Using a Wellbrook ALA1530LN on an RSP2

Useful information regarding antennas for SDR products.
Paul
Posts: 262
Joined: Fri Feb 17, 2017 9:52 am

Using a Wellbrook ALA1530LN on an RSP2

Postby Paul » Fri Apr 20, 2018 8:00 am

Currently, Port A is attached to an active mini-whip antenna that I believe provides really quite good reception from VLF through MF (at all times) and >7 Mhz (most times - haven't done much above 15Mhz at HF).
Port B is populated by three-way external switching to an H/V/UHF discone, an alternative active mini-whip (reasonable from 5 Mhz and up) and a hula-loop or an RF Systems EMF antenna (either with an atu).
The HI-Z is currently attached to an end-fed long wire and preforms well within the antenna's limitations.
May I ask advice or opinion on whether to start by attaching the ALA1530 to the A Port, taking advantage of the MW/FM filter and what is thought to be it's pretty reasonable performance, at least <5 Mhz and >7 Mhz with the antenna currently fitted or attaching it to the Hi-Z input.
I intend to mount it a couple of meters up and about 5 - 6 M from the nearest point of the house, using an existing run of RG-58, but no rotator yet - it may at least help to improve my fitness, going up and down stairs (all my kit's in an upstairs "shack"), in & out to change orientation.

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g1hbe
Posts: 368
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire, UK

Re: Using a Wellbrook ALA1530LN on an RSP2

Postby g1hbe » Fri Apr 20, 2018 9:51 am

Hi Paul

I use my Wellbrook 1530 withthe Hi-z port, as this port is more suited to LF/MF/HF use. It has lower noise, lower gain and better overload characteristics than the other two ports (at these frequencies). I keep the ports A & B for VHF. The one disadvantage of the Hi-z port is the lack of filtering - all it has is a 30 MHz LPF, so I found some pre-selection helped keep some unwanted signals out. I know I've posted this before, but here is the spectrum 0 to 200 KHz as received here. I had a LPF in line at the time to keep out the strong MW signals. You can see all the usual clock/time/frequency signals right down to 20 KHz, and the noise is low thanks to the 1530 loop.

lfsmall.jpg
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Andy

Paul
Posts: 262
Joined: Fri Feb 17, 2017 9:52 am

Re: Using a Wellbrook ALA1530LN on an RSP2

Postby Paul » Sat Apr 21, 2018 6:52 am

Thank you for the guidance Andy.
Just a question though - I had always believed that the MW/FM filters on the RSP2 only apply to Ports A & B.
However (an uneducated) look at this BSD seems to indicate that they are automatically applied to the HI-Z port.
I assume that I'm probably wrong...
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DaveB
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Re: Using a Wellbrook ALA1530LN on an RSP2

Postby DaveB » Sat Apr 21, 2018 8:16 pm

Paul - the two diagrams in you last attachment are for different RSPs. The left hand one is for an RSP/RSP1, the right hand one is for the RSP2.

There are no filters on the HiZ input - check out the document "Optimizing RSP1A performance below 60 MHz" on the SDRPlay web-site See the parargaph at the bottom of Page 7.

The output of the Wellbrook antenna should be matched to 50ohms - so you should be using port A, as you don't need bias-T.

The Hi-Z input is more suited to a long-wire antenna.

Out of interest I'm partway through constructing a shielded magnetic loop antenna for use with an early RSP. The filters in this version do not have very good stop band characteristics so I see lots of images from SW, but the one thing I can see, compared to a short dipole is a huge improvement in reception on the 80,40 and 20 m amateur bands.

Rgds

David

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Paul
Posts: 262
Joined: Fri Feb 17, 2017 9:52 am

Re: Using a Wellbrook ALA1530LN on an RSP2

Postby Paul » Sun Apr 22, 2018 7:05 am

Your loop project sounds really promising David; congratulations and thank you for your comments.
I was, of course, aware of the two different bsd's, but was only interested in the RSP2 flavour and was familiar with the stated filter arrangements, but failed to understand why a direct link from the filters in A?B to the Hi-Z was indicated by the linearrow-head, but then I'm no engineer, so I just accept what I'm told.
Best wishes
Paul

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