Need help with Wellbrook Loop & SDRplay/SDRuno

Useful information regarding antennas for SDR products.
bobcollege
Posts: 1
Joined: Thu Aug 04, 2016 3:03 pm

Need help with Wellbrook Loop & SDRplay/SDRuno

Postby bobcollege » Thu Aug 04, 2016 3:17 pm

I've had a Wellbrook loop for a week or so now but I think I have issues with it.

If I have it connected to the SDRplay directly I find it overloads the front end in Uno on most frequencies under 10MHz so I find myself having to use my Global ATU to reduce gain and tune in. I was under the impression that no tuner is required?

Can anyone offer assistance?

Thanks

Neil
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DanubeBCL
Posts: 125
Joined: Sat Jul 02, 2016 12:39 pm

Re: Need help with Wellbrook Loop & SDRplay/SDRuno

Postby DanubeBCL » Thu Aug 04, 2016 6:05 pm

Sorry to say this. But the simple two frontend filters 0 - 12 MHz and 12 - 30 MHz are not enough to unburden the Mirics tuner from strong signals. This is a matter of cost and effort. A Funcube pro+, which has more filter sections, also has problems to cope with strong outband signals.

And even mid and high cost receivers like a Winradio G31DDC or an Apache Labs Angelia (as in Anan 100D) which have no filters at all suffer from overload in the evenings (DDC blocking as well as IMD) when high level antennas are used (like active wideband loops). The owners of these dear rigs do not believe this, but I have them both and I know what I am speaking about. The use of additional filters (in case the attenuators are not solving the problem) is a must even with expensive rigs.

This no reason to blame the budget SDRPlay, even high priced receivers are not free from flaws. When reduction of tuner AGC amplification does not help I recommend either an external attenuator or a good old style preselector.

In my SDRPlay I have a DRM radio station from 11800 kHz "mirrored" several times on Medium waves (!) in the eveneings even when I only use a 50 cm rod which is not all a good antenna for a 50 Ohm input. But I do not complain. I know that I have not purchased a Rhode & Schwarz for 1000 times the price.

73, Heinrich
Last edited by DanubeBCL on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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borjam
Posts: 1
Joined: Wed Jun 22, 2016 7:46 am

Re: Need help with Wellbrook Loop & SDRplay/SDRuno

Postby borjam » Tue Feb 28, 2017 9:40 am

I know I'm replying to an old message, but this can be useful. I'm in no way affiliated to him, I'm just a satisfied customer. :)

Check out SV1AFN's products. He sells several useful building blocks such as a VHF FM blocking filter, a programmable stepper attenuator module (you can control it through SPI or, manually, using a microcontroller module) and several HF front-ends, among other useful stuff.

The prices are really low: Stepped 0-31 dB attenuator module for $19.00.
https://www.sv1afn.com/rfattenuator.html

A FM notch filter, ideal for urban areas:
https://www.sv1afn.com/band_reject_88_110_mhz.html

And this looks promising: A programmable preselector working from 190 KHz to 30 MHz, different bandwidth options, I2C control (trivial to control from an Arduino or a Raspberry Pi) and usable either as a band-pass or band-reject filter. It's not complete yet but I guess I'll order one when it becomes available! I guess it won't be so cheap but I'm sure it will be a huge improvement for affordable SDRs.
https://www.sv1afn.com/preselector-for-hf.html

He also has a simpler preselector for ham bands:
https://www.sv1afn.com/ham_band_presel.html
Last edited by borjam on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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dsalomon
Posts: 51
Joined: Sat Oct 10, 2015 1:50 pm

Re: Need help with Wellbrook Loop & SDRplay/SDRuno

Postby dsalomon » Tue Feb 28, 2017 11:02 am

I have the SV1AFN ham bands preselector and it works GREAT! SV1AFN makes very high quality kits and finished products. You can't go wrong with his stuff. I am not affiliated with him, just a happy customer. I've purchased numerous items from him over the years and have always been satisfied.

73 - David, AG4F

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dsalomon
Posts: 51
Joined: Sat Oct 10, 2015 1:50 pm

Re: Need help with Wellbrook Loop & SDRplay/SDRuno

Postby dsalomon » Tue Feb 28, 2017 11:04 am

One more note, the higher end preselector has been in the works on his website for several years. If you want a solution now, either go for the other one that's already available or some other solution.

Just my 2p worth.

73 - David, AG4F

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PG3
Posts: 29
Joined: Mon Nov 14, 2016 6:04 am

Re: Need help with Wellbrook Loop & SDRplay/SDRuno

Postby PG3 » Mon Mar 06, 2017 11:03 am

I've had extremely great results using a 1800KHz high pass filter between the antenna and the input of the RSP that attenuates the MW broadcast band by more than 40 dB. The advantage of this over a preselector is there is no need to constantly re-tune every time you change the receive frequency. When I want to chase MW broadcast band DX I replace the filter with a 20 dB attenuater. While many schematics and DIY projects for such a filter can be found, for those not wanting to DIY here is the one I settled on and highly recommend; http://www.cliftonlaboratories.com/z100 ... filter.htm

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