THIS THREAD EXPLAINS WHY IT IS SO DIFFICULT TO UNDERSTAND RECEIVER'S SENSITIVITY IN LF & RELATED MATTERS

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glovisol
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Re: THIS THREAD EXPLAINS WHY IT IS SO DIFFICULT TO UNDERSTAND RECEIVER'S SENSITIVITY IN LF & RELATED MATTERS

Postby glovisol » Sun Jan 13, 2019 12:48 pm

THE RSP-1A on LONG WAVE

- RECEIVER.......................................RSP-1A.
- ANTENNA.......................................135m Beverage.
- IF MODE.........................................Low IF.
- FEED.............................................550 to 50 Ohm Isolation transformer / primary inductance: 3.8 mH.
- ATTENUATOR..................................5 dB type "H", 550/550 Ohm between antenna & Isolation transformer.
- PC................................................IBM X61 laptop with battery supply.


BBC Radio 4 on 198 KHz @ 12:00 GMT / 13/01/19
Attachments
BBC Radio 4-1200GMT.jpg
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ON5HB
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Location: Heppen - Belgium
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Re: THIS THREAD EXPLAINS WHY IT IS SO DIFFICULT TO UNDERSTAND RECEIVER'S SENSITIVITY IN LF & RELATED MATTERS

Postby ON5HB » Sun Jan 13, 2019 3:00 pm

Hi there,

I had this problem too in the past, the main issue is the low frequency and major signals close together.
That is where mixing starts, the I/Q can't be separated well, it simply can't work out a good signal from a bad one.

Baluns and other stuff do not help, tried everything including ordering attenuators a big as -30 and combined got to 60dB, didn't matter.

The solution I use is simple, use an up-converter of 125 MHz like the NoElec (metal boxed with TCXO), it will greatly solve the problem as the local-oscillator and band-filters are very high so mixing doesn't happen that much and the I/Q is far better.

I learned this little trick from using dongles in he past.
I'm running a websdr, so you can see what it does here: http://heppen.be?tune=198am

The antenna is a 54m long-wire, fed with coax, no baluns, just a lot of ferrite clamped on the coax as common-mode-choke (but one can use a plastic bottle too and wind coax round it for about 20 turns).

After the up-converter I did set MW-notches and LNA-on, works great.

As far as the RSP1A is concerned, it thinks it's tuning in VHF rather then HF, but the trick works great.
See for yourself, but do not take the values for real, just set them to what seems to be right:

Schermafdruk op 2019-01-13 16-26-11.png
Schermafdruk op 2019-01-13 16-26-11.png (131.1 KiB) Viewed 2246 times


Or as you look at it:
Schermafdruk op 2019-01-13 16-29-21.png
Schermafdruk op 2019-01-13 16-29-21.png (58.54 KiB) Viewed 2246 times


I do point out, I'm using 5 MHz BW with decimate of 2, as I need the entire 2MHz sampled at the same attenuation, doing so band/low-pass don't work well (if hardly at all) without up-converting.

Just my thoughts on the matter, hopefully it works for you too.

73's Bas.

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Greetings,

Bas - ON5HB

glovisol
Posts: 570
Joined: Thu May 10, 2018 6:42 pm
Location: Piedmont, Italy

Re: THIS THREAD EXPLAINS WHY IT IS SO DIFFICULT TO UNDERSTAND RECEIVER'S SENSITIVITY IN LF & RELATED MATTERS

Postby glovisol » Sun Jan 13, 2019 4:38 pm

Hi Bas,

Thanks for the information and the suggestions, which I will try out.

I am also testing the RSP-1A with just a self made ferrite balun (described in the Low Pass Filter thread) and occasionally I insert attenuators between antenna & baluns. I enclose a PC screen of Radio Stations in the same frequency range as yours. The RSP-1A operated with Decimation = 16 in LOW IF mode and no MW filter inserted. My PC screen looks quite clean to me and I would like to have your comments as you seem to have quite a good experience. I tested every little carrier to check if it was IP3 or Higher Order, but found nothing.

I also wonder why you do not use the SDRuno software: it would be easier to cross check the PC screens back and forth with the same receiver software!

'73, glovisol
Attachments
Radio stations 15.10 GMT_13.01.19.jpg
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glovisol
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Location: Piedmont, Italy

Re: THIS THREAD EXPLAINS WHY IT IS SO DIFFICULT TO UNDERSTAND RECEIVER'S SENSITIVITY IN LF & RELATED MATTERS

Postby glovisol » Sun Jan 13, 2019 4:49 pm

Hi again Bas,

Your WebSDR is FANTASTIC! Very deserved compliments!

glovisol

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ON5HB
Posts: 124
Joined: Sat Dec 29, 2018 1:07 pm
Location: Heppen - Belgium
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Re: THIS THREAD EXPLAINS WHY IT IS SO DIFFICULT TO UNDERSTAND RECEIVER'S SENSITIVITY IN LF & RELATED MATTERS

Postby ON5HB » Sun Jan 13, 2019 4:52 pm

Hi Glovisol,

Well I use the RSP1A's just for people that have no receivers themselves or no place to put antenna's, so they can run my receivers remote.
My own transceiver is an Icom 7300 that covers 0-72MHz with better numbers :D

Do not get me wrong, I love these RSP's but I use them for other people to listen on bands.

As you see on my websdr, it's many people use the 3 RSP1A's at the same time, it's not build for myself but for others.
My problem was people didn't believe my signal-reports, I have a server running anyway so let people check it out themselves.

Just want to share my location/reception with others, makes me happy if they enjoy it. :D

Thanks for the compliment :!: :!: :!: :!:

Reason: No reason
Greetings,

Bas - ON5HB

glovisol
Posts: 570
Joined: Thu May 10, 2018 6:42 pm
Location: Piedmont, Italy

Re: THIS THREAD EXPLAINS WHY IT IS SO DIFFICULT TO UNDERSTAND RECEIVER'S SENSITIVITY IN LF & RELATED MATTERS

Postby glovisol » Sat Jan 19, 2019 8:14 pm

NINE DAYS NOISE FLOOR DATA FOR THE LW FREQUENCY BAND

As anticipated in my post of Sat Jan 12, 2019 5:35 pm in this same thread, I am uploading LW Band Noise Floor measurement data for the last 9 days.

The Noise Floor levels measured, corrected for bandwith (1800 Hz) and for antenna gain (Beverage) should be very near the typical Noise Floor values present in average, quiet rural locations.

Since noise at this frequency is mainly dependent on atmospheric disturbances throughout the world, this data can be used as reference (as described in the Receiver System assesment thread, covering HF Noise Floor) also because it is consistent with data presented by the cited ITU Publication RP372-13 and discussed in previous posts in this thread. The average Noise Floor levels, measured and corrected, are as follows:

17 KHz: -91.2 dBm
62 KHz: -89.9 dBm
120 KHz: -86.8 dBm
211 KHz: -83.2 dBm
323 KHz: -80.1 dBm

With a total spread contained within approximately 10 dB.
Attachments
9 days Noise Flor data(2).jpg
Measured Noise Floor data in tabular form
9 days Noise Flor data(2).jpg (87.06 KiB) Viewed 2108 times
9 days Noise Flor data(1).jpg
Noise Floor data graph
9 days Noise Flor data(1).jpg (94.94 KiB) Viewed 2108 times

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glovisol
Posts: 570
Joined: Thu May 10, 2018 6:42 pm
Location: Piedmont, Italy

Re: THIS THREAD EXPLAINS WHY IT IS SO DIFFICULT TO UNDERSTAND RECEIVER'S SENSITIVITY IN LF & RELATED MATTERS

Postby glovisol » Fri Feb 01, 2019 2:15 pm

TWENTY DAYS NOISE FLOOR DATA FOR THE LW FREQUENCY BAND

DATA TAKEN AT 7:00 GMT EACH DAY NORTHERN ITALY

As anticipated in my post of Sat Jan 12, 2019 5:35 pm in this same thread, I am uploading LW Band Noise Floor measurement data for the last 20 days. This information gives a fair idea of absolute noise floor levels in LW during the winter season. As is immediately evident, noise level is always within a band of -75 to -100 dBm. A very significant difference (10 dB) can be noticed, on average, between 17 KHz and 323 KHz. As for the previous data the Noise Floor levels measured are corrected for bandwith (1800 Hz) and for antenna gain (Beverage).

In next posts I shall upload 20 days data taken at 12:00 and at 19:00 GMT
Attachments
20 days Noise Floor data.jpg
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glovisol
Posts: 570
Joined: Thu May 10, 2018 6:42 pm
Location: Piedmont, Italy

Re: THIS THREAD EXPLAINS WHY IT IS SO DIFFICULT TO UNDERSTAND RECEIVER'S SENSITIVITY IN LF & RELATED MATTERS

Postby glovisol » Wed Feb 06, 2019 8:21 am

TWENTY DAYS NOISE FLOOR DATA FOR THE LW FREQUENCY BAND

DATA TAKEN AT 12:00 GMT EACH DAY NORTHERN ITALY
Attachments
20 days Noise floor data @ 12 GMT.jpg
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glovisol
Posts: 570
Joined: Thu May 10, 2018 6:42 pm
Location: Piedmont, Italy

Re: THIS THREAD EXPLAINS WHY IT IS SO DIFFICULT TO UNDERSTAND RECEIVER'S SENSITIVITY IN LF & RELATED MATTERS

Postby glovisol » Sun Feb 17, 2019 12:55 pm

TWENTY DAYS NOISE FLOOR DATA FOR THE LW FREQUENCY BAND

DATA TAKEN AT 19:00 GMT EACH DAY NORTHERN ITALY
Attachments
20 days Noise Floor data @ 19 GMT.jpg
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