass response of 28 Mhz with a notch at 42 Mhz. ??I believe Ashhar picked the values as a compromise to allow a filter to be used for multiple bands, versus the values used in the article which were picked for single band harmonic suppression. ? Now I need to figure out how to use the ELSIE program to calculate the desired component values from scratch as Ashhar did J ? 73, Dale? K9NN ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Sunday, March 05, 2017 7:25 PM
To: [email protected]
Subject: Re: [BITX20] uBITX - A reboot of the old BITX ? That QST article suggests the return loss might not be acceptable across more than one band. ?The topology agrees but Ashhar's values differ significantly from those recommended, might be something more going on here. On Sun, Mar 5, 2017 at 03:45 pm, dvhammer_99 wrote: I believe the two lowpass/notch filters used by Ashhar in the transmitter output are based on the the W3NQN filter design described in the article. “Second-Harmonic Optimized Low-Pass Filters”.? The article is available at:
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