Shortwave reception help

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illllm
Posts: 56
Joined: Wed Jan 23, 2019 10:26 pm

Shortwave reception help

Postby illllm » Thu Feb 07, 2019 12:25 pm

I wish there were more shortwave music stations, maybe pick some up from European region. This is the primary reason I got the RSP2. It’s nostalgia from back in the 80s when we owned a tube grundig radio and an antenna made of copper mesh. It picked up many stations and it had that awesome magic eye.

Today, I use a shielded loop on one port and a mini whip on one. Each has its advantages and disadvantages. The whip is good for few stations and the loop is less noisy and good for other stations. I tried adding an LNA nearly the loop but the FM stations were overpowering so I ended up removing it.

The loop and the whip outperform the long wire in my situation because I live in an RF noisy neighborhood.

The coax does pick up a lot of noise and grounding attempts have not been successful. Adding an antenna isolation transformer is not helpful as it increased the noise.

Now that I am finally getting accustomed to the RSP2, what are recommendations and suggestions to increase shortwave and medium wave radio from Europe. I am in the US east coast.

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g1hbe
Posts: 456
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire, UK

Re: Shortwave reception help

Postby g1hbe » Thu Feb 07, 2019 8:04 pm

Yes, it's horses-for-courses. I can't use wires or mini-whips here, there's too much noise. The loop is the only way for me, it gets rid of 90% of the hash. I'm a bit puzzled why your antenna transformer made the noise worse, that's really unusual. I've found that a transformer always gets the noise down by some amount, sometimes a LOT, depending on which band I'm on.
Re the number of music stations on SW, I'm afraid things are bad and getting worse. Conditions are terrible, and on top of that many of the big broadcasters are closing their transmitters and going online-only. Not like it was in Ye Olde Days!

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Andy

illllm
Posts: 56
Joined: Wed Jan 23, 2019 10:26 pm

Re: Shortwave reception help

Postby illllm » Fri Feb 08, 2019 1:17 am

With the isolation transformer, the ground of the antenna was also acting as a signal path. I have to figure out a way to ground it separately outside and then it might work. If i grounded the cable shield to the RSP2 ground, the noise would drop but then I have lost isolation.

The only two stations I can pick up now that play music are WRMI Florida and the one from Tennessee and both play classic oldies.

I guess I am getting into this SDR and Shortwave game too late :( . I wanted a powerful and cheap radio so I got an SDR for $20 and one thing led to another and now I am in for about $600 with all the parts and components and wires and regen-receivers and more.

Should have just bought a Grundig Satellit 750 Ultimate, but then I wouldnt have add the cool software running on my desktop looking very official and dandy :D :lol:

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illllm
Posts: 56
Joined: Wed Jan 23, 2019 10:26 pm

Re: Shortwave reception help

Postby illllm » Sat Feb 09, 2019 2:30 am

https://youtu.be/tsMp-bcGN8g

Made some more video. This one shows weird sounds. Any idea what they are?

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Mike2459
Posts: 246
Joined: Mon Jul 24, 2017 8:24 pm

Re: Shortwave reception help

Postby Mike2459 » Sat Feb 09, 2019 4:19 am


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glovisol
Posts: 496
Joined: Thu May 10, 2018 6:42 pm
Location: Piedmont, Italy

Re: Shortwave reception help

Postby glovisol » Sun Feb 10, 2019 9:33 am

Hi Mike2459, well met again....are you sure you have given the right reference to Illllim?

Hi Illllim,

The most effective method to get rid of noise, local noise, is to isolate the receiver's input from noise sources, normally picked up by the shield of the coaxial cable lead-in and / or the grounding system. You speak of an "isolation transformer" as if all antenna transformers were the same. Most of us go to Ebay, or to any one of tens of sites and buys an "antenna balun", sticks it in, hoping for the best and then cries with disappointment. We all have forgotten about solving problems with out own ideas and our own hands, while the point in Amateur Radio is just this: learn and learn more by doing things ourselves.

Getting away from philosophy and into the noise problem, you should first CLASSIFY your site/receiving system, following the method outlined in "Assessing Receiving system performance":

viewtopic.php?f=5&t=3685

This will give you an idea of the size of your problem and of the noise level you are in and more, it will tell you if your main problem is LOCAL noise or not. The referenced thread is focused on HF operation. If you are interested in LW operation, then you should look at the parallel thread:

viewtopic.php?f=7&t=4003

where at present I am uploading noise levels measured over a period of 20 days.

Once you have determined where you stand, you have seen that your problem is local noise and you have determined how constant or erratic your noise is, you should consider BUILDING a LOW CAPACITANCE isolation transformer. I say building because you cannot buy one and it is very easy, taking probably half an hour of your time. The essence is in the low capacitance between primary and secondary. This transformer is NOT FOR MATCHING, but for shorting & blocking noise, so that it does not reach the receiver. It does not matter if it is lossy, as long as it removes noise even if it has a few db's of insertion loss. For low capacitance the ferrite must be small, the wire diameter small and secondary must be on the other side of the core, as far away as possible from the primary winding.

Why low capacitance? In the transformer the low noise path must be inductive only, capacitance makes the noise jump right across and therefore you must get rid of as much capacitance as possible. If one transformer is not enough, you can use two in series, effectively halving the capacitance.

You just need a very common and easily located 7 mm. external diameter ferrite toroid core:

FOR HF RECEPTION
Toroid core: FT-37-43 (material type 43)
Ext. dia.: 0.375"
Internal dia.: 0.187"
Thickness: 0.125"
PRIMARY = SECONDARY: 5 turns enamel copper wire 0.5/0.3 mm dia, for 1:1 / 50 Ohm Z ratio. Primary will be between center and shield of coax lead-in. Secondary between receiver's antenna socket center and common. Most probably you should not connect any ground to the RSP.

If you intend to use the HI Z input of the RSP2 (better choice) then alter turns ratio depending on your antenna impedance, keeping in mind that the HI Z = 1000 Ohm. For a 50 to 1000 Ohm you should use PRI=3 SEC=10, enamel copper wire 0.28 / 0.23 mm. I realise primary inductance is too low and secondary turns should be more, but this is the best compromise I could find.

FOR LW RECEPTION
The transformer above will still work, but you should experiment with a (very) few more turns to reduce loss or resort to a Type 73 material: ferrite core FT-37-73.

For the other (interference) problems in shortwave reception, the built-in MW & FM notch filters are a big help, as well as resorting to LOW IF mode to get rid of spurious & overload. Finally, remember that a long wire is a good antenna (the longer, the better) depending on the space you have on hand.

Hope this helps.

glovisol
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Roger
Posts: 217
Joined: Fri Dec 29, 2017 7:59 pm

Re: Shortwave reception help

Postby Roger » Sun Feb 10, 2019 4:37 pm

illllm ,

In order to provide you with some useful assistance we need to know what type of setup you have at your location. Without knowing the problem it is not prudent to offer solutions. Can you provide some more details ...

- Are you in an apartment, townhouse or a house?
- What type of shielded loop are you using?
- Is the miniwhip a PA0RDT, Ukranian or Russian version or a homebrew?
- What type of wire antenna are you using (end-fed, random wire or dipole)
- Do you have a station ground system?
- You say you are in a noisy RF area. Close to neighbors or your own RFI sources (TV, heat pump etc.) ?
- Do you have the ability or interest in constructing your own equipment (baluns, transformers, tuners, filters etc.)?

As far as shortwave listening goes you should know that many shortwave broadcasters have shutdown and a number of those on the air are not beaming to North America. We are very near the solar minimum so HF conditions are very poor and at night the maximum usable frequency (the MUF) drops so you have to listen on the lower bands (under 10 MHz.). That does not mean that you can't receive lots of interesting SW stations. You just have to use a little more patience and skill to receive them. You can download station broadcast schedules and load them into the SDRuno Memory panel. There are also lots of online schedules that will tell you what is on right now and then you have to see if propagation is right for you to receive them.

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illllm
Posts: 56
Joined: Wed Jan 23, 2019 10:26 pm

Re: Shortwave reception help

Postby illllm » Sun Feb 10, 2019 9:30 pm

see this video . I posted it in the Antenna section

https://www.youtube.com/watch?v=eIzoAdc ... e=youtu.be

I have the same balun/isolation transformer. I have built many and experimented with many of them.

In the first video posted above in this thread, (not the one in this post) , the sawtooth noise is from a plasma TV - My son playing video games. I can get rid of that by switching off the TV.

The other lesson - very important I learnt is to use the presets. When selecting shortwave bands, use the presets and it adjusts the LO and various other settings on its own. Signals are much better.

The only things I didnt build are the RSP2 :P , USB cable. I built everything else. I have a couple of LNAs from ebay but they dont help much in my case. The antenna going directly to the RSP2 produces the best performance.

The Whip is from Ukraine

https://www.ebay.com/itm/MiniWhip-Activ ... rk:14:pf:0

The Loop is made from this design
https://pa0fri.home.xs4all.nl/Ant/Activ ... %20eng.htm

I made the Loop and bought the LNA from Amazon. The same LNA is available. I then modified the LNA for power over the cable.
Video here:
https://www.youtube.com/watch?v=mkd-MwaprkQ

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illllm
Posts: 56
Joined: Wed Jan 23, 2019 10:26 pm

Re: Shortwave reception help

Postby illllm » Sun Feb 10, 2019 9:32 pm

Forgot to add, Thank you all for all your suggestions. I will try out all of them.

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illllm
Posts: 56
Joined: Wed Jan 23, 2019 10:26 pm

Re: Shortwave reception help

Postby illllm » Sun Feb 10, 2019 10:35 pm

Here is a comparision between the Loop on Port A and Whip on Port B. I have disconnected the isolation transformer. Much better now. Sorry about the messy floor :P . Aluminium foils were used to encapsulate the baluns :roll:

but here is the video

https://youtu.be/iYnAO9hc_dQ

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