RSP2 - A bit confused with connecting antennas

Useful information regarding antennas for SDR products.
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espenfjo
Posts: 6
Joined: Fri Dec 28, 2018 7:48 pm

RSP2 - A bit confused with connecting antennas

Post by espenfjo » Thu Jan 03, 2019 7:45 pm

Hi,
I am a bit confused with connecting antennas to my RSP2 for HF/MW usage.

I have tried to build a coax dipole using RG58, each element being around 10meters. It should be similar to this design, using about 13-18m of rg8 as a feed line.Image

Reading the "RSP2 – Guide to using the High Z Port" leaves me with more questions than answers. Initially I would have thought that I should connect the braid to GND and N, and the center connector to P. This gives me (almost) no signal, and a noise floor below -140dBm. Removing the braid from GND/N gives me some signal, and a noise floor around -100dBm. This is stable enough to receive 80m FT8 signals from around 1500-2000 KM around me (Most of wester Europe as Im situated in southern Norway). This is however worse SNR and fewer signals than what I get with a 1.5m antenna (the one to the left). Image

This has left me a bit bummed, as I would have expected the dipole to outperform the antenna whip by far. I've also tried disconnecting the dipole, and just leaving the feed line, it makes more or less little difference.

Since I do not have a BALUN/UNUN (Its somewhere in the mail), or any toroids, should I try and connecting it to ANT A instead?
Last edited by espenfjo on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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Spider
Posts: 6
Joined: Sun Jul 02, 2017 4:40 am

Re: RSP2 - A bit confused with connecting antennas

Post by Spider » Fri Jan 04, 2019 2:06 am

Dear espenfjo, I would suggest the the rg58 feedline be attached to Input A. The HiZ input is just that. Input A expects to see a low (50ohm) feed. Regards, spider vk2tti.
Last edited by Spider on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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Mike2459
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Joined: Mon Jul 24, 2017 8:24 pm

Re: RSP2 - A bit confused with connecting antennas

Post by Mike2459 » Fri Jan 04, 2019 6:22 am

You can use the A input.The A & B antenna ports are both 50Ω inputs. You will get better performance on the Hi-Z port with a balun (4:1 turns ratio) to match 50Ω to the 1000Ω impedance at the Hi-Z port. My balun is connected to P & N with nothing on the G terminal.

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ON5HB
Posts: 140
Joined: Sat Dec 29, 2018 1:07 pm

Re: RSP2 - A bit confused with connecting antennas

Post by ON5HB » Sat Feb 02, 2019 7:46 pm

If you have a bit of room, the most simple and perfect working LF/HF/VHF(50MHz) antenna is the G5RV.
You do not need to do anything special, just have about 33m of space between 2 trees and a bit of coax.
Because of the matching section it will perform incredibly well on most band up to 50MHz, most of the time even higher.

To transmit with it you need a tuner, but for reception nothing special is required and you can connect it with coax to the 50 Ohm input.

If you want to see how good it really is, checkout hackgreen's websdr, they do use the long version but the normal one performs the same.

This antenna outperforms anything except single-band dipoles, but it's on par with most, not for nothing the most used antenna in the world being fed with coax.

Fun part is, it costs near to nothing to build :lol:

More info here: https://www.electronics-notes.com/artic ... a/g5rv.php

If you do not have lots of space, I suggest an End-Fed antenna, that works great too if you are limited on space, little more difficult to build because of a balun.

Both of these will outperform anything you tried so far, and with far I mean really far :D

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Paul
Posts: 355
Joined: Fri Feb 17, 2017 9:52 am
Location: SW UK

Re: RSP2 - A bit confused with connecting antennas

Post by Paul » Mon Feb 04, 2019 6:42 am

Dipole_fig4-257x300.jpg
Dipole_fig4-257x300.jpg (18.71 KiB) Viewed 3056 times
As a complete know-nothing, I hesitated too get involved. However, since I also have experienced issues with connecting to the Hi-Z port of an RSP2 (not replicated on myRSPDUO using the same antennae and connections) may I make thefollowing comments:
If your diplole construction includes a feeder cable arrangement such as that shown in the attachment to this message, then your basic connection as described by you is correct, conforming to SDRPlay's instructions (they do show an earth/ground connection to "shack" earth also).
On the RSP2, I defaulted to using the 50 ohm A port, as Mike commmented (which may or may not suit your interests/wishes) until I sorted out my personal difficulty.
It is not for me to comment on the desirability of including an impedence matching arrangement, but if your problem persists, then I wouldn't hesitate to raise a support ticket, as the support team is increibly responsive and helpful.
Dipole_fig4-257x300.jpg
Dipole_fig4-257x300.jpg (18.71 KiB) Viewed 3056 times

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