Re: LF: MF/160

[DK7FC <selberdenken@posteo.de>]

Hello Hugh,

Maybe it is worth to try a resonated RX loop antenna! It is quickly built, just use some thick wire and form a sqare loop of 3m x 3m in the garden or so. I'm using my modified MFJ-256B to align such antennas on LF and MF. You need a series C to get a pure resistive feed point impedance. Then, this is transformed to 50 Ohm with a small ferrite core with Al=4 nH or so. You will get a galvanic decoupling then.
Such a narrow band loop will help to avoid interference from 198 kHz for example! It gives you the chance to check if the problem comes from the current front end you are using. And a loop can be helpful anyway.
You may need a preamp for maximum sensitivity but leaving out the attenuator will give a first 40 dB gain :-)
It is built in an afternoon like today :-)

73, Stefan


Am 02.11.2017 13:26, schrieb dhchurch:

Hello Stefan.

 

The R5000 agc cannot be turned off but the SDR's can. The R5000 agc range seems to cover over 40dB and I now set the attenuator at -30dB fdor 136kHz,  I don't use it's noise blanker and use the audio notch for DCF39. Below 100kHz the response drops off although things do show up well down to 30kHz. I did modify the input LPF for LF at the expense of the LW and MW bands which are attenuated automatically anyway. It has all the available IF filters so it might be worth a narrower bandpass but I think, in view of the agc range, unwanted products might appear from the front end.

 

I'm still experimenting with the SDR so can try every function over time. Regardless of any settings I can faintly hear chatter from Droitwich on 198kHz but it doesn't show, it is about 60km distant with a small second harmonic. DCF39  appears liike striped wallpaper but the sidebands are no problem. SDR offers an RF notch for this.

 

For apparent sideband level I think -40dB should be a reasonable level, more would be better of course, especially for higher power.

 

73, Hugh, M0DSZ

 

 

 

----- Receiving the following content -----

From: DK7FC

Receiver: rsgb_lf_group

Time: 2017-11-01, 19:35:03

Subject: Re: LF: MF/160

Hi Hugh,

As mentioned in my other mail, a noise blanker can cause multiple decodes on WSPR. Also it is worth to check that all 'sound effects' such as AGC are disabled on the RX path. A narrow band filter may help as well. Maybe the RX has not enough dynamic range is is partly nonlinear due to the strong signals by DCF39 and HGA22. Then another strong in band signal may seem to cause interference.

Same with the sidebands. As Mal recently described, i sometimes see stations uploading decodes from my WSPR signal on 475.685 Hz and 475.785 Hz. The sideband decode is about 42 dB weaker. BUT, from the same transmission, there are stations getting a stronger decode on the main frequency and no decode on the sideband frequency. So the RX side is playing a role too...

Just some thoughts.

73, GL, Stefan

Am 01.11.2017 11:49, schrieb dhchurch:

Hello Chris 

I removed the telephone line from the external shack and installed a cordless system, it made a small difference, and now there is also effectively a 30dB attenuator but it means smaller signals are not decoded which is a shame. I can see them on a  seperate spectrum analyser, Droitwich is about the same.

Now I have to deal with some spurious responses in Opera. This is running Opera, WSPR2 and 15, and Spectrum Analyser simultaneously which I always used to do. Have you checked the erp with anyone externally as any digital notch I put into the RF input is still too broad?

Hugh, M0DSZ

 

----- Receiving the following content -----

From: Chris Wilson

Receiver: dhchurch

Time: 2017-11-01, 07:06:45

Subject: Re: LF: MF/160

Hello Hugh,

It looks like you have managed to resolve the multiple signals from me
at your end, nothing has changed here, I have seen no multiple WSPR
receptions from you reported over the last couple of days, and signal
levels look more appropriate compared with other nearby stations,
here's last nights results:

 2017-10-31 18:40 2E0ILY 0.137550 +15 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 19:00 2E0ILY 0.137550 +16 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 19:40 2E0ILY 0.137550 +17 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 20:00 2E0ILY 0.137550 +16 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 20:20 2E0ILY 0.137550 +16 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 20:40 2E0ILY 0.137550 +15 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 21:00 2E0ILY 0.137550 +15 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 21:20 2E0ILY 0.137550 +14 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 21:40 2E0ILY 0.137550 +14 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 22:00 2E0ILY 0.137550 +13 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 22:20 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 22:40 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 23:00 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 23:20 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-10-31 23:40 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 00:00 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 00:20 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 00:40 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 01:00 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 01:20 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 01:40 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 02:00 2E0ILY 0.137550 +12 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 02:20 2E0ILY 0.137550 +12 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 02:40 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 03:00 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 03:20 2E0ILY 0.137550 +10 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 03:40 2E0ILY 0.137550 +10 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 04:00 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 04:20 2E0ILY 0.137550 +10 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 04:40 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 05:00 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 05:20 2E0ILY 0.137550 +11 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 05:40 2E0ILY 0.137550 +12 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 06:00 2E0ILY 0.137550 +12 0 IO82qv 0.2 M0DSZ IO82ls 31 244
 2017-11-01 06:20 2E0ILY 0.137550 +12 0 IO82qv 0.2 M0DSZ IO82ls 31 244


 Is this now sorted? :) What was it if you don't mind me asking?



Tuesday, October 24, 2017, 7:57:58 PM, you wrote:

>
>
> Hello Jay
>
> There are 2 receivers, one a Kenwood R5000 and the other an
> SDRPlay RSP2. The former feeds a UHF link from shack to house, both
> ends running off 12V batteries with solar chargers. The R5000 can
> also run from 12V dc for the tests but not for long. The RSP2 gives
> the same results both in the shack and the house and powers from a
> USB input. This is the same with a desktop or a laptop running from
> it's own battery. The bandwidth filter is standard USB for the R5000 and 2kHz for the RSP2.
>
> This is where an independent assessment would be handy. There's not
> much point in posting the results but there are traces up to 500Hz
> away. I have only seen large sidebands on Mal's (G3KEV) but not usually.
>
> Hugh, M0DSZ












--
Best regards,
 Chris mailto:dead.fets@gmail.com