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Transmit attenuator

John G0SDF All Messages By This Member #33046 The transmit attenuator is working in that the amount of attenuation is able to be adjusted by the setting in the Menu. However at the 0dB attenuation setting I am getting -3dB. I have a 50 ohm load on RF_OUT (J6) on the RF Board. I am testing this on CW and the peak to peak signal (ignoring overshoot) going into the attenuator chip (U12) is 980mV but the peak to peak signal out is only 696mV. Has anyone else measured the performance of the transmit attenuator?
K9HZ All Messages By This Member #33048 开云体育 Need to calibrate it. ?Its not absolute.? 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@... ? toggle quoted message Show quoted text On Mar 10, 2025, at 7:38?AM, John G0SDF via groups.io <jatkins295@...> wrote: ? The transmit attenuator is working in that the amount of attenuation is able to be adjusted by the setting in the Menu. However at the 0dB attenuation setting I am getting -3dB. I have a 50 ohm load on RF_OUT (J6) on the RF Board. I am testing this on CW and the peak to peak signal (ignoring overshoot) going into the attenuator chip (U12) is 980mV but the peak to peak signal out is only 696mV. Has anyone else measured the performance of the transmit attenuator?
Oliver KI3P All Messages By This Member #33053 The insertion loss of the attenuator chip when set to 0dB is roughly 2dB below 20 MHz and increases at higher frequencies, so the loss you're seeing is expected. See this plot of the receive attenuator insertion loss vs frequency and attenuation setting -- the transmit path should be the same. On Monday, March 10th, 2025 at 10:38 AM, John G0SDF via groups.io <jatkins295@...> wrote: toggle quoted message Show quoted text The transmit attenuator is working in that the amount of attenuation is able to be adjusted by the setting in the Menu. However at the 0dB attenuation setting I am getting -3dB. I have a 50 ohm load on RF_OUT (J6) on the RF Board. I am testing this on CW and the peak to peak signal (ignoring overshoot) going into the attenuator chip (U12) is 980mV but the peak to peak signal out is only 696mV. Has anyone else measured the performance of the transmit attenuator?
K9HZ All Messages By This Member #33054 开云体育 So you probably want to characterize the gain (loss) from the antenna input on the LPF to TP6 of the RF board since we specifically put U2 in to overcome the loss from the BPF and the attenuator on the RF board…? That is the gain that you would calibrate out for the s-meter. ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of Oliver KI3P via groups.io Sent: Monday, March 10, 2025 6:22 PM To: [email protected] Subject: Re: [SoftwareControlledHamRadio] Transmit attenuator ? The insertion loss of the attenuator chip when set to 0dB is roughly 2dB below 20 MHz and increases at higher frequencies, so the loss you're seeing is expected. See this plot of the receive attenuator insertion loss vs frequency and attenuation setting -- the transmit path should be the same. ? ? On Monday, March 10th, 2025 at 10:38 AM, John G0SDF via groups.io <jatkins295@...> wrote: The transmit attenuator is working in that the amount of attenuation is able to be adjusted by the setting in the Menu. However at the 0dB attenuation setting I am getting -3dB. I have a 50 ohm load on RF_OUT (J6) on the RF Board. I am testing this on CW and the peak to peak signal (ignoring overshoot) going into the attenuator chip (U12) is 980mV but the peak to peak signal out is only 696mV. Has anyone else measured the performance of the transmit attenuator? ?

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