Re: SDRC and Airspy R2


jdow
 

That is the best policy. However, I have violated it in the past. Since I don't have to be manly I've been content at 100W generally.

{^_^}

On 20220710 00:02:23, Conrad, PA5Y wrote:

Hi Simon, I use a cheap VNA to measure the coupling between antennas. The 80m dipole most likely won’t matter but 2m will. I bypass my Band II LNA when I TX on any band, in fact I bypass all LNAs when I TX on any band, therefore I use energised relays on RX. Some effort required but it is Conrad proof!

 

Conrad

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Simon Brown via groups.io
Sent: 10 July 2022 08:56
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

The preamp's BPF is important, I wonder how much input signal it can handle as my 80m dipole is ~30cms below the Band II Yagi and I have a 2m antenna ~4m away and I run full legal on all bands when the mood takes me.


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Conrad, PA5Y via groups.io <g0ruz@...>
Sent: 10 July 2022 07:50
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

It should be possible, just about. From the S3 user manual.

 

The FDM-S3 has two antenna biases, one for the HF-2 input and one for the VHF input. The supplied voltage is 5V (max 150mA).

 

 

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of jdow via groups.io
Sent: 10 July 2022 08:46
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

5V at a whomping 150 mA. That latter may be the show stopper if you try to use your front end's Bias-T.

And why that version and not "https://www.tgn-technology-online.com/en/Low-Noise-Amplifier-ULNA3018.html"? The "Specifications" suggest it has the power supply. The "Accessories" suggests not. The pictures suggest it does have the PS. Ah, I see, it lacks the bias-T for its PS. If you determine your front end's bias-t can handle the load they all seem to be the same amplifier so the cheapest one should be good enough.

{^_^}

On 20220709 12:21:49, Conrad, PA5Y wrote:

Ah this one does need 5V, there you are then.

 

https://www.tgn-technology-online.com/en/Low-Noise-FM-Amplifier-ULNA3018.html

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Conrad, PA5Y via groups.io
Sent: 09 July 2022 21:19
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

The active device in the TGN amplifiers will not actually need 10V, as you have a bias T in the S3 you should ask TGN if they can use a different regulator in the LNA so that you can use 5V. There are cheaper alternatives.

 

Conrad

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Conrad, PA5Y via groups.io
Sent: 09 July 2022 21:09
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

Here is a rough and ready analysis with a 6dB attenuator, this would typically be a 10dB step attenuator, set according to conditions.

 

It gives 84dB SFDR based on the S3 user guide and the PGA103+ datasheet. The first 2 stages are typical of a band II amplifier with front end selectivity.

 

Anyway, this gives you an idea.

 

Conrad

 

 

 

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Simon Brown via groups.io
Sent: 09 July 2022 21:01
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

Hi,

 

Please do a noise analysis for 88-108MHz. I think the S3 bias-t is 5v, not sure what voltage these preamps require.

 

I have 25m RG6.


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Conrad, PA5Y via groups.io <g0ruz@...>
Sent: 09 July 2022 19:52
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

I could not agree more, a step attenuator on the output is a good idea. You can of course use the noise free bias tee on the S3 for the supply. These are almost certainly PGA103+ LNAs.  You can use AppCAD and do a system noise analysis. If you like I will do one and put it on here. In fact I may have already done one and posted it some time ago. I’ll have a look.

 

Conrad

 

 

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of jdow via groups.io
Sent: 09 July 2022 20:42
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

The cheapest one would probably be good enough. The next one up might be slightly better because you get a nice noisy power supply and (possibly redundant) Bias-T tap for it. The most expensive one would only be needed if you have some exceptionally strong signals nearby.

 

18 dB gain may be a little high with only 2.5 dB of cable loss. Something like one of the old HP 1 dB step variable attenuators might be good on the receiver input. Adjust it for a suitable compromise for dynamic range and signal strength. I suspect you do not need this 10V version of the amplifier.

 

(Did I just save you a bunch of money?)

 

{^_^}

 

On 20220709 11:12:30, Simon Brown wrote:

Thanks,

 

I'll start saving and buy a masthead preamp (below). My income is way down now due to COVID and other cost of living issues. Not a great time to be relying on donations.

 

 

They have a bit of input filtering already, don't know if it's enough.


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Conrad, PA5Y via groups.io <g0ruz@...>
Sent: 09 July 2022 17:37
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

According to the user manual with the preamp and noise reduction on the MDS at 91.1MHz is -138dBm in 500Hz, which equates to -165dBm/Hz. This is a 9dB noise figure and is probably 3-6dB worse because the NR makes things appear better than they are. If you add 2.5dB to that noise figure you can see that an LNA will be of great benefit.

 

I suggest that a system noise figure of around 2-3dB is optimum for Band II DXing.

 

Regards

 

Conrad PA5Y

 

 

 

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Simon Brown via groups.io
Sent: 09 July 2022 17:29
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

Hi,

 

What's the S3 noise figure on Band II ? I have maybe 2dB loss in the 25m RG6, so am wondering what the total NF is.


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of Conrad, PA5Y via groups.io <g0ruz@...>
Sent: 09 July 2022 16:06
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

BTW I put the BPF before the LNA to help protect it from 144MHz EME high power. I am not suggesting that a PGA103+ will saturate from normal Band II situations. However, it has a little bit too much gain, so a good filter and an attenuator does no harm. The S3 really is excellent. Just like you said 😊

 

73

 

Conrad PA5Y

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Conrad, PA5Y via groups.io
Sent: 09 July 2022 17:01
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

Hello Simon, I have done a noise analysis and you WILL benefit from an LNA. I have a PGA103+ preceded by a band pass filter and it seems to work very well. However, I am still waiting for a bigger antenna. I ordered an OPTDES which never arrived. So, I will ask a few of the local Band II DXers for an alternative.

 

73

 

Conrad PA5Y

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Simon Brown via groups.io
Sent: 09 July 2022 13:22
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

FWIW,

 

The ELAD S3 is the best Band II receiver I have. Am thinking about a preamp on the mast for those very weak stations - if I get close to receiving weak signals from across the pond (USA, Canada).


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of George Stein - NJ3H via groups.io <nj3h@...>
Sent: 09 July 2022 08:08
To: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
Subject: Re: [SDR-Radio] SDRC and Airspy R2

 

Simon and others,

 

I have attached 3 pictures all with Console running.

 

Elad S2,

Airspy R2

RSPdx

 

 

The RSPdx is the only on of these three that has a decent signal. Running uno is fine also.

 

It is the other two that are causing problems.  The native software yields the same lousy signals.  There is a lot of noise on these two receivers for the station in question. I have fiddles with the R2 slide controls in both Sharp and Console. The Elad appears not to have any RF gain capability.

 

The frequency I am using for this exercise is 98.9, 92 watts, 25 km away.  I am using the same antenna for all three radios.  The antenna is pictured in an attachment. Same feed line to all three radios. My HF+ Discovery works fine also.

 

As I said in a previous message, the Elad S2 is the one that really puzzles me.  I would have expected it to come out the best (based only on price, that is).

 

Anyway, please let me know if more information is needed.

 

Thanks for looking into this.

 

Regards,

George

 

 

 

On Friday, July 8, 2022 at 11:38:57 PM PDT, jdow <jdow@...> wrote:

 

 

Frequency?

{o.o}

On 20220708 14:47:30, George Stein - NJ3H via groups.io wrote:

92 watts not 25.

On Fri, Jul 8, 2022 at 2:24 PM, George Stein -  NJ3H via groups.io

<nj3h@...> wrote:

Further to my last message.  The station in question is 25 km away and running a mere 25 watts. 

Using SDR Console:

With the Elad S2 and and the Airspy R2, the reception was very noisy.

With the Airspy HF+ Discovery and the RSPdx, the signal was full quieting. With the edge going to the HF+ Discovery.

This was not a scientific test, just a casual observation. The only thing I am surprised about was the Elad S2 performance.

I then used the native software for each device and had the same results.

Regards and YMMV,
George


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