Faster AGC recovery is possible?

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EA2KV
Posts: 2
Joined: Wed Nov 28, 2018 1:49 pm

Faster AGC recovery is possible?

Postby EA2KV » Tue Dec 04, 2018 12:07 pm

HI, this is José (EA2KV), new on the Community. Greetings from Spain.

Im using a SDRplay RSP2pro as RX, TX is my HF rig + ELAD TX/RX switch box.

I would like to understand how I can make the reception to recover faster from TX, main concern is during contest, when the RX is back I already mised the call sign prefix.

Current setup:
-Automatic mute: ON.
-AGC: Fast
-Rest of other default AGC configurations remains as standard setup on the menus.
-Normal RX signal during my my transmision is 9+60dB.

Thanks in advance for your advices.
José
Last edited by EA2KV on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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Mike2459
Posts: 123
Joined: Mon Jul 24, 2017 8:24 pm

Re: Faster AGC recovery is possible?

Postby Mike2459 » Tue Dec 04, 2018 1:07 pm

It is likely the delay is caused by the inherent latency of SDRs. There is a discussion of this at QRZ at this link: https://forums.qrz.com/index.php?thread ... ys.500423/

It should be fairly easy to measure the delays by making a simultaneous recording of the output of an SDR on one stereo channel and the output of a 'real' radio on the other stereo channel, when tuned to the same signal. Audacity could be used to measure the delay time. By real radio, I am referring to one that doesn't do any digital signal processing.

73's, Mike

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Roger
Posts: 169
Joined: Fri Dec 29, 2017 7:59 pm

Re: Faster AGC recovery is possible?

Postby Roger » Tue Dec 04, 2018 5:31 pm

I have measured the audio latency and it is 300 to 450 milliseconds (varies depending on computer/USB performance). Even without the AGC response delay this is not suitable for contests. The best idea for a contest is to use an RF splitter in your SDR switch and receive your audio on the transceiver with the RSP functioning only as a tracking panadapter.

If your receive level during transmit is S9+60 dB you might look at ways to lower the level into the RSP during transmit. Better cable shielding and using a relay to short the RSP input during transmit. The latest MFJ switch (the "B" model) uses a separate relay to short the input. Make sure you use a quality USB cable with Mix 31 ferrites to reduce signal pickup.

Roger

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EA2KV
Posts: 2
Joined: Wed Nov 28, 2018 1:49 pm

Re: Faster AGC recovery is possible?

Postby EA2KV » Wed Dec 05, 2018 11:14 am

Mike and Roger,
Tks so much for the comments.
Will keep working on these directions.
Tks. José.
Last edited by EA2KV on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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