Compared an RSP1A alternately with an RSP1

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NoelC
Posts: 137
Joined: Sun Nov 27, 2016 11:50 pm

Compared an RSP1A alternately with an RSP1

Postby NoelC » Mon Dec 18, 2017 6:00 am

I've had (and loved) an RSP1 for over a year now.

I bought an RSP1A for a ham friend as a gift. Before wrapping it I decided to try it in place of my RSP1 just to see what differences there are and whether the refinements would yield a better user experience.

TL/DR summary: I still like my RSP1 and probably won't buy myself an RSP1A upgrade.

Now for the details:

The only obvious thing I noticed in SDRuno 1.21 is that with the RSP1A the change in a few buttons in the MAIN panel, including the [MW/FM] band filter button... I've wondered how well that works and whether it reduces spurious signals, etc. Also, the RF Gain Reduction doesn't quite seem to work quite the same; I guess the LNA has been integrated into it. In a way, it feels like it works a little better, though I'm completely used to the way it works for the RSP1 and how it interacts with the AGC control.

I compared performance at Long Wave, Short Wave, VHF, and UHF frequencies using a fairly narrow bandwidth (LOW IF, Signal Rate 2 MHz, DECimation 2).

Honestly, I couldn't sense much difference for Long Wave stuff. When I first tuned some of the beacon signals around 286 kHz I thought the RSP1A was doing better than I'd seen from my older unit, but when I swapped the RSP1 back in I was able to pull in the same signals at about the same strengths. The waterfall displays looked almost identical. I was surprised to see that the aliased signals down near zero were about the same.

I tuned some 160 meter stuff at 1.84 MHz and there I saw more difference, with the RSP1A showing fewer signals but at the same time some oddball background noise I don't see in the RSP1. Both units tuned FT8 ham comm signals and WSJT-X was able to do a good job of interpreting quite a few of them. It's possible the differences I saw between the units could be explained just by changes in propagation. I honestly can't say one was better than the other.

I tuned CHU Canada at 3.330 MHz and the signal strength and whole waterfall display looked virtually identical between the two.

I thought the waterfall display on the RSP1A at 10 MHz tuned to the WWV signal seemed much cleaner - until I realized I had dialed the RF Gain Reduction back a good bit. When I set them similarly both units again showed virtually identical waterfalls and signal quality.

Other spot checks at higher frequencies again netted no great surprises.

I did see a strong reduction in AM (Medium Wave) and FM signals when I invoked the [MW/FM] filter button on the RSP1A, and so I went looking for places where that might matter - e.g., tuning above several hundred MHz. Sure enough, blocking the seriously strong and numerous FM stations we have here in south Florida really made a difference in the imaging in the sub gigahertz ranges. If you're listening to UHF, the RSP1A's additional capability will matter.

I tuned some police frequencies with both units at around 851 MHz and again both units performed about the same.

I checked both units for aliased signals, and this is one area where the RSP1A really shined. At many different frequencies I stepped the frequency up 1 kHz at a time with LO LOCK off and I only saw very faint signals marching the other way on the RSP1A, where I do see more of those in my RSP1. But not a LOT more. Just a few. This alone is ALMOST enough to make me want an RSP1A of my own.

I tempted myself with a thought exercise: What if I gave my friend my old RSP1 and kept the RSP1A for myself? Surprisingly, my emotional response was actually NO - really I don't see much improved performance and somehow I feel more comfortable with the unit I already know and use. It wasn't the answer I expected, to be brutally honest.

I hope this helps others know that the RSP has been and is a fine piece of gear, and while there are small refinements in the new model, they are evolutionary, not revolutionary.

I'll have the RSP1A for a few more days, so if you can think of something I should have checked, or want specific comparisons, screenshots, etc., please ask.

-Noel

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Paul
Posts: 257
Joined: Fri Feb 17, 2017 9:52 am

Re: Compared an RSP1A alternately with an RSP1

Postby Paul » Mon Dec 18, 2017 8:11 am

NoelC wrote:I've had (and loved) an RSP1 for over a year now

I'll have the RSP1A for a few more days, so if you can think of something I should have checked, or want specific comparisons, screenshots, etc., please ask.

-Noel


Perhaps you could try the comparison of NDB reception with and without the AM/FM filter - trying this with the RSP2 makes a dramatic difference.

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g1hbe
Posts: 367
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire, UK

Re: Compared an RSP1A alternately with an RSP1

Postby g1hbe » Mon Dec 18, 2017 12:57 pm

How does the RSP1a do in the Milsat band? RSP1 and 2 both have problems with imaging in this area, mainly from DAB or (possibly FM) broadcasts. The area around 250 to 260 MHz is virtually unusable. There are a few spot freqs used by pirates in south America (255.550 MHz and thereabouts) that get hammered by images. Thanks.

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Andy

Tech_Support
Posts: 377
Joined: Mon Jun 01, 2015 7:00 pm

Re: Compared an RSP1A alternately with an RSP1

Postby Tech_Support » Mon Dec 18, 2017 2:02 pm


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someYguy
Posts: 93
Joined: Sun Apr 10, 2016 7:12 pm

Re: Compared an RSP1A alternately with an RSP1

Postby someYguy » Wed Dec 20, 2017 9:09 pm

NoelC wrote:I've had (and loved) an RSP1 for over a year now.

I hope this helps others know that the RSP has been and is a fine piece of gear, and while there are small refinements in the new model, they are evolutionary, not revolutionary.

-Noel


Thank you for this comparison, it reinforces my original thoughts regarding an upgrade here to the RSP1A. I think that it will be a welcome upgrade for many and the price is certainly oustanding but for me, the RSP1 works well enough to keep.

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NoelC
Posts: 137
Joined: Sun Nov 27, 2016 11:50 pm

Re: Compared an RSP1A alternately with an RSP1

Postby NoelC » Thu Dec 21, 2017 7:38 am

I tried swapping the RSP1 and RSP1A and looking over the spectrum just above 250 MHz.

The two looked a little different even without invoking the notch filters. There was some slight imaging, but not a lot, and we have some STRONG FM stations here.

Then the difference was more striking when I invoked the DAB filter. Thing is, I couldn't find a whole lot of power in the actual DAB part of the spectrum.

Nor did I see signals in the 250-260 MHz area either.

Screen grabs:

RSP1
Image

RSP1A with no specific notch filters on:
Image

RSP1A with notch filters on:
Image

-Noel

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someYguy
Posts: 93
Joined: Sun Apr 10, 2016 7:12 pm

Re: Compared an RSP1A alternately with an RSP1

Postby someYguy » Sat Feb 10, 2018 3:57 pm

Well, as it turns out, I too have had an opportunity to compare both an RSP1 and an RSP1A side by side, same antenna, same frequencies, similar gain settings.

My findings are much like Noel's. Biggest thing for me is I find myself readjusting the LNA & IF gain settings of the RSP1A much more than I do with the older RSP1. I always use manual IF gain settings rather than automatic and with the RSP1A I find that I must use one setting for HF/SWL, and another for the FM broadcast band to avoid overload, and yet another for airband etc.

Not so with the RSP1. I can set IF gain on that radio to 37 - about halfway - with LNA off, and leave it there for most listening with my 50ft. longwire antenna. Only on MW & 160m do I need to readjust. Sensitivity & MDS are good on all ranges according to my calibrated HP signal generator.

The new DAB and FM notch filters are helpful in the 200-400mhz though.

So now I have both receivers but in my case I too prefer the older RSP1 mainly due to the better-for-me gain mapping.

EDIT: I did notice that overall, the noise floor on the new RSP1A seems about 5-7db lower than that of the RSP1.....

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