Problem on RX on all bands (5V on RX pin)?

Post Reply
erossi
 

Posts: 6
Joined: 22 Oct 2022, 10:04

Problem on RX on all bands (5V on RX pin)?

Post by erossi »

Hi,

First of all I'd like to congratulate for this project. I have assembled one but unfortunately I have a problems on the RX, I can only hear noise on all bands. Following various posts in the forum I send a signal on 80mt with a nanoVNA in the antenna, I can follow it trough the relay and the filter but after it I see 5V in the RF pin.
If I detach the main board and send the signal in it, I do not have the 5V on the RF pin and I can hear the tone. Is this 5V presence on RF pin ok?
TX seems to work nonetheless.

Thanks for any help.
73 de IU4JRU Enrico
dl6sez
 

Posts: 399
Joined: 30 Dec 2021, 22:54

Re: Problem on RX on all bands (5V on RX pin)?

Post by dl6sez »

Hello OM,

yes at the RF pin, the 5V are there but also your very small RF signal....
I don't know if you maybe have a soldering problem at dds Si5351 or LT6231 op amp.
Have a look at those ICs with magnifier glasses and reflow the pins if necessary.

Hope you will find the reason why it doesn't receive :)

73 de Chris
Chris DL6SEZ, JN48XL near Ulm, Southern Germany
erossi
 

Posts: 6
Joined: 22 Oct 2022, 10:04

Re: Problem on RX on all bands (5V on RX pin)?

Post by erossi »

Thanks Chris for the answer,

I'm sending 3560 KHz signal from the nanoVNA and I'm tuned to the same frequency (60mV PeP).
I have followed the RF signal to the Q1 when it becomes the RX and enter in the pin9 of the U6. The CLK0 and CLK1 of the U6 are a square wave at 3560Khz.
Now on the pin10, 11, 12, 13 of U6 I can see a 2V DC on top of which I can read a (little noisy) frequency of 271Hz, it looks the diff between the NanoVNA freq and the tuned one, changing the NanoVNA freq change this diff accordingly.
Till now no change in the PeP signal amplitude.
These 4 signals enters in the U9(A/B) and from there I can see on the pin1 and 7 a signal amplified at ~ 300mV PeP freq. the same 271Hz but like a square wave with the top part as a sawtooth-shaped wave.
From here the signal enters in the C22 and C29 where it get reversed with no change in the shape and enters in the microcontroller.

Sorry for the long post, I hope I've been clear enough and thanks for any help.
73 Enrico
73 de IU4JRU Enrico
Post Reply

Users browsing this forum: No registered users and 0 guests