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Hear signals outside RX filter passband

ve2shf
Posts: 2
Joined: Tue Jul 13, 2021 2:35 pm

Hear signals outside RX filter passband

#1

Unread post by ve2shf »

I hear the intended signal clearly plus many other signals that are dozens of Khz away, well outside the passband of my receive filter.

I have a dipole, so most signals are not very strong or overwhelming.

Frequency: any
Mode: any, but effect more dramatic in SSB and CW

Do you know what I am doing wrong? I attached a small mp3 sample with no signal in receive passband so you can ear outside passband signals more easily.

My setup:

* SDR-Radio V3.0.28 64-bit (same issue with 3.0.26)
* SDRplay_RSP_API-Windows-3.07.2
* RSP1 and RSP1A (same issue with both)
Attachments
13-Jul-2021 145604.163 7.261MHz.wav.zip
(51.43 MiB) Downloaded 2 times

jdow
Posts: 389
Joined: Mon Aug 10, 2020 8:17 pm

Re: Hear signals outside RX filter passband

#2

Unread post by jdow »

That's nice. What are your settings? Where is the full size picture showing them? Without that helping you is a fool's game. With the limited data you've sent it sounds like classic front end overload due to front end gains set too high.
{^_^}

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Simon G4ELI
Posts: 1603
Joined: Thu Aug 06, 2020 7:27 am
Location: Mawnan Smith
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Re: Hear signals outside RX filter passband

#3

Unread post by Simon G4ELI »

jdow wrote:
Wed Jul 14, 2021 12:22 am
That's nice. What are your settings? Where is the full size picture showing them? Without that helping you is a fool's game. With the limited data you've sent it sounds like classic front end overload due to front end gains set too high.
{^_^}
Yes, please post a screenshot.
Simon Brown :shock:
www.sdr-radio.com

Do not send me direct e-mail, thank-you!

Max
Posts: 313
Joined: Thu Aug 13, 2020 9:47 am

Re: Hear signals outside RX filter passband

#4

Unread post by Max »

Screen shot would be very helpful and help us to help you with settings:

https://www.sdr-radio.com/screenshot

RSP series, especially the early ones (RSP1/2) are prone to front end overload due to very high gain as the chip used is a re-purposed UHF TV chip. With an even half decent antenna you will need to throttle back the RF gain right back, and maybe even use a attenuator.

To be honest I pretty much relegated my RSP to VHF/UHF duties only and for MF/HF I use my Hermes Lite 2 direct sampling SDR. The performance at those frequencies is far superior and totally devoid of spurii. Not surprising I guess given the different architecture. In this day and age if you are a serious LF/MF/HF listener I think direct sampling receiver is the only way to go. If you try it you will see. Maybe consider RX888 or similar?

However, to be totally fair to RSP receiver, my RSP2Pro did receive Grimeton VLF the other day when my direct sampling HL2 failed, but that's only because HL2 has LF roll off filter built in because it's mostly designed for HF amateur band use.

As you seem to be licensed I would seriously take a look at the Hermes Lite 2. Superb performance for small money!

http://www.hermeslite.com/

https://www.makerfabs.com/search.html?&search=hermes
(Sadly out of stock at mo due to chip shortages, but worth waiting!)

Max

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